Sealing Air Leaks

handy man88

What's the best way to seal air leaks through AC ceiling registers without going into the attic?

Are these registers built kind of flimsy?

Can one just just either spray foam through obvious holes after removing the grille or better yet, use the uber expensive Nashua 324A foil tape on the inside of the register after removing the grille?

What kind of companies out there actually provide this service? Maybe insulation companies?

Ron6519

I don't understand the issue. You have air coming out of the vents and you want to seal what? The vents themselves? Air coming out the sides of the ceiling mounted vents?
Ron

handy man88

From the outside of my house, I can see some hotspots (frost in some areas and not in others) on the roof directly above where the vents are located in the rooms.

I had plenty of insulation installed earlier in the year, so my guess is that the registers have some leaks in them....thus "air coming out of the siddes of the ceiling mounted vents."

With all my insulation, it may be less likely radiant heat getting through, but blown air.

Therefore, I'm considering DIY sealing the registers from the living space using either foil tape or mastic.

Or, hiring a contractor to get into the attic and find all the ceiling penetrations and sealing them.

Ron6519

So go into the attic and look around. Why do you need some contractor to do this? Are the ducts above the insulation? Are the ducts insulated?
Were the duct penetrations through the ceiling sealed before the attic insulation went in?
Ron

handy man88

I have about R-59 of fiberglass insulation in my attic. That means all the penetrations (about 24 of them) are buried in over 2 feet of insulation. Even with the cold weather (compared to summer), I don't really want to climb around on rafters and guessing where I'm stepping.

The flex ducts are insulated. I just think that over time, there may be air leaks where the insulated part meets the actual register. I mean, why else would there be hot spots on the roof directly above where the registers are located? Any guess?

That's why I'm considering applying mastic from the living space first to see if it addresses the hot spots on the roof before hiring someone.

Ron6519

I can't see a leaking duct at ceiling level, under all that insulation causing a hot spot on the roof.
Vents from baths an the kitchen can penetrate the roof and also the insulation level. That can cause warm areas.
Ron

handy man88

I'm probably going to have all the penetrations sealed....heat registers, pipe penetrations, etc.

Looking at the roof from street level, you can see what looks like hot spots in the areas where there are vents in the bedrooms and bathrooms by the windows.

I just want to note that the "hot spots" that I see aren't melting snow, but frost, so maybe I'm overthinking this. Not positive.

Insulation is good at retaining radiant heat, but not blowing hot air.

That's my best theory based on what I see. I can't think of anything else.

Ron6519

If you can post some pictures of the various spots on the roof you've referred to, it might help.
Ron