Today, I’m a card-carrying believer in sealing up our homes against uncontrolled air infiltration. The 24/7 exchange of air between our living space and outdoors is a huge, powerful, very real and negative force.
I didn’t always believe this. In our first few years, we’d been insulating attics with cellulose insulation for homeowners.
- We rarely removed the old, nasty insulation.
- We never sealed around penetrations in the ceilings, like bath fans, AC vents, holes for wires & pipes.
- Chases? We didn’t know what to do with those. So we ignored them.
- Basically, we just put the fresh, new insulation in the attic. As for prep work, we did the obvious and necessary things.
But we never even thought about sealing the ceiling first!
Professional building analyst, (and friend) Jeremy Draper was one of the first to challenge my thinking. You see, I saw those little gaps and voids in ceilings, every day. They are common in every attic I was working in! Those small holes, seams & gaps appeared so insignificant, and unrelated to the comfort issues my clients were suffering from.
My pragmatic leanings led me to discount the total, cumulative effect of the many places in an average attic floor where air slips through!
I was on a project with Jeremy, where we removed the old attic insulation, sealed all of the penetrations and wall plates in the attic floor, before adding the fresh, new insulation.
Before we started, we set up a blower door, and noted the air changes per hour in the house. (Air changes per hour, [ACH] is a number that represents how many times the volume of air inside the living space is completely replaced with air from outside the living space). Note that the air from outside the living space is unfiltered, unconditioned air, that your HVAC system has to heat & cool again.
When we had finished the attic insulation upgrade, we again set up the blower door, and performed the same test to arrive at an ACH number.
I could hardly believe my eyes! We had made a significant improvement in those elusive air changes… something like a 20% reduction I think. (This was around 2005, and I’ve seen way too many blower door numbers to remember that one).
The picture with this article is a piece of fiberglass attic insulation I removed from an attic this week. Those dark black stains are not mold or mildew. No, that’s dirt that is filtered from the air, 24/7, as it passed through this fiberglass insulation, trespassing into (and out of) the living space.
Dust, allergens, organisms, bugs, smells, drafts, hot & cold zones, and noise are among the many negative consequences of uncontrolled air infiltration in our homes.
Does “airsealing the attic floor” really help? Well… science doesn’t lie. We do this every day for Atlanta homeowners. Last week, the test-out blower door number indicated that we had dropped Ms Homeowner’s ACH by OVER 30%… simply by removing the old attic insulation, thoroughly sealing the attic floor, and installing fresh Applegate cellulose insulation to R-40.
In her written review, she was very pleased with the improved comfort in her home.
The Improved Air Quality in her home is an even bigger BONUS!
Those little voids, gaps, and seams the size of your pinky finger, … they really do add up!
We’re here to help. Our mission is to be part of the solution to your uncomfortable, unhealthy home. Call or text our office phone (404-538-9168). Or, use the contact form on this page. Let us help.