How Energy Efficient Should My Home Be?
Beyond a basic economic analysis
I’ve been trying to answer this question for many years. A simple question seemingly impossible to answer. However, it may not be an entirely economic question.
Return on Investment
Energy saving upgrades typically need 10 years or more to “pay back” and “investors” seems stubborn to buy in even at these rates. Energy is simply too cheap and the cost in construction is too high. Maybe the question we need to ask is how much of an “investment vehicle” should our homes be? We don’t expect a return on investment on our cars, our vacations, or the granite counter tops in the kitchen we dream about. Maybe the performance of our homes should be more about investing in quality, comfort and responsibility rather than simple financial gains?
What if energy was free?
Instead of complex math formulas and graphs to project costs and savings over the long haul, I thought I would take a look at the problem another way.
50+ years ago, it almost seemed like energy was free. Wood heated homes across the prairies were heated for “no cost” for 100’s of years. But that story isn’t entirely true. Wood heating a poorly insulated prairie farm house was exhaustive work. It involved hauling, cutting, drying and stacking literally tons of wood as well as the mess and hassle of cleaning out fireplaces. My grandfather talks about moving from the farm to Calgary during the winters and staying in an apartment in Kensington because the farm house was too remote and too hard to heat during the winter months.
But what if energy suddenly became really free today? Imagine a magic technological innovation that makes for no environmental impacts and no cost to the consumer. What would we build for our homes?
We could cut all the insulation out of the walls, go back to single pane glass in the windows and forget about closing the doors in the winter. However, just because the heat is free doesn’t make the home comfortable. Cold drafts, large furnaces blowing massive amounts of air, dryness, dust and dirt would result in terribly uncomfortable homes. There would still be frost on all the windows through the winter and condensation on the walls. Sure it would be cheap to build, but it would be a miserable home to live in.
Performance is key
Even in a “free energy” future we would still want a home that is well insulated, air tight, and well ventilated with good indoor humidity, clean filtered air, a quiet HVAC system, and windows that aren’t drafty or frosted over. All the fundamentals of today’s high performance building would continue to be important in that free energy future.
High Performance Fundamentals:
- R-Values — High level of insulation for warm surfaces even in winter
- Air Tightness — 0.6 to 1.5 ACH for a comfortable draft free home
- Windows — Triple glazed, high R-Value frames and free from condensation
- HVAC System — Small, quiet heating system, evenly delivering heat/cold without spikes in temperature throughout the house and year.
What if energy was 10 times more expensive than today?
At the other end of the spectrum, most people wouldn’t be able to purchase more than a little bit of electricity each month. Heating a typical Canadian home would be impossible and most families would have to make do without. In this case what would we build knowing that we could only afford to buy a tiny amount of energy monthly?
We would want a home that could heat itself, using free heat from the sun and our bodies, and a small amount of electricity used for lighting and appliances. We would want to add solar electric panels so we could make our own power. Using large, well insulated windows facing South we would bring in free heat from the sun and exceptional insulation and air tightness would hold all that heat inside the home. To keep fresh air coming in we would need a very high efficiency Heat Recovery Ventilator, or even the use of ground preheating to provide fresh air throughout the house with no energy loss. Our homes would be so well insulated that they would naturally be very quiet and take a very small, simple heating system to operate. These homes would go beyond being just higher performance and would be classified as “Passive” or “Net Zero”, homes that avoid using energy from the expensive grid.
Passive House / Net Zero Performance Fundamentals:
- R-Values — Very high levels of insulation
- Air Tightness — As tight as possible, 0.6 ACH or less
- Windows — Triple Glazed, high R-Value frames and smaller windows, mostly pointing south.
- Heating System — tiny, or none at all
- Solar Power (photovoltaic) to generate own energy
The interesting thing about these comparisons is that in both extremes the specifications of the buildings look remarkably similar. Either scenario requires very good insulation, air tightness, and high performing windows. Energy cost savings don’t seem to be the driver after all when you look at construction from these extremes.