Duct Sealing - Man vs Machine

        VS.    

(Note: if you would like the full experience and understanding of this article, please go into your crawl space for 8 hours and then come back and read the rest of this post.)

How many of you did that? ZERO. (but seriously, if you did, email me). Why not? Because being in a nasty crawlspace (or even a clean one) for too long SUCKS! My point is, think about how you wouldn't even want to sit in your crawl (or someone else's). Now, think through the list below and tell me how AWESOME of a job you are going to do sealing up a all the ducting in/under the house.

Action Taken to Properly Mastic Seal a Duct System (probable reduction in leakage = 40-50%)

1. Furnace: Any seam that is not part of a maintenance access sealed with mastic.
2. Connections between the furnace and coil or the supply and return plenum sealed with mastic.
3. Joints between the sections of supply and return trunks and branches sealed with mastic. 
4. Long seams running the length of duct sections (manufactured joints) sealed with mastic.
5. Branch take offs from the supply or return trunks mechanically attached with machine screws and sealed with mastic.
6. Connections between the trunk ducts and the branch takeoffs duct to duct connections cleared of insulation and sealed with mastic.
7. Branch ducts runs mechanically attached with machine screws to the branch takeoff fitting and sealed with mastic. (if this is a flex duct run, the plastic duct was fastened with a tension strap, the strap held in place by machine screw and connection sealed with mastic.)
8. Seams on any fitting (Ys, Ts, elbows, boots, etc.) sealed with mastic (this means the seams on elbows, not just the field connections between the elbows and the ducts)
9. Connections between the register boots on the supply and return sides sealed to the subfloor of wall board with mastic.
10. Air side devices that are spliced into either side of the duct sytem (filters, humidifiers, etc.) sealed at the seam where they meet the duct with mastic.

It just is too much to expect from anyone, even someone who is getting paid to do it, to last the whole day in a crawl without missing something. It is just not possible.

So, lets say just by chance that you are an awesome worker and you are ready for the long haul in the crawl (didn't mean to rhyme that...), but you get in there and all your metal ducting is wrapped with insulation...... Are you going to un-wrap all the ducting, do this list above and then put it all back on perfectly? Probably not.

Solution? Below.

Action Taken to Properly AeroSeal a Duct System (probable reduction in leakage = 85-97%)

1. Watch this