Radiant floor heating questions

[Eric Miller]

I have a new addition I installed over my attached garage and I'd like to install Radiant Heat in this new area (destined to be a bathroom). I don't necessarily need to rely on the radiant floor to "heat" this area because I have forced air but because of the unconditioned space below and the fact that it will be primarily a ceramic tile surface I know the floors will stay uncomfortably cool in the Winter if I do not use Radiant.

I currently have a Solar hot water heater for DHW and I think I will try to use that as a heat source -- again just to moderate the floor temp. I'm sure it won't supply enough hot water and will require electric backup but in the future I'd like to install a Wood Boiler and retrofit my whole house with a combination of radiant floor, baseboard and wall mount radiators. One task at a time though... Even if using my DHW as a heat source proves unsatisfactory I still want to install the radiant loops in this area because once the tile floor goes in it will not be possible to go back and add radiant loops latter (I don't have access to the underside of the floor).

I'm hoping I can install on top of my sub-floor with what I've seen referred to as radiant sub floor board, I'd like to keep the height increase to a minimum but I've already accepted that I'll probably have to re-frame my door ways to allow for the increased height of the floors. My drywall isn't in yet but will be soon so I only have a couple of weeks to work this out. If I had thought ahead I could have used a product like Warmboard for my subfloor but I didn't

I've done a Heat Loss but just not sure what to do next and thought I post here for help:

-How do I use my heat loss data to design the floor layout. For instance how do I calculate how far to space my loops etc.

-Any Internet sources for radiant subfloor board? I can't seem to find a supplier in my area (central MD). What are the alternatives?

-If I install a Wood Boiler in the future with the intended purpose of supplying a mixture of radiant floor and baseboard or wall mount radiators zones, how do you regulate the temperature between the two? Radiant floor has a lower temperature requirement correct? I'm assuming you don't want to pump 170-180 degree water through your floor. I guess you can use the return leg of a radiator zone to supply the floor zone but what if you want to keep the two zones independent? If you have a storage system holding 170 - 180 degree water I don't understand how you bring that temp down to 120(?) degrees to supply the floor zones. I know there are such things as mixing valves but where is the cooler water coming from to mix?

-How far should radiant lines be kept from the wax ring of a toilet base?

Thank you.

 

[Nofossil]

You have a great opportunity, but you need a lot of information quickly. Couple of choices:

1) Run, do not walk, to Amazon or your favorite book resource and buy John Siegenthaler's book 'Modern Hydronic Heating'. It costs about as much as a coil of PEX - well worth it.

2) Find a local radiant heating contractor who can help on-site.

3) Do a lot of web research. There are design guides and tools out there.

All the issues that you mention are important and solvable, but way too much detail to answer in a forum format.

 

[Eric Miller]

Thanks nofossil, I ordered that book this morning when I saw your post as I was running out of the house to get the kids on the bus and get to work -- looks like just the kind of resource I need! I'll have it in a couple days.

I've had no luck finding a local radiant heating contractor. These systems just are not very poular around here.

I'll definately be on the web whenever I get an opportunity to search for info. If anyone has any specific links to suggest I will defiantely check them out.

I did find two products that seem suitable for my purposes; Thermofin (http://www.radiantengineering.com/) and Infloorboard ((broken link removed to http://www.warmzone.com/hydronic-radiant-floor-heatin.asp)).

Does anyone have any experience with either of these products or alternatives?

 

[Hansson]

Maybe you can find some info here Eric
http://www.uponor-usa.com/

 

[mtnmizer]

-If I install a Wood Boiler in the future with the intended purpose of supplying a mixture of radiant floor and baseboard or wall mount radiators zones, how do you regulate the temperature between the two? Radiant floor has a lower temperature requirement correct? I'm assuming you don't want to pump 170-180 degree water through your floor. I guess you can use the return leg of a radiator zone to supply the floor zone but what if you want to keep the two zones independent? If you have a storage system holding 170 - 180 degree water I don't understand how you bring that temp down to 120(?) degrees to supply the floor zones. I know there are such things as mixing valves but where is the cooler water coming from to mix?



Thank you.

My hotwater system has a primary loop with separate zones to each part of the house. The basement has radiant
in the slab and is zoned just like the baseboard via closely space tee's.
The cool tempering water comes from the return side which can either go back to
the primary loop or feed into the tempering/mixing valve.. I keep the infow at 110 degrees with the tempering valve,
there is a temp gauge installed below the circ pump that is used to set the mixing valve. The return water
temp can be felt and is really cool until the slab comes up to temp..

I've had a wood boiler hooked into it for a week now and all I can say is wow....really nice.
We are in the middle of an arctic outbreak and the temp this morning is around zero..

Typically in this cold of weather my lp boiler would be running nonstop.. and it would be fairly cool in the house..
I now keep the radiant slab higher than before and it seems to heat the whole house , light duty storage, the main
storage tank is under construction and will be online soon....

 

[Gooserider]

These folks have a product that might do what you want, http://www.ezfloor.com/index.php and the Ditra floor / bathroom membrane people also make a similar panel without the insulation, but using the same "mushroom" style anchors for the tubing.

My recollection is you want to stay about 1 foot away from the toilet.

The Fred Seton / Radiant Design Institute website has a lot of info on it about laying out a radiant setup, and some practical tips on how to actually run the tubing. I've gotten the impression that not everyone agrees with everything he says, but I think the layout sections are probably pretty good, though he may like to use longer loops than are generally reccomended.

Gooserider

 

[Eric Miller]

It's late - early I guess - Got stuck at work and just got home but I noticed an Amazon package sitting on the table for me. Wow - that's pretty impressive, especially for 'free' shipping: I ordered it yesterday morning and it arrived today. I've been trying out their 'Prime' membership and I must say I'm impressed.

Thanks Hannson. I've been on uponor's site but your link made me re-visit it this morning and there is a lot of info available there that I missed before.

mtnmizer, I thought you would bleed off of the return leg to temper the supply but didn't understand how that could modulate the temps enough. Something in your post just made me understand that the mixing valve doesn't have to let any water in from the supply side. It can just keep cycling the loop and only pull in heat as required. I'm sure it wouldn't necessarily operate like that but thinking of it that way helped grasp the concept. Glad to hear your impressions thus far with your wood boiler are positive. Econoburn is a brand I will be looking when I get to the point of installing a boiler.

Gooserider, Thanks for the links. The ezfloor is something I haven't seen before. I don't think it's applicable to my current needs but it was cool to check out. They have some interesting pictures on the site. I will definitely revisit the Fred Seton / Radiant Design Institute at my first opportunity - looks like a lot of info available there.