DIY hydronic floor heating - performance

opiesche · 12-14-12, 04:14 AM

Hi all,

I figured I'd start a new thread because I wasn't sure how many people were still subscribed to the old one (located here: http://ecorenovator.org/forum/renova...tallation.html), and I've got some data that might be interesting to a lot of people.

Our 100% DIY hydronic floor heating system has been in use for about a month now (since Nov. 15th). The custom built controller with custom software is up and running great, and everything is working very well.

I'm running supply temperatures of about 110 degrees from a bog standard natural gas 30gal tank water heater (and only a 32k BTU one, at that!), return is around 98-100. On the coldest nights (~30 degrees), the system can still keep the temperatures at a relatively comfortable 70 degrees, although the pump is running almost 80% of the time to maintain it. We lose a lot of the heat through the subfloor into the crawl space, so the next step is to invest in some crawlspace insulation, which should improve the performance significantly (I actually expect over 50% efficiency gain from that, since we've got more material on top of the heating loops than below at the moment!). I can't tell for sure how much the water heater runs, but I'd say it's less than 20% of the time (9 times out of 10 I go to the garage, it's not firing).
With normal exterior winter temperatures (35-40F), the system has no trouble maintaining over 70 degrees, but it's really unnecessary - 69-70F air temperature is quite comfortable with heated floors.

The feel of the house is really nice. No more dusty air blown through the house means our winter allergies have all but disappeared, and the house smells significantly better. Even though the floor doesn't get really warm to the touch (noticeable, but only maybe a degree over ambient), I can feel the warmth from the floors as soon as I walk downstairs. The distance of 12" between loops means that you can notice cooler and warmer spots on the floor, which I anticipate will improve once the underfloor insulation is installed.

I've also got the first bit of energy usage - thanks to PG&E's web site, I can track my gas usage, which for Oct. 25th through Nov. 26th is:

2011: 97 therms
2012: 50 therms

Exterior temperatures are comparable to last year's. Of course this is less than a month's worth of data, but so far the results are very promising. Not only is it much more comfortable, it also seems to use noticeably less energy - despite the fact that a significant part of the heat is currently lost downwards.

Once I've got more gas usage data, I'll post it here. Now it's time to shop for moisture barrier and fiberglass batts for my crawlspace!

12-14-12, 04:14 AM	#1
opiesche Helper EcoRenovator Join Date: Jul 2012 Location: Rohnert Park, CA Posts: 99 Thanks: 4 Thanked 14 Times in 9 Posts	DIY hydronic floor heating - performance Hi all, I figured I'd start a new thread because I wasn't sure how many people were still subscribed to the old one (located here: http://ecorenovator.org/forum/renova...tallation.html), and I've got some data that might be interesting to a lot of people. Our 100% DIY hydronic floor heating system has been in use for about a month now (since Nov. 15th). The custom built controller with custom software is up and running great, and everything is working very well. I'm running supply temperatures of about 110 degrees from a bog standard natural gas 30gal tank water heater (and only a 32k BTU one, at that!), return is around 98-100. On the coldest nights (~30 degrees), the system can still keep the temperatures at a relatively comfortable 70 degrees, although the pump is running almost 80% of the time to maintain it. We lose a lot of the heat through the subfloor into the crawl space, so the next step is to invest in some crawlspace insulation, which should improve the performance significantly (I actually expect over 50% efficiency gain from that, since we've got more material on top of the heating loops than below at the moment!). I can't tell for sure how much the water heater runs, but I'd say it's less than 20% of the time (9 times out of 10 I go to the garage, it's not firing). With normal exterior winter temperatures (35-40F), the system has no trouble maintaining over 70 degrees, but it's really unnecessary - 69-70F air temperature is quite comfortable with heated floors. The feel of the house is really nice. No more dusty air blown through the house means our winter allergies have all but disappeared, and the house smells significantly better. Even though the floor doesn't get really warm to the touch (noticeable, but only maybe a degree over ambient), I can feel the warmth from the floors as soon as I walk downstairs. The distance of 12" between loops means that you can notice cooler and warmer spots on the floor, which I anticipate will improve once the underfloor insulation is installed. I've also got the first bit of energy usage - thanks to PG&E's web site, I can track my gas usage, which for Oct. 25th through Nov. 26th is: 2011: 97 therms 2012: 50 therms Exterior temperatures are comparable to last year's. Of course this is less than a month's worth of data, but so far the results are very promising. Not only is it much more comfortable, it also seems to use noticeably less energy - despite the fact that a significant part of the heat is currently lost downwards. Once I've got more gas usage data, I'll post it here. Now it's time to shop for moisture barrier and fiberglass batts for my crawlspace!