An Introduction to Passive Houses: What They Are and How They Work
While researching the custom home building process, you might have come across the mention of a Passive House, or Passive Home Building. Below is an introduction to the term Passive House, as well as some ways to tell if this is a possibility for your custom dream home.
What is a Passive Home?
A Passive House is a type of extremely energy-efficient building that requires very little heating and cooling energy, no matter the season. Any building, including single-family, multi-family, and commercial buildings, can qualify as a Passive House.
Passive House buildings look like regular buildings, only they are built using a voluntary construction method or standard that originated in the 1970’s as North Americans were responding to an oil embargo by embracing the idea of building homes that didn’t require supplemental heating.
In Canada, Passive Houses are certified by Passive House Canada and the Canadian Passive House Institute. Note that Passive House is not a trademark, nor a brand name. It’s become a method of construction favoured around the world for its ability to increase the comfort of a home while decreasing its energy costs.
Is a Passive House the Same as a Net Zero House?
Passive Houses can perhaps be considered the early pioneers of green building, paving the way for today’s net zero homes. Both styles of home are extreme examples of eco-friendly building construction, as they are both specially designed and built to reduce the net amount of energy a building uses.
The main difference between the two is that a Passive House isn’t quite as energy efficient as a net zero home. A Passive Home uses around 10-25% of the energy a regular home uses, while a net zero energy homes strives to average out to zero use overall.
A Passive House is all about the maximization of the home’s thermal performance or efficiency, rather than relying on renewable energy systems like solar, wind, or geothermal systems. The primary goal of Passive House construction is to build an extremely well-insulated, tightly sealed building envelope, where fresh air is introduced using a very high-efficiency heat recovery ventilation system. Some Passive Homes also use renewable energy sources, but these would be considered over and beyond what is required for certification. They’re usually add-ons if there is room in the budget.
Unlike a net zero energy home, which typically uses solar power or some other renewable energy source and connects to the electricity grid in order to contribute excess power it generates but doesn’t use up, a Passive House doesn’t “sell back” anything to the grid. It’s not as rigid in its energy reduction as net zero homes are.
Benefits of a Passive Home
The benefits of a Passive-certified home are the same as those of net zero energy homes:
- They reduce your energy costs dramatically, protecting you from inevitable rising energy costs.
- They lead to a more durable home, with more soundproofing.
- They lead to a more comfortable home, where rooms are usually an even temperature and air is filtered.
- They are environmentally friendly, helping homeowners to reduce their energy consumption and do their part to conserve resources for future generations.
- They lead to a potentially high value re-sale, as they are still viewed as unique and special.
- They will receive nation-wide recognition through Canada’s Passive House certification bodies.
Potential Drawbacks of Building a Passive House
- Building materials that are of such high performance are often more expensive, leading to a higher investment up front.
- Building materials of such high performance can sometimes be in short supply, or otherwise take longer to acquire. However, as demand for greener buildings rises, so too will access to such materials.
- The certification process may be cumbersome or overwhelming for homeowners new to the custom home building experience. However, having a professional home builder on your side can help you navigate the process.
- To qualify as a Passive House, you either become certified, or you don’t. It’s a more rigid process than other green building construction concepts, like StepCode or LEED.
Fundamental Passive House Building Practices
The following design fundamentals are key to the construction of a Passive House. Combining all these will be essential in becoming Passive House certified:
Shape and Layout of the Building
A Passive House’s surface area should be minimized to reduce the amount of heat that is lost from a larger building envelope. The “Shape Factor” that Passive House designers use is a ratio of the surface area of the building by its volume.
This means that sprawling floor plans with exposed floors and heated garages, for example, should be avoided, as they have higher shape factors, which will ultimately equal higher heat losses than a two or three storey building with an equal floor surface area.
While not reliant on solar power, a Passive House ought to be designed with solar or sun exposure in mind. This ultimately means incorporating plenty of south-facing windows and minimizing north-facing windows to help the home take advantage of the most amount of sunshine throughout the day.
The building should also be strategically positioned on the lot as to soak up the most sunshine. Another important element to consider will be the amount of tall trees in the landscape plan that could potentially cast too much shade on the home.
A Passive House will require something the industry has deemed as “superinsulation”. This ultimately refers to higher performance insulation than what is currently called for in national and provincial building codes.
The amount of superinsulation required to meet Passive House certification varies depending on your location’s climate data. In a mild climate such as Victoria, which experiences the warmest winters in all of Canada, a Passive House can get by with insulation that is about 3 times more effective than what is typically used. Other regions call for superinsulation that is up to 7 times higher performing.
On top of this, the designer must insist on complete insulation coverage for every part of the building’s shell (i.e. walls, plus floors, and roof to ensure thermal bridge-free design and construction).
Triple Pane Windows
Windows are a critical building material to get right when it comes to Passive Home building. That is because they are thermally the weakest part of any building envelope, accounting for around 50% of all heat loss in a building. No matter which region of Canada you live in, triple-pane or triple glazing is crucial to Passive House certification. This is instead of the typical double-pane windows of regular homes. Window frames must also be insulated, which isn’t typical of window manufacturers that supply Canada.
Passive House buildings must be extremely airtight – much more so than conventional buildings. This really helps minimize heat loss from air infiltration, as well as protects the building structure from possible moisture damage. An air blower test must be performed and can pinpoint any leakage locations. The agency performing the test will often make recommendations for further sealing measures, ranked by affordability.
Ventilation with Heat Recovery
Every Passive House building will require the installation of a high-performing heat recovery ventilation system. This helps with fresh air intake while recovering heat from inside the building. These systems filter the air as well, leading to increased comfort levels indoors. Although the home is airtight, it’s never stuffy. Sometimes these systems come with a geothermal heat exchanger as well, which pre-heats the incoming air when desired.
If you’re thinking about building a Passive House on Vancouver Island, we recommend checking out the following resources:
- Canadian Passive House Institute
- Passive House Canada
- EcoHome Magazine’s Passive House Planning Guide
At LIDA Construction, we would be happy to discuss the green building options available for your next project. Contact us today to get an estimate on the designing, planning and construction of your future dream home.