It's helpful to know the code requirements and unfortunate that the builder was not familiar with them and did not follow the contract documents. Your builder and architect should have already presented you with all of the possible alternatives. One alternative should be to remove the non-complying work and building the roof as required by law and the contract. Section 9.19. Roof Spaces 9.19.1. Venting 9.19.1.1. Required Venting (1) Except where it can be shown to be unnecessary, where insulation is installed between a ceiling and the underside of the roof sheathing, a space shall be provided between the insulation and the sheathing, and vents shall be installed to permit the movement of air from the space to the exterior. 9.19.1.2. Vent Requirements (1) Except as provided in Sentence (2), the unobstructed vent area shall be not less than 1/300 of the insulated ceiling area. (2) Where the roof slope is less than 1 in 6 or in roofs that are constructed with roof joists, the unobstructed vent area shall be not less than 1/150 of the insulated ceiling area. (3) Required vents are permitted to be roof type, eave type, gable-end type or any combination of them, and shall be distributed, (a) uniformly on opposite sides of the building, (b) with not less than 25% of the required openings located at the top of the space, and (c) with not less than 25% of the required openings located at the bottom of the space. (4) Except where each roof joist space referred to in Sentence (2) is separately vented, roof joist spaces shall be interconnected by installing purlins not less than 38 mm by 38 mm on the top of the roof joists. (5) Vents shall comply with CAN3-A93-M, âÂÂNatural Airflow Ventilators for BuildingsâÂÂ. 9.19.1.3. Clearances (1) Except as provided in Sentence (2), where venting is provided to a roof joist space, not less than 63 mm of space shall be provided between the top of the insulation and the underside of the roof sheathing. (2) Where venting is provided at the junction of sloped roofs and exterior walls and where preformed baffles are used to contain the insulation, the baffles shall, (a) provide an unobstructed air space between the insulation and the underside of the roof sheathing, that is, (i) not less than 25 mm in dimension, and (ii) of sufficient cross area to meet the attic or roof space venting requirements of Article 9.19.1.2., and (b) extend vertically not less than 50 mm above the top of the insulation. (3) Ceiling insulation shall be installed in a manner that will not restrict a free flow of air through roof vents or through any portion of the attic or roof space. 9.19.1.4. Mansard or Gambrel Roof (1) The lower portion of a mansard or gambrel style roof need not be ventilated. (2) The upper portion of roofs described in Sentence (1) shall be ventilated in conformance with the requirements in Articles 9.19.1.1. to 9.19.1.3.

There are gaskets you can get for cans and you can caulk the penetration with the trim off also. I'd do that first and see if it helps. The knee walls are a problem but I bet the cans are the real issue. Radiant barrier is not worth a retrofit usually. During new construction, the OSB with barrier is just a small upcharge. I think it was like $200 for our house and so it is worth it. I have a friend who had a similar house to mine built but with no extra insulation etc. He is having a similar problem as yours and he has gotten several quotes including foaming the rafters. His plans include finishing the attic someday (why I don't know since he has a finished basement and is over 6k) so he is thinking of foaming the rafters. I encouraged him to get his cans sealed - sorry I don't know what he did and summer is over anyway... It frustrates me to no end when I hear this story over and over. Comfort issues that are really failures of sealing and insulation. GCs are so oblivious to energy costs but the comfort issues should come back and bite them. Cans into an attic are just always an issue. They are so rarely handled ideally especially in the South. But you can get a lot of mileage from the gaskets and caulking the edge when you take the trim off. I bet you can fix 50% of your problem. You can certainly reduce air movement 80% but you can never have the space taken up by the can to be any better than r-2 that lowers your r-30 by a significant amount. If you can get above the can (and I am guessing you can't), then you can seal 100% and insulate some. The knee walls are an issue for 2 reasons which you probably already know. They often around here are a r-13 batt with no enclosure. Batts work pretty poorly when not enclosed in a space. Also r-13 wall against a 140 degree attic is pretty bad when you are trying to maintain less than 80 inside. The rigid foam encloses the batt, deals with the thermal bridging at the stud and adds another r-4 to the wall. It probably cuts the heat gain by 50% by a combo of all these benefits. It really should be code. The 4x8 sheets cost $12 or so.

Explain the details as to flashing and barrier as you expect/want - if you can't be there during the installation, have them do a certain phase on one day so you can inspect it - and then they will complete it the next day - obviously it should be weather tight to the next day. As to shiming, they are explaining typical replacement window methods - again, if you want shims - insist on them - adjustment screws in the jamb should suffice though.

I rented a thermal camera from Home Depot. What it shows is that everything is a cool temp except for the perimeter/border of the shaft just where the skylight attaches to the curb. In that perimeter it's showing bright red in the thermal camera. Everything else - the glass itself, the shaft, the ceiling - are green or blue in the camera. Outside temps at the time were about 80-82. I showed it to the skylight contractor, and he said he cannot explain the red perimeter. Do any of the experts here have an explanation? I am wondering if the size of the skylight and the curb don't match, or there is some kind of sealing problem between the skylight and the curb. I am hoping for some expert advice from this forum. TIA.