Viewpoint - Wall assemblies and reality

In the past, architects have relied heavily on industry supplied data when designing and assembling different parts of a building. The majority of the time, the components of a typical wall in Canada are derived from several manufactures, each supplying the performance data for the material itself, but not taking into account other materials in the assembly. The reality is that after the final product is constructed, the wall may behave in a fundamentally different way because of how the materials react to one another in the seasonal Canadian environment.

By Mark Driedger, Melissa Smith and Eranga De Zoysa

There is very little research available regarding a holistic view of the performance ratings of complete wall assemblies. The presence of structural members, or fire rating systems, can create thermal bridges that substantially alter the thermal performance of a wall. Using a metal stud wall with batt insulation as an example, the metal studs actually conduct the exterior temperature further into the wall system, negating some of the effects of the batt insulation. Therefore, the batt insulation that says “R-20″ on the package actually performs as “R-10″ when the wall materials are taken into account. If the wall is not designed correctly, on winter days these cold metal studs in contact with warm moist air from the interior of the building, can actually condense water causing rust and mould problems.

With the help of the National Research Council of Canada’s Industrial Research Assistance Program [IRAP], we leveraged our knowledge of building systems and computer modelling software creating an Innovative database that addresses the performance issues of different materials.
The database is designed to allow the architect to make informed decisions quickly on the repercussions of their designs. The walls are sorted by their structural and cladding components and then further subdivided into divisions based on fire resistance ratings as assigned by ULC. Within each individual assembly, fire, insulation and sound ratings are embedded in the Building Information Model [BIM] file to allow the architect to have as much information available up front in the design process.

We gathered materials from testing laboratories, from government organizations and from manufacturer’s data while using an energy modelling software to calculate the thermal properties of the assemblies. When all the information was formulated for the individual wall, it was modelled in Autodesk Revit, the specific data was inputted into the model and the data was plugged into a central database, using Atlassian’s Confluence software.
Staff can now search the database, using a keyword search, or browse for specific walls using the graphical interface. The desired wall can be then downloaded, and plugged straight into the Revit building model, saving a substantial amount of time in the design process.

The research falls in line specifically with our philosophy towards energy conservation and sustainability, which focuses on the effective production of energy within the building envelope and; equally important, its retention within the Building. The understanding and subsequent design of high- performance building envelopes is essential to the firm’s sustainability strategy.
As buildings represent approximately 40% of the total energy consumption, it is important that architects make informed decisions early in the design.

The role of the architect developed from that of the Master Builder, the person most knowledgeable about the methods of construction. By utilizing the database and software, the performance of specific conditions can be modelled graphically to illustrate which assembly performs best.
We believe it is essential that architectural research continue not only in regard to social change but to keep up with the technical evolution that is constantly taking place.

By Mark Driedger, Melissa Smith and Eranga De Zoys

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