Tips for Building a Warm Floor in 3-Season Room
LESLIE: Jay on the line who’s got a question about a three-season room. What’s going on over there?
JAY: Building a three-season room and I want to use passive solar: the sun coming in. And I want – it’s concrete foundation. And I was thinking of putting a 2-inch rigid foam but it’s above ground. And then the 2-inch – above the 2-inch rigid foam is about a 2-inch layer of concrete. And then I want to use red terracotta on top of that. So when the sun hits it, it absorbs the heat and absorbs the concrete and I’m thinking of the insulation, it wouldn’t – it would keep there.
TOM: You’re talking about only using 2 inches of concrete in the floor, on top of the foam?
JAY: Well, it’d be on dirt floor.
TOM: Yeah. But you need more than 2 inches of concrete. It’s not going to be self-supporting if it’s just 2 inches. If you get any movement, that’s going to crack. So, I think you have to put the foam insulation down first and then woven-wire mesh and then at least 4 inches of concrete, so that it doesn’t crack and so it’s dimensionally stable.
Now, what kind of windows do you have in this? How are you going to get the solar gain into this?
JAY: Well, that’s my second question. What do you have for ideas?
TOM: Well, a common mistake that people will use is they’ll use low-E windows, which we always recommend. The problem is that if you use low-E, you’re not going to get any heat gain at all. Because low emissivity inside the gas of – that makes up the thermal-pane windows is going to reflect the heat back out.
So, rather than relying on the entire section being heated just by the sun, you might just want to consider making this as insulated as possible and then adding a minimal amount of heat, supplemented by the sun. Because you’re going to need something, because it’s not going to be heated by the sun all the time.
TOM: So I would just make a really well-insulated structure here. If you can orient it to the south to take up the heat of the sun, that’s great. But remember, what heats that room in the wintertime is going to heat it in the summertime, as well.
JAY: That’s great help, guys. Thank you very much. I appreciate it.