Did you insulate under your slab at all, or just rely on the radiant? That’s where I see a lot of folks miss out on performance.
Couldn’t agree more—insulation under the slab is huge. First time around, I skipped it thinking the radiant would be enough. Big mistake. The heat loss into the ground was way higher than I expected. Second build, I used 2" rigid foam and it made a massive difference in both comfort and energy bills. It’s one of those things that’s easy to overlook but pays off for years.
Definitely agree that under-slab insulation makes a difference, but I’ll admit I was skeptical at first. The upfront cost seemed like just another thing contractors try to upsell. But after seeing my neighbor’s heating bills (he skipped the insulation), I changed my mind quick. Still, I wonder if 2" is always necessary—maybe in milder climates you could get away with less? Just feels like every dollar counts when you’re building from scratch.
TITLE: Building base structures—what if you had to start over?
I hear you on the cost side. Honestly, I’ve been crunching numbers for months and 2” of rigid foam under the slab just adds up fast, especially when you’re already stretching the budget. I’m not convinced it’s always worth it in areas where winters aren’t brutal. My cousin built in a zone 4 area and went with 1” — he hasn’t noticed any comfort issues, and his energy bills are still pretty low.
Contractors do love to push upgrades, and sometimes it’s hard to tell what’s actually necessary versus just “nice to have.” If I were starting over, I’d probably put that money into better windows or air sealing instead of maxing out slab insulation. At some point, there’s a law of diminishing returns… especially if you’re not planning to live there forever.
Totally get where you’re coming from. In milder climates, I’ve seen people skip the extra slab insulation and put that cash toward tighter air sealing or better windows, like you mentioned. Sometimes it’s just about balancing comfort with budget. That said, I do think even a little under-slab insulation helps with moisture and long-term durability, not just energy bills. It’s easy to overlook that part when you’re staring at the upfront costs, though...
Totally agree about the tradeoff—it’s so easy to get sticker shock and just cut corners on insulation. I used to think it was overkill too, but after dealing with some minor basement dampness a few years back, I kinda wish I’d gone for even a thin layer under the slab. It’s not flashy, but it does make a difference in the long run. You’re right though, sometimes you just have to pick your battles when costs start piling up...
