Suggestions for taping insulation

[Navigatorman]

I'm going to seal and insulate the steel HVAC in the attic.

I've been unable to find Polytek or Nashua 367-17 tape at Home depot or Lowe's but did find foil tape by "duck" rated UL181B-FX.

Talking to customer service at "duck" they said the tape would work fine on the metal duct work but not on the "frost King" insulation.

Calling customer service at Frost King about how to tape their insulation, I get this, "Well, if it twas up ta me, I'd git me some of dat dare duck tape"

Can't seem to find Oregon code or suggestions on what to use to seal foil backed insulation.

Code calls for R-8, should I add more for a new variable speed fan unit that runs on low 24-7?

Thanks for any help

Mel

PS Tried to get an answer from the local HVAC people that installed my unit and it's like some kind of secret society, even after spending over 7k with them.

[Ed Imeduc]

First Id have to ask who put just steel duct up in the attic?
Why doesnt it have insulation pin and glued on the inside.
Or why isnt it made out of ductboard??????
You can do a much better job if you take and cut and fit duct board over it all on the outside of the metal. That way you could make it go around the duct and have only one seam. WE us the aluminum iron on duct tape.

ED ;)

[Grady]

I've never seen R-8 ductboard. Is there such a thing (2")?

[Navigatorman]

Ed, thanks for the reply,

I should have been more clear.

It's galvanized metal ducting in the attic with about 1" to 2" of insulation on it with no backing.

I can see the insulation is black from acting as a filter where it's been sucking in air all these years.

I was going to seal then add insulation over the existing.

Should I go more than R-8 with a variable speed blower?

Any suggestions on foil tape that a Home owner can buy?

Thank you

Mel

[Grady]

What you need to do before adding insulation is to strip off the old & seal the joints in the ducts. The prefered method is mastic. Also seal where the duct joins the air handler. This needs to be done on both the supply & return duct systems. As strange as it may sound, the return side is more important than the supply. When installing the insulation, paint the duct with insulation adhesive, wrap the insulation around the duct, & seal the overlap with tape. I use a UL 181 tape & press it down with a squeege. Yes it is a P.I.T.A. but you have a first class job.

[Ed Imeduc]

Grady
I have only use up to 1 1/2" Duct board dont know if it goes to 2" The tape I like to use is Fortifiber-Therm-lock HD
You iron it on. It has green dots on it all over. You have to iron it till the dots turn black. Its listed per UL 181,class1 Then you know its on for good. Im with you for sure seal all drives and slips with masitc.

I can see the insulation is black from acting as a filter where it's been sucking in air all these years.
I think this means that it has no V/B on it "AND THAT AINT GOOD." :eek:

Get started it can get hot up there. Had my AC on now for 2 weeks.

ED :coffee:

[Grady]

Sounds like good stuff. I'll look into it. I can hear my guys now. They gripe about using adhesive & a squeege. You know the attitude....

[Navigatorman]

I haven't heard of using an insulation adhesive :coffee:

I've got the mastic goop also and was planning on giving it a day or two to dry before putting the insulation on and taping it in place.

So just about any UL 181 tape should work?


I duct is sitting hard on the ceiling joices, so do I overlap the insulation 2 " and staple it as I go followed by the tape?

In the crawl space, you can see the duct is insulated and wrapped, but beyond that it's bare. That will come later.

I've got the time right now, the attic is cool and boating season is just around the corner, after that my Wife and I are on the water almost every weekend and nothing else gets done around the house :cool:

Thanks guys for the help!
Mel

[Grady]

I haven't heard of using an insulation adhesive :coffee:

I've got the mastic goop also and was planning on giving it a day or two to dry before putting the insulation on and taping it in place.
So just about any UL 181 tape should work?
I duct is sitting hard on the ceiling joices, so do I overlap the insulation 2 " and staple it as I go followed by the tape?

Thanks guys for the help!
Mel

If you have to, take the duct apart, raise it 6", & re-assemble. Duct can be supported by 2x6's on edge every 4' or so. The key to getting tape to stick is having a clean & dry surface. I'm afraid if you don't raise the duct, you will get condensation which leads to rust, mold, & mildew.

[Navigatorman]

Thanks Grady,

I ended up disassembling a whole section of duct and just starting over on it.

The were one or two sheet metal screws at each joint and zero sealant.

There was a thick coating of dust inside so I just took one of my backpack vacuums up there and filled it up with years of accumulation.

Since we added AC, do I need to wrap the insulation with something to further seal it or is the foil back insulation enough after it's taped.

I'll raise the duct off the joices as much as I can, good idea ;)

Thank you

Mel

[Grady]

I have to commend you on your efforts. Few people would go to the efforts you have. Once sealed, the foil backed insulation is all you need. GOOD JOB

[Ed Imeduc]

The foil on the insulation will work as a V/B for you.
I haven't heard of using an insulation adhesive
yes you can get it in just spray cans might help some. We use it for the black insulation and also pin it.

In the crawl space, you can see the duct is insulated and wrapped, but beyond that it's bare. That will come later.

We dont use or put insulation on the duct work in a crawl space. 6 mil poly on the ground and insulation on the walls.
Might go to http://aboutsavingheat.com/crawlspace.html

ED ;)

[Navigatorman]

Grady and Ed, thank you for your comments and compliments, it's especially appreciated when coming from the pros to an amateur.

The crawl space is vented during the summer months.

I was thinking if I insulated the ducts in the crawl space, it would help save some energy when the AC is on :confused:

I would also insulate the water pipes to prevent freezing.

The furnace/AC is a downdraft type.

Thank you

Mel

[Ed Imeduc]

Did you go to that www. If you vent a crawl space in the summer. The hot moist air from out side comes in and hits the cool ground there and just makes everything down there wet. This humidity just goes up into the home That the poor AC is trying so hard to get out of the home. We put registers in the duct down there for heat in the crawl space.

ED ;)

[Navigatorman]

Well, we have the insulation and tape and it's time to go to work in the attic.

The plan is to move the duct and lay the insulation down and put the duct back in place, elevate the duct as suggested then seal the seams.

Running the insulation the length of the duct, what's the best way to cut it to size and how much overlap should there be before taping it?

The insulation is R-10 and is 4' x 50'

The duct is 22' of 12" and 25' of 16"

Thank you

Mel

[Grady]

WOW, R-10 duct wrap. Where did you find that? The heaviest they have around here is R-7.5, & it is special order.

I would cut the wrap about 20" longer than the circumference of the duct. There might be a little trial & error on that measurment but it should be close & allow a 3-4" overlap. The easiest way I have found to cut the wrap is either with a big pair of scissors or a sharp utility knife. If you use the knife, be sure to use some kind of straight edge as a guide. Put a board under the wrap to give yourself a hard surface against which to press & cut.

[Navigatorman]

Grady,

They sell it at Familian nw in Portland along with all the tapes, great people and friendly help!

Thanks for your help!

Mel

[Grady]

When you get done, or at least into the job, please post back & let us know how things went.