Hi,

We are undertaking a renovation project, not the best time I understand and we are already feeling the pain, and are at the point of insulating the building. I have been reading through the questions and answers and learned a lot already but feel like my situation is somewhat unique which warrants asking the community directly.
We started with single story ranch about 1700 SF in zone 5 (Chicago suburbs). the house was built in 1950s. We are adding a second story about 1500 sf and gutting the inside of first but keeping the footprint of the building as it. Second floor being the addition I have blank canvas but first floor we have to deal with existing 2×4 walls. Here are the details:

– Flat roof with 2X12 double joists and mod bit roofing material in black. The roof is already done, so I cant put any rigid foam on the outside. With the lumber prices as they were in summer I couldn’t have put another layer of plywood on top of the insulation.
– Second floor 2×6 Walls.
– First floor 2×4 walls. with brick exterior. I think the sheathing  has some insulation in it as its not plywood.

What are my options to insulate the place most economically and having the most efficiency. I am pricing my options and trying to figure it out in these crazy times. I have already gotten a quote to use a combination of open cell and close cell for the whole building but i think i can do better.

This is what I am thinking and looking for options.

Siding will be hardie board on second floor. We have brick on the first floor and are debating about doing hardie unless brick has advantages for insulation purpose and we should keep it.

– Second floor: Rigid foam insulation (reclaimed for cost saving) on the outside on the second floor and dense packed cellulose inside. I am planning to seal the gaps for e.g. where studs meet joists. Is that overkill if i have continuous insulation outside. Furring strips to hang the siding.
– Ceiling: Spray foam insulation in the ceiling cavities. I still have the joists which will be uninsulated so I was thinking of putting rigid foam (open to ideas which one)  on the joists under the drywall. Is that a bad idea besides time consuming ?
– First floor:  i can get R-19 with closed cell spray foam and that seems to be the only option to me besides Mooney wall. If we don’t keep the brick then i will be able to add rigid foam outside , which will help with filling the gap between foundation and studs (another thing to think about if we take down the brick).

Apologies for the long post. I figured if I provide more information to the experts i will get a better solution. I am a home owner taking on this project so looking for expert opinions and open to ideas.