Radiant floor heating (on the cheep)
I’m planning on building a small bathroom on the top floor of my house and want it to have a warm tile floor. My idea is to remove the existing flooring to the joists and run one 3/4″ copper pipe between each joist about 2″ under the new sub flooring with insulation under that. I’ll add a section of baseboard radiator and “balance” valves with separate control of the flow of water through the baseboard and piping under the floor. This whole thing will be connected to the existing forced HW heating system. I can’t imagine over heating the floor since heating pipes are run under the floor all the time. I remember as a child living in a house where the hot water pipe to the bath room ran under a spot next to the sink and how nice and warm the floor felt in this area after a shower.
I’ve always wondered why I’ve never seen this kind of radiant floor heating before. Radiant floor heating with separate pumps and controls make sense for a cement slab, but why go to all the expense and risk driving a nail into it on an above grade floor?
Replies
What is your system water temperature? Running 180 degree water may overheat your floors. Above 87 degree floor temp, the room will be downright uncomfortable. If you run less pipe to compensate, it will have hotspots. Could cause undesirable expansion and contraction as well.
The whole idea with RFH is to have a large low temperature mass providing comfortable heat.
Without ripping out the subfloor, you could install conventional RFH in a thin slab or with warmboard. Cost may be less than you think.
There are many schemes to get low temp supply.
See:
http://www.pmengineer.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2732,62497,00.html
We have zone lines that run about 4" below a section of Pergo flooring on their way to the baseboard radiator and they do a decent job of gently warming that section of the floor. I wouldn't put high-temp lines under hardwood though as it might cause long-term issues with expansion/contraction.
With a tile floor, I suppose some metal heat spreader plates or fins clamped to the pipes and spaced 4-6 inches below the subfloor would be even better. They would spread the heat over a wider area but you'll have to experiment to get the correct # of plates, width and spacing.
Edited 12/2/2004 5:26 pm ET by TJK
Thanks TJK,
Unfortunately I will not be able to experiment with adding fins to the plumbing. Once the tile is down that's it I will be happy if the tile floor doesn't feel cold. There is plenty of wall space to adjust the size of the BB for heat if I need to.
Take a look at electric. Not so expensive to install but somewhat expensive to operate. It's hard to reduce installation costs after the fact, but usage costs can be controlled with a timer.
Make sure you size it right...my contractor installed a wimpy system that works only if left on continuously. The Jerk.