What is a Passive House?
The term 'passive house' refers to an extremely high performing energy efficient home, in the sense that the heating and cooling is largely passive. To achieve this, homes have to be designed to take advantage of the free heat available from the sun, and heavily fortified with insulation to hang onto that precious heat.
Passive cooling comes from the insulation as well, in that not only does it stop heat from leaving your house in winter, it stops it from coming in during the summer. Important to note, any home can be planned and built to Passive House standards, but Passive House Certification is mandatory to call a home "Passive House Certified." Allow us to explain...
What are the problems of Passive House in North America?
The original Passive House certification program originates in Germany and is referred to as PHI - and the parameters of that program were specifically designed for that climate. The certification process has found its way to Canada, (slightly ironic when we consider that the world's first passive house was built in Canada in the 70's) but without any key changes to the performance requirements... at least not if you choose to certify via the PHI system.
In Canada and the cold zones of the USA our bottom end temperatures can be much more extreme than those of Germany, and this is not reflected in the PHI certification process. This can make achieving Passive House Certification in cold climates of US or Canada a far more costly undertaking, which could dissuade some from exploring it as an option, and likely be very disappointing to those who tried but didn't quite make it.
The main hurdle to certification is the maximum energy consumption of 15kWh per square metre per year in operation. There are some success stories with Passive House certification, but to get to that point in Canada & US can require so much additional capital that the return on investment takes a serious beating. Excuse us for being pragmatic, but maybe your overall carbon footprint might be better if you settled for a 16 or 17 kWh (still extremely high performance home) and put that extra money into something like a Prius perhaps?
We stumbled upon one homeowner who, in an attempt to build and certify to Passive House standards, found the additional cost needed to squeeze the last bit of energy from the total modelled consumption pretty prohibitive and decided to back off a bit. We found this interesting, and it's a good example of why we shouldn't look at any green building endeavour as an 'all or nothing' sort of thing. They still have an exceptional home, just not quite to Passive House certification standards.
Anyone can build a Certified Passive House when money is no object, but are they cost effective? We started to question that when we were designing the Damn Near Passive House.-Roy De Vries
Taken from the Damn Near Passive House blog, these are the objectives they had set out with:
- Design and build an affordable single family home that is highly energy efficient and environmentally sensitive.
- Assure that the house is designed to accommodate the ageing process.
- Complete the entire project on a reasonable budget that should accommodate many potential builders.
- Meet recognized PassivHaus standards for energy efficiency if proven to be cost efficient.
- Assemble a team of highly skilled journeyman trades craftsmen and women that appreciate the value of doing it right and want to participate.
- Work with suppliers in achieving our budget while maximizing awareness of how we selected their products in regards to merit and cost benefit analysis.
Within the realm of sustainable building, most of us will have financial limits that we need to be realistic about. This does not mean that building an efficient home has to be a costly and selfless gesture, in fact it is quite the opposite. A well designed high-performance home design will generally mean less money spent overall, not more, with the huge advantage being the reduction in monthly outgoings, increased comfort and a reduced environmental footprint.
The EcoHome Team decided to prove the point when we built the economical yet high-performance Edelweiss, which was the second certified LEED Platinum V4 home in the world and first in Canada (see here) and which coincidentally was built to Passive House standards. Canada Green Building Council President Thomas Mueller called Ecohome's Edelweiss House "A phenomenal achievement" for achieving the LEED Platinum V4 certification and a Passive House standard Passive Solar index of only 15 kWh per square meter - yet with a build cost equivalent to a standard code built home in the same area - which would only probably have managed a rating of 100 kWh per square meter.
To read more about Passive House Certification & Design in North America see here, or for specifics about the differences between PHIUS & PHI certification for Passive House see here, from the EcoHome Green Building Guides - North America's favorite Sustainable & Green Building Resource