Replies

1. Expert Member
   Michael Maines | Apr 20, 2023 09:16am | #1

   Better by what metric? How will this building be used? Obviously the first one would cost less and have lower environmental impact; the second one has more insulation and would cost less to operate. But there is a lot of room for discussion between those observations.

1. 
   shedworkshop | Apr 26, 2023 04:11pm | #2

   I suppose I'm optimizing for cost/performance. It will be used as a small, conditioned woodworking workshop. I'm going to see if I can use reclaimed EPS if possible to lower the environmental impact. The second one actually comes pretty close in cost to the first one surprisingly.

1. Expert Member
   Michael Maines | Apr 26, 2023 07:32pm | #3

   In a small space like that, I would go with the least amount of insulation that does the job. The environmental impact of using new foam will never be recovered. One caution about using reclaimed EPS: I used to recommend it, but a client used it on the exterior of her new house and she found that its tendency to crumble left a lot of micro-plastics which will pollute the local environment.

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   shedworkshop | Apr 27, 2023 03:44pm | #5

   Interesting, thanks for the heads up on reclaimed EPS. Maybe I'll see if I can find any rockwool comfortboard on Craigslist.

   The biggest reason for so much exterior R value was trying to keep the sheathing warm to hit the required ratio for condensation. Adding rockwool to the stud bays and rafter bays adds ~7% to the project costs, but increases their R values by ~2.5x.

2. 
   fromPok | Apr 27, 2023 01:42pm | #4

   I am doing zip-R + Rockwool. Lot easier to manage the construction process. zone 5a