Red Devil 0841DX F-Seal 181 Fiber Reinforced Water Based Duct Sealant, 1 Gallon, Gray

I sealed my ducts in the basement and now my basement is not that cold anymore in the summer when my A/C is running. Now I know how much money I had wasted for the last 10 years :-). Now my upstair has more air flow and cooler.

I bought this to fill a small ducting leak in my a/c but also applied it to my house when doing stucco repairs on holes left behind by the last sprinkler timer on the outside of my house. It dried perfectly and painted over very well. I docked it a star because I noticed the canister developed a leak while dispensing the contents on the first use. I wasn't using much pressure with the caulk gun so not sure why it happened so easily. However, it did seal itself so I can continue using it. The packaging needs some improvement, though.

great buy great buy great buy

I used Red Devil F-Seal 181 to seal the joints and seams on my HVAC ductwork, and I'm very impressed with the results. It was easy to apply, spread smoothly, and dried into a durable, flexible seal. After sealing the ducts, I checked the surface temperatures with an infrared thermometer. The photos show the difference—one section measured about 78°F, while the sealed insulated duct measured around 69°F. That gave me confidence that sealing the leaks helped reduce air loss and improved the system's efficiency. A little goes a long way, it cleans up easily while it's still wet, and once cured it forms a tough seal. If you're looking to improve your HVAC system and stop air leaks, I highly recommend this product. Made in the USA is an added bonus

I purchased this mastic in order to seal all of the joints in my heating and return ducts that were accessible in my basement ceiling. It was exceptionally easy to apply…much like spreading toothpaste with a paint brush. It goes a long way! The mastic did not have an odor, and it dried very quickly after application. This job took me a few days to complete, and I used a new brush each day. I also put a layer of plastic wrap on top of the mastic before closing the lid with a rubber mallet each day, and this kept the mastic from drying out. Because the majority of the duct work in my basement is up in the ceiling between the joists, and close to the plywood of the flooring above, I adapted some cheap 2-inch paint brushes so that I could actually brush the mastic on top of the joints. I bought cheap paint brushes that have wooden handles, and I trimmed the bristles quite short. Then, I cut off about half the length of the wooden handles with a hacksaw, which made little “stubbie” brushes. These shorter brushes allowed me to apply the mastic at the top of the duct work, and they made the application easier and more affordable. I do recommend that you wash the joints of the duct work before applying the mastic so that the mastic adheres well. I actually washed all of the outer surfaces of my duct work before starting this job, and I was stunned at the 38-years of dirt and dust that I was able to wash off. I also wore disposable vinyl gloves when applying the mastic, as doing this job was quite messy. It was, however, easy for me to rub the dried mastic off of my skin with hot, soapy water. After the whole job was finished, my husband and I definitely noticed an improvement in the heat flow in our home. No more cold spots upstairs in the bedrooms, and no more hot spots in the basement due to leaky ducts. I hope we also notice a change when the air-conditioning is turned on this summer!