I am now considering making the entire home ICF- not just the basement. Does ICF sense if I don't live there full time? At some point we expect to live at the place in CO four 4-5 months but will be coming home (for a week or more at a time) several times during that period. I am wondering if the ICF walls will take a long time to heat back up if I turn the heat off while we are gone. With mini splits would I need WIFI enable units so I could turn them up several days before we headed back? How will ICF do if I need a/c in the afternoon but heat at night? Will the thermal mass of the warm walls work against me? Here is the climate data for the months we will be there: June 77° / 41 July 81° / 45 August 78° / 44° September 72° / 37° October 61° / 26 Finally does an ICF house make more financial sense over an ICF basement/ conventional home with the house being 2x6 with R23 in the walls and R15 Dow Thermax? I enjoy low utility bills but only living there for 5 months out of the year, what would the payback be for a 100% ICF home over my stick built? Thanks

In general, you don’t want to do temperature setback with high thermal mass (e.g., ICF walls, HR slabs, etc). With your diurnal climate, you wouldn’t need AC at all if you used ICF. For your July 81/45, the ICF concrete core will hover close to 63 and your maximum indoor temperature will likely not exceed 2 or 3 degrees higher that that without any AC, assuming the home is well-sealed and ceiling is well-insulated. However, in the colder months you will see a significant heating performance hit if you do frequent temperature setback. In general, it is usually better spending your budget on improving the building envelope as opposed to spending it on expensive HVAC solutions. In addition to payback, you should also probably consider fire resistance, security, structural durability/lifetime which ICF tends to maximize. Cost of ICF varies from being the same or even less than stick to being much much more than stick depending where, how and who accomplishes it, so you should also evaluate if you can move that needle too before making a decision. Personally, I would never want to live in anything other than an ICF home.

Thanks, that helps a lot. As far as I know you can't buy a mini split that doesn't both heat and cool. So would you suggest a 95% AFUE propane furnace instead?

To be honest, I am not the best source for information. However, with that said, I have a vacation home in Zone 6 (I live in Zone 4) and my heating bill is......outrageous. I hired an "architect" to build a 26,000 cubic foot barn and it was an absolute disaster. Looking back, years later, I would have absolutely built an ICF barn. I'm currently looking to build an ICF home on the site. I have 7 Nest thermostats and they're great. I'm implementing a Crestron system in my primary home so I'll be switching to that, too. Nest, though, through ADT (We only have dial up), was a pretty good system all things considered. Actually, not really :P. But, for a secondary home, I would highly recommend ICF!

ICF homes take LESS time to heat up than other homes. The thermal mass is slow to react, but remember that there is a thick layer of insulation between it and you.
You won't ever need heat at night and AC during the day. The interior temperatures are a reflection of what is happening inside the home, not so much outside it. However, passive solar heat gain happens inside the home, so consideration of that is important.
Your climate looks absolutely ideal for ICF construction!