Jacq Smyth

I'll offer my opinion. Please remember that you asked for it.

The impact of the decisions of the few people who control massive systems, coupled with the impact of the activities of the other 8 billion people on the planet, means that your actions don't matter. What you do or don't do doesn't even rise to the level of a rounding error.

Step 1: Get over yourself, and get on with living your best life.

Step 2: Review your diet for its possible biochemical impacts on your psyche.

Posting for everyone's future reference

https://www.aaha.org/your-pet/hospital-locator/

Post-project follow up. The existing roof rafters couldn't bear any additional load, so I added a set of ceiling rafters below and structurally separate from the roof. That gave me space to use cheap pink fiberglass batts as well as 5/8" drywall. So far I'm pleased with how it turned out. I'll probably be adding foamboard exterior shutters later this winter to replace the blankets that get hung up over the windows every cold night.

Troy Rhodes, the builditsolar calculator link you provided is exactly what I needed. Thank you! I just used it to run a quick analysis and I think a single layer of 1/2" polyiso foam board is the right way to go for now. Also, your idea regarding an additional layer of glazing is well-taken. I do intend to do rudimentary movable insulation, specifically blankets over the windows at night. It might make sense to run some plastic up as well.

John Wolfram, thank you for another idea that I hadn't considered. I'll check the economics of the other options before I buy the polyiso.

I have what used to be a 12' x 16' carport that I've double-glazed on three sides. The fourth side is against the house. I'm right in the center of USDA Zone 6, and I intend to use the carport to overwinter potted citrus trees, hoping to keeping the room at least 40 degrees Fahrenheit with passive solar and electric heat backup. This will be a step up from the basement, where the plants have overwintered the past two years. In the longer term, I hope to build a walipini to take over this function.

The ceiling is currently solid plank roof sheathing on exposed 2x4 rafters, and I want to insulate it. Is there a rule of thumb I can apply to determine what R-value I should insulate the ceiling to? I've seen the charts showing the diminishing returns of added inches of insulation, but I have a feeling that heat will be pushed out the R-2 glazing of the walls long before reaching the spot on the charts that assume conventional R-19 walls and R-30 ceilings (but I certainly could be wrong!). The rafters are puny, so another factor is weight, so foam board is probably what I'll use, so cost becomes an issue at conventional ceiling R-values.

I'm not necessarily looking for citations to academic studies. I'd just like to hear the opinions of those who have experience considering these kinds of insulation tradeoffs in design situations that are a bit off the charts. Thank you.