Insulate an Attic Door

Sealing and Insulating an Attic Door
Our attic door leads to an attic stairway, we don't have the pull down attic stairs or hatch type access. If you have have an attic hatch or pull down stairs, see the bottom of this article (after "resources") for ideas to insulate and seal those.

Our house has an unfinished/uninsulated attic (no insulation in the attic at the roofline). That means it is considered an "unconditioned space". What that means is that in the Winter, our attic is almost as cold as the outside air. Our Winters are very cold, so air sealing and insulating the boundary between our second story living area and the attic is very important.

"Air sealing" and "insulating" are two different things. In this simple project to seal and insulate my attic door you will see that.


Here's the attic door. This is an after picture, as I don't have a before picture. I also don't have a photo of me holding a smoking incense stick where you would have seen the smoke sucking into the attic, at a ferocious speed through the gaps around the attic door and door frame. All that represents huge amounts of precious heated air escaping into my attic. That's a "air sealing" problem. The other problem caused by poor air sealing, is that when that hotter air hits the colder surfaces in the attic, it condenses, thus creating a moisture, and potential mold problem. (Note: click on photos to enlarge them)

If you put your hand on the living space side of the door, it was very cold indeed. That's an "insulation problem". The insulation level of your attic access, (door, hatch or kneewall door, should match the recommended attic insulation (R-Value) for your region. For my region an R-value of 49 is recommended. Here's an Insulation R-Value Calculator to determine your regional needs.

Insulation on the Attic Door

I bought a piece of 2" rigid foam insulation (see details below), cut it to size with a drywall saw, and screwed it to the back of the attic door. That's the insulation part of the solution. The insulation doesn't go all the way to the floor because I have a step in the way there. (Note added: The solid wood door has an R-value of about 3. Adding one layer of this rigid foam makes it a total of R-16. I should have this door at R-49, so really it needs another R-33 added. I actually realized this after I finished the project. So I may go back and sandwich another 2 sheets of insulation to it, to get to R-42, if there is room.)

Rigid Foam Insulation

DOW, TUFF-R Commercial polyisocyanurate insulation with reflective/radiant barrier foil on both sides. It comes in 4' x 8' sheets and I used the 2" thick stuff (R-Value: 13). Note from DOW: Local building codes may require a protective or thermal barrier. For more information, consult MSDS, call Dow at 1-866-583-BLUE (2583). This is because this insulation is flammable.

Attaching the Insulation to the Attic Door

I used drywall screws with larger washers so the screw heads wouldn't puncture the foil on the insulation.


Be careful though... My screw gun (blame the tools) put this one in too far. You might what to start them with the screw gun and then hand tighten them with a screw driver, so you don't do what I did.


And while we're showing mistakes, here's a screw that's come out the other side of the door. I did this several times before I shut the door and saw them poking through. I had measured the width of the insulation and the width of the edge door for the total thickness, but what I didn't take into account was that parts of the door aren't as thick as the edge!

Caulk Around the Insulation and Attic Door

You can see here a bead of clear silicon caulk applied to keep cold air on the attic side from getting between the rigid foam insulation and the attic door. I caulked around all four sides of the foam.


After cutting a hole on the attic side for the doorknob, I also caulked there, between the insulation and door.

That completes the attic door "insulating" part of this project.

Air Sealing an Attic Door

I used Frost King's highest grade of door weather stripping from HD to "air seal" the door. You might have to try a few thicknesses before you get a good fit. If the weather stripping is too thick the attic door won't close, if it's too thin, you won't make a good seal. You should adhere the weather stripping to the door frame, as shown above, for the door knob side, and top, so that it compresses when the door closes. There are many different flavors of weather stripping, and you might find a different type to best work with your project. Note Added: Here's a link to better weather stripping.


On the hinge side of the frame, you want to put the weather stripping on the same piece of wood as the hindge is mounted. The weather stripping will be compressed when the attic door closes. Be sure that the weather stripping sections create meet well in the corners.


My door closed tightly after adding the weather stripping, but when closed and standing on the attic side, I could see that the attic door, at the top, was not making any contact with the weather stripping. Turns out my door was warped, and didn't meet the door frame at the top, even when the bottom made good contact. So I added this mini deadbolt that can only be latched when I push in at the top of the door. This really sucks the door in place. Over time it might even help convince the door to straighten a bit.


The final step was adding a door sweep to the bottom of the door. It's metal with rubber on the bottom edge. They come with the screws to mount them, but you'll have to cut them down to the width of your door. You'll need a hacksaw to cut through the metal. The rubber makes good contact with the attic door threshold, so now we have "air sealed" the attic door all the way around... Well, there is that tiny open space between the door sweep at the sides of the door! Perhaps I should removed the door, frame in the opening and drywall it over, for the perfect seal! That's a joke of course.

Materials:
DOW, TUFF-R Commercial polyisocyanurate insulation (PDF)
Drywall Screws
Washers
GE Silicone II Window and Door Caulk
Frost King EPDM Rubber Self-stick Weather-strip
Frost King Aluminum and Rubber Door Sweep
Better Weather Stripping

Tools:
Drywall Saw or utility knife (to cut the rigid insulation)
Johnson Drywall T-Square (to measure and cut against)
Cordless Drill (to attach the insulation and door sweep)
Hacksaw (to cut the door sweep to length)

Resources:
Department of Energy: Insulation calculator by zip code
Energy Star: Air Sealing and Insulating Introduction
Energy Star: Do-It-Yourself Guide to Air Sealing and Insulating
Amazon Book: Insulate and Weatherize—By Bruce Harley
2009 Federal Tax Credits for Energy Efficiency
Colorado Energy: R-Value of Materials
Healthy House Institute
HGTV Insulation Forum
Home Energy Articles to '99
DoItYouself Insulation Forum
U.S. Department of Energy

Thanks to Paul Button at Energy Audits Unlimited
Energy Audits Unlimited (Manchester, New Hampshire)
- Highly recommended
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Insulating Pull Down Attic Stairways, and Attic Hatches

How to Make Your Own Insulted Box for Drop Down Attic Stairways
1. Buy some rigid foam insulation, like what I used (DOW, TUFF-R Commercial polyisocyanurate insulation with reflective/radiant barrier foil on both sides. It comes in 4' x 8' sheets and the 2" thick stuff has is R-13). Also buy some Great Stuff.

2. Cut pieces needed to make a box over the hatch (top, long sides, short sides). Peel back the foil on the glue lines, Great stuff the box together, and duck tape it while the Great Stuff sets. If you want a box with greater R-value, double it up with 2, 2" layers and it'll be R-26.

3. That's the general idea. You can decide if you want a removable top, hinged top, and how you want to create a good air seal there, and where the box meets the attic floor.

Here's a Similar Approach for Making a Box:
Danny Lipford: How to Insulate Attic Drop Down Access Stairs

Additional Solutions for Attic Hatches:
Home Addition: Properly Insulate Attic Door
Renovation Headquarters: How to Insulate Attic Accesses

Prefab Solutions:
ESS Energy Products, Inc. - Energy Guardian Kits
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My Standard Disclaimer: This is what I did. This does not mean this is the best way, the right way, to building code, or even safe for your needs. So you are on your own with your project. I make no promises about the information presented here. I'm just a do-it-yourselfer, not a professional at all, sharing my story. So if something goes wrong with your project, you are on your own. Good luck, and have fun!

All content and photos, copyright 2008, Dover Projects.

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