Hello all, Long time lurker, first time poster. Great forum! We (wife and I) are planning to build a home just south of Little Rock, AR. Zipcode is 72132. We will be acting as the owner/builder. Here is what we are planning: (1). ~3200 SF one-story home with a bonus room over garage. (2) 4.5" PU SIPs on exterior walls. I really like the PU SIPs. Wish I could do the whole thing (walls, roof and bonus room) but can only afford the walls. (3) Geo heat pump. Great HVAC guy close to my town with lots of geo experience. I am not as well versed in geo yet as I am in SIPs but I am pretty sure I want one! Need to do a little more research on exactly what we need. Also, planning on ERV. (4) Trusses in attic. (5) Insulation for attic and bonus room....hmmmm. This is where I am stuck. I would like to do all foam but it is fairly pricey. I was considering an inch or two of open cell foam on attic floor and seal all around the bonus room with it then blow in cellulose for more R. Basically, foam to air-seal and then cellulose for more R. From my understanding air-sealing is very important and it is hard to accomplish with a caulk gun so that is why I was thinking some open cell foam then cellulose. I am sure several of you will probably say spray the foam on the rafters and do not vent. I am not sure I am as comfortable with that as I am having a vented attic. Several reasons for that but I really don't want to get into that now. Just want to get some feedback/suggestions from some the experts out there about the insulation or any glaring issues you see with this brief description and any other helpful tips. Thanks!

Mr. Thomas,

Which PU SIPS have you considered?  OSB/PU and Metal/PU SIPS are available.  I am just curious.  I do not sell any products but I do donate a lot of time to interesting projects since I retired from teaching in the School of Architecture at Auburn University.

We are planning to use OSB SIPs. I appreciate any input you have.

Thanks
Jeremy