Energy Planning on the Scale of a House
If the state of Maine had a comprehensive energy plan, we would now be busy weatherizing our buildings, optimizing transportation, electrifying a range of things from heating to cooking, driving, creating light rail service and more. We would be building solar systems and wind farms and establishing islandable community microgrids to make our electric power supply more resilient and more secure. In short, we would be building a sustainable economy.
Let’s not let the lack of such a state plan distract us. No one can stop us from laying our own plans and executing them at our own scale. The more we engage in such planning, the more prepared we will be to participate in planning on a larger scale.
A house that is super-insulated on all six sides with no thermal bridges, sealed air-tight, supplied with fresh air pre-warmed by heat recovered from any exhausted stale air, and equipped with “passive house grade” windows and doors, that house would use 90% less energy than a typical Maine house. That house could even end up using no purchased energy at all—or even be a net-positive renewable energy producer. Such houses are built every day in all climates around the world.
Alas, most Maine houses—even new ones—fall far short of such performance. Since each homeowner is solely responsible for everything about his/her building, he or she is exclusively to blame for 40% of our local share of climate change—not to mention our wastefully spent energy dollars. Why not, instead, be a part of the solution?
Typically up to half the heat loss of a Maine house is due to air leakage. The rest is due to insufficient insulation, thermal bridges and poor quality windows and doors. To determine how a specific house stacks up against the average, rely on a professional energy audit report for itemized recommendations, including an estimate of energy cost-savings to be expected. Use this information to make a plan and to decide what, if any, work to hire out.
Our sample house used $4,610 worth of energy per year at the time it was audited. Of this, $3,513 went for heating, $317 for water heating, and $780 for electricity. The house has excellent solar potential—over 96% year round. Air leaks account for 42.2% of the home’s heat losses—equal to 7.1 complete air-changes per hour, as measured by a blower door— followed by 25.1% lost through the basement ceiling, 18.6% through the walls, 9.2% though the attic floor, 3.6% through the windows and 1.4% through flawed pipes and ducts. A potential annual energy cost reduction of 72% could be realized from executing the improvements recommended in the following chart:
|Recommendation, (7 year payback)||1st year savings1||Break even cost2|
|Lower hot water temperature to 120ºF||$40||(no cost)|
|Remove window screens for winter||$96||(no cost)|
|Seal air leaks||$1,420||$18,736|
|Insulate crawl space / basement ceiling(s)||$834||$11,000|
|Install interior storm panels||$211||$1,268|
|Insulate hot water pipes||$47||$627|
|Insulate knee walls||$106||$1,397|
|Install heat retaining ventilation||$131||$1,728|
First, let’s set an overall energy goal, e.g., zero purchased energy consumption in 15 years (by 2033). Among several ways to realize this goal, let’s work on reducing current energy consumption by 72% by 2025. The remaining 28% can then be realized by replacing the fossil-fired heating system (left in place as a back-up and saving the cost of removal) and the water heater with electric heat pumps, and by installing a solar PV system.
15 years is a long time, so let’s be flexible in planning. We may be able to accelerate this schedule, and improved or new technologies may emerge. The home’s current energy cost can serve as the annual budget to finance as many improvements as possible, in effect “reprogramming” that wasteful expense.
However, it could be advantageous to borrow money up-front to accelerate the improvement process and use the sooner-realized savings (vs. the current costs) to repay the loan. Flexibility in planning is important, but so is the discipline of staying within our “budget” of current costs, based on which all projected savings have been calculated.
More on this next time. For now, I’d like to challenge you to lay out the task-schedule for the first 7 years, either for this sample house, or for your own, based on recommendations in your own energy audit report.