EcoRenovator  

Go Back   EcoRenovator > Improvements > Renovations & New Construction
Advanced Search
 


Blog Register 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 12-14-12, 05:14 AM   #1
opiesche
Helper EcoRenovator
 
Join Date: Jul 2012
Location: Rohnert Park, CA
Posts: 99
Thanks: 4
Thanked 14 Times in 9 Posts
Default 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!

opiesche is offline   Reply With Quote
Old 12-14-12, 08:22 AM   #2
Daox
Administrator
 
Daox's Avatar
 
Join Date: Aug 2008
Location: Germantown, WI
Posts: 5,467
Thanks: 1,110
Thanked 367 Times in 298 Posts
Default

Glad to hear it is working out good so far!

Do you have the number of heating degree days for last year and this year? That really helps compare how cold it is and give a better compairision.
__________________
Current project -
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
&
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Daox is offline   Reply With Quote
Old 12-23-12, 10:14 PM   #3
opiesche
Helper EcoRenovator
 
Join Date: Jul 2012
Location: Rohnert Park, CA
Posts: 99
Thanks: 4
Thanked 14 Times in 9 Posts
Default

The only thing I could find is the 2010 data:

Annual Heating Degree Days (Tot Degrees < 65) 2,749
Annual Cooling Degree Days (Tot Degrees > 65) 1,237


Generally, we of course won't see how efficient the system is compared to the forced air until we've got the full winter's worth of data, but what I'm seeing so far is encouraging
opiesche is offline   Reply With Quote
Old 01-23-13, 09:21 PM   #4
opiesche
Helper EcoRenovator
 
Join Date: Jul 2012
Location: Rohnert Park, CA
Posts: 99
Thanks: 4
Thanked 14 Times in 9 Posts
Default

December data is in:

Nov. 29th - Dec. 27th 2011: 142 therms - 52F avg.
Nov. 27th - Dec. 26th 2012: 126 therms - 50F avg.

So, that's almost 20 bucks saved over the same period despite 2 degree lower average temperatures. I'm currently installing insulation in the crawl space, so we'll see how that changes the usage further.

Of course the heating isn't the only thing using gas, but I'd expect our domestic hot water usage to not have changed significantly year over year.
opiesche is offline   Reply With Quote
Old 02-01-13, 01:41 PM   #5
gasstingy
Journeyman EcoRenovator
 
Join Date: Feb 2010
Location: Arab, AL
Posts: 491
Thanks: 109
Thanked 48 Times in 42 Posts
Default

Are you installing a radiant barrier above {or below} the insulation you're installing under the floor?

I'm not suggesting it is required by any means, but it seems like it might be of some value.
gasstingy is offline   Reply With Quote
Old 02-01-13, 08:43 PM   #6
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

Radiant barriers are ONLY useful if there is an airspace of at least 3/4" between the barrier and the heat emitter (concrete floor or anything else). Otherwise it is a conductor.
Mikesolar is offline   Reply With Quote
Old 02-01-13, 09:14 PM   #7
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 712 Times in 532 Posts
Default

Quote:
Originally Posted by opiesche View Post
Nov. 29th - Dec. 27th 2011: 142 therms - 52F avg.
Nov. 27th - Dec. 26th 2012: 126 therms - 50F avg.
I've kind of forgotten how you are heating your water... I seem to recall that there was a water heater involved in your hydronic system... is correct? A separate water heater?

I keep seeing estimates of 20% of total energy for DHW.

If that's true, and your DHW didn't change, then I'm calculating that your heating costs went down by 14%.

That's enough right there to make it worth it.

But, as you have said, you haven't insulated yet...

But what you didn't say is that your heat source is right in the floor, next to an unheated area, with a big delta-T.

I mean with convection heating, you are heating up all the surfaces and not at all concentrating that heat on the floor... with that big delta-T waiting on the other side, just looking for BTUs to munch.

So when you get that insulation in, you should see a very large jump in efficiency.

* * *

And regarding what Mikesolar said in the previous post, I have seen studies that suggest that 3/4" (or greater) is optimum, but that smaller spaces are also effective, but progressively less so as distance is reduced... and direct contact is where you lose all radiant reflectivity effect.

Best,

-AC
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Old 02-03-13, 11:39 PM   #8
opiesche
Helper EcoRenovator
 
Join Date: Jul 2012
Location: Rohnert Park, CA
Posts: 99
Thanks: 4
Thanked 14 Times in 9 Posts
Default

Yes, it's a separate water heater (30gal) in a closed loop system. It seems that the cost went down noticeably, yes - and I agree, floor insulation should make a huge difference, more so than with forced air heating.

I am noticing this in my gas/electric bill, too. The two are combined, and for some reason PG&E won't show me my electric usage over time, but assuming that that's been roughly equal, I'm saving between 20 and 50 bucks a month, which would put the payback period for the heating system at about 5-6 years - pretty good if you ask me.
I've insulated part of the floor now, and the difference in feel is noticeable. The colder areas of the floor in between the heating loops are now noticeably warmer, and I've had to close the valves for those zones a bit, because it was getting too warm in the insulated areas. I hope to get most of the rest of the insulation installed next weekend, at which point I'll likely need to lower the water temperature a bit, too.
opiesche is offline   Reply With Quote
Old 02-04-13, 12:40 PM   #9
Exeric
Apprentice EcoRenovator
 
Join Date: Aug 2012
Location: California
Posts: 274
Thanks: 19
Thanked 37 Times in 28 Posts
Default

Opiesche,
I'm glad you didn't take my advice and decide to not insulate the floor and ONLY insulate the perimeter of the foundation. When I gave that advice I didn't know you were using a hydronic system. I was thinking forced air. This is good advice you are getting here for your situation.
Exeric is offline   Reply With Quote
Old 02-04-13, 01:06 PM   #10
gasstingy
Journeyman EcoRenovator
 
Join Date: Feb 2010
Location: Arab, AL
Posts: 491
Thanks: 109
Thanked 48 Times in 42 Posts
Default

Quote:
Originally Posted by Mikesolar View Post
Radiant barriers are ONLY useful if there is an airspace of at least 3/4" between the barrier and the heat emitter (concrete floor or anything else). Otherwise it is a conductor.
If the fiberglass insulation he's installing is directly under the floor {and the water loop} and the radiant barrier is not crushing the fiberglass up to the floor when installed, I am of the opinion that there would be adequate airspace. I believe it could be of some benefit in this instance. However, I can't say it as a fact because I've not done it myself.

gasstingy is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 08:31 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design