Last night I was trying to explain to my wife what a frost-protected shallow foundation was. (Such wild nights we have!) The reason: Our architect is supposed to be coming over tonight; he's bringing along another member of the local energy-nerd mafia to talk about options for heating the new studio we're (eventually) building. So I was trying to explain to Hil why we needed such a big cheese to do the thinking for us. 

You and I, dear reader, have gone through this before. Above the frost line, the earth's temperature varies with the seasons: cold in winter, warm in summer. Put a building directly on top of the earth, and in winter the cold ground underneath will want to suck out your building's heat; in summer, to a lesser degree, it will want to radiate heat into your cool interior. So you've got to insulate against that connection to the earth, thermally separating your structure from the fickle ground's temperature changes. 

The studio, as it is now, sits on top of an uninsulated concrete slab; the heat just leaches out of that slab in winter. For the new place, we're going to dig a frost-protected shallow foundation (FPSF) around the perimeter of that slab – basically, a wall of insulated concrete stuck in the ground. The earth inside that wall will thus be insulated from the earth outside that wall. The temperature of the earth outside that wall is conditioned by the seasons-cool in winter, warm in summer. (Again, we're talking about above the frost line.) The earth inside that wall will be conditioned by – well, I don't really know. And that's why I need a big cheese to come talk to me. 

From what I understand, there are two ways we can heat the studio. (Cooling the studio is easy – that's what shade is for.) The first is mechanical: We'd place a layer of insulation on top of the existing concrete slab, lay down some radiant heat pipes and pour another layer of concrete on top, attach the whole thing to some solar thermal panels , and voilà – a radiant heating system. The second is wholly passive: The south-facing windows allow the sun to heat the concrete slab, which then warms the studio space; the walls also absorb the sun's heat and radiate it, ever so slowly, into the studio. (Yeah, it's more complicated than that, but we'll get to that later.) But that depends on a more or less daily supply of sunshine. Here in Boulder, we get plenty of sun, but there are periods – sometimes a week, very rarely even two – of consistent storms or cloud cover. What then? That's the question for the big cheese. 

There is, apparently, a solution – something called annualized geo-solar, wherein the heat collected by the earth in summertime is somehow stored for wintertime use. It's a bit over my head – and maybe over the limit of what's physically and financially possible with the new studio – but, again, that's why the big cheese is coming over. 

Frustrating, isn't it, all this ruminating?