Zero Energy Homes (Home Energy Part 20)
The holy grail of the home performance industry and eco-builders are zero energy homes. A zero energy home is a home that produces as much or more energy than it uses. This is not that complicated if you have a lot of money to throw at power production. We have to be very clever to perform this feat economically.
It is always cheaper to reduce your energy usage first, before calculating how many BTU’s of energy you will need to produce to net zero in terms of energy usage. If you are building a new house it is important to incorporate a passive solar design, and don’t overbuild. The smaller the house, the less volume that needs to be heated and cooled. Also using the earth is a great way to lessen the energy needed to keep a house comfortable. For existing homes it is important to tighten the thermal envelope, insulate as much as possible, install LED or CFL light bulbs, install energy star appliances or remove them altogether where possible, and install a solar hot water heater or an air source heat pump water heater. Then you can work on the behavior of the occupants. Basically common sense behavior such as turning things off when not in use, drying clothes outside, and reducing unnecessary electronic gadgets.
Choosing the Right Power Production
Now the fun part! The top of the list is of course a micro hydro system, if you are lucky enough to live next to a running stream. If not solar is a great option for those with good true south facing exposure without shade. Wind can also be a good option in conjunction with solar if you have the space and wind resources. Wood heat can be a great option for those with a woody property. This will greatly reduce your energy needs, as heating in cool climates tends to be the biggest draw of energy by a home.
I am fortunate that my home produces more energy than it uses, making it beyond net zero. However, if I could do it over again, there are some things I would do differently, but some things were really smart.
First the smart things
-The ICF (Insulated Concrete Forms) walls have been tremendous for energy efficiency, but also for strength and durability. Most people don’t realize that if you have a stick frame home with siding (most houses today), that someone with a box cutter could come right through your walls if they wanted to.
-Insisting on no intrusions, and no ducts in the attic, with an R-50 attic.
-Spray foaming all intrusions, and around windows before drywall and trim were installed.
-Facing the house true south to take advantage of the sun.
-Having the bulk of my windows on the south side to take advantage of passive solar gain, and limiting windows on the north and east side to limit cold northerly winds.
-Geothermal heat and A/C was worth it for me, because I do not have a natural gas line, and I wanted to not have to purchase any energy for the home.
-Solar photovoltaic system installed facing true south with the perfect pitch.
-Battery backup for the solar system.
-Air source heat pump water heater installed.
-Root cellar installed.
-Getting solid double pane windows, but not overspending on expensive windows.
-Painting the metal roof a light colored grey, and the paint lasts longer. This keeps the attic cool in the summer.
-Collecting my roof water runoff into a concrete cistern to water my gardens.
The not so Smart Things
-I should have used the slope of my land to put most of my home under the earth.
-I should have built a smaller home. Granted we use the entire house, but we would have been fine with maybe 500 or so less square feet.
-We should have put up less solar panels. We produce almost twice the electricity that we use. It was overkill, and the resources could have gone elsewhere. I let the builder calculate our projected energy use, I should have done it myself, but I was just learning my trade at the time.
-I should have partitioned the root cellar to have one part be dirt floor, and the other part concrete to vary the humidity levels for different types of produce. I plan to fix this, but it would have been cheaper to do it right the first time.