How We Carried Out Our Attic Door
Insulation Project, Step-by-Step

Sealing and insulating an attic door is notoriously difficult -- even more so when folding attic ladders are involved. (Folding attic ladders are also called folding stairs, loft ladder, pull down attic stairs, telescopic attic stairs, etc.)

This page about attic door insulation is the natural continuation of the installation of a folding attic ladder to provide access to the second floor, which I had turned into an attic because I did not need the extra space.

As you will see here, this insulation project involved multiple steps in order to keep the heat on the main floor where it was needed, and prevent it from escaping or seeping into the attic where it could cause damage.

Before getting to this point, you may remember that we had sprayed the ceiling with foam insulation which we then sealed with a seamless 6-mil polyethylene vapor barrier.

Given all that effort and expense, it would have been counterproductive to make a big hole in the ceiling, and let it suck all the heat up into the attic!

Sealing an attic door is as important as insulating it, so my first job was to look for gaps and there was one all around the frame. A bead of caulk was squeeezed all around, and smoothed with a finger.

I used painters' caulk for this. It's cheap and takes paint really well.

When the ladder was installed, it was flush with the ceiling, but now the frame had created a 3/4-inch space between the bottom of the trap door and the edge of the frame. I decided to start the attic door insulation project right there.

I opted for styrofoam rigid foam insulation. The table shows an R-value of 4 for a 3/4-inch thickness.

It's not much but for this kind of situation, every little bit helps.

I used a product called "No More Nails" as an adhesive.

I had tested that product first on a waste piece of foam, aware that some types of adhesives create a chemical reaction that dissolves the foam.

The No More Nails passed the test, and it worked very well. We taped it all around with painter's tape until it set.

We then painted the frame the same as the ceiling -- and in the above picture you can see how seamless the caulking turned out around the frame, once it was smoothed and painted.

I also tested the paint on the pink foam itself. During the summer, the plywood cover gets removed, and the pink colour is a bit obnoxious. The paint test was satisfactory.

While I was doing all this, winter sneaked up on me, so to minimize the heat loss I inserted some rigid foam insulation between the stairs and the masonite cover. That's where the folding attic ladder manufacturers recommend that you insulate their products.

I used some 1-1/2-inch foam that I had leftover from the sunroom-office floor insulation project.

I wish I could leave it there but it's too thick. It takes away some precious toe room and makes it dangerous to use the stairs.

I took this picture, then I removed the foam.

I had another plan: my attic door insulation solution would consist of a box above the stairs, inside the attic, over the folding stairs opening. I had seen prefabricated insulated boxes, and had found them either too expensive and complicated or ridiculously easy to copy for a fraction of the cost.

I had never seen the attic ladder from above, so that was the first step. You need two people for that, so I asked my handyman if he could come over and close the ladder while I was upstairs. To my surprise, the side hinges stuck out a good foot above the floor. This is not at all the impression that you get from looking at some manufacturers' photographs.

The moral of this story is before building or purchasing an insulated box be sure to check how much your ladder sticks out above the attic floor.

I decided to use 2-inch-thick rigid foam insulation. It's light, easy to cut and assemble, solid, and very cheap.

However, it comes in 4' by 8' sheets, and that didn't fit in the basement stairwell, so I turned the kitchen into a workshop for a day. (If you do that, don't forget to protect your stuff against the styrofoam sawdust that will fly about when you cut the material.)


These are the tools I used for this attic door insulation project.

At first, I used only the hacksaw blade for cutting (you need teeth and the finer, the better if you're aiming for a clean cut), but later, I had to add a regular hand saw to keep long cuts straight

Keeping the cuts straight and clean is important for fitting the pieces together as tightly as possible. I was trying to avoid the large teeth due to the rough edges created, and the mess of white "snow" all over the floor, which eventually got tracked all over the house.

The ideal cutting tool is a table saw, but I was unable to manoeuvre the huge board down to the basement, and it was too cold to work outside as we had done for the sunroom-office floor insulation project... I had to turn the kitchen into a workshop for the day.

My two $10 workbenches came in very handy.

Materials Used For This Attic Door Insulation

  • One 4 x 8-foot piece of 2-inch rigid foam insulation. (R-value of 8 approx.)
  • One tube of latex caulk
  • Tuck tape or similar house wrap tape (Do not use duct tape, it will not resist the cold. I've seen aluminum tape being suggested in a similar attic door insulation project, and though it will stick well and resist the cold, unfortunately it doesn't like being bent. I do not recommend it. For a more attractive result [I admit, the red colour is kind of jarring!], try to find some white vinyl tape, of the kind used to assemble water heater blankets.)

How I did it

1. Measure the opening. This will be the minimum size of the foam cover. (A standard opening is 24" x 54".)

To fit my particular configuration, I added 2 inches on each side and 10 inches at the top of the stairs.

Due to my discovering that the side hinges stick out about a foot into the attic, I decided to make the sides of the attic door insulation frame 14 inches tall.

I went through a rehearsal of myself going up and stepping over a 14-inch obstacle (the height of the frame of the attic door insulation), after reaching the last step.

Well, I don't know how long your legs are, but I couldn't possibly do it, and I found myself having to add a little landing at the top, an extra step, as it were, to the length of both the attic door insulation cover and the frame it would rest on. I allowed 10 inches for that.

This meant that my attic door insulation foam box had to measure 65 inches long (54 inches for the opening plus 1 inch for the ledge at the short wall end plus 10 inches for a landing).

2. Measure the ledges where the frame will sit and adjust the cover measurement to suit your own circumstances. For instance, this may not be clear from these photos, but there is a wall on the left and another at the back, leaving a ledge of just over an inch there. The ledge on the right is about 12 inches.

3. I trimmed and stapled the loose edges of the ceiling vapor barrier on three sides of the opening, and taped them down with tuck tape. (Yes, tuck tape again: it's the only tape that will stick to wood.)

This would make the installation a lot easier and provide a smooth surface for taping the attic door insulation frame later on.

4. Draw a sketch, showing all measurements and indicating exactly where each ledge is. After marking the cover and one of the sides, I realized that with a 65" x 28" cover, I would have just enough material, and that I would have to join some pieces.

5. Trace all the pieces on the foam board.

The cover must be all in one piece, so trace it first.

Next, I had to trace the long piece along the wall, which I felt should also be in one piece to maintain its rigidity, due to the narrowness of the ledge it would sit on.

6. Measure twice, cut once! With every square inch of material spoken for, be sure to check measurements before making the first cut.

Cut the cover and check it for fit. Trace around it (see red arrows) to see where the frame will fit, and how much each frame component should measure.

This view is from above, but I also looked at it from below, to see if the floor was even, and it was.

7. Check the measurements of the other pieces against the rest of the foam board, to avoid running out of material. In my case this was very critical -- see the next photos!

8. These photos show how the piece at the wall end ended up being assembled out of the leftovers. I taped the pieces together on one side, leaving the end free so that I could open them to glue them together with a bead of caulk.

I filled the gaps with some more caulk, then I taped the caulked side. I put that assembly aside to set.

Once the caulk had set, I taped the end piece to the wall at the top and right side, and to the ladder opening at the bottom.

9. The second long side of the frame was made up of two pieces, assembled in the same way.

All the pieces got checked and adjusted to make sure that they fitted as well as possible and their best position was marked with red marker.

Remember that the total size of the frame must be exactly the same as the cover; therefore, the thickness of the material must be taken into consideration, and subtracted from some of the components.

10. All frame pieces were taped to the walls and/or the floor, and taped together at the corners, creating a very solid base for my attic door insulation box.

I used Tuck Tape exclusively because of its resistance to the cold, and red colour doesn't bother me, but for a prettier effect you could investigate the qualities of the white vinyl tape that comes with water heater insulation kits.

Do not use duct tape:
it will not stick to the foam and it will not resist the cold.

Finishing Up the Attic Door Insulation

11. Walk down the steps, dropping the attic door insulation cover into place as you do so. It weighs but a few ounces. You're done!

The box, viewed from above...

...looking towards the new landing at the top...

...from below...

...and confirming that the hinges are clearing perfectly.

A Final Embellishment

As an added protection against air infiltrations, in the early winter I screw a cover over the whole opening, seal all the gaps, and forget about using the attic for a few months.

The cover is merely a sheet of meranti board cut to fit over the frame, and painted white. Meranti board is a very light and very inexpensive type of plywood.

Screw holes have been drilled through the cover and into the frame, to make it easier to install and remove every year.

Another gap to take care of is this one, located at the end where the ladder's piano hinges are.

When we glued on the pink insulation, we had to leave this area clear to allow for the lowering of the ladder.

That's where one of my favorite products comes in.

It's made out of flexible foam, it comes in different diameters and it fills a need that neither caulk, nor spray foam, nor other types of insulation can fill.

It's removeable, and therefore, it's reusable.

In this case, a length of it was pushed into that gap just before sealing the attic ladder trap for the winter with a plywood cover and removeable caulk.

In the spring, when I unseal the attic, I simply pull it out and put it away until the following winter.

Here's the plywood cover, with the screws in place...

...and with the screws painted white. (Of course, you can use white screws instead.)

Around the plywood cover, I used to use transparent removeable caulk, which I had applied around some windows the previous year, but they must have changed the formula because it now has a very obnoxious odour which feels very toxic. I have switched to transparent removeable tape, though I'm not sure it's even necessary, now that the foam box is in place.


When I was researching the subject of attic door insulation, I found dozens of solutions, some cheap and not very effective, some very expensive and not much more effective.

One of the few DIY projects involved building a sort of box out of pink rigid foam insulation, a mere 3/4 inch of it. That only provides R4 of insulation but I also found it awfully flimsy. Still, I liked the idea of the homemade box, and this project is based on that article.


Foamboard $12
Caulk $3
Total cost $15 (plus about a dollar's worth of tuck tape from a roll I already had).


My goal in carrying out this attic door insulation project was to keep the heat from the house from leaking into the attic.

Any project whose goal is to reduce energy consumption is green by definition, even if the materials used (such as Styrofoam) are not always as green as one would like!




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A few years ago, I bought this fixer-upper for $10,000.

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