Best Practices in Net-Zero House Design

Leonard

There is increasing public and government demand for low-carbon-footprint solutions across the building industry, which today accounts for 40%-50% of all energy used in North America.

In the residential sector, net zero construction using Passive House Design is one such solution. Passive House Design, with its minimal heating energy requirements, provides an excellent foundation for any net zero project.

Passive House Design as a Foundation for Net Zero Projects

A net zero house is not necessarily built using Passive House design, and a Passive House is not necessarily net zero.

Net zero is defined in a number of ways: A useful definition says: “A site ZEB (zero energy building) produces at least as much renewable energy as it uses in a year, when accounted for at the site."

Canmore East Interior. @ Elemental Photography

“Passive House describes a set of design principles and defined boundary conditions that—if applied holistically—lead to a building that remains comfortable with only minimal active heating or cooling during extreme climate conditions.” (Klingenblog, 2012-03-22)

Net zero, then, is a calculation, one that ensures site energy supply and demand are in balance; Passive House design results in ultra-low heating-energy demand.

Net zero construction costs are divided between a) building construction, and b) on-site power production and storage. Expenditures in both areas are required, but the more efficient the building envelope, the less power generation is required to reach net zero.

The Passive House uses between 60% to 80% less site energy than an average house. This saving is achieved as follows:

• Siting the structure to take advantage of solar energy and prevailing winds for heating and natural ventilation for cooling;
• Designing the envelope to be air-tight, super-insulated, with upgraded windows and doors, all to minimize heat loss/gain in all seasons;
• Using compact building shapes that reduce exterior surface area and opportunities for air infiltration and thermal bridging;
• Designing and orienting the roof to anticipate installation of solar photovoltaic panels;
• Specifying that mechanical systems have ultra-efficient ventilation, thus ensuring consistent indoor air quality without unnecessary energy loss; and
• Avoiding fossil fuels and specifying the electrical systems to have only high-efficiency components.

Modern Lake Front net zero/Certified Passive House.
@ Elemental Photography.

A Passive House provides a practical way to balance the net zero equation at modest cost. Construction costs may increase 5% to 15% over code-built alternatives, but Passive Houses achieve a 75% to 90% reduction in heating costs, with annual heating bills as low as $150.00. The reduced demand for on-site energy production means fewer solar-voltaic panels are needed to reach net zero.

Solar System roof mounted on the Modern Lake Front house. 
@Passive Design Solutions

Net-metering grid tie-in eliminates the need for batteries and greatly simplifies power management. The result is a much less expensive power generation system that can be amortized in five to 12 years, depending on local costs and availability of efficiency incentives.

Opportunities

Advantages of building net zero Passive Houses:

• Increasing market demand for net zero and Passive Houses is bringing these products into the mainstream of residential construction;
• Builders with net zero and Passive Houses construction skills enjoy prestige and unique advantages over their competition;
• Passive Houses rely primarily on locally sourced materials and labor, and less on imported technology, which is good for the local community: they support local trades and suppliers while building a skilled labor pool; and
• Financial incentives are becoming available at every level of government for shifting to sustainable buildings such as net zero and Passive Houses.

Challenges

The widespread adoption of net zero Passive House construction involves challenges:

• Overcoming inertia—changing entrenched construction practice can be a slow and difficult process that takes people out of their comfort zone.
• Understanding financial risk—developers and builders, especially larger ones, may be reluctant to incur the additional up-front construction costs without the certainty of recovering them in the sale price.
• Managing regulatory barriers—prescriptive building codes can present obstacles and often lag behind best practices; conversely, codes that describe desired outcomes provide more flexibility for innovations like net zero and Passive Houses.
• Recognizing Green Washing—the practice of claiming or inflating environmental benefits without hard evidence creates a confusing marketplace of competing ideas, which can leave many unsure about where to find the best information.

Summary

Many home buyers today want the quality, comfort and energy savings that come with Passive Houses, and they want the carbon emissions reductions that come with net zero houses. They also want lower energy costs and increased energy security, two goals that are especially important to young cost-conscious families and seniors needing to manage fixed assets. Net zero Passive House design that uses modest on-site, grid-tied, electrical power generation is a simple and practical path to reach these objectives in most North American regions with heating dominated climates.

About The Author

Natalie Leonard is a Certified Passive House Consultant and Certified Passive House Builder. As an engineer and the President of Passive Design Solutions, she has completed over 100 Passive House projects that are net zero ready.