I am a fairly new homeowner. I own a "raised ranch" style home in suburban Chicago (main floor above grade, mostly furnished basement below). The stairs to the basement are roughly in the center of the home. The stairwell is drywalled on sides and overhead. Together with adjoining interior walls it forms a void in the interior of the main story that is open to the attic on top. Some attic insulation may have previously spanned the "top" of it, but at the present it's just a wedge-shaped well/void in the joist surface of the attic.

I think this void is the cause of major thermal loss in the adjoining hall closet and bedroom. I would like to insulate the void, but keep the project scope small and cost efficient - mostly interested to see what difference it would make this winter. Current idea is to dump blow-in insulation into it, as that can be done in an hour or so. Wondering if that's acceptable or DIY gone wrong. Only negative I can think of is difficulty in scooping that up in case the need to undo.

sketch of void

Area in attic where insulation opens to the void

Thermal camera image of void wedge from the bedroom that has thermal issues

  • I'm not understanding what it means to be "drywalled overhead" and "open to the attic on top". Could you add better photos? Oct 13, 2023 at 8:30
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    Adding insulation to your attic is almost always helpful. I'm with @RobertChapin, though, and I'm a bit confused. You've got 2 green arrows in that first pic, but we can't really see what they're pointing at. If you could get us a better view of those joist bays and better explain what you're looking to do there, I think that would help us help you. TBH, what I can tell of the rest of the attic it looks like you would do well to add an extra layer of insulation (maybe roll insulation instead of blown) running across the joists in addition to the layer between them.
    – FreeMan
    Oct 13, 2023 at 11:58
  • I have added an "elevation view" sketch of the void to my post to help illustrate the situation.
    – DmitriyV
    Oct 13, 2023 at 14:14

2 Answers 2


Thank you for the sketch. I would ensure the closet wall and the staircase ceiling are insulated. It is okay to have a void between the insulation and the extra joists in the attic.

To directly answer your question, blown-in insulation will only work for that ceiling surface, unless you're planning to board up the closet wall or add an enormous amount of material to fill the whole void. I think that would be a waste of effort. If the closet wall is not boarded on the back side and not insulated, then it would be easier to go with rolled insulation.

Update: The comment below indicates you are unwilling to work inside the ceiling void. In that case, I would encourage you to hire someone to do this job correctly. One of the main challenges with blown-in insulation is that it tends to settle over time. Even if you filled the entire void up to the attic joists, it would gradually pack itself down to where the top of the closet wall is exposed again. Given the enormous depth of insulation proposed here, it would settle more than normal and cause a repeat of the original problem.

  • Thanks for the input! Rolled insulation is also under consideration, however I perceive that it would be more difficult to install. I would have somehow to lower it into the void without entering it (may be difficult for me to get out). I also don't know how rolled insulation will remain in vertical spaces if I am not back-boarding it. I do agree it would be much more blow-in material, but all I have to do it "toss it in." My main concern there was what the weight would do to the stair ceiling.
    – DmitriyV
    Oct 13, 2023 at 14:33
  • @DmitriyV None of that information was in the original question. I will try to add 1 or 2 sentences to my answer. Oct 13, 2023 at 15:00

I think your best bet is to rent the blower! Your only downside is having someone loading the unit while you’re operating the hose.

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