The “Certified Passive House” Window Trap

Are you designing a passive house and have to chose windows for your construction project? There seems to be a common misconception that you need certified #PassiveHouse [PH] windows for your PH project in order to receive PH certification here in Canada.

PH is a design methodology and not a prescriptive “please-check-these-boxes-here” design process. (LEED ;-) ). Energy losses are calculated and not just assumed.

You may even put your buildings PH certification at risk, if that is the criteria by which you chose your windows. A window that qualifies as a Passivhaus :-) window in Germany, which is why it received the PH certificate by PHI, is most likely not the right window for your project here in Canada. You need to first look at your specific local climate to determine the exact U-value (Uw,avg: average U-value for the installed window). With this value at hand you can extrapolate all the other technical criteria your windows need to meet (glazing, spacer, frame, installation) and then go and chose your windows accordingly.

Why look at local climate?

In order to eliminate drafts from convection (air cooling down on the window surface - and condensation which is a given if you eliminate drafts), the interior temperature of the window should be kept at >17° C. This means you need to consider your local weather data and determine the glazing, framing and installation types.

A practical example of choosing the right window:

Where I live, in the Niagara Area in Canada, the minimum daily temperature is -17.1°C, which translates to Uw,avg = 0.83 W/m2K.  This is pretty mild compared to the rest of Ontario, but without knowing this specific value at hand, I would be tapping in the dark when choosing windows for a project here in Niagara. If I did end up using windows that just meet the minimum of 0.85 W/m2K required for the PH certificate, I’d put the PH certification at risk.

How to get the specific Uw value?

The best way to get this value is to ask Andrew Peel, the certifier here in Canada for the specific value you need for your project, (or calculate it yourself according to the minimum daily temperature). The last I heard, Andrew was also creating a calculator for this purpose, which uses weather data from CWEC (I don’t think this calculator is online yet.)

  • Don’t just use PH certified windows
  • Find out specific Uw-value for your location
  • Have fun shopping for windows with the value
  • Give us a call: 905-321-3905

Give us a call 905-321-3905, if you are looking for passive house windows. Heckel makes premier wood and wood/aluminum windows, and we can match the passivehouse values you need. Heckel also sources uPVC windows from Schweiker, one of the largest window manufacturers in Germany (read: very economical, high build quality, we pass on excellent value and price to you). These windows have PH certification by ift (the testing organization in Germany).