Tags: glazing layers

11 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: IDP — An Example of Oppor tunity for Synergies—“Tunnelling Through the Cost Barrier”

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How do these elements come together on a project? We often hear talk about “capturing synergies” with integrated design but what do we really mean? Let’s look at a common example. Typically, high-performance glazing costs more than standard glazing that satisfies the Code requirements, and so it is rarely specified. What happens if that highperformance, solar-control glazing reduces the air-conditioning load enough that the mechanical system duct size can be reduced significantly? Now the structural beams can be reduced in depth, and floor-to-floor height can be reduced. Mechanical, structural and cladding costs have come down—perhaps enough to pay for the high-performance glazing. If the building is tall enough, perhaps an extra floor can be added while still fitting under height restrictions.

What happens if the better glazing and insulation improve wall and window thermal properties enough that perimeter radiant heating is not required to maintain cold weather comfort or the window properties are able to reduce overheating in summer?
Now you have gained back at least an extra six inches of leasable space around the building perimeter, saved energy costs and have more satisfied occupants. These measures can increase the client’s rate of return—again paying for the improvements in envelope performance.

Any one of these improvements, if looked at in isolation, would not be considered affordable. Savings like this will not be realized unless there is an integrated process where the mechanical and structural engineers, energy modeller and likely the cost consultant and property management, are all sitting down very early on with the architect and talking about building envelope and its impacts on other systems.
Without the dialogue at an early stage, no system will be supportive of any other system and the synergies won’t be captured. These are some examples of synergies, but nearly every project will reveal other opportunities. Improvements like this are more affordable if done together than if done separately. Amory Lovins of the Rocky Mountain Institute, first identified this possibility which he calls “Tunnelling Through the Cost Barrier,” Reviewed by Marty Lapedus.

3 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: Window Installations – General

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It is important to ensure that sealants are applied at the appropriate point in the installation process and at the appropriate location to ensure that the air barrier is continuous. In the case of a metal window, the thermal break should be properly situated over the insulation in the wall, to maintain the continuity of the thermal barrier. If this is not done, a thermal bridge will result in high heat loss and condensation problems.
Improper installation can also impair window performance. For example, improper fastening or shimming of the frame may result in operable units not working properly. For example, casement units or awning windows will not open or close without considerable force. The CSA A440.4 Standard is a reasonably good guide to installation.
Installation details for a specific product should be reviewed as part of the design stage, to ensure that installation details do not conflict with the intended applications. For example, using a strap anchor to fasten the top of the window is not advised, as it is difficult to provide an air and water seal around this type of anchor.
For more information on this topic, refer to the CMHC report Design of Durable Joints between Windows and Walls. A mock-up installation during construction is strongly recommended.
This allows all parties (designer, installers, contractor, etc.) to review the installation details and sequencing. It is also appropriate to field-test the mock-up to fine-tune the installation details so the installed window passes the E1105 test (see Section 3). Sequential photographs of the installation process are often useful, especially if additional installers are expected to be added to the contractor’s forces. The new staff can review the photographs of the mock-up as a supplement to the installation instructions.
In general, the CSA A440.4 installation procedures should be referenced in the project specifications, but project-specific details may require special attention.
Wherever possible, designers and specifiers should maintain a design philosophy of continuity of air barrier, thermal barrier, water-vapour retarder and weather barrier. Checklist for window specification The following list is a general guideline for preparing specifications for window projects. These suggestions are in no particular order and individual projects may require additional items.
Site measurement of rough openings is critical to ensuring that the windows will fit. This measurement is usually the responsibility of the contractor or installer.
Windows should be delivered to site as shortly before they are to be installed as practical. They should be stored vertically in a clean, dry area, away from possible sources of breakage.
Shop drawings for windows are often useful. The design drawings may address a specific aspect of the design (waterproofing details, structural considerations, etc.) for a generic window. Shop drawings show how the specific window design is to be integrated into the wall assembly, including structural loads, anchorage, and drainage of hollow elements.
The window supplier should provide information on proper maintenance procedures, to ensure long service life of the installed products.
The designer should request full laboratory test reports for the ABC ratings (unless the designer already has that information).
Specifications should explain which field tests will be conducted (see 4. “Achieving Field Performance”) and at what level of performance and with what frequency. Specifications should state who will do the tests and the pass-fail criteria. State what happens in case the windows do not pass, and must be re-tested.
The window supplier should clearly state all warranties and guarantees, and should provide relevant information in writing. Installation and maintenance instructions should be reviewed to ensure that they do not contain any directions that will void the warranties.
Where “equivalent” and “approved substitution” products are permitted, the designer should clearly state the parameters that define the desired performance. If resistance to wind-driven rain is the primary concern, for example, then the desired B rating should be clearly stated. Then, if the contractor proposes an alternative, the contractor knows what information to provide the designer for evaluation of equivalence.
Note that it should be the contractor’s responsibility to provide such documentation for the designer to review, rather than making the designer obtain the appropriate data to determine whether the contractor’s choice of products is acceptable.
Installation specifications should ensure that weepholes and related drainage paths are not blocked
Specifications should ensure that hardware is properly adjusted for use and windows are cleaned before the project is completed.
For low-e coatings, the type of coating (product name and emissivity) should be defined, and which surfaces are to be coated. Reviewed by Jan Luistermans.

3 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: Window Installations – Number of glazing layers

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Most building codes do not permit singleglazed windows in small (“Part 9”) buildings because of the potential for condensationrelated problems. The glazing options are therefore limited to a minimum of double glazing, with an IGU providing the most common form of glazing system.
An IGU can comprise many layers, although practical considerations limit the maximum to four. Multiple layers reduce heat loss not because of the additional glass (glass is in fact a good conductor of heat) but because of the additional layers of insulating air trapped by the glass. Double-glazed windows (two layers) are most common, but triple glazings are now more common in certain areas, such as Manitoba. A double-glazed window with a storm panel is effectively a triple-glazed system, and is usually treated as such.
Quadruple-glazed IGUs are rare, but becoming more common, especially with the introduction of thin plastic films instead of glass layers. A window with four layers of glass is heavy, and difficult to move, install and operate. On the other hand, a window with two glass layers and two films weighs about the same as a double-glazed window, yet provides the performance of quadruple glazing. Reviewed by Moishe Alexander.

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AIR Alexander Building Canada Canadian Funding Corp. Canadian Funding Corporation CFC cmhc construction Design IDP integrated design Moishe Alexander performance report Reviews Window Window Installation
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