Abstracts & Access to e-Prints.
The majority of papers presented at the conference are available here, subject to copyright under Attribution-Share Alike 2.5 Canada, with the provision that full attribution to both the conference and the author(s) must accompany distributed copies, quotations, or content used in derivative works of any kind.
There are exceptions. Some papers are available here only in abstract, with or without author contact information. Others are represented by abstracts with links other than the Adobe Acrobat logo. In these cases different copyright restrictions apply: see the links provided, or contact the authors. Some papers can only be obtained by buying a copy of the printed proceedings. Return to HOME for further information.
A Model for the Design and Evaluation of Energy-efficient Northern Housing
In addition to being a region of extreme cold temperatures with total darkness for almost half the year, the arctic territory of Nunavut suffers from, a housing shortage (in reality a crisis) that is the top of every political and economic agenda. In response to this crisis, the Nunavut Housing Corporation (NHC), in partnership with the Canada Mortgage and Housing Corporation (CMHC), initiated a design and development plan through the Infrastructure Canada program, to develop a sustainable solution to housing in the arctic. The result was the development of a new energy efficient housing project named the NHC 5-Plex.
This paper will examine and illustrate the design and development process undertaken by the NHC and CMHC for this project. The paper will describe how the integration of new construction materials and products, specifically designed for cold climates, strategic project management, and cooperation between the NHC and CMHC in the fields of design and building science were used to address the goals of energy efficiency and affordability for arctic housing. The paper will describe the process used to produce a multiplex public housing design that recognizes and compliments the life styles of the typical Inuit family, including insights into the occupants’ level of acceptance of the design and the integration of their recommendations into the design of future public housing.
The study will illustrate the energy conservation calculations, the comparative and cost analysis used for the project, and provide insight into a design process which, working backwards from shipping delivery dates, supported the completion of 18 5-plex units by Dec. 2005. The paper will illustrate important issues for designers working on housing in cold climates, demonstrate the use of new products and innovative construction methodology, and provide important insights for designers and builders everywhere who are interested in better performing and functioning buildings.
The paper will illustrate the success of this joint project between the NHC and CMHC, demonstrate the potential for improving the sustainability of housing in perhaps the harshest climate in the world, and highlight the importance of cultural sensitivity in the design process.
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The New Baha’i Mother Temple for South America: Some Aspects of the Façade Design
A new Baha’i Mother Temple for South America, designed by Canadian Architect, Siamak Hariri of Hariri Pontarini Architects, will be built in Chile close to its capitol city Santiago. The authors of the paper are part of the design team and are responsible for the design of its inner and outer facades.
Nine identical leaves connected at the top by a glass dome form the shape of the 30 m high and 30 m wide structure. The vertical space between the leaves is filled with glazed curtain wall. The leaves are clad on the outside with 32 mm thick cast glass and on the inside with Spanish alabaster. The exterior cast glass cladding is a four-sided structural silicone system and a “rain screen” design. Both the cast glass and the alabaster are supported by the main supporting structure, which is an irregular tubular steel space frame, which through the translucent façade resembles the veins of a leaf. The steel structure is supported on concrete foundations.
The paper describes some interesting aspects and challenges of the design process which deals with a number of complex issues such as evaluation of the uncommon architectural use of cast glass and alabaster materials; the design and development of a complex cast glass “rain screen” system; relatively severe loading conditions – Santiago is an earthquake prone area with temperatures fluctuating from below zero to plus thirty to forty degrees Celsius within 24 hours, complicated structural shape and the choice of uncommon cladding materials with unfavorable material properties.
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Balancing the Control of Heat, Air, Moisture, and Competing Interests
The design of a building for either new construction or rehabilitation must consider the control of heat, air, and moisture (HAM) flows. A large number of buildings in the Lower Mainland of B.C. have been rehabilitated because of extensive deterioration of the building envelope as a result of rainwater penetration. Rehabilitation designs have focused on eliminating rainwater penetration as a damage mechanism, which has typically included an increased control of air flow through the envelope. Because these designs have resulted in buildings that are more air tight than before rehabilitation, there is an increased need for mechanical ventilation to maintain good building performance. Without adequate ventilation the balance humidity levels in the suites increase and, depending on the wall design, this can result in condensation on the windows or interior drywall, or within the wall assembly itself.
This paper draws on one rehabilitated wall assembly with high humidity levels to explore the assumptions and decisions faced by the design team when completing a rehabilitation project with respect to controlling heat, air, moisture and the resulting affect on building performance.
Decisions and assumptions discussed include:
Indoor environment: acceptable and assumed ranges of conditions for temperature, ventilation, moisture generation, and the resulting balance relative humidity.
Cost and existing construction: constraints of the existing construction including wall dimensions and the cost of rehabilitation.
Current norms for building design and construction: current accepted norms for the control of heat, air and moisture transport and the importance of balancing these controls.
This paper presents a combination of calculated values for the indoor environment using a moisture balance between the exterior and indoor environment, HAM computer modeling, and field measurements of a rehabilitated project to support this discussion. Conclusions and recommendations are drawn from the lessons learned from completing this work.
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Relationship Between Moisture Content and Mechanical Properties of Gypsum Sheathing – Phase 2 Research
A lack of information exists regarding acceptable levels of moisture content for gypsum-based sheathing products and on the consequences of exposure to moisture in terms of mechanical properties and the integrity of the wall assemblies. A complementary need is the assessment of a method to measure moisture content of these products using hand-held electric resistance meters.
Previous work examined the relationship between moisture content and mechanical properties of gypsum sheathing (i.e., gypsum wallboard intended for use as exterior sheathing on buildings).
Gypsum wallboard is typically specified to conform to ASTM C1177 or C1396 performance criteria, and it was the particular interest of this study to determine whether moisture content affects this performance (and if so, to determine the moisture content at which the product no longer meets the ASTM criteria). Specific properties examined included:
adhesion or delamination of facer material (either glass-fibre mats, treated paper or untreated paper)
ability of the sheathing to resist fastener pull-out
flexural strength of the sheathing, for seismic considerations and as a common index of overall mechanical integrity
water absorption
The study also determined whether hand-held electric resistance meters are suitable for measuring moisture content are reasonably accurate, or if some new apparatus or protocol is required.
This paper discusses Phase II of this project, which examined the possibility of rehabilitating gypsum sheathing that had been wetted and subsequently dried out. The above mechanical properties were assessed for three subsets of the specimen group:
one subset was tested before wetting to predetermined moisture-content levels;
after wetting to predetermined moisture-content levels, half the remaining samples were tested; and
the remaining samples were oven-dried, and then tested to determine the same mechanical properties
The focus of this paper is on whether the re-dried samples regain the original level of mechanical properties that were exhibited by the first set of samples.
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Case Study: Carleton Lodge – Recladding for a Better Environment
Carleton Lodge, situated on the banks of the Rideau River, is a 160-bed long-term care facility that opened on April 8, 1989. The structure is light wood frame construction with insulated stud walls, vertical aluminum siding, and pitched roof trusses. The Lodge, with a central core and four 2-storey residential wings, has private rooms with en suite bathrooms, which project beyond the face of the main walls, and vent directly outside. There is perimeter hot water heating and ventilation from central make-up air units. Since construction, problems have existed with water infiltration, condensation and mould within the exterior walls. The residential wings were cold and drafty in winter and hot in summer. Whenever mould has been encountered since the building was completed, the City of Ottawa (and formerly the Regional Municipality of Ottawa Carleton) has taken immediate action to remove and remediate and conducted frequent air testing to ensure residents and staff were safe. The project objectives were to solve the problem of water penetration into the exterior walls, carry out mould decontamination, and re-clad with a system that will provide trouble free service with a reasonable degree of maintenance. A holistic approach was applied using integrated design and assessment techniques to investigate and design solutions for the building envelope problems. Remediation considered the possibility of mould, potential for salvaging materials and buildability of the details. A mock up was constructed during the design process to verify constructability and test the improvements to the exterior walls. As residents could not be relocated during construction, the project’s greatest challenge was limiting disruption and noise. Construction areas were tarped and negatively pressurized to eliminate dust infiltration. Following exterior inspection and wall reconstruction, interior remediation proceeded on a room-by-room basis and generally without displacing residents. The existing un-vented aluminum cladding assembly with minimal capillary break was replaced with a new rain screen pre-finished aluminum cladding system, consisting of high permeance membrane air/moisture barrier, galvanized z-girts and exterior insulation, new windows, ventilation grilles and dampers, and pre-finished metal siding. Exterior sheathing was improved to act as the primary air barrier, and a continuous thermal barrier was achieved with sprayed on foam insulation at difficult locations. Despite many fixed elements of the building, the project has corrected water penetration problems, decontaminated exterior walls, greatly improved the interior environment, and reduced heating and air conditioning costs. Energy use data is still being collected. Client feedback indicates that the project objectives were achieved.
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Cast-in-Place Concrete Cladding; Is it all its Cracked Up to Be?
No abstract available due to copying restrictions. You can download the full paper and read, but not copy from it.
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Considerations For Re-Cladding Highrise Panelized EIFS Buildings – A Case Study
An eight year old, highrise building in a Canadian cold climate zone was diagnosed with systematic water penetration through the Exterior Insulation and Finish System (“EIFS”) building envelope. This building utilized a factory-manufactured, modular panelized cladding system for the exterior walls that included EIFS building envelope components. The original panel design had some components intended to perform as a “drained” system which, when coupled with a factory controlled manufacturing environment, is normally considered a lower risk, good practice approach. Nevertheless, there was water penetration into the interior, with resulting water damage and related environmental problems to panel structural components and interior finishes.
This building has undergone a large-scale exterior re-cladding in the affected areas. The repair involves the removal of all exterior wall building envelope components, a re-design of the building envelope system that includes the use of a new drained EIFS approach, and the installation of the new wall system on the building. All rehabilitation work was completed while the building remained operational.
This paper describes the methods used to re-clad the facility while maintaining the mandated original appearance. Key discussion will focus on how the new EIFS system was designed, and how it was constructed to address reasonable durability expectations. Content will also focus on how designers and builders can improve the actual performance of these systems “as installed” to reduce the risks commonly associated with highrise EIFS.
The benefits of this paper to the reader will hope to include; discussion of real-world application of panelized EIFS design concepts, identification of factors not always considered in the design and installation of these systems, practical advice on methods for improving performance while managing potential risks, and considerations for the application of this approach on other projects.
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Cost Effective Levels of Thermal Insulation for Basements in Canadian Housing
This paper is based on recently completed research funded by Canada Mortgage and Housing Corporation to investigate cost effective levels of thermal insulation for basements in Canadian housing. The work is an update of a life cycle economic assessment appearing in Performance Guidelines for Basement Systems and Materials Project undertaken for the Institute for Research and Construction, National Research Council Canada in 1999. Since that time, the cost of space heating energy has escalated sharply and new methods and materials for insulating basements have emerged. The paper addresses the conference themes of new research and revised design understanding, and basement construction methods.
A methodology for energy modeling and life cycle cost analysis is presented in the first part of the paper followed by an assessment of the energy efficiency of current practices. These results are then contrasted with cost effective alternatives when several energy price escalation rate scenarios are examined using the Modified Uniform Present Worth method according to ASTM E917, Measuring Life-Cycle Costs of Buildings and Building Systems, ASTM Standards on Building Economics, Fifth Edition, 2004.
The final part of the paper presents recommended basement envelope assemblies for achieving cost effective levels of energy efficiency while improving basement system performance with respect to moisture protection, thermal comfort and reduced susceptibility to mould. The paper is of interest to designers, builders and house occupants because basements are increasingly becoming viewed as liveable spaces that are expected to perform as well as above-grade areas of the building. For energy policy and building code agencies, the substantial energy savings cost effectively afforded by advanced basement envelope systems are compelling factors to update minimum thermal insulation requirements for basements.
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Design Considerations for Curtain Wall Parapets in Cold Climates
Aluminum and glass curtain walls have gained enormous popularity across Canada and the United States as an engineered system used as the vertical envelope for a variety of low-rise and high-rise building types, particularly in the office building sector. Improved standards, research and testing have contributed in significantly improving the performance of curtain wall systems, whether it be with respect to resistance to water penetration, air leakage resistance, wind load resistance or condensation resistance. The reality however is that many buildings are still experiencing problems with the field performance of recently installed curtain wall systems.
Although these problems are often the result of poor installation and fabrication due primarily to the lack of adequate quality control during construction, poor design applications are frequently a source of several common problems associated with inadequate field performance.
This paper shall focus on design considerations for curtain wall parapets in cold climates. Water infiltration problems due to condensation behind curtain wall parapet assemblies is a recurring issue which often entails costly remedial repair measures. Despite the recurring problems encountered on several buildings, there are still very few guidelines available to assist designers with proper detailing considerations.
The primary objective of this paper is to provide an increased level of knowledge to the design community for improved curtain wall parapet performance. Case study examples are used to illustrate condensation related issues commonly encountered in curtain wall parapet applications.
Test results of actual in-service performance, obtained through field monitoring in occupied building environments, are presented and the contributing causes and conditions which lead to the most commonly encountered problems are highlighted. Examples of both poor and good detailing are illustrated by means of drawings and photographs. Remedial repair measures and alternative design considerations are also presented through practical examples.
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Determination of Surface Convective Heat Transfer Coefficients by CFD
Heat and vapour convective surface coefficients are required in practically all heat and vapour transport calculations. In building envelope research, such coefficients are often assumed constants for a set of conditions. Heat transfer surface coefficients are often determined using empirical correlations based on measurements of different geometry and flows. Vapour transfer surface coefficients have been measured for some specific conditions, but more often, they are determined with the Chilton-Colburn analogy using known heat transfer coefficients. This analogy breaks down when radiation and sources of heat and moisture are included. Experiments have reported differences up to 300%.
In this paper, the heat transfer process in the boundary layer is examined using Computational Fluid Dynamics (CFD) for laminar and turbulent air flows. The feasibility and accuracy of using CFD to calculate convective heat transfer coefficients is examined. A grid sensitivity analysis is performed for the CFD solutions, and Richardson Extrapolation is used to determine the grid independent solutions for the convective heat transfer coefficients. The coefficients are validated using empirical, semi-empirical and/or analytical solutions.
CFD is found to be an accurate method of predicting heat transfer for the cases studied in this paper. For the laminar forced convection simulations the convective heat transfer coefficients differed from analytical values by ±0.5%. Results for the turbulent forced convection cases had good agreement with universal law-of-the-wall theory and with correlations from literature. Wall functions used to describe boundary layer heat transfer for the turbulent cases are found to be inaccurate for thermally developing regions.
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Development of a Rain Screen System for Adhered Manufactured Stone
Due to recent changes in the Building Codes for Coastal regions there is a need to develop cladding systems which implements a drain screen system. To meet this new requirement, existing concrete stone cladding systems had to be modified to incorporate wood strapping to create the drainage space. Though initial impressions were the issue was simplistic, treating the façade as a system revealed it to be a complex problem. It was imperative the system be able to withstand the wind loads of coastal applications while at the same time still being flexible to not have permanent displacement of the stone and therefore façade failure. This paper outlines the development process of determining the system, iterative testing of the system and interaction with CCMC to come to a final application technique.
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Development of High Performance Stucco As Cladding Material
Recent computer simulation studies at the Institute for Research in Construction (IRC) of the National Research Council (NRC) Canada have indicated that the combined wetting and drying potential of the wood-frame face sealed stucco clad wall is significantly influenced by the water vapour permeability and liquid diffusivity of the stucco material. Lower liquid diffusivity and higher water vapour permeability of the stucco material can positively influence the overall moisture management capacity of the wood-frame face sealed stucco clad wall. This paper presents preliminary experimental results from a pilot research project that aims to use the lessons learned from the simulation studies for the development of new materials or modify existing materials. The results from the experimental study show that it is possible to reduce the water absorption coefficient (a measure of liquid diffusivity) of the stucco material without reducing water vapour permeability through appropriate mix design.
(NRCC-45580) http://irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc45580/
Exterior Basement Insulation for Cold Climates: Further Proof of the Need to Build Better Now
Given housing costs, basements are now no longer just utilized as storage spaces, but are often utilized as part of the interior space. Unfortunately, poor moisture management across these walls often leads to mould and mildew growth and poor air quality in basement spaces. As well, basement walls are a substantial component of all heat loss through the building envelope. Considering these problems, and the associated heightened consumer expectations, there are increasing demands on the below-grade portion of the building envelope. This paper compares model thermal and moisture performance and the life cycle economics of exterior basement insulation for four locations across Canada (Halifax, Toronto, Calgary and Vancouver). For each location, three scenarios will be analyzed: one basement built to the prescribed minimum standards established by local building codes, one built to the Model National Energy Code for Houses, and a more sustainable option built to meet the higher thermal and moisture performance needs of tomorrow. Each of these basements will be analyzed and life cycle cost analyses will be carried out using various energy price inflation factors. Considering the relatively long life cycle of homes built today, this paper will show that, from an economic as well as from a performance point of view, there is a compelling need to build better basements now.
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Field Assessment of the Effect of Different Spectrally Selective Low Emissivity Glass Coatings on the Energy Consumption in Residential Application in Cold Climates
The question: “How large an effect can changing the glazing system’s solar heat gain characteristics have on the overall energy consumption of a house?” can be posed by energy analysts, homeowners and glazing specialists alike. In an effort to quantify such an effect, two sealed, low emissivity, insulating glazing systems (with different solar transmission properties) were evaluated in a side-by-side experiment involving twin-houses, comparing their respective effects on house heating energy consumption (i.e., natural gas for space heating and electricity for air distribution) in a cold climate. This research project was conducted at the Canadian Center for Housing Technology (CCHT) located on the National Research Council Campus in Ottawa. This facility consists of two R-2000 houses that are very nearly identical in every aspect, and are fully instrumented.
First, benchmarking of the two houses was performed using a high solar transmission low emissivity coating on surface 3 of all double glazed argon filled windows and patio doors in both houses (29 windows and both the fixed and sliding portions of a patio door were included). Then, all insulating glazing units in the Test House were replaced by insulating glazing systems with a low solar transmission low emissivity coating on surface 2 of double glazed argon filled windows. Air leakage tests for both houses, using a blower door, were also performed before and after replacing the glazing units.
During the winter monitoring period (four weeks from January 19 to February 15, 2006), natural gas and electricity consumption and air and window surface temperature measurements were recorded and analyzed. The preliminary results showed that the use of low solar transmission glazing systems increased the gas consumption in the Test House by about 8.7% relative to its performance with the high solar transmission glazing. In addition, the electric consumption was also increased by about 1.3% as a result of the reduced solar heat gain during the monitoring period.
This paper provides details about the CCHT, testing protocol, and the variation of the interior and exterior glass surface temperatures on a selected number of windows at different orientation. This research program also includes monitoring of energy consumption during summer cooling period, and computer simulation using HOT2000 and other simulation tools to compare actual testing and computer simulation results. However, the summer monitoring and computer modelling results are not part of this paper.
(NRCC-49481) http://irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc49481/
Field Measurement of Wind-driven Rain on a Low-rise Building in the Coastal Climate of British Columbia
The amount of driving rain received by the building envelope is an important environmental load for building envelope design; however, there is limited information on the rain load to which the building envelope is exposed during its service life. To date, most of the research effort in Canada has focused on assessing the wind-driven rain exposure of a region using historical meteorological data recorded at weather stations rather than wind-driven rain exposure of specific buildings. The actual driving rain load received by building façades is also influenced by the building geometry and design details, for example the size of overhang.
Current best practice guidelines for building envelope wall assemblies lead the user to identify exposure conditions for wind-driven rain in order to select an appropriate type of assembly, especially in the coastal climate of British Columbia (BC). Because of a lack of data, current practice depends on professional judgment. To bridge the knowledge gap, a research program has been designed to instrument an inventory of buildings throughout the lower mainland of BC to collect wind-driven rain data and quantify the influence of building geometry on rain wetting at various locations on the façade.
This paper presents the preliminary results of wind-driven rain measurement on a one-storey low aspect-ratio building. The on-site wind speed, wind direction, and horizontal rainfall were recorded. The spatial distribution of the wind-driven rain on the east wall was reported. A 130 mm overhang reduced the wetting on the wall surface below it by about two to five times depending on the wind and rain characteristics. The field data will enable the verification and improvement of existing empirical methods and the comparison with Computational Fluid Dynamics models to evaluate the effect of design details.
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Field Performance of Spray Polyurethane Foam: The Role of Vapour Diffusion Control
A research project was implemented at the University of Waterloo to study the performance of both open and closed cell spray polyurethane foam insulation (SPUF) in frame wall applications typical of residential construction. The project involves the testing of full-scale wood frame walls exposed to natural climatic conditions for a period of two years. Results of the first year of study are presented, as well as results from hygrothermal simulation to show the impact of climate, materials, and interior operating conditions based on a validated model. Based on field testing and validated hygrothermal simulation recommendations on the need for supplemental vapour diffusion control layers for either open or closed cell SPUF are developed.
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Glass Fiber Lath in Exterior Portland Cement Plaster (Stucco)
Glass Fiber Lath was introduced as an alternative to metal plaster bases which have been the primary mechanism used to secure Exterior Portland Cement Plaster (Stucco) to framed construction for many years. The product evolved, in part, as a result of recent technology that enables glass fibers to be woven as a three dimensional fabric that can be produced in various configurations and serve as a lath or plaster base for both One- and Three-Coat Stucco applications.
The primary objective of this paper is to create an awareness of the technology, its development, as well as potential features and benefits in stucco applications. This will be accomplished through discussion about the use and evolution of glass fiber reinforcement, lessons learned during development, as well as a review of testing and field/application trials. Additionally, there will be a summary of research and comparative testing that is underway at a major university.
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Green Assessment Tools: The Integration of Building Envelope Durability
There has been a recent trend in the North American building market towards green buildings. This trend has resulted in the development and increased popularity of several green building assessment tools, including LEED™, Green Globes™, Built Green™, and GBTool. The tools attempt to measure the “greenness” of a project, typically by awarding points or credits for achieving certain prescriptive or performance based requirements. However, to allow adaptability and flexibility within the tools, there are a great number of variables, ranging from natural light infiltration, location of material manufacturing, to the site selection. In most projects, the selection of credits or points is predetermined by the building use, given site, geographic area, project cost restrictions and determined rating level. For this reason, assessment tools have come under a considerable amount of criticism. Ultimately, the tools attempted to provide a means in which to compare fundamentally different building traits, and in the end provide a numerical value to compare with other green buildings.
The majority of green building assessment systems focus on the design to the constructed building, with little focus on the effect of the building system’s life during operation. This tendency has resulted in a failure of many rating systems to properly consider durability, lifecycle cost, and the effects of premature building envelope failures.
This paper will discuss green building assessment tools, their prime focus areas, the importance of designing for durability, and a proposed basis for evaluating durability. It also includes a review of four Canadian green assessment tools, the degree to which these systems include durability of the building envelope, and suggestions for future improvements.
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Hygrothermal Performance of Ventilated Cold Roofs an Experimental Study
Attics with an insulation on the ceiling plane inherently are more prone to moisture damage than conventional attic construction. This paper will describe a series of realistic field tests on different types of ventilated roofs in order to evaluate their hygrothermal performance. During the testing period wind washing, thermal performance and relative humidity in the cold roof, on the interior surface of the underlay, moisture of the rafters and amount of condensation were monitored. The room under the insulated ceiling was air-conditioned. The amount of migrated warm air into the cold area of the roof was well defined and controlled. The influence of different underlays and ventilation strategies was studied. Investigations show that there are only very slight differences of the individual roof constructions especially in the climatic conditions to be reached in the attics. Yet, at times, the differences between the constructions and ventilation strategies are principally only visually discernable.
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Hygrothermal performance of passive house wallsystems - simulation and monitoring
In the European Union, especially Germany and Austria, low energy building concepts, like “passive house technology” were developed to minimize the energy demand of buildings. Comfortable internal space temperature is achieved in a largely “passive” way with the free heat gains of solar irradition through windows as well as the heat emissions of the occupants and household appliances. The necessary heating energy consumption of a passive house is lower than 15 kWh (kilowatt hours) per square meter and year and can be achieved by heating the supply air in the ventilation system. One of the essential premises of an efficient passive house is a highly-insulated and airtight building envelope without thermal bridges.
This paper will present the hygrothermal performance of new light-weight wall assemblies in passive house technology. Together with representatives of different insulation manufacturers as well as timber-frame construction professionals, several wall assemblies were developed, simulated, and monitored.
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Building Envelope and Structural Performance of Wood Structural Panels under Climate Loads
Wood structural panels are the most common structural sheathing components used in light-frame wood structures built in North America. Compared to other structural panels, OSB and plywood panels provide strength and versatility, are light-weight, easy to work with, and have been used successfully for decades. The fundamental performance requirements for walls and/or roofs as part of the building envelope include the structural strength and stiffness, and fire control. In addition, control of light, solar and heat radiation, and control of rain penetration, heat, air and water vapor flow and durability should be included as part of building envelope requirement as well. Performance problems involving wood structural panels are usually related to excessive moisture exposure and/or installation errors, although occasionally non-conforming product is also to blame. This paper reviews some of the wood structural panel performance problems that have been observed during numerous field investigations of construction projects and existing buildings.
A case study is presented that describes an evaluation of exterior wall performance problems resulting from wet and cold weather. Explanation of the design problem and recommended steps taken for correcting the problems related to poor design details and installation issues is presented.
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Energy Conservation Considerations During Building Enclosure Rehabilitation of Large Multi-Unit Residential Buildings
In the Pacific Northwest and especially the lower mainland of British Columbia, many large residential buildings have experienced premature failure of the building enclosure largely due to moisture. Often extensive and costly remediation is needed and consequently there is considerable pressure to minimize the short term capital costs. One potential benefit of the situation, is that there is an opportunity to improve the energy efficiency of building enclosures during major rehabilitation. Typically the thermal resistance of the enclosure is improved as a result of replacing cladding, increasing insulation levels and reducing the amount of air leakage across the enclosure. Collectively this will provide higher levels of occupant comfort and reduce the operating energy requirements of a building, especially the space conditioning energy requirements. However these are the consequences of rehabilitating the enclosure. The issue for us and the tenants, alike is how to use the occasion to directly and effectively reduce energy consumption given that the overall cost of rehabilitation will increase and the benefits will only be gained over a number of years. More precisely how does one, as the Consultant, make the case for an increase in present costs, that are already an unwelcome and expensive necessity, against future savings. To examine this issue is largely the objective of this paper.
This paper presents the effect that major enclosure rehabilitation has on overall building energy use using, as a case study, the rehabilitation of a large high-rise residential complex located in Burnaby, BC. Heating is primarily provided by electricity and actual energy use data has been provided by the local utilities; there is no mechanical air conditioning (cooling). Various methods of estimating building energy consumption performance before and after rehabilitation are considered.
The actual building’s energy billing data is compared with modeled figures to validate the analysis model for predicting building energy consumption. The modeling is also used to compare the relative impact of enclosure characteristics such as air leakage and thermal resistance on energy consumption. Field measurements of air leakage are used to further refine estimation techniques. Air leakage and natural ventilation are probably the most difficult variables to quantify. The case is then made for seriously considering the option of providing additional conservation of space heating energy over and above that needed for enclosure rehabilitation.
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Laboratory Demonstration of Solar Driven Inward Vapour Diffusion in A Wall Assembly
On-going discussions on various forms of moisture transport in buildings have often focused on the nature of vapour diffusion in wall assemblies. Recent field investigations at the Institute for Research in Construction (IRC), NRC Canada, have yielded data on the effect of solar radiation on the exterior surface temperature of wall assemblies. On a sunny day in August 2004, on the exterior surface of a south-facing wall, a temperature rise close to 25°C over the surrounding air temperature was recorded. Coincident increases in the absolute humidity ratio of the air in the cavity behind the brick were measured, suggesting inward drive of brick moisture into that cavity. A laboratory facility at IRC, called the Envelope Environmental Exposure Facility (EEEF) has been used to launch an investigation on the behaviour of the vapour diffusion in exterior walls exposed to solar radiation. A 2.4 m by 2.4 m test specimen of a simple wall assembly was constructed, the exterior surface of the specimen soaked in simulated rain conditions and subsequently heated by infrared heaters to mimic the rise in surface temperature due to solar radiation. The wall was fully instrumented for temperature and relative humidity measurements at both surfaces as well as at every interface. This paper presents a brief description of the EEEF, details of the test specimen and data collection, and data from the above experiment. A clear indication of an inward diffusion of water vapour across the wall as the exterior surface is heated is derived from both laboratory controlled and field experiments.
(NRCC-49203) http://irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc49203/
Assessing the Effect of Attic Moisture in Wood framed Multi-unit Row Housing Blocks.
This paper represents the results of poor moisture management and control of an extensive stock of row housing dwellings in Ontario specifically the National Capital Region. Damage caused by excessive build up of moisture in attic spaces, during the winter months affects all the roof components of the assembly in this region. A cumulative number and a variety of causes can be associated with this condition related and not limited to building orientation, roof construction, pitch, air leakage and design. Roof vents, usually required by the local building code, may require modifications to the formula to meet or exceed the requirements based on building design and other environmental effects.
Condensation in the attic space is generally more severe than condensation in the wall cavity even thought the wall area is normally greater. The best strategy for preventing attic moisture problems is to prevent or reduce the amount of warm, moisture-laden air to migrate into the attic space. Residential wood framed multi unit row house type dwellings constructed in the early to mid seventies experience significant deterioration around the fire separation walls between units. Moist interior air travels vertically up the wall and condenses on the underside of the roof sheathing at this area.
This paper will discuss the various solutions experienced in the prevention of moisture accumulation inherent to multi unit low-rise wood frame construction.
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Moisture Recovery Rates for Walls in Temperate Climates
Moisture recovery rates have been measured in 24 specimen walls fixed to an experimental building in New Zealand. All of the walls were timber framed and most included a water management system between the building wrap and the cladding of one of the following types, drained and ventilated, open rainscreen or drainage plane. The remaining walls were direct-fixed systems. Controlled introduction of water into the insulated spaces of each wall was undertaken eight times over one year and cavity humidity records used to plot drying times as a function of climate and the physical properties of the walls. The strongest factor in drying time was the sophistication of the water management system, followed by climate differences due to the season and wall orientation. This is not surprising in walls built for temperate New Zealand without vapour barriers, air barriers and sheathing. WUFI2D simulations of the drying process also illustrated the importance of ventilation processes in removing moisture from insulated spaces in the wall. A similar series of moisture recovery measurements was completed following the introduction of water into the water managed cavities of 22 of the 24 walls. In this case, drying times were deduced from timber surface moisture content measurements. These results underline the importance of non-absorbent drainage paths on the backs of claddings and give useful hygrothermal responses to water trapped in the water managed parts of walls. One interesting outcome of these measurements is an explanation for the successful moisture management record of weatherboard claddings on New Zealand houses.
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Mould Growth Experiments of Full Scale Wood Frame Wall Assemblies
This paper reports on a full-scale experimental investigation of the mould growth on different types of wood products used for sheathing and framing wall assemblies. Objectives included examination of the difference in mould growth in full-scale wall systems under different temperature and humidity conditions for treated and untreated wood products.
Importantly this study used full scale wall assemblies; to date mould growth studies have only been performed within a laboratory on small samples of materials. Moreover, this study recreates the conditions which evidently cause mould growth on full scale wall assemblies. Tests were performed within a climate chamber on three wall assemblies. The scope of the study includes both the sheathing and framing components, but this paper focuses mainly on the sheathing.
Results indicate that the relative humidity conditions needed for mould growth to occur on wood in a reasonable time (less than several months) are higher than a surface relative humidity of 80%RH. During the first eight weeks of one test, the conditions at the surface of the sheathing was held constant at 26 ºC and 95%RH and little mould growth was observed on the untreated sheathing and little or no mould growth was seen on the borate-treated sheathing. The other tests demonstrated that the presence of liquid water greatly reduced the time to germination, the amount of mould growth, and the rate of mould growth. All three tests clearly showed that borate treatment reduced the amount of mould growth; however, the concentration of borate treatment, and the types of materials treated, does influence the resistance of mould growth. Furthermore, there was some evidence to suggest that borate treatments of the plywood increased the time to germination significantly, from a few weeks to 16 weeks in this study, but once mould growth was initiated, the rate of mould growth was similar to that of the untreated plywood. Recommendations include improvements to the test method and for future work.
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Partial Rehabilitation: The Challenges of Tying-in a Drained Glazing System with a Face-seal Wall System
A high-rise building located in Vancouver was diagnosed with water penetration at the windowwall system. The opaque walls were clad with panelized, face-sealed EIFS. The investigation found no major deterioration in the EIFS area and it was decided that the rehabilitation would include only the replacement of the window-wall system. Retaining the existing, face-seal EIFS in place brought on a number of challenges:
The size and layout of the new window-wall differed greatly from the existing window system: The existing window-wall was installed before the panelized EIFS making it difficult to remove without damaging surrounding elements. The new window-wall had a thicker mullion than the original, and needed to be installed in a different vertical plane. The continuity of the air barrier required special attention.
The existing EIFS had no internal moisture barrier: The new window-wall system is a drained assembly with an interior secondary moisture barrier that needed to be connected to an existing system that does not incorporate an interior moisture barrier. Because of the nature of the two systems, the connection between them was very challenging and required an innovative approach.
The existing EIFS was very fragile: The removal of the existing sealant and the installation of the new components at the transition details were very difficult. Because of the face-seal nature of the existing EIFS system, damage to the remaining system could have a great impact on future performance.
The demands of external stakeholders: The owners were seeking a 10-year warranty period on water penetration from a third party. The interest of the warranty provider was to prevent any water entering the existing EIFS system from contaminating the new window-wall system. This brought another level of detailing that is not essentially required for the overall performance of the wall.
This paper will discuss innovative details that were used to solve some of the design issues brought on by keeping the original EIFS system in place. In particular, it will cover how the new window-wall system was installed in the existing EIFS system, and the influence this had on the scope of work. For this purpose, the author will draw on her experience with other projects of similar nature.
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Performance Properties of Interply Adhesives Used with SBS-modified Bitumen Membranes: 2007 Update
Application alternatives for adhering SBS (styrene-butadiene-styrene) modified bitumen sheet materials include hot mopping asphalt or bitumen, heat welding , liquid cold process adhesive, and self-adhesive. When SBS-modified bitumen roof membranes were introduced in the United States in the late 1970s, the majority of the North American contractor base was built-up roofing oriented. Familiarity with hot asphalt application and practicality of dealing with existing equipment made installation of SBS-modified bitumen membranes in hot oxidized asphalt an easy choice. The early history with SBS-modified bitumen systems in Canada reveals that torch applied SBS membranes were more popular. Laboratory testing and field experience have demonstrated that solvent-based (cold) adhesives, heat welding, and heat-activated self-adhesives offer higher interply performance than oxidized bitumen. Across North America, torching applications have come under the increasingly heavy scrutiny of the insurance industry, and there have been historic shifts in the world of petroleum refining. Some fundamental characteristics and performance differences of various types of interply attachment methods specific to SBS-modified bitumen roof membranes will be updated in this paper. As a result, practical considerations in choosing the appropriate application method will be addressed.
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Understanding Vapour Permeance and Condensation in Wall Assemblies
The use of polyethylene vapour barriers is well integrated into building codes and the Canadian construction industry, a result of significant investment in research and training. Their use has resulted in significant improvement in building envelope air tightness when properly detailed. Contractors and inspectors have developed a strong understanding of the details and practices required to achieve tight and reliable enclosures. However, some groups have expressed concerns that polyethylene vapour barriers may reduce drying and entrap moisture. In particular, problems have been encountered with below-grade walls where inward drying of initial construction moisture within the concrete foundation walls is trapped by polyethylene sheets. Problems have also been identified in above-grade walls where absorptive and non-ventilated claddings are employed.
A research program is currently underway to determine the significance/insignificance of potential moisture problems due to plastic sheeting in above-grade and below-grade wall assemblies. The research is aimed to outline cases where performance can be improved, and changes that could reduce inappropriate use. Finally, the research aims to address the benefits/risks with polyethylene sheeting with clearer delineation of the situations in which it is necessary, potentially damaging, and unimportant.
This paper presents key findings from the research work and field test results collected to date within the following framework:
The literature review;
Field testing of four common below-grade wall assemblies (with and without polyethylene sheeting) in a southern Ontario home;
Field testing of six common above-grade wall assemblies (with and without polyethylene sheeting) in the University of Waterloo test exposure facility (BEGHut);
Comparison of the field testing data and computer models, to provide validation of the model against this installation.
Extending the test results to broader practice across Canada through computer modeling.
Future papers will provide more detailed analysis and computer model verifications after the project is complete.
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Predicting Time-to-fogging of Insulating Glass Units
The service life of an insulating glass unit is considered to have come to an end when water vapour condensation (fog) has developed internally on glass surfaces, obscuring clear vision. Estimates for time-to-fogging from manufacturers, consultants and others vary widely, without any clear consensus on a reasonable length of time. Standard laboratory performance assessment methods, such as CGSB-12.8 or ASTM E 774 et al. in North America, were intended to improve short-term durability to beyond the typical manufacturer 5-year warranty period and have been successful in this regard, but as a result are no longer correlated to life span and thus cannot now be used to estimate time-to-fogging. This same limitation applies to newer, similar standards such as ASTM E 2190 et al. Accurate time-to-fogging estimation is necessary for building owners who must (or choose to) establish and maintain capital repair and replacement funds that include replacement of insulating glass units. An aggressive accumulation of funds would result from a pessimistic assumption of time-to-fogging whereas an inadequate accumulation would result from an optimistic assumption; in both cases, the effect would be unnecessary short-term financial hardship. An accurate method to assess remaining service life span (‘time-to-fogging’) is required.
The time-to-fogging of insulating glass units installed in buildings can be estimated based on repeated measurement of the dew point temperature of the cavity gas fill, analysis of the trend of increase, and extrapolation of the trend to future years. Coincidence of the extrapolated trend with normal outdoor ambient air temperatures reveals time-to-fogging. The efficacy of this Canadian method was assessed via a laboratory program funded through the CMHC External Research Program. This method, the test program and outcomes are detailed in a report published by CMHC in early 2006. A summary of the report is presented in this paper.
Further research has revealed a precedent for the test program by the Norwegian Building Research Institute as part of a study of long-term field performance of insulating glass units in 1963. The study and its outcomes are summarized in this paper, and are presented together with a summary of another prediction method proposed as an outcome of a study to correlate the ASTM E 773 and 774 laboratory performance assessment methods to field performance in the 1980s in the USA, previously reported in the CMHC report and elsewhere. A critical assessment of both methods supports the method developed by the author. Further research is also presented regarding the influence of temperature on cavity gas fill dew point temperature suppression by desiccants which confirms that time-to-fogging predictions should be based on dew point temperature measurements made during warm weather.
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Case Study: Renovation of the Heritage Core of the UBC I.K. Barber Learning Centre
The original UBC Library was built in 1924 of Hardy Island granite and brick masonry. Additions in 1948 and 1959 expanded the library but not sufficiently for modern collections. The library is currently being renovated into the IK Barber Learning Centre, a modern information resource centre, retaining and incorporating the oldest portions of the original building. The new building employs a high-efficiency building envelope with insulated precast cladding and triple-glazed curtainwall to moderate the interior environment, which is heated and cooled with in slab circulated water systems. Insulation levels and humidity control in the new building required improved performance of the masonry portion of the building to make it functional with the new mechanical systems and modern requirements for storage of collections.
This paper describes the work required to reduce water leakage through the original masonry construction, provide continued adequate drying of the exterior walls to the interior without overloading the interior air humidity, and protecting the wood structure from moisture damage where it bears on the masonry. The design process involved modelling of moisture movements, evaporation rates and moisture removal mechanisms, heat flow, as well as detailing for the design of a modern interior environment into an intricate heritage masonry building.
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The Role of Small Gaps Behind Wall Claddings on Drainage and Drying
A common rain control strategy to help minimize moisture damage is the rain screen wall system. This approach requires a rainscreen, a drainage plane, flashing, weep holes, and a drainage gap. Although this approach to rain control is becoming the most common, and is sometimes even mandated by codes and standards, very little research has been undertaken to define the minimum or optimal gap size required for either drainage or ventilation drying.
A test method and experimental program were developed to investigate the gap size required to ensure drainage, and the role of small gaps on ventilation drying. Because of the importance of small geometrical details, full-scale wall systems were tested. The experimental method was able to gravimetrically determine the amount of drainage, storage and drying during and after a simulated wetting event. The test apparatus and method developed were shown to provide repeatable results over multiple tests as well as in an independent laboratory.
The experiments to date have conclusively shown that even small gaps (less than 1 mm) can drain more water than would normally be found in a drainage gap. It was also found that in some cases small gaps will store less water than a large drainage gap. It was also found that ventilation drying can play a role in very small gaps of approximately 1 mm, at a pressure difference of only 1 Pa. More research is required to further analyze optimal ventilation gap sizes and compare the laboratory results to hygrothermal modeling.
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Results on Assessing the Effectiveness of Wall-Window Interface Details to Manage Rainwater
Inadequate detailing practice and defective installation of windows has accounted for a significant number of premature failures of the building envelope. This has spurred the development of alternative construction details to manage water intrusion at the wall-window interface. Laboratory investigations focused on assessing the effectiveness of wall-window interface details to manage rainwater intrusion in the wall assembly have provided an effective way to obtain useful information on the varying performance of different interface details. Previous studies undertaken to investigate the effectiveness of details typically used in wood frame low-rise wall assemblies have shown the degree to which different details manage rainwater intrusion and the extent of fault tolerance of these systems. This paper offers a report on more selected results obtained from evaluating the watertightness of a series of four wall-window interface details representative of construction practice across Canada. A brief overview of four sets of wall-window interface details and variations on their implementation are described in general and details for a set, comprised of two specific wall-window interface details evaluated in the study are provided. The set of two variations of interface details described were configured for a fixed PVC window incorporating mounting flanges and installed in a rainscreen wall. The results of water penetration tests are provided in terms of water entry through deficiencies in the cladding, water collection within the assembly and the severity of the simulated wind-driven rain loads. The effectiveness of the two approaches to window installation in managing rainwater entry is discussed.
(NRCC-49201) http://irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc49201/
Wind-Rain Relationships in Southwestern British Columbia
The ongoing focus on building envelope failures in western Canada, especially southwestern British Columbia, have brought to light the strong influence that wind-driven rain can have on the building envelope. Although designers are given some guidance on the concept of designing appropriate envelope assemblies for a given exposure, there are no specific design tools to determine the actual exposure to wind-driven rain for a given location and orientation in this region. The closest design data are the DRWP (driven-rain wind pressure) values in the CSA A440 standard, but these are nondirectional.
A study (CMHC, 2004) was conducted to correlate wind direction with rain events for southwestern British Columbia, including Vancouver Island and the Lower Mainland. The results of the study provide climatic load data that could be used to modify existing climatic data in building codes, including the revised methodology using moisture indices, which are now incorporated in the National Building Code of Canada. The study suggested that it may be appropriate to consider a directional DRWP guideline to supplement existing information in (for example) the CSA A440 Standard and related design guides.
This paper discusses the methodology used to select appropriate weather stations for inclusion in the data set. Criteria for completeness and reliability of the data are discussed, with the intent of providing guidance to others wishing to investigate the seasonal variation of the wind/rain relationship for other locations. Specific topics addressed include assessing the quality of the data, data gaps and length of record, with different criteria used for different record types (e.g., wind speed, wind direction, rainfall intensity). Then, typical examples are used to show how specific stations were selected for the study, and how the data were analysed to show the relation of wind direction, wind speed and rainfall intensity. In the examples, the seasonal variability of wind-driven rain is also investigated (again, this is examined in more depth in the report upon which this paper is based, but this paper provides a reasonable example of that variability). The possibility of extracting useful rainfall data from existing radar weather data is also discussed.
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Hygric Performance of Portland Cement and Cement-lime Plasters (Stucco) for Frame-wall Construction
Rainscreen walls are typically recommended for all regions of North America with humid climates. This approach was accepted by the Exterior Insulation and Finish Systems (EIFS) industry and drainable air gaps were introduced behind the insulation after well-publicized failures of wall-window interface in the North Carolina state. One may also expect that the same solution used for stucco cladding would improve the moisture protection provided for those walls.
Questions arise if this approach is necessary for less severe climates than in coastal areas. Are there other options for providing sufficient moisture protection in continental climates, e.g., in Minnesota or Alberta? If so, such approaches should be examined.
The authors claim that properly detailed stucco cladding with adequate design of material when placed on two layers of water resistive barrier (WRB) is able to provide sufficient moisture protection in most of North American climates. Yet, this statement is conditional on good detailing of the wall assembly and the provision of hygric properties that are appropriate for the climatic and service conditions. This paper reviews the use of Portland cement and cement-lime plaster (stucco) for frame-wall constructions highlighting the difference hygric performance of traditional lime-cement and modern polymer-modified cement stucco.
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“TAKING INVENTORY” Feeding the Loop: The Role of Professional Education in Successful Building Science Technology Transfer
What is feeding this loop? If the conference theme wishes to examine the circular flow of cutting edge information and practice throughout the industry, we must also recognize the importance of education as it informs the new graduates that continually flow into the field. Is education at the cutting edge of building science technology? Do students have the opportunity to take specific courses in building science? Are they core? Are they elective?
Are there reasonable standards and expectations in current curricula across Canada with respect to the teaching of building science? If there is deemed to exist a break in the loop, as defined by the conference theme, in putting principles into practice, then the role of education must be examined to see its potential for reducing the gap. If we are continually feeding graduate architects and engineers into the building profession, then their relative degree of technical preparation will ultimately impact building envelope design. As not every project team can include a certified “Building Scientist”, the level of expertise of the “general architectural and engineering practitioner” has the potential to either raise or lower the quality of building science that is normally included in the envelope design of everyday buildings.
The scope of this research sought to examine the curricular content in Accredited Programs of Architecture and Engineering across Canada for evidence of the teaching of courses in Building Science and Building Envelope Design, as well as the opportunity for a Building Science specialization. The examination was restricted to University level programs in Architecturei, and the 21 CEAB Accredited programs in Civil or Building Engineering.
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The Differences Between Large Buildings and Residential Infrared Thermographic Inspections Is Like Night and Day
New low cost, low-resolution infrared Focal Plane Array (FPA) imagers and radiometers are becoming commonplace in the commercial market place for condition monitoring (electrical and mechanical systems) and roofing applications. These low cost infrared systems are also being used for detection of the heat-related signature of moisture within buildings (by means of phase change, capacitive, or conductive mechanisms). When inspection distances are between 0.5 and 5 m (a typical interior inspection) the limited spatial resolution of such equipment still allows for adequate spot size detection, thus resulting in acceptable image quality and thermal pattern resolution. Reasonable temperature measurement with this equipment is also achievable at distances typically less than 2 m. Therefore, the use of these new imagers can be considered quite appropriate for many building diagnostic applications for low-rise residential buildings.
Inspection conditions for envelopes of large buildings over 5 or 6 stories pose problems resulting in equipment limitations that in many situations cannot be overcome by operator inspection procedures, data collection and analysis methodologies. This paper will detail requirements for equipment specifications, inspection methodologies and knowledge base of both the equipment operator and image analysis professional required to accurately conduct inspections of large buildings. By pointing out the differences between inspection requirements for large buildings and residential buildings, this paper intends to ensure that clients and consultants call up appropriate levels of services thus create a level playing field for all professionals involved in commissioning and building condition assessment by means of non-destructive testing.
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Hygrothermal Performance and Drying Potential of Wood Frame Rainscreen Walls in Vancouver’s Coastal Climate
In 2001, a study was implemented to monitor the field performance of five buildings constructed with rainscreen clad walls in Vancouver, BC. Data from the three wood frame residential buildings in the study are presented in this paper. Five years of data from the monitoring study observe seasonal wetting and drying trends, with wood sheathing moisture contents bordering safe storage limits during the wet and mild winter season. High relative humidity levels within the stud cavity at the exterior sheathing were also observed during the winter season, which may be a potential issue for microbial growth. Accidental rainwater leaks have the potential to increase the sheathing moisture content to unsafe levels and may lead to localized damage. The field results were used to validate the WUFI 4.0 hygrothermal model and perform a number of parametric simulations. Further improvements to rainscreen wall designs are recommended in this climate to protect the sheathing from humid ventilation air, enhance drying, and increase the safe storage capacity of moisture sensitive materials.
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The Impacts of Green Building Strategies on the Durability and Performance of Building Enclosures
Over the last 10 years the concept of green buildings has become an important, and an increasingly large part of building design and construction. The success of LEED, and similar rating system, (both in terms of environmental performance, and more conventional evaluation criteria) have demonstrated the benefits of green design. The well-publicized success of green buildings reinforces demand for more green buildings and requires that all design professionals have, or purport to have expertise in this area. While the impact of sustainable design and of green building rating systems will no doubt be positive over the long term, there may be dangers associated with the rapid application of these systems and associated green design strategies involving the use of innovative materials and technologies.
Specifically, the question of whether the application of specific green design strategies may result in problems of building durability and performance has been raised. Of particular concern is the potential for inadequate building enclosure performance. A recently published paper on the subject of building enclosure commissioning focuses on a LEED Platinum building in the US and makes a direct connection between building green and a range of identified building enclosure problems.
The history of earlier attempts to improve energy performance in buildings can provide useful lessons for green design. The implications of increases in insulation levels and increases in air tightness for building performance, and in particular on enclosure performance were often not fully understood, resulting in a range of problems.
This paper will present the results of an investigation into the implementation of green building strategies and their effects on building enclosure durability and performance. Various green building rating systems will be reviewed and the strategies typically applied to achieve specific ratings will be analyzed. Based on surveys of practitioners, case studies of completed green buildings, and practical experience of building enclosure design and construction the positive and negative impacts of these practices, potential or actual, will be documented.
The conclusions of the study and recommendations for improving green building strategies and communication between building enclosure practitioners and green building designers will be presented. This paper is based in part on research carried out for a study commissioned by CMHC on the subject of green buildings and durability. Limitations on the length of this paper have required that detailed discussion that forms part of the larger study be curtailed and that background information and analysis be summarized.
The CMHC study addressed the performance and durability of both the building enclosure and of HVAC systems with an emphasis on residential buildings. The primary focus of the paper is on issues relating to durability and performance of the building enclosure. However, the survey of practitioners provides a wider context for these issues by also identifying a range of other potential impacts of green design. It is assumed the reader will have a basic understanding of the LEED (Leadership in Energy and Environmental Design) rating system and of the integrated design process (IDP).
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The New Ice Age - A Practitioner's Perspective on Ice Damming Across Canada
There is significant property damage to buildings in Canada as a result of ice damming. Ice dams form through the repetitive melting and freezing of roof top snow that can cause ice to build up at the eaves. The accumulation of ice can prevent the passage of melt water drainage and cause it to back-up below the roofing materials. The resulting leakage may only be evident in the form of a water stain; however, the deterioration can affect concealed components ranging from the roof deck to wall assemblies. Safety can become a concern if ice builds up beyond the building’s structural capacity, or if ice starts to fall.
Proper design can help avoid ice dams and/or limit their affect. The primary design features required to avoid ice dams include a sufficient thermal barrier and air barrier to prevent heat loss from the building reaching the underside of the roof deck. Adequate ventilation is required to help replace any heated air under the roof deck with exterior air to maintain as cool an environment as possible to minimize snow melt. Finally, if ice damming still occurs a waterproof barrier, called “eave protection” or “ice dam protection”, is installed under the primary roofing material to direct water back out of the roof assembly.
Even when the above are included in the design, ice damming can still occur for two general reasons. One, poor design/construction techniques resulting in heat loss, and/or insufficient ventilation to remove the heated air from under the roof deck. Two, while the design/construction may meet local code requirements, it does not address local climatic factors that tend to promote ice damming. Case studies are used to review the affect of the climate with buildings built to code and also using similar design/construction techniques. Readily available test procedures to identify ice damming causes are discussed. Case studies referenced illustrate common causes of ice dams and options to manage these specific cases.
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Impact of Sealant on the Water Shedding Performance of Metal Flashing
Rain wetting pattern on buildings revealed that horizontal projections have a major impact on the wetting and staining of building faces. Metal flashing is typically used at these locations to shed water away from building surfaces. Guideline manuals such as building codes, CMHC best practice guides and other technical documents do not provide any specific requirements for the flashing design. Neither do they provide any guidelines for flashing implementation, in particular the sealant application below the drip-edge of the metal flashing. Observation of buildings during rain-events revealed that buildings with excessive wetting and staining below the wall/flashing interface had no standard procedures for the design and/or the implementation of the flashing. Further, the extent of sealant application varied between projects. In some instances sealant was applied flush with the drip-edge, directing water on the building face. Previous studies have shown that the geometry of horizontal projection affects the water flow over building faces. Previous investigators have also studied the importance of variables such as the angle and length of the drip, in the performance of the drip-edge. However, the impact of sealant application on the effectiveness of profiles has not been studied. The current research attempts to build on the study of water shedding effectiveness of metal flashing by studying other dominant factors influencing its efficiency. The extent of sealant changes the geometry of the drip-edge, which may significantly impact the water flow over cladding.
The effect of these variations on the water shedding performance of flashing was determined by conducting an experimental study. A test method was developed and a test apparatus was constructed. Specimens of various drip-edge profiles were tested under low, medium and high water flow rates. Results on water shedding effectiveness for different drip-edge profiles with and without sealant are presented and the effectiveness of different details is highlighted.
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Thermal and Air Leakage Characteristics of Canadian Housing
No abstract available, due to copying restrictions in the original paper (you can download and read the full paper, but not copy content from it.)
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Variations in Position of Columns and Slabs
Design details often lack tolerances, causing problems in construction. Though standards and codes may supply them, tolerances are uncoordinated from trade to trade, and are usually neither mandatory nor enforceable. Designers should allow for them, but to do so rationally, must know what variations occur in practice. This information is often not available. What is to be done to supply it?
This paper describes measurements on 4 buildings, three recently constructed, and one around 20 years old, of differences in cast-in-place (CIP) concrete slab edge position, in CIP floor to floor dimensions, in spacing of precast concrete (PC) columns, in spacing of steel structural members, and in spacing of CIP columns.
Measurements that were evidently intended to be identical were grouped into sample datasets for statistical analysis. Tolerances required in details to avoid chipping, patching, and other ad hoc fixes for all but extreme cases (defined by confidence intervals based on estimated population standard deviations) were determined for the corresponding populations.
Even building on the existing literature of construction variations, these limited measurements clearly cannot fully supply the rational foundation needed for assigning tolerances, but a start has to be made somewhere. The paper offers guidance on reasonable approaches to take, even in the face of missing information. However, the primary objective is to highlight the urgency, as well as the benefits, of investigating variations in the sizes and positions of building components.
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Water Distribution Patterns in Cladded Walls Subjected to Simulated Rain Penetration
As rain can be the most important source of moisture in wall assemblies, the experimental investigation presented in this paper compares the wetting patterns of 12 walls subjected to simulated rain penetration in the stud cavity. The experiment was performed in a large environmental chamber. The walls studied considered three different types of sheathing – oriented strand board (OSB), plywood and fibreboard, two exterior claddings – wood cladding on furring and cement stucco on metallic lath (no air space), and two different interior finish permeance – paint with/without polyethylene sheet. All walls were built with 38 mm x 140 mm studs and insulated with glass fibre insulation. The frequency of the simulated rain infiltration followed a schedule based on the analysis of the weather data file of Montreal. The loading scenario imposed one month with water infiltration followed by one month without water infiltration, repeated twice for a total of 4 months of test. The indoor and outdoor temperature and relative humidity were controlled to reproduce August through November conditions. The 12 walls were monitored with moisture content sensors and gravimetric samples to allow the determination of the moisture content of the bottom plate and of the sheathing in each wall. Gravimetry results obtained for the different wall specimens are presented and discussed. The moisture content distribution and levels through the wetting and drying phases illustrate the potential influence of the sheathing material, of the cladding with and without air space, and of the level of permeance of the interior finish.
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Wetting Pattern of Sheathing Panels in Wood Stud Walls
Water infiltration in wood frame walls leads to different water transport phenomena: water runoff and spreading of water on the sheathing, water infiltration into the insulation, water flow on the bottom plate and into the bottom plate-sheathing joint, water uptake by sheathing, stud and bottom plate, and leakage of water from the joint sheathing-bottom plate. A laboratory test was designed to quantify the different transport flows. For the water infiltration rates and duration tested, water infiltration into the insulation and leakage are found likely to occur. Water uptake and spreading of water on the sheathing can lower these flows. OSB and fibreboard show no spreading. The spreading of plywood depends on the surface characteristics and fiber direction. Leakage will more likely occur at high infiltration rates. The amounts of water flowing on the bottom plate and taken up by the bottom plate are more limited. Water infiltrating at the stud and flowing down the stud into the stud-bottom plate joint, will be substantially taken up by the stud in longitudinal direction.
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Hybrid Rain Screen and Face Seal Enclosures “The About-Face of Rain Screen Systems”
Confidence in the performance of building envelope systems in the Coastal Climate of British Columbia and elsewhere can only be achieved by applying a sufficient level of protection to guard against the local level of weather exposure. The industry has become reasonably confident in well-built rain screen assemblies and often has reasonable faith in the water management performance of a properly-constructed mass wall of concrete or masonry when certain back-up safe-guards are incorporated. Both are expected to perform if the weather exposure for which they are designed is not exceeded. When hybrids of rain screen and face seal approaches are constructed there is a legitimate concern for the exposure experienced by each of the two enclosure types at the interfaces, where the two assemblies come together.
Exposure has recently been re-defined in quantitative terms in practice guides. Wall assemblies have evolved under the influence of Building Code minimum standards, through experience of failures, and recently, careful risk reviews carried out for third-party warranty firms. When it became obvious that certain levels of exposure were not being adequately addressed by conventional face seal assemblies, rain screen principles and new interface details were introduced to manage water that could not be kept out and tended to accumulate in those assemblies.
Face seal approaches to water-proofing, air-sealing or repairing of walls has almost become synonymous with ‘failure’. There are however, lower levels of exposure where appropriate applications of certain robust face seal approaches such as absorptive mass walls can perform adequately. Many proponents of face seal repair approaches to building enclosures eventually lost confidence in non-rainscreen assemblies after repeated and failed attempts to repair poorly designed walls in a manner in which they would no longer leak and deteriorate.
Absorptive mass walls built of concrete or masonry have generally escaped the need for a comprehensive remediation by virtue of their tolerance to the amounts of water they absorb compared to their capacity, while other less absorptive walls are much more vulnerable to deterioration when water leaks in. In an absorptive mass wall, two independent lines of defense against water entry and a separation between the wall and non-absorptive interior furring wall is usually all it takes to achieve a reasonable (though often not perfect) level of performance to prevent the multi-million dollar remediation requirement. A number of strategies can be employed in mass wall assemblies to enhance their positive attributes such as good air and water infiltration resistance, high water storage capacity and high tolerance to moisture that does enter.
These strategies include:
the application of a closed-cell moisture-cure spray-foam on the interior face to help air seal cracks and improve thermal properties,
the incorporation of a two-stage seal at each carefully-located control joint so that two independent lines of defense are at work to keep water from entering,
the application of breathable water repellants on the exterior face to reduce water entry,
the incorporation of well-sealed interfaces between the concrete and curtain walls, windows, doors and other installed components.
Building enclosures are still being designed, built or remediated in severely exposed locations that are not entirely rain screen-clad assemblies. Many unremediated buildings in this category have failed to some degree in keeping water out of the structure, putting their long-term performance and durability in doubt.
A great number of West Coast building enclosures are absorptive mass wall – rain screen hybrids, which appear to put them in a more risky and less materials-efficient category than either of the wall-types of which they are composed. The subject of this paper is the challenge faced by the design and construction teams to produce buildings that are a hybrid of architectural concrete or unclad structural brick with in-filled rainscreen panels designed for medium to high exposures.
The paper identifies some of the more significant increased efforts required by all parties to the project to produce a successful hybrid enclosure, should this still be the preferred objective after considering the associated extra costs, efforts and risks. When a rainscreen assembly is utilized in a structure that also incorporates unclad absorptive mass wall or face-seal components, it can be exceedingly difficult to achieve the level of rain penetration resistance and durability required by the design. This is high-lighted in examples of projects where a multitude of factors made it difficult to prevent the highly-trusted pressure-moderated rainscreen system from turning an ‘about-face’ and not deliver the performance expected of rain screen technology. The case histories uncover the ‘about face of the rainscreen’ when forced to marry-up with non-rainscreen technology.
There are numerous construction-related pitfalls or hazards in trying to achieve a good hybrid enclosure using rain screen and non-rain-screen assemblies. Our experience did not indicate that successful hybrid enclosures are impossible to build, but rather, that trying to succeed with such a hybrid, requires more resources, special knowledge and skillful cooperation by the designers and builders alike to bring the two types of assemblies together in a manner that they can perform. Building system tolerances, project team coordination, and false confidence in the forgiveness of rainscreen technology are examined in the analysis of problems that have to be overcome when the hybrid enclosure project gets derailed by poorly-integrated systems that might normally be accepted as quite functional on their own.
The recommendations stemming from the experience and analysis documented in this paper include:
Assessing a hybrid enclosure on the basis of its weakest link rather than on the ratings of its predominant cladding system;
Incorporation of course-of-construction quality control protocol that will (in theory) be capable of constructing a hybrid rainscreen and face seal enclosure;
Executing a high standard of wall component lay-out accuracy and mock-up review during construction to ensure that the various trades’ wall components will have the dimensional compatibility required to fit together;
Strategies to isolate, yet integrate the two enclosure types to prevent mutual degradation of their individual performances, and to make it clear which wall section was leaking if a problem should occur.
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