I am attempting to take care of air leaks in the attic before new insulation is put in and I have a few questions.

  1. Along areas of the roof line there is light that comes through. I don't have soffit vents. I assume I should seal these? What is the best method?

  2. I have two ceiling fans that have pretty large gaps between the box and drywall. This seems too large for foam without getting foam into the box. I was thinking of just using recessed light cover. Is there a better idea?

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Here is a pic from the outside of the same area where the light was coming through. The gap scene there is just the space between the gutter and soffit and not the actual gap scene from inside the attic. The roof was replaced 3yrs ago and proper roof vents were installed too.

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  • 2
    Having open gaps like that is really bad...think of all the critters that could get in: bees, birds, squirrels, raccoons. Are you sure you don't have soffit vents...with screens? Commented Mar 6, 2020 at 5:36
  • Yep, there is an old wasp nest up there. No soffit vents.
    – junta
    Commented Mar 7, 2020 at 17:53

3 Answers 3


The reason eaves have this open space is so that moisture doesn't build up in the attic and cause rot. Completely sealing them off is generally not a great idea.

Attic insulation generally goes on top of the ceiling surface -- the space between there and the roof will generally be outside of the temperature-controlled part of the house anyway. It shouldn't really matter if the attic itself gets too hot or too cold. The main issues are vermin and moisture. There are vents you can install, and wire mesh will help with the vermin.

If you want to insulate a larger space than foam can handle, there are things called foam backing rods you can buy to fill large gaps -- once you've inserted it, there will be a much smaller gap between the foam backing rod and the surfaces, which can be filled with spray-in foam.


Your attic needs to be vented. That area that the light is entering into is probably some deteriorated eaves and if so need to be replaced, fixed. There really shouldn't be unscreened, opened areas going into your attic. Insulation usually goes to the wall cap and shouldn't cover any soffits.

Filling the gaps around the junction boxes can be solved with the low expansion foam or just by stuffing some extra insulation in there before the final layer is put it. A picture from the other side of that opening in the attic would help.

  • Do the additional photos help? I can get a better photo tomorrow along the gutter and roofline if that helps too.
    – junta
    Commented Mar 10, 2020 at 0:56
  • That new picture sure makes it looks like everything is sealed. Any views that show the opening from the outside?
    – JACK
    Commented Mar 10, 2020 at 1:01
  • I added a photo from outside, but the gap is behind the flashing. In the attic, I noticed that the gaps are off and on but not consistent throughout. I do have 5 static vents throughout the 1,500 sq foot attic. I have never noticed moisture up there and we don't have ice dams in the winter, which makes it seem like it is vented correctly. It seems like I should just fill the gaps with foam before insulation happens up there?
    – junta
    Commented Mar 15, 2020 at 20:58

I'm not rep'd enough to reply to comments, but re: venting: it looks like you should have ventilated soffits, and then the gaps above those soffits allow air to come in, flow up the roof and out your static vents. That circulation is a common design. Personally, that's what I'd do -- get ventilated soffits, make sure there are no other openings into the attic, then put in soffit baffles before insulating the floor of the attic -- the baffles would just have to run higher than the insulation. The baffles would let you put the insulation all the way into those corners without obstructing the air flow.

For the can lights, I think you're supposed to build a box around them so they have air space around them and aren't packed into the insulation. They look old -- I think there are newer ones that are ok with being surrounded with insulation...and maybe if you use LED lights, they wouldn't heat up too much.

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