Air Seal Your Attic for Energy Savings




About: I'm a computer engineer - but please don't judge me by that. I heat with wood, fix broken things and love camping with my family. I'm a closet solar nerd, love coupons, not scared to dumpster dive and love...

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!

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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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    107 Discussions


    5 months ago

    This great article points readers in the right direction for them to create a warmer home.

    I have been spreading a similarmessage in England for over 50 years 'without much success'. I have tried to educate householders about how important air-sealing the attic and roof spacewas. My company booked 5000 air-sealing orders from City Councils in 1972-1973, but just 1000 orders from private house owners which was not enough to make it
    worth our while to persevere. So what did we do instead; we sold
    straightforward Loft/Attic insulation and never mentioned that without
    air-sealing the attic its completely worthless, let’s be honest would you buy
    attic insulation if the person selling it told you in all honesty "What
    you have read and know about fibrous insulation is wrong- the heat saving
    figures are falsified- they might be correct if you were sealing a square box,
    or a fridge, but definitely not when you are sealing a roof." Why?

    (1) Fibreglass and Rockwool
    Insulation is porous, water trickles through it, and take it from me if water,
    steam or smoke can seep through it then so can HEATED AIR.

    (2) If you’re not convinced try the water test, or hold
    some insulation up to the light and see the Sun, better still climb inside your
    attic on a cold day and feel how cold your insulation is? Feel it, touch it,
    even take its temperature and guess what "It’s always cold," in fact sometimes
    freezing cold. Because it succumbed to cold air entry from outside, it got
    Frost Bite, and died from Hypothermia.

    (3) I have insulated thousands of homes, guess how many
    people phoned me afterwards, who thanked me and told me how wonderful it was,
    ZILCH. A great big zero. And be advised we can lay and install insulation better
    than any other UK company I know off. The answer to improving cold homes lies in reducing cold air entry and stopping draughts. It’s as simple as that. You must have planned
    escape routes for moisture to exit the property (ventilation). And, what is the
    miracle product to use: The Oscar Winner, The Triple Crown Winner, the Epsom
    Derby Winner is: made by Dupont and called Tyvek and Housewrap.

    *This post was written by an English Cousin,who still gripes about the land snatch that occurred in British-America in 1766 (we wuz robbed). A proud person who finds it incredible what a handful of determined individuals and their descendants achieved when they stepped of two boats, the Godspeed and the Mayflower. Hard men and even harder women who built houses with axes and saws? God Bless Our America, my America.


    3 years ago

    Great walk through. My only question is : If I spray elect. , fans , and the like. What happens if down the road something needs repair or replacement? Will the foam come off easily?

    1 reply

    Reply 1 year ago

    Great Stuff scrapes away pretty easily. It won't clean off easily, but you can scrape it to the point of servicing something.

    Hi, nice documentation. But you will still have heat bridges on the wooden beams and thus energy losts. You have to put insulation also over the beams otherwise you take risks that your ceiling starts to turn black under the wooden beams. Best regards from blown insulation experts from europe - .

    1 reply

    Greetings from the US! After I air sealed the conditioned space from the unconditioned attic I blew in about 35cm of cellulose over the existing fiberglass.


    3 years ago

    very interesting and useful bar the comments on foaming electrics and ventilation pipes shouldn't run uphill to the outlet in case moisture dose run back


    3 years ago

    Excellent instructions!!! I have a terrible moisture issue in my attic due to poor ventilation and now I'm realizing because of all the warm air seeping in through the leaks. I've started foaming. I wanted to hire insulation companies, but it seems no one wants to do the hard work of removing the boards and pushing away the insulation; they just want to add vents. Any advice on my chimney, I will get the fire retardant sealer, should I add flashing around the bottom. I am having the chimney re-pointed this week, which is also an issue I didn't realize until recently. I will take any and all advice. I see you covered the bathroom vent with a box, I also have 4 recessed lights that need to be covered; I am assuming this has been the largest issue. Thank you so very much for this, I love the photos. Very informative.


    3 years ago

    Hello More Cowbell! I commented on your post without reading all of it and seeing rhe photos! I'm nor really good on the computer ot at negotiating sites like this...bit I GET IT...Thankyou for posting such an well explained idea! Apologies that I said it was not clear...its ver clear thanks! Love it! Stebe abx replied to what I wrote and I replied thinking it was you the author of the post...and owner of the attic.

    I discovered this when it was suggested I put doen fibreglass batts...when I'd explainrd, so I thought, that this is not an option.....never mind. I've re-read your post very carefully...ALL of it and several times and thoroughly GET IT! Fortunately I have a very old house (never thought I'd say rhat because of this problem of insulation) but it makes implementing your system even easier since there are no modern things in the attic...just wiring and a lot of dust that falls through thr VJ boards.

    Thanks so much for such a simple solution to my age old problem and again, apologies for not attributing the invention to you!. Now for a hardy fellow who can follow your instructions and foam in and seal all the cracks!



    3 years ago

    I live in Queensland Australia...the really cold part. It frosts and snows in winter and in summer we drink wine and eat every kind of fruit you can 3000ft above.. Really wish I understood what you are explaining, I would have it done without question. I am a woman of 71. I've lived in a wooden house with VJ board ceilings in every room for 30 years...the dust that comes down is amazing! Cannot put blow in insulation in the attic because...dust!! No other insulation either...dust!!! The electrical wiring is all up there encased in conduit so no foil backed insulation. Two years ago the Government put out a FREE insulation scheme....everyone and their dog was installing...the dogs were not qualified..resulting in many homes burning down and three people getting electrocuted in the attics where the foil touched wiring. I've not been able to decide what to do. So....sad for me, I find your explanation too lacking in detail..not your fault...just.wish I understood. Would be great to halve my fuel bill and have an insulated looks just like the one in the photo.


    2 replies

    Reply 3 years ago

    Hi Jusirela.

    I used to live up there too. Now I live further south in the cold.

    I am happy to advise you if you like.


    Reply 3 years ago

    Thanks Steve-Anx! That's so nice of you!
    I've had to learn to do a lot of DIY over the years so know what the materials and tools are and have a stanley knfe or two, a caluking gun and goggles and masks...
    As I mentioned, I've been here for 30 years and am now an old...lady' afflicted with the problems of old won't be me crawling up into the attic...and doubt if the man hole would be wide enough now....So, I think if you would be kind enough to list the materials, tell me what each one is usually used for and where to buy them, then explain what you used them for and how you fitted and fixed them in place...and what your overall brainwave was in.making use of.materials generally used for something else and how and where you used them...that would be help enough. Then, having a good idea of how you effected your attic insulation invention, I could explain it to an able bodied fellow who would be willing to do the job for me.
    How does that sound, Steve? How are you at doing little sketches to illustrate? I've found that some of my unconventional inventions made better sense when I did sketches for the person doing the job...who had not a clue what I was on about! All they knew was that "Esther" was at it again! (They learnt a few tricks too).
    I had a closer...( with magnification) look at your photo of the attic.
    Did you wedge the weather sealer strip into the joins between boards and then..calk/stick/glue it in? What did you de-dust-de-yuk and generally clean the edges of the boards with so the caulk etc...would attach? My attic will need a really good vacuum and clean before anyrhing at all happens. if you did what I just suggested...That makes sense to me...What did you do with the other material you showed in the photo? .Thanks for your offer of assistance. I appreciate it. J


    3 years ago

    I had a home inspection done several years ago, and the inspector fashioned something out of a large box to trap air from seeping through the door into the attic. He flattened the box and notched it for the stair railing leading up into the attic. When I want to go up there, I just open the door and push the flattened box up into the attic and then pull it back down when I am leaving. Unbelievable the difference a little thing like that made in my heating and air conditioning bills. It sealed it nice and tight, and has probably paid the inspector's fee many times over in savings in energy bills.

    Mark 42

    3 years ago

    I got a fever, and the only prescription is More Cowbell!

    1 reply

    3 years ago

    Any concern about the great stuff being in close proximity to electrical connections in a junction box (or similar) as shown in Step 4? Thanks!


    3 years ago

    As an addendum to my original posting.

    In regards to the net free air exchange rate:
    Some well meaning home builders, contractors, and home owners will install powered attic exhaust fans to augment the net free air exchange rate. This is a good idea which can quickly backfire if not calculated, and implemented properly. As mentioned previously, there is a specific formula to calculate the appropriate net free air exchange rate for a building, "net free air" meaning the total volume of naturally free flowing air into and out of the attic space. A powered attic exhaust fan will increase the exhaust rate of the air pulled from the attic space. However if the volume of air coming into the attic is less than what is being exhausted, a vacuum condition may develop in the attic space. The volume of air exhausted from the attic space must be equal to or less than the volume of air capable of coming in through other vents. Therefore make sure all soffit vents have unimpeded air flow!
    So why is this important? A vacuum condition in the attic space can pull air from the living space, thus in part, transfer a portion of that vacuum to the living space. Combustion exhaust gasses can be pulled into the attic from leaky exhaust flues, and/or more importantly, directly from combustion sources into the LIVING SPACE! Combustion exhaust gases can come from various sources, such as, wood or gas fired fireplaces, wood or gas fired stoves, wood or gas fired water heaters, wood or gas fired heaters (space or central), gas fired clothes dryers, or even from an engine running in the garage.
    From a safety and health perspective, any building with combustion source inside may be well advised to have a free flowing source of fresh air coming into the building from the outside.
    Breathing combustion gasses is harmful to health, and can cause carbon monoxide poisoning, and even death.
    To be optimally effective, a powered attic exhaust fan should be installed at the highest level possible (because heat rises), and away from any other naturally free flowing vents. Optimally a powered attic exhaust vent should only pull air into the attic from soffit vents, or any other vent specifically placed to bathe the bottom of the roof deck with its air flow.
    As a recommendation, only install a powered attic exhaust fan that has a temperature sensor and switch designed to turn the fan on/off at a predetermined attic temperature. Optimally this temperature sensor and switch should be adjustable. Furthermore as a convenience, a switch could also be installed outside and near the attic entry to easily control power to the fan.

    Hope this helps!

    Sent from my iPhone

    Sent from my iPhone

    2 replies

    Reply 3 years ago

    actually the minimum air infiltration rate is mainly dependent on the maximum expected number of occupants and type of heating used. gas burners, requires an additional infiltration source.

    and also it is most likely better to have a slight positive pressure from fans pushing air in rather than exhausting with negative pressure. and in the summer, use the fans to push more air through keeping the level below cooler.

    and if you are concerned with maintaining heat, in the winter. you might want to consider, an air exchanger. warmer air in the attic, forms a heat inversion layer in the daytime. but tends to become a heat sink at night with the roof radiating heat to the night sky.

    but the biggest killer for heat loss, is infiltration rate. not the r factor of the walls and celling. heat is vertically polarized, so insulation in the attic should be at least twice as much as in the walls. and having thermo pane windows, are worthless if air is leaking around the sill. so it is important to seal, the window frame to the window with sealer.

    and as i, have stated further down in the replies. it is easy to do a leak test with a window fan sealed good, and using smoke sticks to detect the leaks.


    Reply 3 years ago

    The reason for the adjustable temperature sensor and switch is because there will be a point of diminishing returns. In other words, the cost of running the powered attic vent fan will, at some point, exceed the value of savings. For example if the temperature of the outside air is 95 degrees F, then the best you could hope for is a 95 degree F attic temperature. Realistically, on a sunny day with an outside air temperature of 95 degrees F, an attic will significantly hotter than 95 degrees F, but no less than 95 degrees F. So there is no sense having the fan running trying to get the attic cooler than 95 degrees F.
    I think a ball park temperature to start with would be the average summer air temperature for the previous year.
    Hope this makes sense.