Passive House
By  Thomas House, AIA, CSI, Principal, THA Architects
 
   

  
The holy grail of ecological home design is a completely passive envelope, and the original standard for that evolves from the German Passivhaus. In the US, the standards are governed by the Passive House Institute (PHIUS, phius.org)
 
PH is an ethos integrated into every aspect of the architectural design, and is not a series of add-ons or point-scoring techniques (as valuable as those are). The goal is clear from its name, and the standard is not limited to houses – it extends to office buildings, schools, markets, and skyscrapers as well.
 
The two main objectives, depending on the climatic zone the structure is located in, is maximum solar gain (or its opposite in Arizona) and minimal thermal exchange between indoor and outdoor environments.
 
Ergo, Passive Houses make efficient use of the solar energy and thermal retention methodologies to render conventional heating and cooling systems unnecessary. Fresh air is circulated quietly with thermal recovery taking place at the point of exhaust.
 
The official documentation states “Internal surface temperatures vary little from indoor air temperatures, even in the face of extreme outdoor temperatures. Special windows and a building envelope consisting of a highly insulated roof and floor slab as well as highly insulated exterior walls keep the desired warmth in the house – or undesirable heat out.”
 
The supplemental energy supply required in a temperate climate is as low as 1W per 11SF - roughly 1% of the energy required for large conventional systems. A true Passive House will require no conventional heating or cooling system, with supplemental systems acting only on the ‘post air’ in the exhaust system -  peak load on the supplemental system is less that 10W per 11SF except in the most extreme conditions - International Falls MN is a very different climate than Manchester NH, which lies in the sweet spot.
 
A single standard for the widely varied thermal zones of the United States, however, is not totally possible - places such as International Falls MN or Tuscon AZ have seasonal extremes that can be substantially mitigated, but not entirely zeroed out.
 
SInce New England is in a northern temperate zone (warm summers, cold winters) the primary concern concerning livability and comfort is for heat. And where does the heat come from? In a certified Passive House almost all of it comes from solar gain - including solar panels -  and the thermodynamic gain from appliances, light fixtures, warm-water drainage, and - yes - body heat.
 
When the supplied electrical supply is coming from renewable resources, the result exceeds net-zero to become energy net-positive.
 
The energy-conditioned air is kept in by making the envelope non-thermodynamic by means of insulation, thermal glazing, airtight construction, and the elimination of ‘thermal bridges.’
 
The additional cost of this standard of construction is offset by the elimination of conventional heating and cooling systems (to say nothing of 90% or more of utility costs). In a multifamily or commercial structure, this scales to a highly significant cost advantage.
 
For locales at America’s thermal extremes, Tuscon or Duluth, a completely net-zero facility will require a boost from on-the-grid renewable energy, such as wind towers or solar farms. Though the ideal in a few places is hard to achieve - the benefits of doing it anyway would put the country well down the road toward sustainability.