Introduction: Air Seal Your Attic for Energy Savings

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Hot air rises. Without air sealing your attic you are allowing warm air to escape from your home carrying with it your hard earned winter heating money. Most people just add insulation to their attic - this will not stop the escaping warm air. The EPA estimates that the typical American home has enough leaks, holes and gaps to be equal to an open window every day of the year. That is significant. We need to seal the air in our conditioned living space from the unconditioned attic space. Every attic needs proper ventilation. We are not stopping the proper air exchange in the attic - we are only stopping the exchange between the house and the attic.

In the past year I’ve been on an energy hog hunt in my house and landed on air sealing my attic before adding blown insulation. I was a bit shocked at the $1,500-$2,500 contractor estimates for attic sealing. I’m all about DIY when it saves me time or money. My cost was under $150 and it took me less than a day. Initially the EPA DIY document seemed overwhelming but once I got started it was straight forward. If you can operate an aerosol can and a utility knife seal your attic. You would not try to carry water in a bucket with a hole in it - so why do we allow our heated air to escape through the many holes in our ceiling. Lets get to work. Save some money, save energy and stay warmer with less effort this winter!

Every attic is different – but I consider mine very average. This is my story and I hope it helps you!

Step 1: Tools and Equipment:

Mask – If you have loose, blown in insulation I highly recommend the 3m changeable filter mask.

Long Pants
Long Shirt
Spray foam – I used 8 Great Stuff and 1 Daptex because I had it.


Caulk Gun
Fire Caulk
Utility Knife
Scrap metal (flashing, drip edge, recycled scrap)
Foam Insulation Board or Recessed lighting Covers
Self stick weather stripping
2 Draw Hasps (for attic hatch)
A few pieces of scrap wood to sit/lay/stand on.

Step 2: Find the Leaks

I live in a standard brick ranch house that has a gabled roof and about 1,000 square feet of attic floor space. It is big enough to sit, but not tall enough to stand. It has old very low R value blown in fiberglass insulation. (About R-12 according to my measurements). Your house might have a different kind of insulation but that is ok – these theories will work for you too.

Hot air rises and carries with it dust particles that find their way into your attic. Your insulation acts as a filter and traps this dirt. You will be able to spot leaks by finding dirty insulation. This will be on insulation that sits on the attic floor. I was skeptical at first – until I found an unusual amount of dirty insulation all over my attic. Places to look: the tops of walls, drilled electrical wire holes, electrical outlet boxes for lights, pipes, recessed lighting, bathroom vent fan, chimney flashing, dropped soffits over lighting, cabinets, and slanted stairway access.

I removed my attic floor - I suggest you do the same if you think it might be covering leaks or additionally in my case hiding poor insulation coverage.

*Danger – only step on the roof rafters/trusses or sturdy wood placed on
top of the rafters. Otherwise you will put your foot through the drywall ceiling.*

Step 3: Wall Top Plates

Look for the interior wall top plates. Start in one corner and work your way out. Find the dirty insulation and follow it. Push it out of the way. Follow the gaps with a good bead of spray foam.

Step 4: ​ Find Electrical Wires and Boxes

Find the lighting electrical box for each room and cover it with a dose of spray foam. Find Electrical wires that are penetrating the ceiling. Stick the spray foam nozzle in the hole with it and give it a quick squirt. You are not trying to shove foam down the wall – but rather make an air tight cap on top.

Step 5: Recessed Lighting

Recessed lighting can be tricky. They come in two types – IC (insulation contact) and Non-IC (non insulation contact) It is a fire hazard to have insulation on non-IC fixtures. Unfortunately I had halogen non-IC lights. Basically I had 4 large holes in my living room that not only did not have any insulation on them and were not air tight to the ceiling. If you have a situation like me you can build or buy recessed lighting boxes. I built mine out of R-10 foam board. You need to leave at least 3 inches on all sides of the light. So if you have a 4 inch wide by 8 inch tall light you would 10x10x11 box. Notch a hole for your wire and spray foam around the bottom and any gaps in the box.

If you are creative – you can also use spray foam to “glue” your boxes together.

Off the shelf products are available but would have cost me more…however it would have significantly reduced my time in the attic.

This was also a good opportunity to swap my bulbs for dimmable LED’s I picked up off eBay for about $3 each.

Unfortunately mine are currently covered in new insulation. Apparently I neglected to take a photo! Companies like CanCoverIt and Tenmat sell off the shelf boxes.

Step 6: Pipes

I was unable to get a photo of me air sealing around my bathroom vent pipes. It would have looked like a terrible selfie – I had enough space so shimmy over there and hit it with the foam. Pipes will be easy to spot. Be careful some home builders have been known to just shove batted insulation down in the hole around the pipes. If this is your case – grab your utility knife and some foam board or drywall. You will need to fill the hole with something solid and then foam the gaps.

Step 7: Bathroom Vent Fan

The bathroom vent fan is an anomaly. Many people don’t pay much attention to them. Most are installed incorrectly, don’t work properly, leak air and let hot air into your house.

Here are some pointers.

They must be vented to the outside – and not just dump into the attic. This causes moisture issues when they run. It also allows the hot air in the attic to be pushed into the bathroom through the vent tube when not in use. Since my house is brick with no access to the soffits I vented mine to the gable vent. Typically they are vented through the exterior wall or the soffit.

Vent pipes need to be insulated. My bathroom vent fan had a flimsy short plastic dryer like vent hose attached to it. It had no insulating value. So even if it was vented properly (which mine was not) summer heat would penetrate into the bathroom through the vent tube. My suggestion is to buy some insulated duct work from a HVAC supply house. In theory you need as much R value as your attic floor. I picked up some R10 and I plan to wrap it in additional insulation at a later date. This same principal should be applied to your AC duct work if you AC unit Is in your hot attic.

Like recessed lighting bathroom vent fans need a sealed box. Measure and build one out of foam. Leave room to attach your vent. Hit the gaps with the foam.

Step 8: Attic Doors

Access hatches and pull down ladders are notorious for leaks. I have an access hatch. The easiest thing for me to do here is attach weather stripping to where the hatch rests against the casing. This is single sided adhesive - and the sticky side goes down on the casing. Two draw hasps are installed to pull the down down. If you have trouble keeping the hasps down - use a piece of wire, a nail or a screw through the lock hole to keep them shut and tight. Additionally you should have batted or foam insulation on top of your access hatch equivalent or greater than the insulation in your attic.

Step 9: Other Considerations

These things are not in my attic, but they are worth mentioning.

Hot stuff:

Small gaps around hot things like chimneys, chimney flashing, stove/furnace exhaust pipes need fire sealer. This is fancy flame resistant high temp caulk. DO NOT USE SPRAY FOAM! If you find large gaps you will need to fill them with some scrap metal. You can find inexpensive pieces of drip edge in the roofing section of a home store. Some home stores sell smaller sheets in the hardware section as well.

AC Unit and vents:

Any ceiling vents need to be foamed and sealed where they meet the ceiling.

If you have an attic AC unit you should take this opportunity to check the air seals on the duct work. Loose connections should be clamped, taped and caulked. Consider swapping out or upgrading any duct work that is not insulated properly.

Step 10: Rafter Vents

Side note:
Rafter vents should not be completely sealed. Home stores sell rafter vents that can be stapled on to the roof deck. They sit between the roof rafters and extend downward through the insulation and into the soffit. This gives cool fresh air a clear unobstructed path to travel which allows the hot attic air to be vented through the ridge or gable vent via convection. The rising heat will escape and the cool air will be pulled in. If you do not have any installed this would be a good time to put them in.

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