As the title would suggest, this blog is a means of documenting the design, construction and challenges associated with Kingston’s (in Ontario, Canada) first Passive House.
What is “Passive House” ?
It is the world’s most comprehensive and ambitious energy-modelling standard. Although relatively new to Canada, the Passive House Standard (PassivHaus in Germany) dates back over 20 years, has become very popular in Europe and is gaining traction all over the world. Passive House is non-prescriptive, meaning it does not require you to use specific materials or building systems. Stick-frame, ICF, SIPS, and even straw-bale can be used. At the heart of this standard is the ‘Passive House Planning Package’ (PHPP) which is a very thorough energy modelling software tool. PHPP gathers every detail of the house (orientation, areas, volume, windows sizes / placement, all wall/ceiling/floor assemblies) and computes energy consumption, taking local climate data into account. Although there are many requirements for meeting the standard, the most widely referred to are:
- Air-tightness – 0.6 ACH50 (air changes per hour at 50 Pascals pressure – positive and negative) is the maximum allowable. Passive houses frequently go well below this number, but for comparison’s sake, an R2000 home allows 1.5 ACH50 and modern code-built homes are normally in the 4-8 range.
- Ventilation – A home this tight requires active, controlled ventilation to remove indoor air polutants and bring fresh air in, while recovering over 80% of the heat (or cooled) energy from the outgoing stale air. The HRV or ERV runs continuously and Passive Houses are very healthy to live in for this reason.
- Annual Space Heating and Cooling demand – A passive house is designed to use no more than 15 kWh/(m2a)… that’s 15 kilowatt-hours per square meter of floor area, per year. Essentially this gets heating down to a level where the house can be heated without a conventional furnace or boiler. The house still requires a heat source but it’s almost negligible in that it can be delivered to the rooms by post-heating the fresh air from the HRV/ERV.
- Windows – They must have total (frame, spacer/glazing and installation) U-values of 0.8 W/m2K which translates to R-values of 12.5 or better. Common double-pane windows are roughly R4 so this marks a dramatic improvement in window performance – justified by the fact that windows are the single largest source of heat-loss in a typical home. Passive House windows are triple-pane with one or more low-E coatings and must also have a high Solar Heat Gain coefficient (SHG of 50% or more solar transmittance) to take full advantage of solar gains in the heating season.
More details on the standard will pop up as the build progresses. For now it’s all a numbers game… taking an optimized (for Passive House) floor plan and adjusting glazing, wall, roof and floor assemblies in PHPP in order to meet the standard. These numbers will of course be verified prior to certification.