Your SO has just gotten the power bill and launched in to a 20-minute tirade about how you worked two and a half days last week just to pay that fucking bill.

It's been common knowledge between you since the power company inspection last summer that the heating and air conditioning duct work through the attic is starting to show its age. It became even more apparent three weeks ago when you were up in the attic late one night to put away kitty carrier and thought, "Heavens! It's quite pleasant in here." Then, closing the attic door, realized, "It's not supposed to feel that way."

Instead of succumbing to my lovely and talented wifey's demand of turning off the AC during the day (not a healthy option here), I decided to fix the problem: climb in to the attic and reseal the ducts.

If your home was built before 1972, chances are that only heavy-duty staples and masking tape were used to seal the duct sections or "boots" together. After a while, as you can imagine, that tape will crack and peel, and the frosty air you've earned by the sweat of your brow will whistle merrily through the rafters.

OBLIGATORY DISCLAIMER: If you are prone to heat stroke or are claustrophobic or afraid of the dark, do not do this!!! You will pay handsomely to have someone do it for you, but you will avoid the physical toll. The urban spelunkers among us may read on.

What you will need

  • mastic tape -- a thick, fibrous, light tack mesh tape, officially called a "fiberglass reinforcing membrane". Sheesh!!
  • 12 lb. tub of RCD #9 Mastic -- a gooey vinyl paste sealant
  • paper towels -- to wipe your hands after each application. You're gonna need plenty.
  • scissors
  • flashlight with fresh batteries or (highly recommended) a headlamp
  • dust mask (optional)
  • clothes you never expect to wear again in mixed company (see notes below)

What you will do

The process is quite simple. Think papier-mâché. Then think papier-mâché in a pizza oven. Easy task, harsh environment.

Unseal, open, then close the tub of mastic so you don't have to wrestle with it in the attic. Put all the loose items in a plastic grocery bag so you only have to make one trip. Believe me, you will not want to go back up a second time to retrieve it after you are done. Climb in to the attic with your supplies.

Select your first boot. Brush away any dirt or insulation. Measure two lengths of tape to overlap each other and cover the seam. It will barely stick to the duct but don't worry. Now comes the fun part.

Scoop a tiny handful -- enough to cover about half your fingers -- of mastic from the tub and smear it on the tape, top of the seam first. Use your palm to press the edges of the tape flat. You may need a few scoopfuls to completely cover the tape. Work it in to the mesh tape.

At this point, switch from thinking "papier-mâché" to thinking "frosting a cake." You want to cover the tape and ensure a good seal, but smothering the boot with mastic is just going to waste your time and create an unprofessional mess.

Repeat with all the sides you can reach. I was unable to get to the bottom of ones in my attic since they rest on the return ducts. Continue to reseal all the boots. Some you may just be physically unable to reach. You do what you can.

The amount of mastic will vary with the size of the boot and the size of the gap. On several I used just enough to keep the tape down. Others required 20 strips of tape and grapefruit-sized gobs of mastic to seal. The mother of all airflow transgressors was a 1" gap at a vent connection and a half-inch space all around the vent itself. When I held my breath, I could hear the AC whistling in derision. For this, I created a Grand Coulee Dam of tape and mastic. Take that, sucka!

At this point, I had resealed almost all the boots in the attic and repaired a couple of holes. The only ones remaining I could not reach due to the geography of the rafters. That is probably a good thing.

My tongue was swollen, and I couldn't close my mouth. My head pounded. When Vix called up to see how things were going, I had trouble answering. Winding through the beams my abdominals cramped. Sweat saturated everything, including my old running shoes. In an effort to relieve an anaconda of pain wrapped around my lower back and hamstrings, I burned my back on a rafter and impaled my skull on a nail.

Once back on terra firma, I stepped in to the backyard and tore off all my clothes. Sure, it was 2 p.m., but I had been in that oven for four hours and was almost delirious. I jumped into the pool, gliding softly in the cool but womblike water to the bottom.

Later on, beer in hand, I toured the vents and found significantly greater air flow in each of the rooms. I pulled a butterfly chair over and sat just below the Grand Coulee Dam vent and dozed in its cool breeze.


  • The best time to do this is during spring or autumn. The conditions in the attic will be less extreme. I was just a procrastinating idiot.
  • Also, to avoid extreme itchiness from fiberglass insulation, I recommend wearing long sleeves and long pants. I wore a tanktop and shorts and am ( scratch-scratch) paying the price.
  • Regardless of what shape you are in, you will hurt like a motherfucker afterwards. You've been warned.