Can I seal vent to drywall with Duct Tape?

9 years ago

This actually relates to bathroom ceiling vent fans that were recently installed to replace some older units. Due to a size different between the new and old fans there is a gap between the edge of the fan and the drywall. Also the bottom of the fan sits on top of the drywall and does not actually enter the drywall hole in the ceiling.

There is also a small cosmetic issue: You can see through the grill and see the rough "seam" between the drywall and the edge of the vent.

I'd like to run some duct tape to wrap slightly around the edge of the drywall onto the painted ceiling to seal this. The vent grill overlaps the vent opening by an inch or two so a 1/2 inch or so wrap of tape on the ceiling wouldn't be visible. Also, the ceiling was recently painted with a nice semi gloss finish so I'd think this would be a nice clean surface for the tape to grip.

It seems to me this would be good both for the cosmetic visual issue and to seal the gap between the vent and ceiling. But I was wondering if there are reasons this wouldn't work well.

Also - should I use regular "duct" tape for this or HVAC foil tape?

This post was edited by lsimon77 on Thu, Jun 19, 14 at 20:53

Featured Answer

energy_rater_la

9 years ago

duct tape won't last.
order Hardcast brand 1402 mastic tape from hvac supply.
this is the only tape I use...because I'm not big on re-doing
work. Hardcast is strong with a thick mastic backing &
will stick to both sheetrock and metal. surfaces must
be clean & dry, press well to seal tape in place.

bath fan covers, supply grill covers etc cover oversized
holes. use the hardcast to seal all these areas.

it is worth every penny of the $30 you'll spend for the tape.

best of luck

see pic:

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Comments (7)

ken_adrian Adrian MI cold Z5
9 years ago
I'd like to run some duct tape to wrap slightly around the edge of the drywall onto the painted ceiling to seal this.

++>> a picture might be worth a thousand guesses ..

what about something like at the link ... i used it as an edge to drywall in a certain application ...

ken
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Here in California the regulations require that a different company test the duct system for leaks (it can not be the outfit which installed the heating/cooling system) this is a good practice imo. wish we had those standards in place here. flex people diss hard pipe hard pipe people diss flex. here is my experience. flex leaks at the plenum and the supply box. hard pipe leaks at all 90's the long seams and all connections. most hard pipe that is unwrapped has dust marks at the leakage sites where air has moved thru insulation. flex usually is dirty at plenum and supply box. hard pipe is more expensive, and is wrapped when installed, leaving little time to mastic seal. and once it is covered up...who knows how well it was sealed? sealed hard pipe is a beautiful thing. flex does have more resistance to air flow, but the ducts are usually sized to overcome the resistance. pros and cons for both. try to avoid the companies that bad mouth the other ducting. make sure that connections are mastic sealed. not duct tape, foil tape. paint on mastic or mastic tape. I test both types, unsealed hard pipe leaks much more than unsealed flex due to the sheer amount of leakage areas. both can be well sealed. just takes the want to do so. best of luck
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jackfre
9 years ago
Duct tape is good for just about anything other than that for which it is named. In an HVAC application it will generally blow away in about 90 days. That is for the good tape. ER is right on the money with his suggestion and experience.
lsimon77
Original Author
9 years ago
Thanks for the info.

Just to confirm your thoughts: Is this a completely different tape then the HVAC foil tape sold at the big box stores like Home Depot or Lowes? Would those work for me?
energy_rater_la
9 years ago
you are welcome.

Hardcast 1402 is not sold at box stores
it is a hvac supply product.
foil tapes won't adhere to the sheetrock
and the metal flange. mastic tape will.
as you can see in pic it is silver with red
writing.
box stores may carry Nashua brand mastic tape
an inferior product in my experience.
mastic is thin, adhesion is not as strong.
not worth the labor to replace when it fails IMO.

here is an ebay link..not where I purchase from...
but quick google search of product:

http://www.ebay.com/itm/HVAC-Hardcast-AFG-1402-Rolled-Mastic-Duct-Sealant-Tape-3-x100-Topmost-Quality-/321032199173

take a look at the link..so you'll have an idea of what
the roll looks like. not silver with blue writing...red writing..
other types do not seal long term

pricy, but worth it as it lasts...according to johnston supply specs for 40 years. I can only vouch for 15
years when I first started using Hardcast.
I have a real problem with having to go back & re-work
previous work..thus the use of this specific brand of
specific tape.

if surfaces are clean & dry...it will seal to just about
everything, stucco, cement & dirt excepted.

once you use this product...you'll use it for
lots of things.

best of luck.
Eva Kuo
6 years ago
We followed energy-rater-la's advice and sealed all of the indoor duct boots to our drywall plus the mastic on the inside of the duct boots. We picked up the tape at Ferguson's / Air Cold Supply in Phoenix. I just walked into the supply house, picked up the tape and paid cash. Roll of tape was $80 and the CCW mastic was about $20. We ended up using 2 rolls of the tape and a few buckets of mastic - but we have (2) AC units and lots of ducts.

We took our time and sealed a few duct boots and registers each weekend.

WOW! ... Noticeably less dust in the house. We can really tell the difference in our master closet where the dust would collect on our clothes. Less dust in the filters, too. We've also seen our AC usage drop by roughly 20%.

What a great, easy to implement home improvement!! Paid for the mastic tape in 1 month. We could not be happier.

Thank you energy-rater-la.
energy_rater_la
6 years ago
great! and kudos for using the right product.

prices sure are higher in Phoenix for mastic tape!

Can I seal vent to drywall with Duct Tape?

energy_rater_la

Comments (7)

ken_adrian Adrian MI cold Z5

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