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For some background on how my flexible heating duct was ripped to shreds by a family of skunks, check out this blog.
After evicting my family of skunks, I ventured down under my house to make sure that there were no baby skunks left behind, and to also assess any damage done under the house. Since two of my heater vents just stopped blowing air I was pretty sure that some duct work was damaged under the house. To add to that, we had noticed that we could feel hot air coming out from under our house through one of the air vents. That too was likely a bad sign.
As I crawled under the house, it was clear that there was very little clearance. There were areas where I needed to flatten out and crawl with less than 2 feet above my head. I immediately saw a problem with the ducts. Two pieces of the aluminum ducting had come apart. I was thrilled, as this would be a simple fix.
Separated pipes was the easier of the fixes
As my eyes followed the piece of disconnected pipe, my heart sank, as I saw that the hard aluminum pipe was converted into flex pipe before it attached to one of the main ducts. The flex pipe was torn in several places, and actually ripped all the way through near the pipe. I looked at it closely to see if I could just patch it with tape, but there was just too much damage. My guess is that the skunks ripped open the flex duct to get shelter, and warm air. As they crawled around inside the now exposed aluminum pipe, it became dislodged.
Torn flex duct was a much harder repair
I crawled back out from under the house to think about what to do next. As I crawled out, I noticed that my arms and knees were in pain. I looked at my arms and they had numerous scratches on them. I also had several abrasions on my stomach where my shirt pulled up as I crawled. The problem was that there were tons of cement chunks and pieces under the house… apparently from when the house was built. Sure, just throw whatever junk you don’t want to deal with under the house. Great.
I started watching some Youtube videos on how to replace the flex duct. The steps seemed really simple and I found out that I could purchase the Flex Duct from home depot in a 25 foot section. Plenty for what I needed. Again, the only issue was the clearance. If I had the space, then I was confident that I could do the work. With so little space though, I wasn’t even sure if I could drag the pipe to where it needed to be installed. I’m not claustrophobic, but the thought of being under the house for any length of time at all filled me with dread. I was close to calling a service, just to get an estimate, but I knew that if I did that, I would probably just have them do it. I decided to give it a shot myself instead.
I ordered the flex duct from Home Depot. I had no idea how big the box was going to be… after all, it was 25 feet of 12 inch duct work and that included the insulated layer which was pretty thick. When the box arrived, I was pleasantly surprised. It was only about 3 feet tall and about a foot wide. Note, don’t open the box until you’re ready to use the flex pipe. It is really compressed into the box and will immediately start expanding out of the box when it’s opened.
Flex Duct came in a smaller than expected box
You can see from the images below that the duct is made up of 3 layers. The core is reinforced with a wire wrap. Then the insulation and finally the reflective jacket. As explained in the Youtube videos, the core needs to be secured by tape and straps first, then the insulation and jacket are folded over and secured afterward.
Three layers, wire supported core layer then outer insulation layers
I had bought very long 3 foot zip ties, along with aluminum foil tape to make my connections. The Youtube videos were very clear that you should never use duct tape. Despite its name, it is not suitable for use on heating ducts. The Aluminum tape was a bit of a pain since you needed to first peel off its backing first before applying it but apparently it was far superior to duct tape. There was also another option mentioned in the videos, and that was a mastic sealant that you could use that was apparently even better than the tape. Given the little space that I had to maneuver, I thought it would be cleaner to just use the tape.
I had my tools in a little plastic carrier. I didn’t want to be leaving tools behind under the house. You’ll need wire cutters since the inner lining of the flex duct is wrapped in wire to reinforce it. I pre-cut mine while I was in the back yard and came pretty close to the size that I needed. Since it’s flexible, you don’t need to be exact.
Finally, I had bought some elbow/knee pads. This would help me avoid getting scraped up as I crawled around over the concrete chunks under the house. I also had an old/used N95 mask as well that I brought with me, remembering that it got really dusty under the house.
Step 1, I laid out some cardboard under the house where I was going to be crawling and spending most of my time. Yes, I had my pads, but it still hurt crawling over the concrete chunks and the card board added some padding over the ground.
I made the easy fix first, re-connecting the two aluminum duct pipes. One piece fit nicely into the other, then it was just a matter of wrapping the connection with the aluminum tape. Again, removing the backing was a real pain, especially lying on your side with no clearance, but I was able to get it wrapped. Instead of a single long piece, I used several lengths of the tape, about 12-18 inches in length. That helped me manage the tape with the room that I had to work with.
Connected and taped the aluminum pipes
Next came the harder fix, to replace the ripped up section of flex pipe with the new section that I had purchased. First, I removed the old pipe. I needed my box knife and wire cutters to cut away the old stuff. Box cutters weren’t as efficient for this since the thick insulation required a longer blade to cut through. The wire cutters were fine as I cut through the wire in the inner lining. I was able to cut away much of the tubing that was attached to the ducts. I wanted it as clean as possible so I could attach the new pipe.
I needed 12 feet of the new piping so I slowly dragged it across the crawl space to where I needed it. That was a huge accomplishment on its own and probably the hardest task of the day. Finally, I had both ends positioned where they needed to be. As instructed in all of the Youtube videos, I first pulled the inner plastic lining over the duct. I then taped and secured it using the aluminum tape. For good measure, I also used one of my zip ties as added support. There are ridges on the aluminum pipe so make sure to work the flex duct over those ridges.
Taped then zip tied inner core layer
I then folded over the insulation layer and used two more straps to secure that onto the duct. The videos were adament about securing the first layer with the tape, or paste if you prefer, and then the insulation layer with the zip ties. They sell tools to tighten the zip ties beyond what you can do by hand. I thought this was excessive so didn’t bother.
… fold over outer insulation layers
… and then zip tie that as well
I followed the same routine with the other end that attached to the aluminum duct. I had a bit more room to work with on this end so it was a bit easier.
Same fix for other end of flex duct to finish the job
I was finally done. Now I just needed to haul away the old ripped up duct work. I also crawled around and collected all of the card board. I was finally finished. I was pretty impressed that I was able to do everything in one day. I was happy to be done and out of there. My muscles took a few days to recover. I made one more trip under the house just to check to make sure that everything was staying in place as I turned on the furnace. Luckily, so far, I still have heat coming through all of the vents.
One final job before I wrapped this project up. I was pretty sure that I heard some animal scurrying around inside one of the disabled vents during the winter. Sure enough, when I removed the vent cover, there were mouse droppings inside the duct under the vent. I sprayed everything with disinfectant, and vacuumed up all of the droppings. I repeated these steps for all of our downstairs vents. Hopefully, with the ductwork repaired, nothing else would be making their way through the ducts anymore.
A final note about my project. According to the videos that I watched, usually flex duct is strapped up onto the beams so that it is off of the ground. This would prevent animals from going under the house and ripping it up. In my case, I think the original installers needed to use the flex duct in order to thread it through the low beams and the limited space. There might have been a better path to take, but I didn’t care to solve that problem with this project. I was content to follow the same route for the duct work as before, and to try to keep the animals from getting under the house.
This project would have been much much easier if there was more space under the house. I wasn’t claustrophobic before spending a day under the house, but by the end I was borderline. It was definitely a bit uncomfortable trying to work for a day in such tight quarters, especially while also wearing an n95 mask. Well, if it was hard for me, then I’m sure a company would have charged me a premium to go down there to complete the task. I felt better having saved myself the money.
Video References
Here are some reference videos that we watched to show us how to install our flex duct
Nice video. It’s much harder than this when you’re laying flat under the house. I didn’t use a cable tie gun to tighten. I just hand tightened and it seemed fine.
Another good video. He did more work than I needed to but the flex duct sections were helpful.
