Green Building: the Passivhaus Standard
the Passivhaus (aka “passive house”) standard is the construction technique of the future, reducing utility bills by 90%! As energy prices rise, buildings will have to be more efficient. There is no excuse to not build a green home, and the Passivhaus standard is the best choice.
- Compact size – 50 square meters (approx 538 sq ft) per person
- Super insulation of floors, walls and ceilings
- Air-tight envelope with no thermal bridging
- High-performance doors and triple glazed, insulated frame windows
- Heat recovery ventilation (HRV)
- Passive solar
- HERS score 20-30
- PHPP Certification (Passivhaus Planning Package)
- Space heating must be no more than 15 kWh/sq m (4.75 kBtu/sq ft)
Overall energy use must be no more than 120 kWh/sq m (38 kBtu/sq ft). HRV air exchanges must be 0.6 or less per hour at a pressure rating of 50 Pascals.
Benefits of passivhaus building
- Improved indoor air quality
- Increased physical comfort
- 90% energy reduction
- Minimal conventional heating system
- Suitable for retrofits
The point of passivhaus construction is to minimize energy loss by restricting airflow into and out of the building. The building stays warm in winter and cool in summer. Style does not matter, as long as the efficiency and air circulation goals are achieved.
The envelope is super-insulated, up to 16″ beneath the slab and in exterior walls (R 60-70). Strawbale, SIPs and ICFs (insulated concrete forms) or Rastra are suitable. Ceiling insulation of dense-pack fiberglass, cellulose or spray foam has an R-value anywhere between R 60-100.
The triple-glazed windows have a very low U-factor of 0.14. Some in Germany are as low as 0.17. The U-factor rating of the National Fenestration Rating Council (NFRC): the lower the number, the more efficient the window, based on the glass, frame and spacer material.
Thermal bridging is essentially eliminated. A blower door test is run several times during construction to test for air leakage before the building is completely closed up and finished.
A heat recovery ventilator (HRV) keeps indoor air fresh, exchanging indoor air with outdoor air with minimal heat loss.
Energy savings in passivhaus construction
Because passivhaus construction is performance-based, buildings are monitored after final construction. The CEPHEUS project monitored 250 passivhaus’s in the EU, and their results showed an energy reduction of 90% on average.
I have heard varying estimates of the extra cost to build a passivhaus in a range of 5-10%. This is offset quickly with the huge energy savings. The payback period depends on each individual home’s energy use. Passivhaus construction is not catching on quickly in the US, and education is key. Components are available, so homeowners need to be aware of its benefits, and builders need to learn how to build these homes.
The addition of solar and wind power can turn a passivhaus into a net-zero home, but the energy creation and consumption of passivhaus construction is meant to be just that – passive. To me, that is a gentler way to live, and there are no moving parts to maintain. A 90% reduction in the energy consumption of a passivhaus is good enough for me!