Sealing my Air Ductwork

GvilleRenovator · 11-08-09, 08:22 PM

After looking around in the attic, I noticed that the ductwork was leaking at nearly every joint. I have not done this before, nor did I stay at a Holiday Inn Express last night.

I HAVE watched a crew replace the duckwork in a rental of mine though. I watched very closely thank goodness.

This is how most joints looked before I started.

I cut off the tie wrap holding the flex duct.

Oddly, on this side of the house, each duct was sealed with duct tape. Even after 20 plus years, the duct tape was holding strong.

After removing the tape and straightening the tabs some, I removed the steel adaptor from the duct board.

At least at the beginning the joint probably did not leak as much. Since the tiny bead of silicone was coming off though it leaked now.

GvilleRenovator · 11-08-09, 08:37 PM

I used Mastic from a local big box Hardware store.

I slathered up the joint good and messy.

Carefully slid the adaptor back into the duct board and bent the tabs back over to hold it in place. (Be Careful NOT to cut your fingers!)

Then I slathered up the joint on the ouside, making sure to get more on than I figured was needed just for good measure.

I also put a generous amount of mastic on the outside of the adaptor for the next step.

GvilleRenovator · 11-08-09, 08:50 PM

Then I slid the inner plastic portion of the flex duct back on to the adaptor and put on a tie wrap to hold it in place.

Then another layer of Mastic over the duct to help seal things up.

Pulling the fiberglass back down and getting it covering the whole joint.

Then pulling the outer layer of the ductwork down and putting the last tie wrap in place.

I have finished about half of the house. I am doing both joints at either end of the flex.

Daox · 11-09-09, 06:57 AM

Nice work. It looks like you could have been loosing tons of air out of that leak! Hopefully you'll see your energy usage drop accordingly.

How do you like the mastic? I tried to find it around here but ended up just going with aluminum tape (which I have yet to use).

GvilleRenovator · 11-10-09, 11:58 AM

I like the Mastic.

The only issue would be if you did not like getting your fingers messy.
(cleans up MUCH easier than Great Stuff)

I used a utility brush from the paint department for spreading it around. It was the closest thing I could find to what the A/C crew was using.

I have not found it in all of the big box stores, I had to keep my eye open.
I always keep a list of things to look for when I visit another city too.

AC_Hacker · 11-19-09, 09:34 AM

It's interesting that with hydronic heating, water is piped around the house rather than air. Since water has a much higher heat carrying capacity per unit volume,much less of it is required to do a particular heating job, so the pipes are much smaller and easier to route and insulate than air ducts.

Probably no consulation with your current project.

Regards,

-AC_Hacker

11-08-09, 08:22 PM	#1
GvilleRenovator Greening Renovator Join Date: Aug 2009 Location: Gainesville FL Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	Sealing my Air Ductwork After looking around in the attic, I noticed that the ductwork was leaking at nearly every joint. I have not done this before, nor did I stay at a Holiday Inn Express last night. I HAVE watched a crew replace the duckwork in a rental of mine though. I watched very closely thank goodness. This is how most joints looked before I started. I cut off the tie wrap holding the flex duct. Oddly, on this side of the house, each duct was sealed with duct tape. Even after 20 plus years, the duct tape was holding strong. After removing the tape and straightening the tabs some, I removed the steel adaptor from the duct board. At least at the beginning the joint probably did not leak as much. Since the tiny bead of silicone was coming off though it leaked now. Attached Thumbnails

11-08-09, 08:37 PM	#2
GvilleRenovator Greening Renovator Join Date: Aug 2009 Location: Gainesville FL Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	Part 2 I used Mastic from a local big box Hardware store. I slathered up the joint good and messy. Carefully slid the adaptor back into the duct board and bent the tabs back over to hold it in place. (Be Careful NOT to cut your fingers!) Then I slathered up the joint on the ouside, making sure to get more on than I figured was needed just for good measure. I also put a generous amount of mastic on the outside of the adaptor for the next step. Attached Thumbnails

11-08-09, 08:50 PM	#3
GvilleRenovator Greening Renovator Join Date: Aug 2009 Location: Gainesville FL Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	Part 3 Then I slid the inner plastic portion of the flex duct back on to the adaptor and put on a tie wrap to hold it in place. Then another layer of Mastic over the duct to help seal things up. Pulling the fiberglass back down and getting it covering the whole joint. Then pulling the outer layer of the ductwork down and putting the last tie wrap in place. I have finished about half of the house. I am doing both joints at either end of the flex. Attached Thumbnails

11-09-09, 06:57 AM	#4
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Nice work. It looks like you could have been loosing tons of air out of that leak! Hopefully you'll see your energy usage drop accordingly. How do you like the mastic? I tried to find it around here but ended up just going with aluminum tape (which I have yet to use). __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

11-10-09, 11:58 AM	#5
GvilleRenovator Greening Renovator Join Date: Aug 2009 Location: Gainesville FL Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	Mastic GOOD I like the Mastic. The only issue would be if you did not like getting your fingers messy. (cleans up MUCH easier than Great Stuff) I used a utility brush from the paint department for spreading it around. It was the closest thing I could find to what the A/C crew was using. I have not found it in all of the big box stores, I had to keep my eye open. I always keep a list of things to look for when I visit another city too.

11-19-09, 09:34 AM	#6
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Hot Air vs. Hot Water.. It's interesting that with hydronic heating, water is piped around the house rather than air. Since water has a much higher heat carrying capacity per unit volume,much less of it is required to do a particular heating job, so the pipes are much smaller and easier to route and insulate than air ducts. Probably no consulation with your current project. Regards, -AC_Hacker