Great Stuff Foam used intead of end cap ? Dangerous ? Crazy ? Okay ?

Old 02-14-17, 10:32 AM
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Angry Great Stuff Foam used intead of end cap ? Dangerous ? Crazy ? Okay ?

Not a DIY, but don't know where else to turn to for good answers !
Hired contractor to remodel kitchen.

Needed vent pipe capped off .

He was supposed to cap off an open hvac pipe that is blowing hot air from the ceiling.

It used to lead to a heating vent in the old wall that was removed.

Instead of using foil duct tape, he sprayed "Great Stuff" foam INSIDE of the 8 inch in diameter active vent/pipe.

I told DH to turn off HVAC heating to avoid drywall dust. Sub didn't even mention turning anything off.

I have looked and looked online but can't find anyone using foam to seal off the entire end of an HVAC vent/pipe.

His excuse for not using the foil tape he had was that it would stick.

Anyone ever use Great Stuff to seal off an entire vent ?

It says it uses a highly flammable gas to expel it form the can and that Great Stuff itself is hugely flammable.
Should we be scared to turn the HVAC back on ?
He used ton in the hole ?
Is this really bad form to use that intead of an end cap ?
Old 02-14-17, 10:50 AM
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Not something I would ever do, sounds like he was to lazy to go to Home Depot. I don't think it would dangerous to leave it.
Old 02-14-17, 11:26 AM
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From the manufacturer.....

6. Cured foam is combustible and will burn if exposed to temperatures above 240F (116C). Do not apply GREAT STUFF™ foam around heaters, high heat lamps or recessed lighting fixtures, radiators, furnaces or fireplaces where it could contact heat conducting surfaces. Do not use GREAT STUFF™ foam inside electrical boxes or panels (applications around the outside of the boxes are permitted).

Probably not the best choice of closing off the end of the duct.... but it shouldn't be a problem.
The ductwork will never get to that high a heat.

You could also still put a metal cap over the end.
Old 02-14-17, 11:43 AM
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Suggestion: Did you pay by credit card? Get him back out to make it satifactory for you on his dime. Tell him to remove the foam and install a cap.
Old 02-14-17, 01:03 PM
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Lazy is a nice word. He was just arrogant enough to not do it right. For $6 he could have done a proper termination. Master Flow 8 in. Round Duct Cap-8DC - The Home Depot

He probably used two cans that cost nearly $5 each. Did I mention dumb?
Old 02-14-17, 04:23 PM
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I'd be more worried about just closing off a duct without replacing it or knowing how it impacted airflow.
Old 02-15-17, 03:34 AM
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Should not be left the way it is IMO.

The foam will likely shrink due to heat and eventually leak and is not a recommended use for this product..
You presumably hired someone to do their job to accepted professional standards which this is definitely not.

Whatever shape this duct is would not use foil faced tape to close.
You would use a metal end cap, either round or square, fastened to the duct with screws and then sealed with foil faced tape or more appropriately mastic duct sealer.

Hopefully he has not yet been fully paid.
Old 02-15-17, 06:34 AM
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Was the contractor licensed and permitted to work in your area? If so sue! If not, you did not do your homework. Sue and report to better Business and the town authorities. You don't want this guy going around doing work for others.

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