Sustainability Insights

What You Need to Know: Passive House for Commercial Buildings

By Helen Sanders

Passive House design may be the next trend in sustainable building design. And it’s not just for residential homes. “Passive House” is a translation from the German “Passiv Haus,” where “Haus” relates to buildings in general.

Passive House design applies to commercial, institutional and multi-family construction, and there are many examples in Canada[1] and Europe[2]. Although most buildings built to these standards are in Europe, the adoption in the U.S. is growing.

Although most non-residential passive house buildings are relatively small, project size is growing. According to Monte Paulsen of RDH Design speaking at a recent Façade Tectonics Institute event, once built, 1488 Alberni, a 48 story, 490-unit condo tower in Vancouver, will be the world’s largest passive house building.

WHAT IS PASSIVE HOUSE DESIGN?

The premise of the passive house design is simple—minimizing energy use through simple strategies:

• Super-insulating the building envelope: meaning thick wall insulation, triple-pane glazing, warm-edge spacers and insulating frames.
• Elimination of thermal bridging: ensuring that the excellent insulation is not circumvented by thermal shorts at connection points (e.g. slab edges, sun shades, panel attachments, and fenestration interfaces).
• Air-tight building envelope: air in-filtration rates of no more than 0.6 times the building volume per hour.
• Use of passive solar heat gain to supply heating: Optimum placement of glazing on the envelope and the use of highly insulating fenestration to balance heat loss with solar heat gain.
• Use of natural ventilation where possible or mechanical ventilation with at least 75 percent heat recovery.

The maximum heating energy demand is 15 kWh/m2/year (4.8 kBTU/square feet). This compares to a cur-rent average heating demand (in Canada) of 150 kWh/m2/year (48 kBTU/square feet), according to Paulsen.

KNOW THE DIFFERENCES

European vs. U.S. U-factors: Com-paring the two is like comparing apples to oranges because the calculation methods used in Europe (ISO 10077-1) and the U.S. (NFRC 100) use different algorithms and climate boundary conditions. Differences of up to 18 percent can occur between U-factors calculated using the two methods for the same window[3]. PHI also requires use of climate-specific outdoor temperatures in the ISO method. Always check from which standard the U-factor in question is derived. Never simply convert the units of a European derived U-factor from W/m2K to Btu/of.hr.ft2 and assume that the result will be meaningful in the U.S. (or vice versa).

Certified components: Just because a fenestration product is labeled “Passive House Certified” does not mean that it will automatically work for a North American project, or even meet local minimum energy codes. PHI identifies the appropriate climate type(s) for a certified component, so a certified window that is listed for temperate climates would be inappropriate for use in cold climates.

The Passive House Institute U.S. (PHIUS) in collaboration with the U.S. Department of Energy, created an alternative certification standard PHIUS+[4]. According to PHIUS, buildings constructed to its standard have 60 to 85 percent better energy consumption than a building constructed to IECC 2009.

FENESTRATION IMPLICATIONS

According to Paulsen, adoption of passive house standards will drive changes in fenestration by forcing:

• The widespread use of triple-pane glazing and super-insulated frames to achieve NFRC U-factors of 0.14 Btu/of.hr.ft2 (0.8 W/m2K) and below;
• The reinvention of curtainwall (e.g. double skin façades, etc.; and
• The use of either much less glazing or much better glazing.

As an industry we need to provide high thermal performance solutions or lose glazed area on the building.

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