Replies

1. 
   walta100 | Aug 17, 2024 11:45am | #1

   It does look like you have almost deliberately made unfortunate choices that have precluded the low cost affective options.

   I am not saying this to be mean or hurtful consider you made the choices that limited your options and were given poor advice.

   Given the steel frame roof the only affective place for insulation is on the outside if the steel! That means the current roof must be remove insulation installed and a new roof installed. If you spray foam between the 16 inch on center steel joists, when it is below zero outside the tops of that joists will get very cold and since steel conducts heat and cold so well the bottom of each joist will be almost as cold and almost certainly below the dew point of the air in the home. That part of the drywall will get wet often, the screw that hold up the drywall will rust and make brown spots and mold seems likely to grow.

   The same is true for the exterior walls they will need exterior foam.

   Are you in zone 3 or 4?

   Seems like the code min insulation R38 or 49 for the roof that is 7-10 inches of foam. The wall will need R 20 so about 4 inches of exterior foam. Maybe the windows and zip can remain but you will need a well thought out plan for flashing them and water management.

   Walta

1. 
   JG423 | Aug 17, 2024 06:20pm | #4

   Walta,
   I came here for constructive advice, not to be criticized.
   Trying to make the best of a tough situation, thanks.

   Zone 4
   T&G interior on the roof line, and board and batten on walls. No drywall anywhere.

2. Expert Member
   Michael Maines | Aug 17, 2024 02:36pm | #2

   I agree with Walta; unfortunately, steel is so conductive that it renders cavity insulation of any type not quite useless, but not far off. Encapsulating the interior of the steel with continuous insulation would be better than having no continuous insulation, but the right approach is to insulate the exterior.

   The good news is that if you don't have claddings installed yet, you can go right over the Zip sheathing with rigid foam (or mineral wool, or ideally wood fiber) and install your claddings over that. Or you can install Zip-R over the existing Zip sheathing.

1. 
   JG423 | Aug 17, 2024 06:19pm | #3

   Thanks Michael, We still do have the option of doing rigid foam over the exterior walls, cladding is not up yet.

   Im not willing to rip a brand new roof off however, so at a loss as to how to handle the roof, hence coming here for constructive advice.
   .

3. 
   walta100 | Aug 18, 2024 12:35am | #5

   I am sorry if your feeling got hurt.

   Your question was up for a full day with zero replies. What that tells me is lots of people read you question had similar thoughts to mine and made the choice to ignore you rather than risk hurting your feeling.

   Consider the first step in solving any problem is admitting there is a problem.

   Since you have taken removing to roof is off the table. Given that insulating between the steel is impractical. The possibility left is 7-10 inches of foam on the interior but I am guessing you will not give up that much ceiling height.

   Before you have the foam put on the walls be sure you have a detailed written plans for water management and window flashing.

   With you wood interior you will need an air and vapor barrier on the interior side of most insulations generally painted drywall under the wood is the low cost way to get them.

   Walta

4. Expert Member
   Akos | Aug 18, 2024 09:35am | #6

   You are not quite south enough for some of the simpler options. In zone4 you still have to worry about winter time condensation in the roof.

   You are also in warmer climate so R values are not as important as in snow country. Even when it is scorching hot outside the dela T might only be 30F, so big R value doesn't hurt but not needed.

   The easy way to get R value has already sailed since you have a steel structure, but can still improve on it.

   The last thing you do want is to fill all your walls and roof with spray foam. Never mind the environmental footprint of that much foam but because of the steel, it makes almost no difference form batts. For example, in your roof, 5.5" of cc SPF has a center of cavity value ~r35. You put that between steel studs you get an R10 assembly. Insulate with fluffy and it is an R9 assembly:

   https://up.codes/s/metal-stud-wall-effective-r-values-for-metal-framing-and-cavity-only

   The issue is you have built an unvented roof now your only option is spray foam. In your case, I would recommend a flash an batt for the roof. In your climate you need 30% of your R value as closed cell spray foam, so for an R38 roof, that is only R11 so not that much foam. You will need some more thickness to get up to R38, the best option is to fur out your steel rafters with 2x4s on edge to add some more depth and install batts. This also gets you a decent thermal break for the steel plus it is way easier to attach T&G to it than to steel.

   T&G is a also pretty leaky you want something under it. Drywall is the simplest but one of the variable perm membranes will also work. You don't want something impermeable though, so no poly. You can skip any barriers if you up the spray foam layer a bit, I think it is something around 50% of you overall R value.

   For the walls, spray foam makes zero sense, gets you no R value bump and costs a lot. Insulate those with batts. The R value is pretty low but you are not in cold climate, not ideal but will work. If you want better than that the above suggestion of Zip R is really your best option.

   Attaching wood paneling to steel is not fun (possible but needs special screws, regular self tappers don't work), might be also easier to strap the walls with 2x3 or 4 on edge. This will give you an interior thermal break plus more space for insulation which would let you skip the exterior insulation.

1. 
   JG423 | Aug 18, 2024 11:18am | #7

   Thank you Akos, that’s a super helpful answer and makes sense. Appreciate it