How effective is adding insulation to attics without air sealing?
HelenRein
| Posted in Energy Efficiency and Durability on
It seems to be a big challenge to get contractors in the home efficiency industry to highlight to customers the need to do both air sealing AND insulation work in their attics. My question is, have there been any studies to show the difference in energy efficiency effectiveness between adding insulation only to an attic without also doing air sealing work? Are there also other articles to point to possible dangers associated with not performing air sealing work prior to adding or replacing insulation?
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Replies
From an energy use point of view adding insulation can still be pretty effective, but not air sealing first creates a serious risk of moisture accumulation and mold growth in cold climates. I'm not sure if anybody has done large field studies on this, but acute problems of dripping ceilings and moldy attics are very common when insulation has been added without the requisite air-sealing. This isn't a rocket-science issue requiring parsing the numbers of large databases or anything.
Helen,
On this topic, I like Bill Hulstrunk's opinion. (When I interviewed Bill a few years ago, he was still working for National Fiber, a manufacturer of cellulose insulation. You might think that Bill would have been interested in selling as much cellulose as possible to any customer who wanted it -- but that wasn't true. Bill cared about building performance.)
I'll reprint a section of the interview below. (Your can read the whole interview here: How to Install Cellulose Insulation.)
Q. What is the most important thing to remember when installing loose-fill cellulose on an attic floor?
Hulstrunk: Since you are installing the insulation at a lower density, be sure you do all of the necessary air sealing work beforehand. Air sealing is critical. When homeowners say, “I don’t have enough money to do both air sealing and insulation,” I tell them, “Then it’s better to wait until you have enough money to do the air sealing — otherwise the insulation doesn’t make any sense.”
-- Martin Holladay
if the house is leaky, you're basically using the insulation to filter incoming cold air. Why not simply stop the incoming air so the insulation can work? I built an addition to my house many many years ago with 9" walls and 15" of insulation in the roof. I always wondered why it was so hard to heat and somewhat uncomfortable. When I finally learned, and worked on air sealing, the heating magically started to work better and comfort in the house increased dramatically. Air sealing is critical.