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I have an attic door which is a hollow core bedroom door and my thermal camera measures it at a good 7 degrees F cooler than the wall around it, which means that I am probably losing heat. The door is noticeably cool to the touch.

I know I can upgrade to a solid core door for pretty cheap and adding gaskets can help further, but I am curious to know how much more an exterior door would benefit me but don't have high hopes for its cost benefit analysis.

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  • How often is the hatch used? I'm guessing it's pretty much just for access? Dec 10, 2021 at 17:04
  • Wow so many fantastic answers! BTW it is a full door with a full walk up staircase. So the staircase is kind of a heat trap too.
    – Steven Lu
    Dec 10, 2021 at 18:10
  • @stephenlu would you contemplate closing in the attic stairwell? Such that there is a door at the bottom and a wall around it? Or removing the stairwell, replacing the top door with a fold-down ladder/hatch? Both would be a lot of work/expense.
    – Criggie
    Dec 11, 2021 at 3:33
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    @Criggie This has been considered but I think I would need to do a thermal analysis to determine the number of years it would take to break even on getting that done. I would put up some blankets or something but my wife would not be down for that, it would be too ugly.
    – Steven Lu
    Dec 20, 2021 at 19:13

7 Answers 7

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You could glue and/or screw some type of insulation to it:

enter image description here

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    Do this first. It will probably give the most bang for the buck and install a gasket too since that's cheap and easy. A solid door will help a little, an exterior door a little more, but probably not worth it once you've added the insulation and a gasket. In this picture the crawl space itself is insulated. OP if yours is not, you should consider that.
    – jay613
    Dec 10, 2021 at 15:00
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    Note that any insulation added to the door must be fit snugly to the door, or must have a perimeter seal against the door. If there's any gap at all the air will flow behind and almost completely negate any benefit.
    – isherwood
    Dec 10, 2021 at 16:42
  • Thanks for the concept. This is even less wasteful than replacing the door and likely to be more effective.
    – Steven Lu
    Dec 10, 2021 at 18:13
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Answers suggesting that you add insulation are good, but that solution doesn't accomplish much without sealing against airflow. You can have R-500 and it's worthless if air is pouring around it.

Install some sort of seal, even if it's simple foam tape. Adjust the latch to be sure that it closes snugly all the way around. Also install a flexible sweep against the floor, or a threshold block and more foam tape.

As to the exterior door option--that would be superior to retrofitting insulation and seals, but then you're looking at an exterior door in your bedroom. So there's the aesthetic factor. If you can find one cheap, and if you don't mind the look, it's worth considering.

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You could make a door filled with foam sheet insulation. I've made a hatch that way for a storage attic over my (insulated but unheated) garage. It was a frame of 44x18mm (planed 2x1") softwood with 6mm (1/4") ply faces. For a door you'd need bigger timber near the latch and hinges,a crossbar in line with the latch, and possibly some internal bracing, but it's not hard to make from scratch. Then prime and paint well.

If you wanted something to match existing interior doors, I'd take a matching door and cut away most of the attic-side face, filling with foam and replacing with thin ply, before painting only the new stuff and overlaps at the edges. Again I'd use sheet foam (polyurethane), though expanding foam could be used in odd corners so long as you keep it out of moving parts.

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For door access in a ceiling, we used to attach a bag of insulation to the back of the panel - made a big difference but would never get a perfect seal.

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  • How does one attach a bag of insulation to a door in such a way as to have good coverage?
    – isherwood
    Dec 10, 2021 at 16:38
  • @isherwood staples and the insulation held its shape - different markets different products & different solutions...
    – Solar Mike
    Dec 10, 2021 at 17:00
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    If the door opens up into the ceiling, you could also just use a bag bigger than the opening, so when shut it overlaps on the sides.
    – Khrrck
    Dec 10, 2021 at 17:00
  • @Khrrck could do lots of things, but quick and effective is necessary when it is a time-critical job... Different if it is your own property...
    – Solar Mike
    Dec 10, 2021 at 17:03
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Consider simply installing a curtain rod over the door and hanging a heavy lined curtain. Of course this would depend on your decor choices

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You have two sources of heat loss.

  1. Through the door panel itself
  2. through the gaps around the door.

You need to address both of these.
The air gaps are often bigger cold culprits, and do not show on a thermal camera because the allow cold air directly, not having cooled surfaces to show on the IR.

Ceiling access door, that opens upwards?
Tack a carpet or thinner insulation blanket or even styrofoam over it, with about 6 inches overhang on all sides. This gives moderate insulation and very good air seal. Larger or thicker insulation would tend to jam the works, unfortunately.

Vertical door, or ceiling door that opens downwards?
Nail a larger piece of board/plywood/whatever over it, that again overlaps the gaps. This provides both an extra layer of insulation (even if just a 1/4 inch of wood) as well as sealing the air gaps on the sides.
For both of these, a generous layer of insulation can be added to the attic side of the door, as long as it does not interfere with the opening, to reduce heat loss through the door itself.

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A cheap solution that takes no space is to either drill access holes into the rear side of the door, or to peel the rear skin off completely and pack the door with insulation like batts/rockwool etc.

A particularly budget solution would be to cut corrugated cardboard to fit and fill the door with layers, then reattach the rear skin. Given it is on the attic side, appearance is relatively low in importance. Main benefit is the door ends up no thicker than it started. You might use a layer of underfloor-type foil insulation as well.

As others said, you need door jamb seal too, which can be some cheap sticky-backed tape with either bristles or closed cell foam on the other side.

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