Are Net-Zero Passive Houses the Industry’s End Game?
Originally published by: Bloomberg Environment — January 30, 2020
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The energy savings from net zero passive houses can reduce heating costs by 75% to 90%, and these new dwellings have a much longer life span, writes Passive Design Solutions’ Natalie Leonard. She says ensuring that all new structures achieve significant and permanent energy reductions will require financial incentives to facilitate the replacement of existing homes.
The building sector accounts for 50% of all energy used in North America but has not achieved significant improvements in energy efficiency and carbon emissions like that of the transportation and durable goods sectors.
One part of the building sector deserving attention is detached single-family housing. In 2018 the U.S. had about 83 million detached houses and Canada had about 7.67 million. From January to September 2019 there were 653,300 single‐unit housing completions in the United States, and 45,086 single-family house completions in Canada.
Retrofitting existing houses is expensive and may, at best, only result in energy savings of 30% compared to other dwellings in the same location that have not been retrofitted. On the other hand, the energy savings of new construction can reduce heating costs by 75% to 90%. Moreover, new buildings have a much longer life span over which to amortize and enjoy the additional energy and cost savings.
Photographer: Daniel Acker/Bloomberg
Simply renovating existing houses to improve their energy efficiency, although important, does not give optimal results. Nor is it the most cost-effective approach in every instance. The gold standard for optimizing the energy efficiency of an existing house is its replacement. At first, this may seem excessive. However, there is a rationale for this approach, and it has to do with the rather slow rate at which older, less energy efficient housing is replaced with new, more energy efficient housing.
Given the large inventory of new and existing detached houses, it is clear that any public policy intending to make meaningful reductions to national building energy use must address this housing sector. A net zero passive house replacement can provide significant energy savings, with a design that is durable and low maintenance.
Net Zero Passive Houses
Net zero is defined in a number of ways. A useful definition says that a net zero building is one with zero net energy consumption, meaning the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy created on the site.
Passive house is a voluntary standard for energy efficiency in a building, which reduces the building’s ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or cooling.
Net zero houses are not necessarily passive designs, and passive houses are not necessarily net zero. But augmenting passive house design with modest on-site, grid-tied electrical power generation provides a simple path to net zero that can be implemented for a modest premium: 5% to 15% over code-built alternatives. And they achieve a 75%-90% reduction in heating costs, with annual heating bills as low as $150.00.
Canada’s National Energy Code for Buildings (NECB) 2017 says the “most cost-effective time to incorporate energy efficiency measures into a building is during the initial design and construction phase. It is much more expensive to retrofit later. This is particularly true for the building envelope”, which is the single most important element of an energy efficient dwelling.
The Environmental Change Institute at Oxford University has argued that between 2005 and 2050, 3.2 million dwellings must be demolished and replaced for the U.K. to reach its national energy reduction targets for housing.
The Oxford research recognizes that some dwellings require prohibitively expensive repairs before energy reduction measures can be implemented, and even then, the results are unimpressive.
In the same vein, Low-Income Energy Efficiency Program (LIEEP) contractors in Maryland found significant pre-existing health and safety deficiencies in houses identified for efficiency improvements. The improvements could not proceed until repairs were completed.
Many Attractive Benefits
A net zero passive house is not a “new-age” compromise. Instead, it is a versatile housing solution that provides a number of attractive benefits:
- Significant reduction in heating costs over code-built houses;
- Reduced carbon footprint;
- Superior indoor comfort—the bright, draft-free and consistently warm spaces are what owners most love about their passive house;
- Exceptionally quiet spaces that are isolated from outside noise, even during storms;
- Less complex operational and maintenance requirements due to simpler mechanical systems;
- Comfortable, conditioned fresh air in the living spaces through the use of high-quality ventilation equipment;
- Increased safety and security during storms: even when power is out for weeks, a passive house will maintain temperatures above 50F (10C).
Financial Incentives Needed for Adoption
Providing financial incentives for the adoption of net zero passive house technologies will hasten acceptance by the marketplace and its adoption into the building code, and in our uncertain climate future, this is good public policy.
A net zero passive house is slightly more expensive to build, but excels in the total cost of ownership, a fact not always well understood. Hence, without some inducement, the higher up-front cost of net zero passive houses can present a disincentive to their adoption. Financial incentives can help to overcome this reluctance.
Research in North America shows that financial incentives are particularly effective in overcoming the public’s reluctance to switch to energy-efficient technologies such as the net zero passive house; Research in Europe showed similar findings—“financial incentives and energy performance standards play an important role in promoting energy efficiency improvements.”
It seems likely that increasing the energy efficiency of new and existing North American detached homes will require public intervention. A good first step is changing building codes to emphasize net zero passive house level energy efficiency. Such code changes will ensure that all new structures achieve significant and permanent energy reductions. These code changes should be accompanied by financial incentives to facilitate the transition.