What Is a Net Zero Energy Building?
A Net Zero Energy (NZE) home is one that is designed and constructed to produce as much energy as it consumes on an annual basis. There is also a level that focuses on high value air-tight and super-insulation, and allows the Renewable Energy equipment to be easily added later, named Near Net Zero Energy, (NNZE).
Why are Net Zero Energy Homes important?
Buildings consume approximately 40% of energy and carbon emissions. Homes are 17% of National Green House Gas (GHG), problems – mostly from Natural Gas in space and hot water heating applications. Getting to Net Zero Energy and Zero Carbon requires reducing base electrical, heating, and hot water loads by 50-90% first by Energy Efficiency measures like super-insulation and solar heat pumps to reach the heel of the diminishing returns curve. The final 10% is still quite expensive using Solar PV, although the installed cost was coming down in the past few years.
Natural Resources Canada and Department Of Energy in America have been working for close to 10 years on developing the path to Net Zero Energy Buildings. It has grown from obscurity to inevitability during the past five years. California law requires all new homes (~60,000), to be Net Zero by 2020, only three years from now. Plans also include retrofit and commercial buildings by 2030. Ontario and BC plan to achieve zero-carbon buildings with targets for 2020, 2025, and 2030.
The EnerGuide rating demonstrates the energy performance of a home with Zero or lower being the best on the rating scale. The lower the number, the better energy performance of the home. A rating of zero Giga-Joules per year meaning it produces as much energy as it consumes yearly. As a guide, it takes approximately 1 PV panel to offset 1 GJ at a $1000 cost. Conservation is the critical first step.
Benefits of Near Net Zero Energy Homes
- Low utility bills — save money on annual energy costs and be protected from future energy price increases.
- Highest comfort — enjoy healthy indoor air quality, even temperatures, more natural light, and silencing from noise sources.
- Lowest carbon choice for the environment — minimize the home’s greenhouse gas emissions and environmental footprint, conserve resources and reduce pollution.
- A sustainable future — help make sure that future generations have healthier housing choices, clean air to breathe, clean water to drink, and a safe, healthy world to live in.
Achieving Net-Zero Energy
In order to create a net-zero energy home, there are three basic elements or steps to consider when designing and building the house:
- Conservation. Minimize the home’s energy requirements. An average 100 GJ home would insulate to R60 ceilings, R40 walls, and R10 under slab, and make air tight to 1.5 ACH @50pk to achieve 40 GJ total. Minimize the appliance, lights, and water heating consumption. Energy Star appliances, LED lights
- Recovery. Include a Heat Recovery Ventilation system to pre-heat fresh air using exhaust air, Drain Water Heat Recovery to pre-heat city water using shower water, and Solar or Air to Water Heat Pumps for efficient space and water heating.
- Generation. Add Solar PV or Wind power (can be purchased), to balance the home energy demand.
How Much Does Net Zero Energy Cost?
The current Building Code baseline in Canada is EnerGuide 80. According to a recent NRCan study the cost to achieve 25% better is 3%, 50% better is 6%, 75% better is 15%, and 100% Net Zero is 35%.
It makes economic sense today to build 25-75% better than EG-80, when the cost vs. savings favor Near Net Zero Homes. By comparison a Passive House is approximately the same efficiency at the 75% lower than EnerGuide 80 level. The US DOE uses a figure of $2-8 per square foot of added incremental cost after incentives.
The Energy Efficient Mortgage
When the additional 5-10% cost to reach Near Net Zero Energy is part of the mortgage, the net payment amount for Principle, Interest, Tax, and Heating is often less than a Code Home. This is because the incremental mortgage amount is completely offset by the Utility bill savings.