What is a Passive House?

By: Doug Selby

I recently completed my training to become a Certified Passive House Consultant, a rigorous program with about 100 hours of intensive training complete with three separate testing modules to ensure that the consultant understands both the concepts and applications of Passive House construction.

As you might imagine, this subject matter is pretty complicated and highly scientific in nature; so much so than it can’t quite be fully explored in a single blog post. But we can start with the basics — what is a Passive House?

A Passive House is a structure that is built to use the minimum amount of energy that a building can use while still “making sense” — that is to say not overly expensive or difficult to construct — before any renewable energy systems, e.g. solar panels, are added. The cheapest form of energy is that which is never used in the first place, so it behooves us to make sure the building is as efficient as it can be. At that point, a renewable energy system can be fairly modest in size and less costly to make a building that can go net-zero energy.

If very low or zero consumption is a goal, building a Passive House makes a lot of sense. The extra money spent on an excellent structure and low-energy lighting, appliances, and mechanical systems will pay for itself over time faster than the payoff period of solar photovoltaics. The efficient building envelope also means that mechanical systems can be significantly down-sized, which also represents a savings in build cost for that component.

Ultra-low energy consumption is just one of the benefits of a Passive House, however. Frequently, the benefits to the health and comfort of the occupants can get lost in the conversation. Because the building loses so little energy through the structure, there is little fluctuation in temperature. The surfaces on the inside of the home are very close to the air temperature inside. In conjunction with this, a Passive House also must have fresh air introduced as part of its mechanical system. That means we can direct fresh air to the places where the occupants live, and pull polluted air from the bathrooms, kitchens, and utility areas where chemicals and other pollutants are more likely to be stored. You’ll get outstanding quality air in a Passive House.

In addition, due to the high-performance building envelope, we can keep the humidity inside significantly higher in the winter without any risk of condensation that can introduce mold inside the walls. Higher humidity in the home will also make the occupant feel warmer, while also keeping skin and nasal passages from drying out. Not to mention woodwork, furniture and things like musical instruments.

There are a few key areas of a home that we focus on when designing and building a Passive House — insulation, thermal bridging, air sealing, mechanical systems, and windows & doors. Each of these are topics unto themselves and must work together as a system to create an outstanding structure. We’ll explore each in a subsequent blog posting — so stay tuned!