I have a 12x24 building that I built for band rehearsals last year and since it has gotten very cold here in Alabama (was 9 degrees F today) I have noted that it is almost impossible to heat. It's a wood frame building. Barn style. Upstairs is blocked off with trap door access. The roof is insulated with a gap at the ridge for a vent. Metal roofing. Downstairs the walls are insulated and sheetrocked. Outside is covered in vinyl siding and moisture barrier under that. It's temperature controlled downstairs with a infrared space heater at the front, and a conventional one at the back. When it gets below about 40 degrees, I can't get it to an acceptable temperature. There's some really cold spots in it too. They feel like drafts, but I'm pretty certain I did a great job on the insulation. I can feel cold air at the floor radiating inside. The floor is super chilly. Half the floor is carpet and half is wood flooring. Both are cold. THe carpet has padding under it. Subfloor has 2 layers of plywood under it and tar paper between the layers.

Ive pretty much figured out that the cold is radiating through thhe floor despite this. I could insulate under it as I can access it, but at the rear, it is just inches off of the ground. Putting traditional insulation under there isn't a viable option due to that and I don't want to invite rats under there either. So my question here is, what options do I have to insulate? If I were to underpin the building and face the underpinning with insulation would that work? Could someone do spray type insulation on a building that close to the ground?

Any advice is much appreciated!!!

The floor is not insulated. This was a major dumb move on my part. I figured in Alabama that wasn't an issue. I was apparently wrong. What insulation options do I have seeing that the building is so low to the ground at the rear? Would underpinning and insulating the underpinning be worthwhile instead?

I store things upstairs so I didn't want it to get super cold or hot up there. My research told me that this was ok to insulate the roof instead of the floor below it to achieve a not so hot or cold space. Is that not the case? Should I pull up my upstairs floor and put the insulation in there?

What about venting? I've shook my head over and over on this. Do I need to vent this roof? What I did do was I installed an exhaust fan in the rear of the building that kicks on at a predetermined temperature. It works incredibly well during the summertime. Even when it is blisteringly hot outside, it is tolerable in there. Maybe 90 degrees at the hottest. I felt like that with metal roof and no insulation it would be unbelievably hot during the summer which isn't good for the stuff stored up there. My house on the other hand is so hot inside that I feel like I'm dying in the attic. I bet it's 130 degrees in there in summer.

During the summer, a 12000 BTU ac unit cools the downstairs easily. And fast. It remains cool all the way into the afternoon the next day with the ac set to 85 and it stays about that till later afternoon. I was very impressed with how well the building retains cool air.

I can post some pics if that helps.

  • Is the floor insulated? (Carpet padding and plywood don't count.) I'm confused by your description of the attic insulation. Normally an attic is a sealed space, with insulation between it and the building's interior. Sounds like you have an open path for heat escape.
    – isherwood
    Jan 17, 2018 at 20:18
  • FYI, and not to be too pedantic, but "cold" isn't a thing. It can't radiate or move. Heat is a thing, and it moves via air (convection), conduction, or radiation. What you feel is heat moving out through the floor... not "cold" coming in. Again, pardon the pedantry.
    – isherwood
    Jan 17, 2018 at 20:20
  • 1
    One more question: What is the upper level used for? The obvious fix from my perspective is to insulate the ceiling of the main floor, including the attic trapdoor. The insulation in the roof then should be removed, as you've created a hot roof, which isn't ideal.
    – isherwood
    Jan 17, 2018 at 20:22
  • To address the new information posted as an answer below, I don't think you absolutely have to insulate the floor. The open vent in the roof is what's killing you.
    – isherwood
    Jan 17, 2018 at 20:53
  • Okay. That was kind of my thinking. So your opinion is to block that open vent? Since I have this exhaust fan is venting even necessary? Also, your opinion on the floor insulation? Jan 17, 2018 at 20:59

1 Answer 1


I'm going to assume that the attic is for storage and isn't needed as a "conditioned space".

  1. Remove the insulation from the roof. It's detrimental to ventilation and cooling in the summer and won't do you much good in winter.

  2. Insulate the attic floor. You can probably reuse your roof insulation, and as little as R-19 will probably solve your problem for all but the very coldest days, but ideally you'll get to R-30 or better. Also insulate the attic trapdoor with foam sheets or whatever, and seal it against air leakage. You can still use the attic for storage, but the floor may need to be lifted to accommodate the insulation.

  3. Improve attic ventilation. Ridge venting is part of the system. You also need soffit venting or something else low in the roof. Ideally you have a flow path that moves air upward and out across the entire attic area. It's critical to vent heat in the summer and moisture in the winter.

It's that simple. Let us know in a comment or an edit to your question if this isn't feasible for some reason. The uninsulated floor isn't ideal, but it's a minor component of your overall problem.

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