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So I just bought a house and discovered the upstairs was what felt like 5-10 degrees difference from the main level. I'll try and add pictures of the insulation below. It seems well done but for some reason it's still very hot up there. I'm an hour away from Canada located in the far north of Minnesota so my climate zone is very cold. Not only do I worry about the heat in the summer right now but I'm also worried about it's performance this winter. It seems like it has adequate insulation, R-39 on the attic floor and around the 20 mark for the knee walls if not more. It has a ridge and soffit vents however the soffit vents seem small to me? There are quite a few of them however.

So I think the issue lies in either poor ventilation or poor air sealing, maybe both. The other issue could be that there's only 2 AC vents in the entire upstairs. One in each bedroom and no return vents anywhere (the upstairs consists of a large master suite, a walk in closet, and one smaller bedroom).

What do you think the problem is?

I want to check to see if they smothered the soffit vents or didn't allow for ventilation on the slanted part of the knee wall. I also want to seal the power outlets, switches, etc with spray foam. Should it be fire rated foam? The next thing to look at is air sealing but I would hate to have to tear into a wall insulation job done so well and have to redo horizontal fiberglass like that.

And yes I know I have to fix that pipe venting into the attic.

(EDIT) Okay so I climbed into what little attic I have access too and found that the soffit vents are not working as it's clogged by insulation. Under the Fiberglass is dense pack cellulose, quite a few inches of it, well above the joists. In the addition they did put air channels to the ridge vents but the only supply with the soffits clogged is a small gable vent. In the older part of the house, the room with the pipe in the picture there's no ventilation to speak of. Soffits most likely clogged I didn't climb all the way to it. There's nothing connecting this space to the mini attic above, where the ridge vents are.

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    5 degrees is to be expected. Ten is quite a bit but not out of the ordinary. It could simply be a matter of balancing your AC vents. I'm also in Minnesota and do some seasonal shifting. Windows matter (solar gain), as do activities in the home such as cooking. It'll be difficult to provide a confident answer with so many variables.
    – isherwood
    Jul 10, 2018 at 20:19
  • You need return vents as close to the ceiling as possible to remove the hot air from near the ceiling
    – d.george
    Jul 10, 2018 at 20:55
  • I keep the blinds closed throughout the day and the kitchen is under renovation right now so cooking doesn't happen much. Return vents to where? Wouldn't you need them to be active vents to push the hot air down and even then hot air still rises.
    – Cortland
    Jul 10, 2018 at 22:16
  • put something like this on the outside of the window so that the sun is cut before it touches the window glass .... amazon.com/Oriental-Furniture-WT-YJ1-8B50-24W-Natural-24-Inch/…
    – jsotola
    Jul 10, 2018 at 23:14
  • It already has nice blinds. Solar gain isn't a huge issue the house has a huge pine tree on the south side of the house and the windows aren't that huge.
    – Cortland
    Jul 11, 2018 at 4:11

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The soffits need to be cleared of their insulation. Otherwise you risk having mold forming due to the humidity not being able to get out.

There should be vent baffles installed to allow the air to continue to flow over the insulation.

You may have an HVAC contractor install additional events to push more air into the area.

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