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Community and Q&A

Prioritizing Insulation Upgrades

ThomasC001 | Posted in General Questions on

I recently purchased a home in Northern Virginia that was built in 1989.  Since I moved into the house in December, I’ve found that there are multiple issues with the insulation.  These issues result in the second floor being 5 degrees cooler than the main floor.  There is a walk out basement, and that feels about the same temperature as the top floor.  I was hoping for some advice on what to prioritize.  The issues I’ve found are:

·         Skylights insulated with batt insulation – some is falling off. The framing is such that it was done with 2×4 lumber, that was installed with the 4” side toward the drywall, so it’s only about 1.5” deep.  There are three of these. One in the hall, and 2 in the master bedroom.  Those 2 would be more difficult to reach, and I’m not sure how good they are insulated. The one I can see has insulation blown around one side of it.

·         The master bedroom is partially above the garage. I suspect the garage ceiling is not well insulated – if it is insulated at all. There is also an HVAC duct running through the garage portion, and I don’t think this is insulated either.

·         There is a dormer in this area above the garage that has batt insulation installed around it, but there is no OSB or foam board to air seal it, so the batts are visibly open on one side.  Where there are outlets near the batts, the insulation batts are pushed to the side of the outlets. I used spray foam insulation around the outside of the junction boxes to seal them. I was either going to move the batt insulation around them or cover them with spray foam.

·         The attic appears to have lots of insulation (the measuring sticks show about 24” where it’s not disturbed. Much less where it is.)  In many places, it looks like the insulation was added in an attempt to resolve the comfort issues.  It was placed on top of wood planks that were put down (probably above other insulation in the rafter bays.)  Near the eaves, there were insulation baffles to prevent insulation from getting in the soffits, but for the second application, they put foam baffles about 4 ft away from the far end of the baffle, so no new insulation was placed past that “wall”.

·         The attic is likely not air sealed. I can feel air blowing in through outlets on all levels. I’ve done some sealing of the worst ones, and some bad areas of the house on the main floor (like underneath the front door) and the basement where you could feel the breeze coming into the house.

·         There are three cantilevers. One that goes into the basement, and I could feel cold air coming in.  The floor above all is cold, and two of the three are easily accessible from the ground outside. The third in a bedroom may not be too bad, as the floor isn’t as cold there as it is in the other two.

I rented a FLIR i7 camera from one of the big box stores.  There are a lot of areas of the house on the top level along the walls in the 50-60 degree range.  My thought was to use the results of the pictures I took, and prioritize fixes based on the temperatures and positions.  I was thinking taking care of the dormer area with the open batt insulation first, followed by the garage ceiling/bedroom floor. However, I’ve read so much about air sealing the attic that I wonder if that might be a better return on my time/money.

I’d appreciate any thoughts on what people with more experience think I should prioritize.  For example, if I was only going to be able to get to one task this Spring, and one this Fall, which should come first, and which second.

Thanks for any help.


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  1. walta100 | | #1

    Air sealing comes first starting with the highest 33% then the lowest 33%


  2. Expert Member
    BILL WICHERS | | #2

    +1 for air sealing. You probably have a lot of air leakage, and that's canceling out a lot of your insulation that you do have in place. Blower door directed air sealing (which can be done DIY with a box fan or two and some smoke sticks if you're careful) is a good way to go about this. Once you've gotten the air sealing done, then you can move on to insulation. If you do the insulation and not the air sealing, you have far worse results than you'd expect.


  3. ThomasC001 | | #3

    I appreciate the feedback. I'll go forward with the air sealing and try to do it with a DIY blower door test to help focus where I need to work.

  4. user-723121 | | #4

    Those skylight shafts can be insulated with polyiso. Cut to fit 1 1/2" between the framing and then cover it with an appropriate amount of polyiso to get continuous insulation over the framing. Foil tape the seams.

    1. Expert Member
      BILL WICHERS | | #5

      Be sure to air seal around the skylights well. Any air leaks there tend to result in condensation within the assembly that will then run down, leak out somewhere, and mess up the dryall on the ceiling. I'd also recommend you try to avoid any air spaces between layers of the skylight shaft assembly -- fill any voids completely. Ask me how I know... :-)


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