Getting Active on Passive
How Passive Design is changing the future of residential and commercial construction
Public awareness of the global climate crisis is increasing rapidly, and so is Net-Zero Passive House building in residential and commercial construction. Now is the perfect time for builders to specialize in this rapidly growing market sector. Builders with Net-Zero and Passive House construction skills can not only differentiate their companies from the masses, but enjoy prestige and unique advantages over their competition.
The Net-Zero Passive House approach to design and construction can be applied to small single-family homes and large commercial or residential buildings. Reducing energy use by to 70 to 100 per cent, these buildings make a significant reduction to the carbon footprint and carbon emissions. With 50 per cent of energy savings accomplished in the design phase, and the remaining energy reduction coming from how the building is constructed, savings are achieved in multiple ways, for example by:
- Strategic use of building site to maximize solar gains;
- Using compact building shapes that reduce exterior surface area;
- Designing the roof for the installation of solar photovoltaic panels;
- Ensuring the envelope is air-tight, super-insulated, has upgraded windows, doors and no thermal bridging;
- Specifying mechanical ventilation systems that are ultra-efficient thus ensuring consistent indoor air quality without unnecessary energy loss;
- Avoiding fossil fuels and utilizing high-efficiency heating and cooling systems.
The principles of Net-Zero Passive Design are quite straightforward, however the strategies to implement these principles require builders to change their conventional approach. Let’s look at how these strategies may impact conventional construction methodologies.
Air tightness: A Passive Design building is six times more airtight than a conventional one, but air tightness detailing may be the biggest change for builders, meaning conventional approaches to air sealing must be replaced with new materials and processes. A continuous air-tight layer connecting all assemblies and building components requires careful attention onsite. Air tightness is the secret sauce of high performance.
Super Insulation: A Passive Design building has significantly more insulation than a code-built one. These levels of insulation create very thick assemblies. Careful detailing is needed to comply with structural requirements, the elimination of thermal bridging, proper installation of flashing and the accurate installation of windows and doors. It is also important to choose low embodied carbon insulation materials, as some materials emit more carbon during manufacturing than they will save over the life in the building.
Upgraded Windows and Doors: Passive Designs typically use triple-glazed windows and doors with better insulated frames, and many projects specify European high-performance products (although triple-glazed North American products can also work). Longer lead times can impact the construction schedule and remote suppliers tend to leave the builder responsible for addressing any service issues onsite.
Thermal Bridge Free: Thermal bridging can result in significant energy use in a Passive building, meaning thermal bridge-free details require attention from the builder. Materials such as concrete and steel are highly conductive and must be covered with insulation to insure they don’t create cold spots or condensation points in the building.
Ultra-Efficiency Mechanical Ventilation: Air-tight buildings require mechanical ventilation to supply fresh air and remove exhaust air. As humans we don’t breathe through our skin, so our buildings shouldn’t either. A heat recovery ventilator (HRV) supplies constant fresh air while recovering the heat from the exhaust air. Although installing HRV systems will be new to many residential builders in the U.S., it is part of the building code in Canada.
Heating and Cooling Systems: These systems in Passive buildings are a fraction of the size of those required in conventional buildings. New technologies such as ductless mini-split heat pumps and hot water heat pumps are electrical-based systems that work well. Typically, the heating and cooling systems in a Passive building are simpler for the builder than in code-built projects.
Renewables: With the super efficiency of a Passive designed building, reaching net-zero is easily achieved for most projects. Net-zero can be defined as a building that generates as much energy as it uses annually. Photovoltaic (PV) solar systems are usually the most cost-effective technology to install. For small buildings, a simple electrical rough-in is required from the builder and a solar installer will install the PV panels.
There is no prescriptive method to building a Passive design. Building methods will depend on the local availability of materials, local climates, regional costs, and designer preferences. All aspects of the building envelope and mechanical systems change from those used in code-built projects.
Tackling your first Net Zero Passive Building project will require a willingness to learn and patience to implement. Builders usually find their stride for the Passive Design approach after three or four projects. It is rewarding work to learn new construction methods and build higher quality buildings that contribute to a healthier planet.
Natalie Leonard is the first Certified Passive House Consultant licensed to deliver Certified Passive House Builder training in Canada. As an engineer and the president of Passive Design Solutions, she has worked on over 100 Passive House projects that are net-zero ready and provided support to 30+ builders on their first Passive House projects.