Fixing a Major Attic Heat Leak (Before & After Thermal Scan), by David M on YouTube. 1 min 8 s.
- Video length
- 1 min 8 s
- Time to do it
- 3 hours
- Difficulty
- Medium
- Steps
- 9
What you need
Steps
Warm the house first. Run the heating for an hour so the temperature difference between the rooms and the attic is big enough to show up clearly on camera.
Climb into the attic with the infrared thermal camera and scan the ceiling plane above the warm rooms. Bright patches mark where heat is escaping.
Mark the outline of each hot spot with tape or a marker so you can still find the gap after you put the camera down.
Seal every gap at the ceiling transition with vapor barrier sealing tape. Press it flat across the joint so no air can pass through.
Measure the bays between the joists. Standard framing is 15.5 inches wide, which takes an R-19 batt.
Cut framing lumber to fit each bay and fix it in place so the insulation has something to sit against and stays put.
Cut R-19 fiberglass batts to length and press them into the bays. Butt them tight together and do not squash or leave gaps.
Lay plywood across the joists to make a solid walkway so you can move around without stepping through the ceiling.
Scan the same area again with the thermal camera. The hot spot should be gone or much cooler than the before shot.
Tips and common mistakes
Wear gloves, a dust mask and safety glasses when handling fiberglass, and step only on the joists, never on the ceiling between them.
Seal the gaps before you add insulation. Batts slow heat loss but do nothing about air moving through an open joint.
Keep insulation at least 3 inches away from recessed light fittings and flues unless the fitting is rated for contact.
Take a before and after thermal photo of the same spot so you can judge whether the fix actually worked.
Questions
Do I need a thermal camera to find attic air leaks?
It makes the job much faster because hot spots stand out instantly. On a cold day you can also find leaks by feeling for drafts or watching for dirty marks where air has been moving.
How thick should the insulation be?
R-19 fiberglass is about 6 inches thick and suits a 2x6 bay. Check your local recommended R-value before buying, since colder climates need more.
Can I walk on the joists after adding insulation?
Yes, but only on the joists or on a plywood walkway laid across them. Insulation is soft and will not hold your weight.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
