Comfort and Common Sense
by: Paul Kando
Highly energy efficient houses are more comfortable and cost less to heat. Comfort depends on the seasons. It is nice to lose heat on a hot summer day, but in winter we need the warmth of a heated room, perhaps the radiant heat of a wood stove. On a hot day it feels good to have a fan blow air toward us, something we certainly don't want on a cold day. We sweat on hot days to lose moisture, cooling us as it evaporates. In summer high relative humidity makes us uncomfortable because the humid air will not absorb our own moisture. In contrast, higher humidity in winter keeps us from being chilled due to moisture loss. In short, our comfort depends on (1) whether we are absorbing or losing heat, (2) whether moving air blows toward or away from us, (3) whether we are absorbing or losing moisture, and (4) have an ample fresh air supply. A highly energy efficient house will deliver such year round comforts at a reasonable cost, even as it provides plenty of clean fresh air, free of pollutants like mold, radon or combustion byproducts.
Common sense suggests that a comfortable house must, first, control the flow of heat, air and moisture and, second, provide external energy, as needed for heating, hot water, lights, cooking and other necessities. Unfortunately, because it relies on once-inexpensive heating fuels, the typical American house has these priorities backwards: most of us are stuck with houses that are under-insulated and leak air like a sieve, but have over-sized heating systems.
Moisture freely moves around a house in the form of water vapor until the air that absorbed it cools. Then the vapor condenses, often where we do not want it -- inside our walls, on the underside of our roof, on windows and doors, even on walls or ceilings. In a liquid state, moisture causes mold problems and rotting of the structure, often unnoticed until the damage is severe.
The traditional remedy has been to "let the house breathe". Indeed, leaky houses "breathe" profusely, enough to let excess moisture escape with the warm indoor air. Leaky houses waste a lot of energy, burning more fuel to make up for all that lost heat. Our last century builders must be forgiven: for one thing, they didn't know any better; for another, heating fuel was plentiful and inexpensive. No more.
Our challenge now is to make up for these built-in defects of our charming old homesteads. How, short of demolishing what's there and starting on a more sensible footing anew? It would be easy to talk in generalities if all old houses were alike. Alas they are not. Some were built using one framing system, with additions using another. Attempts to add insulation over the years may have met with various degrees of success. The average Maine house loses over one-third of its heating energy through air leaks, but some houses leak much more than others. In some houses it is fairly easy to access trouble spots in need of remedy, in others only with difficulty. Where does your house fit in?
It would be foolish and shortsighted to build any new building but the most efficient, i.e. one that meets the Passive House (PH) performance standard, which, regardless of first cost, will save thousands of dollars on heating costs. As for existing buildings, the general principles of PH construction -- super-insulation, air-tightness, no thermal bridges through framing members, heat recovery ventilation and good windows/doors - apply as well, but must be tailored to each individual case. For this reason the common sense approach to reducing heating costs in an existing house begins with determining current conditions and carefully planning what must be done and in what order. Only an energy audit can reliably provide the necessary information, including an idea of how the cost of every step to be taken will be paid back from energy cost savings within a reasonable time.
Common sense also suggests that we treat our current energy costs as our energy budget. The $3,000 or more one spent on fuel oil last winter is that budget. It will rise if fuel prices rise. We can keep spending this budget on oil or propane year after year, or spend some part of it each year to permanently reduce our fuel consumption. One thing is certain, the longer we delay in "reprogramming" our energy budget in favor of permanent improvements, the more money we waste.
Once we have "stopped the bleeding", by maximizing our home's energy efficiency, exciting new avenues may open up to get off expensive oil or propane. In these columns we regularly explore energy conserving techniques that have worked in existing houses, in the hope that some of these will help you tackle your own home. We also consider alternative ways to heat an already energy efficient house. It all begins with energy efficiency and knowing where to begin.
Being energy-wise doesn't mean a chilly winter home. Passive houses are noteworthy for both their energy-efficiency (at least 90% better than the average house) and their comfort. Energy efficiency means even indoor temperature, comfortable humidity, and healthy, clean air at the lowest cost. Keep this in mind in your planning.