The Frustrating Realities of Cold Climate Design:

1. The Frustrating Realities of Cold Climate Design: Piercing the Skin: Ins-U-lation versus Ins-O-lation Terri Meyer Boake University of Waterloo

2. From First Principles: First Ins-U-late then Ins-O-late Walls are thick and have a very high (mandated) thermal resistance Windows are thin elements whose thermal resistance remains a fraction of the wall Energy efficient window (design) is costly If windows are improperly specified, designed and constructed, energy losses are significant

3. The Model National Energy Code of Canada for Houses 1997: MNECH is a stand-alone document Addresses environmental protection and resource conservation only Suggests but does not enforce its rules/ideas Relies heavily on CSA Standard A440.2 Energy Performance of Windows and Other Fenestration Systems

4. MNECH Minimum Insulating Values: Minimum RSI and R values for up to 5000C Degree Days (9000F) for above ground opaque elements are: Attic-type roofs: 5.6 m2xoC/W or a U-value of 0.178 W/m2xoC 31.8 hxft2xoF/Btu 0.031 Btu/hxft2xoF All other roofs: 4.3 m2xoC/W or a U-value of 0.233 W/m2xoC 24.4 hxft2xoF/Btu 0.041 Btu/hxft2xoF Walls: 2.9 m2xoC/W or a U-value of 0.345 W/m2xoC 16.5 hxft2xoF/Btu 0.061 Btu/hxft2xoF Floors: 4.5 m2xoC/W or a U-value of 0.217 W/m2xoC 25.5 hxft2xoF/Btu 0.039 Btu/hxft2xoF Windows must only have a maximum U value of 2.60 W/m2xoC (0.457 Btu/hxft2xoF). This will permit 7.5 times as much heat transmission per hour compared to wall elements! Skylights must only have a maximum U value of 3.4 W/m2xoC (0.599 Btu/hxft2xoF). This will permit 14.5 to 19 times as much heat loss as the roofs they displace!

5. The Energy Rating (ER) for Windows: The MNECH uses a new Energy Rating system to compare the overall performance of windows Previous standards relied only on separate U, SC, SHGC and air leakage values The ER combines Solar heat gain coefficient (SHGC) Overall heat transmission coefficient (U-value) Air leakage

6. Solar Heat Gain Coefficient SHGC: Fraction of solar radiation incident on a window that appears as solar heat gain in the building Dimensionless, expressed as a decimal, always less than 1.0 Center of glass of a clear single glazed window has a SHGC of 0.87 Shading Coefficient (SC) is no longer used SC is the SHGC of window relative to the SHGC a single glazed clear window under the same conditions The SC times 0.87 provides a good approximation of the SHGC for most glazing systems if that is the only data provided

7. ER = total performance The ER gives a single number to indicate the combined response to solar heat gain, conductive heat loss and air leakage in typical Canadian (cold) climate conditions Based on total performance, including glazing, spacers, glass and frame (many other U-values do not include other than center of glass values) Developed in CSA Standard A440.2: Energy Performance of Windows and Other Fenestration

8. Understanding the ER: Only applicable when comparing windows and sliding glass doors in houses under specified heating conditions Assumes vertical installation Based upon AVERAGE conditions for solar radiation on windows facing 4 cardinal directions (i.e.) north, south, east and west Minimum requirements are based on climate and fuel type

9. ER: positive or negative The ER may be positive or negative A positive ER means that the window gains more heat than it loses in the heating season A negative ER means that the window has an overall loss of heat during the heating season Most windows have negative ER values

10. ER Requirements for Houses:

11. ER Limitations: Good for builders who in a subdivision will have the same number of windows facing all directions Not good for passive solar buildings that do not have evenly oriented windows N,S,E,W (CSA A440.2 does include a calculation method to differentiate based on solar orientation or on cooling rather than heating design) Not the correct number to be plugged into simulation programs (most want U and SHGC) Values are developed by window manufacturers Not presently many available for comparisons except through www.enermodal.com, CATALOGUE program

12. Ontario Building Code Requirements for Window Design

13. Minimum OBC Energy Requirements: For windows that meet the previous criteria, the only energy requirements are: (a)Air infiltration shall not exceed 0.775 dm3/s for each meter (0.5 cfm for each foot) of sash crack when tested at a pressure differential of 75 Pa (0.011 psi)) (b)All glazing that separates heated space from unheated space shall have a thermal resistance of not less than RSI=0.30 m2oC/W (1.70 ft2xhxoF/Btu) The OBC requirements are slightly more stringent for residences with electric heating and copy the MNECH in their requirement of an ER of not less than �13 for operable windows and sliding glass doors, and an ER of 0 for fixed glazing. Additionally, the Code requires that the maximum amount of glazing (including windows, skylights and doors) can not exceed 20% of the floor area of the story being served by the glazing nor exceed 40% of the total area of the walls of that story.

14. OBC and Passive Solar Design: The Code does allow for passive, aka �Thermal Design� This design is considered alternative to normal thermal insulation requirements and allows for window areas that exceed the 20%/40% rule Increases in window area allowed is proportional to the increase in its thermal resistance value;

15. OBC and South Facing Windows: Glazing areas can also be increased where the design is using passive solar gain principles on �south� facing orientations. In such cases the glazing area may be calculated at 50% of what is actually being constructed, provided that: (a) the area contains clear glass or has a shading coefficient of more than 0.70 (the MNECH uses a value of 0.61), and (b) faces a direction within 45o of due South, and (c) is unshaded in the Winter (calculating angles based on Dec. 21 at noon), and (d) the building is designed with a system that is capable of distributing the solar gain from such glazed areas throughout the building. Where houses are designed to be cooled, window areas cannot be increased, as outlined above, except where the glazing is shaded in the summer with exterior devices. The shading is to be calculated using noon sun angles for June 21.

16. CMHC Comparison of Typical Window Thermal Efficiencies:

17. Unrealistic Expectations? From the previous charts very few windows would meet the MNECH criteria of ER -13 for Ontario and Quebec No windows would meet ER criteria for Manitoba, Yukon and NWT (severe climates) Most call for low-e, argon fill and triple glazing, which is beyond most housing budgets All but one would exceed the minimum thermal rating of the OBC of 0.30 m2oC/W (1.70 ft2xhxoF/Btu) If codes were to mandate the new ER requirements, we would save energy, but capital building costs would skyrocket -- what would window manufacturers do??

18. Finding the Right Information: A very tough job!! Varies from Canada (SI) to US (Imperial) Must rely on window manufacturers for accurate information! Manufacturers� info usually not there at all or inconsistently presented Use great terms like �super energy efficient� without data backup

19. Sample Manufacturer�s Test Data:

20. Understanding the Data: The values achieved through Loewen testing are comparable to the CMHC �ideals� in some cases but not all Most of the windows exceed the 0.30 RSI OBC minimum so could be used to proportionately increase fenestration areas None have a SHGC that would permit increases based on passive solar south facing glazing Low-E coatings increase the RSI and decrease the SHGC indicating suitability in energy efficient thermal design but not passive solar design

21. Low-E wins over Solar Gain: In the Loewen advertising, windows with low-e coatings are pushed for their insulating qualities and ability to reduce solar gain Anti-passive solar which would use differentiated glazing on the south side to promote solar gain and shading devices for cooling

22. Insulation is better than Insolation??? Again the advertising clearly shows that insulating glass and protection from the sun�s free heat are the most important attributes of windows.

23. Balancing Ins-U-lation vs. Ins-O-lation The codes (and manufacturers) clearly favor insulation over insolation It is possible, however more complicated to design fenestration for passive solar design in order to achieve reasonable heating values through window design It requires separate design tactics for south facing windows, different windows than are used on the E,W,N elevations, and additional calculations Simpler to use computer simulation programs to be able to differentiate the elevations and design for solar passive

24. Balancing: Insulation + Insolation + Daylighting: 1. INSULATION: Calculate heat loss. Uses R/U values and infiltration 2. INSOLATION: Calculate heat gain. Uses SHGC, precise orientation, shading, thermal mass. 3. DAYLIGHTING: Calculate how windows reduce electrical/lighting energy requirements.

25. Selling Energy Efficient Window Design: Most clients and builders regard Code requirements as maximum rather than minimum standards Up to Architects and educators to approach window design in more environmentally responsible manner Need to simulate performance to show long term energy savings over short term capital costs i.e. Frame Plus, Energy-10, Solar 5 or Hot2000 can be used to run more accurate comprehensive simulations for different window solutions However, simulations are time consuming and can be expensive to run -- most clients not willing

26. In Conclusion: Windows and skylights that simply meet the minimum energy standards as set by the Code account for 7.5 to 19 times the heat losses based on the same area as a wall or roof. These losses can be drastically reduced if energy efficient strategies are responsibly applied. To properly design energy efficient openings for cold climate applications is not an easy task. It is, however, essential. The Building Code provides us with minimum standards. The National Model Energy Code asks that we aim higher. Good conscience says that this is not enough. Tools exist which help to make this frustrating, complex task a little bit easier. It is up to us to use them.