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How to Insulate Air Ducts in Crawl Space [Guide]
Insulate air ducts in your crawl space and save money.
Photo: Catherine Falls Commercial / Moment / Getty Images
Photo: Catherine Falls Commercial / Moment / Getty Images
SKILL LEVEL
Intermediate
COMPLETION TIME
4 hours
COST
$100–$500
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What you'll need:
TOOLS
- Respirator or dust mask
- Knee pads
- Headlamp
- Lineman's pliers
- Safety glasses
SUPPLIES
- Fiberglass or natural fiber duct wraps
- Aluminum duct tape
- Caulk
- Steel wire for fixation
Crawl space ducts are often easily neglected when someone is insulating the crawl space. However, uninsulated ducts in the crawl space can lose up to 30% of their capacity, wasting your heating and cooling while driving your energy bill higher. Fortunately, you can insulate air ducts in the crawl space by yourself at an affordable cost. Nonetheless, this is an intermediate project and may be challenging for some.
Angi Tip
Correctly installing insulation can be difficult. Health and safety risks are involved; therefore, we highly recommend contacting a pro to ensure the job is completed safely and correctly.
Purchasing Duct Wraps
Star by purchasing duct wraps for insulation. You will find fiber and fiberglass insulation options in the market. Since fiberglass insulation can be dangerous and also harder to install, we recommend you go for other alternatives. Woolen duct insulation wraps cost somewhere around $100 per 25 feet. We recommend you purchase at least 50 feet of wraps so you don’t need to run back out mid-project to get more.
Make sure you check your local residential building code before buying anything. Most areas will require an R-8 insulation for crawl space ducts, but some places may have a different requirement.
Preparing Your Work Environment
Always ensure a clear path anytime you work in a confined space. Remove any nails, hanging wire, or wood pieces above your head to avoid injury. Declutter the space by removing obstructions or pushing them to the edge. Lay down tarps to gather whatever dust, caulk waste, and insulation waste that may occur.
Cutting the Wraps to Size
Measure the circumference of your air duct in the crawl space and add two inches to the number. That’s the measurement for your insulation wrap. Peel away the foil backing, cut that additional two-inch off, and discard. You now have an insulation wrap with a flap you can use to seal with.
Cut out enough pieces to cover all your air ducts. Stack them aside and make sure they are easily reachable so you don’t have to go back and forth during the insulation project.
Removing Hanging Brackets
Remove the supporting brackets around your air duct with a cordless drill. Remove the screw from the joist then rotate the bracket to take them off. Make sure you have a small bowl to hold the screws since it is easy to misplace small objects in the darker crawlspace.
Furthermore, removing brackets in sections will make your project go a lot faster than removing everything all at once.
Wrap the Crawl Space Ducts
Photo: BanksPhotos / E+ / Getty ImagesSlide the insulation around the top of the air duct. Make sure the aluminum backing is facing upward. Keep pushing the wrap forward and wrap the other side around the air duct. Ensure your hand still has a good grip so it’s easier for you to fasten the edges together.
Overlap the 2-inch foil onto the end of the wrap and seal together with aluminum duct tape. Gently pad or press the tape for extra security. Rinse and repeat until all rectangular ducts are insulated.
Secure the Ducts
Place two steel wires on each section of the duct wrap and twist them tight with a pair of pliers. This relieves stress and prevents your wraps from falling apart by the seam. The section length is determined by your wrap’s dimension. For example, if you purchased a 4ft by 25ft roll, your sections should be 4 feet each.
Wrap the Round Ducts
Repeat the same steps to wrap the round ducts. They typically have a smaller circumference and are easier to conceal. Tape shut and secure with steel wires.
Put the Brackets Back
Put the brackets back as you wrap and secure each section. This is far more efficient than reattaching all brackets in one sitting at the end of the project. Cut a small hole in each bracket, rotate it back up, and reattach it to the joist. Seal the brackets along the edge with duct tape.
DIY vs. Hiring a Pro
Crawlspaces create a tight work environment that poses multiple challenges to someone who is not familiar with insulation work. Additionally, insulation projects are almost always intermediate projects given the associated duration, labor, and risks.
We recommend you hire an insulation company specializing in crawl space and air duct insulation. On average, an insulation contractor charges $40 to $80 per hour plus material cost. Therefore, it’s a better deal for you if you hire someone to insulate your entire crawl space – just make sure you ask them to insulate the air ducts as well.
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