What's Better?
Air Sealing and Insulation
Sealing attic leaks and ducts and installing high-quality cellulose insulation is a cost-effective way to improve your home's energy efficiency and comfort.
When you heat air and send it to the house via the ductwork, the house heats up and satisfies the thermostat, and the furnace shuts off. Well, why does the furnace turn on again minutes later? Answer: because the heat leaked out of the house!
Warm air rises and causes positive pressure between the top of the house and the attic and outside. The warm air leaks out of the top of the house at any holes, leaks, gaps, and seams that it can. This causes negative pressure between the lower parts of the house and the inside. So cold outside air leaks in any holes, joints, or gaps at the bottom of the house.
Besides that, heat moves out molecule by molecule through solid materials that are not insulated well.
Lastly, ducts leak — a lot. The HVAC industry admits that ducts leak a whopping 47% of the air that is forced through them by the fan on the furnace — air you paid to heat. And if the ducts are in the attic, that is the most wasteful kind of leak because the attic is “outside” since it is vented.
If we stop air from leaking out at the top of the house, less air will leak in at the bottom (even if we do nothing at the bottom of the house) because less air needs to be replaced since less leaked out. If we seal and insulate ducts in the attic, it makes a huge difference in the amount of air delivered to the rooms and the temperature of that air.
What are some attic air leaks that need to be sealed? There is a 2” gap all the way around your chimney, can lights in the ceiling, pipe, and wire holes, duct chases, seams between drywall and framing at the top of every wall, the attic hatch, around ceiling fans, and many other potential leaky building assemblies. Knee wall spaces in cape cods and contemporary homes are very problematic, making the adjoining rooms cold in winter and hot in summer.
Once the attic is air-sealed properly, then 17” of cellulose insulation (not fiberglass) is blown in. That’s the amount you need. It’s R60. Most people have R19 or less now.
Air sealing and insulating costs far less than solar or a high-efficiency furnace. The return on investment is far, far higher.
Think about it. If your house is leaky (and ducts are leaky), why spend lots of money on more expensive energy (solar is “free energy,” but costs $35,000 — or some such number plus 25 years of interest, so it is NOT free!) only to waste that more expensive energy on a leaky house? And if heat doesn’t stay in your house very long, why worry about how efficiently you are extracting that heat from the natural gas (or other fuel) you buy? Your furnace may be 80% or 94% efficient, but you are running that heat into 60% efficient ductwork into a 40% efficient house!
Fix the house and the ducts first! That is the answer.
It’s cheaper, faster (one or two days), you’ll save more money and have a higher rate of return, and it will make your home more comfortable with fewer drafts — something the other two options do not do.
