A net zero home produces as much energy as it consumes
Troy Media – by David Dodge
Belgravia Green is an innovative project where three families built three net-zero homes in a row. It all started when Jeanette Boman and Kevin Taft advertised in a community league newsletter looking for two other families to join the project.
After 40 interviews they selected Les Wold of Effect Homes and another family as their partners.
Today two attractive, modern infill net-zero ready homes bookend a net-zero show home with a large solar array in the middle. All three homes feature different heating systems.
A net-zero home is a home that produces as much energy as it consumes.
While each home has a different heating system, all three homes are very airtight, super insulated and have triple pane windows. This gives Effect Homes the opportunity to see how different heating systems work for future net-zero projects.
All three homes are gas-line free. The three heating systems have replaced the typical gas-fired furnace.
House #1: Geothermal heating
In the first home the heating comes from a geothermal heating system that uses a ground source heat pump. Think of a ground source heat pump as a reverse refrigerator.
A refrigerator uses a heat pump to move heat from inside the fridge to outside the fridge to maintain a pleasant fridge-like temperature. A geothermal system uses a heat pump to move heat from the ground into your house to keep it at a pleasant temperature for humans.
Upfront costs are high for geothermal: the system for this 1,540 sq. foot home costs about $40,000. However, without a gas line and monthly gas bills the operating costs tend to be lower – on par with natural gas when gas prices are really low and much better at other times. There is also a second potential major benefit – you can run it in reverse and use it to cool the home in the summer.
This home reached an EnerGuide rating of 91 which means the home requires little or no external energy.
House #2: Air source heat pump
An air source heat pump is the same as our geothermal system with a major difference. Instead of pumping heat from the ground into the house it pumps the heat from the outside air into the house.
Think of it as a reverse air conditioner. Instead of pumping the warm air out of the house for cooling you’re pumping warm air into the house for warmth. It does this all the way down to minus 15 degrees. After that it uses electric heating to help out on cold winter days.
This system costs about $12,000-$13,000, about the same as a gas furnace with an air conditioner. The operating costs are about 30 per cent less than a conventional system.
Fifty-eight solar PV modules power the house and export electricity to the grid when it produces more than the house needs. These cost about $58,000.
This net-zero show home gets 30 per cent of its heat from passive solar design. Large south-facing windows let the sun shine on a very comfortable concrete floor to store the heat.
The mechanical room in this otherwise whiz-bang home is remarkably empty. The air source heat pump and electric heaters look like a conventional furnace. There is also an on-demand hot water heater and aheat recovery ventilator to provide lots of fresh, preheated air to the home.
House #3: Baseboard heaters
These are simply electric heaters that are scattered throughout the house. While not the most cost effective form of heat, this house has double stud, R56 walls and an R100 roof. While the other houses are super insulated, this house is super-duper insulated
This system costs very little up front, about $4,000. The costs to operate are around double that of low-priced natural gas, but this home is also solar ready so the electric heaters will eventually get their electricity from solar panels.
It costs about 7 to 8 per cent more to make a home net-zero ready. The secrets of net-zero, according to Les Wold, are creating an energy efficient envelope, use of passive solar heating and adding an energy supply such as solar.
While the two near net-zero homes don’t have solar modules at the moment they are solar-ready. Effect Homes is demonstrating that there are many ways to reduce your energy consumption in your home, and you only need to do what makes sense for you.
Troy Media columnist David Dodge is the host and producer of Green Energy Futures, a multi-media series presented atwww.greenenergyfutures.ca. The series is supported by TD, Suncor Energy and the Pembina Institute.