Warming Up a Floor

saikosis

I have about 340 square feet of floor in my house that's above a crawl space. This room has the biggest radiator in the house (one pipe steam) so the air is pretty comfortable, but the floor itself is always very cold in the winter. Previous owners added fiberglass batts up in the joists above the crawlspace, but the floor is still cold and drafty. I've never been in the crawlspace, so I'm not sure what's there is sufficient to insulate the floor or if it was done properly. I have a insulation contractor coming today to check it out. I have a feeling though there's not much I can do with insulation by itself.



We're currently sizing up a new steam boiler for a switch from oil to gas. I believe you can run a radiant zone off a steam boiler using the tappings below the water line. I'm wondering if a radiant zone like this is a viable way to warm a floor above a crawlspace. We'd keep the original radiator (61.33 square feet), so I'm not talking about heating the whole space. I just want to bring up the floor temperature a bit so you can stand in the room without wearing snow boots.



Will this work? What calculations do I need to make? The boiler will have between 125 to 150 MBH output. Of that 30 to 50 MBH is for the pipe pickup factor, which I believe becomes available again once the pipes are heated. Is that enough to warm a floor?