Barriers to Net-Zero Energy Housing
Existing houses can be retrofitted so they will produce as much energy as they use every year — the technology is available and doing the work would save owners thousands of dollars in energy bills. But most homeowners won’t bother because there are too many barriers in place, a report by Canada Mortgage and Housing Corp. (CMHC) concludes.
The CMHC report, Approaching Net Zero Energy in Existing Housing, says that current energy-efficiency programs aim for overall energy reductions of 20 to 30 per cent, but that in order to achieve a net-zero retrofit, energy use would have to be reduced by 70 to 90 per cent in existing homes.
Among the methods that can be used to reduce energy consumption:
- create a high-performance building envelope using insulation and air barriers and high-performance doors and windows;
- use energy-efficient appliances and lighting;
- use high-efficiency mechanical systems;
- use passive-solar cooling and heating techniques;
- use solar thermal systems and heat pumps;
- offset electrical use with grid-connected photovoltaic (PV) systems.
Last week in Toronto, a demonstration home called the Now House was unveiled to the public. It’s one of 12 demonstration homes in CMHC’s EQuilibrium project, and the only one that is aiming for a net-zero renovation.
It’s a 60-year-old “wartime” house with 1.5 storeys and 1,200 square feet of living space, located in a subdivision of about 200 similar homes. It’s estimated that there are about one million houses in Canada with similar footprints and structure, according to the Now House team. It says if the Now House retrofit design was implemented at a national level, “We could achieve an annual green house gas reduction between 5.4 million and 26.3 million tons, contributing up to 14 per cent of Canada’s Kyoto Protocol emissions-reduction targets.”
The team says if the program was implemented in the U.S., “nearly 4.5 million homes built in the wartime period and up to 70 million single detached homes would benefit, accomplishing an annual reduction of 423 million tons of greenhouse gas emissions. This would equal a seven per cent reduction of the total greenhouse gas emissions produced in the U.S. annually.”
To retrofit the Now House, insulation was upgraded on the flat and sloped roof, exterior walls and basement. A south-facing window was enlarged with high-performance glass. A solar PV system was installed. New appliances and lighting were added, and ultra low-flow showerheads and faucets were installed, along with a grey water heat recovery system.
The CMHC research simulated what would have to be done to retrofit houses of various ages and style across the country to net-zero. “As could be expected, there were differences between climatic regions that influenced the challenge,” says the report. “The region where retrofits were most likely to come close to net-zero energy, mainly through building envelope improvements, was Vancouver.”
Comparing two bungalows built in 1969 – one in Vancouver and one in Whitehorse – the study found that with improvements to the building envelope and a rooftop PV system, the Vancouver house was able to reach net-zero. But the Whitehorse home still fell far short with the same improvements, and the only way to achieve net-zero would be to install a high-efficiency, ground-source heat pump. This would be unlikely to happen because of the cost.
Houses that have larger roof areas, and are thus able to accommodate more PV panels, have an advantage when attempting to reach net-zero energy. The easiest house retrofit is a bungalow, because it’s the most straightforward when upgrading the insulation and air sealing.
“Barriers to actually getting to net-zero energy in existing homes include the challenge of coordinating the timing of a retrofit,” says the report. “Making a project cost-effective depends on some planning – for example, if the siding is to be replaced on a home, that is the time to insulate the exterior and upgrade windows. Mechanical equipment is usually replaced under emergency situations, so a change-out to a higher-efficiency, smaller output unit that coordinates with an envelope upgrade requires a clear plan and timely financing.
Other barriers are the logistics of finding contractors willing and able to do the work required.” But the biggest barrier of all is financial. The report says, “Energy conservation retrofits in the $30,000 to $50,000 range were cost effective when refinancing a mortgage. In many cases, the monthly energy savings outweighed the incremental increase in a mortgage payment. However, a full net-zero retrofit would cost more than this.”
While Canadians have shown they are not shy about spending money on renovations that include flashy kitchens and materials, the report says, “Recent studies show comfort and esthetic benefits far outweigh energy concerns, and very few homeowners assess the economic benefits of their investments by monitoring energy bills or calculating payback times.”
The report concludes that because PV systems are expensive and have long payback periods for small systems, “Unless there are reasonable incentives to purchase and operate these systems (tax rebates, purchase incentives, ‘green power’ premiums for grid-connected systems), most homeowners will not opt to retrofit their house to a net-zero energy home.”
by Jim Adair Published: September 16, 2008
