# Radient underfloor/in floor heat



## Kevingr (Mar 10, 2006)

Ok, now that I've decided on my storage tank (see my other thread on that topic) it's time to get the PEX laid out for the underfloor heat.

Two story house, goal this fall is to only get the first floor done. The second floor will be done with in floor heat using new subflooring since those floors all need to be re-leveled (think old farm house!).

So, I plan on using 1/2" pex tubing 8" on center between all the joists (in my case it's actually log joists, not dimensional lumber). I will insulate between the joists with appropriate material to keep the heat up and not going down into the basement. 3/4 of the main floor is either tile or vinyl, the other 1/4 is carpet. 

I've been doing lot's of reading on underfloor heat, some companies recommed to not use underfloor heat with carpet on top. Other's say it's fine but you need to use the aluminum sheets to spread the heat out. Most companies say water in 120F range is adequate, even with carpet. I just got off the phone with one guy and he says the underfloor heat needs to be 140-180F (ouch! that's baseboard heat hot!) regardless of floor covering.

Anyone with real world experience have any tips/tricks or words of wisdom? I plan on starting this part of the project this weekend. I already understand balancing the loops and maximum loop length with 1/2" pex, I guess I'm wondering more about floor coverings and water temperature.

Thanks!


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## wendle (Feb 22, 2006)

What made you decide to go with that instead of baseboard heating? I'm working on the same thing, but thought baseboard and/or exchangers was the way to go. I also live in an old farm house, but no carpeting, two story. I'm going with solar water heat and an outdoor boiler. I haven't purchased the pex or baseboards yet.


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## ET1 SS (Oct 22, 2005)

I put my PEX underneath the subflooring. I cut notches in the tops of the joists and laid the PEX before I laid the subflooring. I used 5/8" PEX as I figured it would present less resistance to the circ pump, and extend the life on the circ pump.

I used aluminum flashing 14" wide. I cut the flahsing in 3' lengths, and I made a jig to wrap the flashing around a 5/8" blackpipe. Each piece of flashing is shaped like:

----u----

I tried to show you the shape that I got from each peice of flashing. A 'U' shape that snug grips the PEX with 6" of flashing like wings on either side.

I then applied the flashing, up from underneath and I stapled it in place.

Metal sheeting gripping the PEX and taking the Btu out away from the PEX to distribute it across the floor.

I read about sealing the underside of the joists to insulate it, and I spoke with others. the thing is, where does heat go? It tends to go up. It will not radiate downward much at all. Heat just does not do that very well. It wants to go up, So even if 40% of the Btu goes downward immediately, it soon is traveling back upward again.

We like it.


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## Kevingr (Mar 10, 2006)

Wendle, In the heart of the winter I was figuring on 120F water in my storage tank, which I figured would be hot enough to run through the underfloor PEX. Baseboard heat needs to be in the 150-180F range, the return water is around 140F. If I run 120F water in the baseboard heaters I would in effect be lowering the temperature. I do have baseboard hot water today with a propane fired boiler. That's with my current baseboard/boiler arrangement. I plan on keeping my current boiler and baseboard as backup heat, I do not want to go to the expense of changing that out since it does work as is, although not the most efficient. 

ET1, do you know what your water temperature is? My problem is with the underfloor heat I have 1" planks on top of the log joists, then 1" rough wood flooring, then a carpet pad, then carpet. That's why this new guy is telling me I need at least 140F water to make any difference where the carpet is.


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## ET1 SS (Oct 22, 2005)

For the past two winters we have kept our propane water heater set to 120F.

We have 3/4" subflooring in place [Advantech brand]. We do not have a floor covering down yet. We ran out of funding. We are looking at Terrazo.

Water from our water heater is circ'ed through the home's loops, through a thermal bank and back again to the water heater.

Our wood stove heats water, which circulates through a thermal bank. That water can be kind of hot.

The thermal bank should temper it down a bit. Also going into the thermal bank is the return water [rather the water returning from the home's loops]. At that location in the home's loop, the water is the coolest, right before it goes to the water heater.

Water from our woodstove and water returning from the floor loop are mixed in a 100 gallon tank. Before it goes to the water heater. When it stays above 120F, then our water heater does not kick in.

It may take days for the heat to be 'felt' from a radinat heating system. Heat from a radiant floor feels different.

Baseboards have fins which heat the air. The air is warmed while the floor remains cold. to heat the floor using baseboards will take a great deal of fuel. A thermostat mounted on a wall at 4' high will measure the air temp at that height, and not the floor temp. And of course the heated air will gather along the ceiling.

Radiant floors heat the floor, and therefore your feet and legs. We have thermometers mounted on a wall at 4' high, they measure the air temp at that height. They may say that the air is 50F, but it will feel 70F to us.

With radiant floors there is much less hot air along the ceiling. Less waste, and less fuel is burned.


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## tallpines (Apr 9, 2003)

We have radient heat "in" the floor....or in the ceiling of the basement.

New house-------built with the standard flooring panels (is it 5/8 inch) nailed over the joists.
Then we nailed down 1 X 1's on top of that paneling but lined up with the joists leaving the end spaces (next to the walls) open.

I laid down and stapled into place 6 sections of 250 foot PEX. Each section is hooked up to its own "on and off" control so incase of a leak, or to regulate the amount of heat in a certain room, just one section of the PEX can be adjusted without affecting the other sections.

Then we poured a lite weight cement over the PEX just to the top of the 1 X 1's.
The cement helps hold the heat.
And then over the top of the cement we put wide pine boards which were nailed to the 1 X 1's..............and varnished the whole works.


The water is heated with an outdoor wood boiler.
We've used the system for 6 years now and really like it.
This was our only heat source.
Howerver, when DH doesn't get some logs on the fire early enough in the morning, it will get chilly in the house, and takes awhile to warm up again.
Or---on the coldest of cold Wisconsin days it was impossible to get the house temp much above 62.

Once the fireplace (gas) was built we were able to leave it's thermostat set on 60.
Now when the outside fire gets low, the gas fireplace kicks in to help keep the place much more cozy.
We burn about 100 gallons of propane a year plus lots and lots of wood in the outdoor boiler.

Before the fireplace was built We had the water temp set too high and apparently that was causing the water pump to burn out too quickly (about twice a year).
Now that we have the fireplace heat, the water temp is turned lower-------saves on the pump but increases the use of the propane.

About 1/3 of the house is the Great Room with vaulted ceiling 22 feet high and lots of windows.
In this area of the house I placed two rows of PEX between each joist.
In the other areas there is just one strand of Pex.

I'm really glad we put in separate controls for each 250 feet section because this allows us to adjust the heat in the bedroom areas where we prefer it to be cooler.


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## wendle (Feb 22, 2006)

I'm glad I didn't already get some baseboard heaters. I sure like what I'm seeing on the ideas on here. It looks like my old farmhouse would be pretty easy to install like ET1 SS did. 
. 
I was also thinking about adding a couple of air exchange units upstairs where it will be impossible to get under the floor. 

Where do you all get your pex? 
I've been looking on ebay and that looks the best so far.


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## ET1 SS (Oct 22, 2005)

Pexsupply.com

I only used 600'. I bought a 1,000' roll. I plan to use the left over 400' as a groundloop for cooling.


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## tallpines (Apr 9, 2003)

We bought all of our supplies at our local Menards (home improvement) store.


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## Jackpine Savage (Jul 4, 2002)

Hey Kevin -

I'm in the middle of a similar project. 

I had a company that specializes in radiant heating do the system design. They did heat loss calcs on each room. To get down to a 120 degree supply they recommended the extruded aluminum plates. We have one room with carpeting, the master bedroom, and they said it will be marginal. But we planned on removing the carpet in the future anyway.

Basically our system is a Tarm indoor wood boiler heating a storage tank with an off peak electric boiler for backup. Most of the basement has tubing in the concrete. The first floor has extruded aluminum plates, 1/2 tubing, 8" on center. The main portion of the second floor will have a radiant ceiling. The two upstairs bedrooms will have Runtal radiators, and the upstairs bath with have a Runtal towel warmer/radiator.

I have most of the first floor tubing in. The second floor won't get done this year.

If you are interested in the extruded plates I have a direct source.

If you get up this way, stop in!

Craig


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## Kevingr (Mar 10, 2006)

Hey Craig! Nice to hear from you again!

Sounds like what you're putting together is very similar to what I'm doing except I want to use solar instead of wood. I've got a local guy doing some calculations for me now. he thinks that my current boiler is way oversized and that I have to many feet of baseboard now. He thinks I might be able to get by with a lower water temperature in my baseboard because of that. If that's true then I could use solar as a preheater to an offpeak electric boiler and use the current propane boiler as a backup. In the early winter/fall and late winter/spring the solar could possibly supply all the heat.

So far every "expert" in the field seems to have a different idea on how it should work, and none of them are the same! Makes it a little difficult to go out and spend the money on this stuff.

I should come up for a visit and see how you've got your's setup, maybe help you run some PEX!


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## ET1 SS (Oct 22, 2005)

Kevingr said:


> ...
> So far every "expert" in the field seems to have a different idea on how it should work, and none of them are the same! Makes it a little difficult to go out and spend the money on this stuff.


A good basic method of heating a home, and there is no 'one' method of making it work.

When I was shopping around I found that the on-line suppliers were cheaper for the PEX.

And that making my own fins cost me 25% of what pre-made fins cost.


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## Jackpine Savage (Jul 4, 2002)

Mine is still a work in progress. I still need to get the boiler downstairs, get the storage tank built, and put together the piping, but you are welcome anytime Kevin. I do hope to add a solar heating option down the road.

There are a lot of options and opinions out there. Most of it balancing upfront cost, comfort, and efficiency, but sometimes the 'experts' are also lacking knowledge and experience. My BIL is in the business so I see some of what goes on behind the scenes. In many cases the contractors rely on their supplier to size and design. This pretty much ties them to the brands that the supplier carries, and not necessarily to the best technology or fit for your application. I would definitely get references.

My BIL has been called in to fix some real messes. But sometimes there isn't much you can do about a 1000' foot loop in concrete.


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## painterswife (Jun 7, 2004)

With radiant heat, you need the higher temps for a non-mass system(staple up) Unless the pex is used with a diffuser, you are usually heating the air around the tube first and have not enough mass to hold and spread the heat.

For mass systems( pex in concrete) you can get away with lower temps because the mass holds and spreads the heat .


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## Kevingr (Mar 10, 2006)

So, using 1/2" pex at 8 inches on center with diffusers and insulation could make the 120degree water actually work. Granted, higher water temperature and/or no carpet would make it work better. But I would think with that much tubing and diffusers it would have to make some kind of a difference.


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## mdharris68 (Sep 28, 2006)

I have only done a couple of infloor jobs, both in concrete. That being said, the temps that we were shooting for were around 110 delivered to the concrete mass with a 20 degree temp diff. The loop design is what is most important. You need to send your hottest water to the coolest area, (like the outside wall) first and then loop back to your manifold. The design manual reccomends 300 ft loops as the largest. I would think that if you could get your floors to 65 to 70 degrees to the touch, it will work great. I have read that if your feet feel 65 degrees, you will be comfortable at lower temps. Have you looked at the Uponor Wirsbo website? They used to have a design manual online. You might check it out.


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## painterswife (Jun 7, 2004)

"So, using 1/2" pex at 8 inches on center with diffusers and insulation could make the 120degree water actually work. Granted, higher water temperature and/or no carpet would make it work better. But I would think with that much tubing and diffusers it would have to make some kind of a difference."

This all depends on space heated, insulation etc., are your loops all onder 300 feet etc. You need to do of math to get the right configuration.


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## Kevingr (Mar 10, 2006)

Yes, all the loops were going to be under 300' and of equal length. As far as the layout of the piping I think I have that under control. I purchase some CD's from a couple manufacturers that I've gone over and lots of info on the internet. But as I stated in my first post, none of them are the same. Some say no carpet some say it's ok, some say diffusers and some say they're not needed. It's just kind of all over the board as far as advice goes, makes me a little nervous about spending the money on it. As far as insulation goes I just had the entire house reinsulated with dense pack cellulose so I'm pretty tight now.


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## Jackpine Savage (Jul 4, 2002)

Kevin, are you going with underfloor or sticking with your baseboards? I would be very skeptical if someone told me to go without plates. Here's one article talking about it: http://www.radiantengineering.com/PlatelessInRadiantville.pdf 

John Siegenthaler is one of the who's who in the radiant business. I popped for his book: http://www.hydronicpros.com/publications/index.php?id=24 Of course some of the technology stuff is outdated, but the basics are the same. Too bad you aren't closer, you could borrow it but I need access to it for the next month or so.

If you go with light weight plates it would probably be good to go with pex-al-pex rather than just pex. Pex-al-pex expands and contracts much less than regular pex. Regular pex will tend to be noisy.

Another big variable is how you control the system. The better thermostat systems can monitor floor temp as well and keep the floor at a more consistent temp. That increases comfort and can also be better for floor coverings and preventing noise from expansion and contraction. The downside is cost. I'm going with http://www.tekmarcontrols.com/tn4.html .


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## Kevingr (Mar 10, 2006)

Craig, I was going to go with underfloor, but another heating contractor has suggested that maybe I could just use my baseboards. He's working out the heat load, he thinks I have to many feet of baseboard and that I could get buy with running lower temp water through the baseboard. It all depends on what he comes up with.

You're still a techie at heart Craig, you know we're always hiring good techies! 

That's all good info, another reason why I'm so confused. The article talking about plates pretty much answers some of my questions and really explains why I'm confused. Some web sites say no plates, or some plates or always use plates. I just find it hard to believe that there's such a wide range of opinions/advice/direction from installers of the product. It's been around long enough to have created "standards in the industry" so to speak. It's just hard to find it.


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## mdharris68 (Sep 28, 2006)

[QUOTE

Another big variable is how you control the system. The better thermostat systems can monitor floor temp as well and keep the floor at a more consistent temp. That increases comfort and can also be better for floor coverings and preventing noise from expansion and contraction. The downside is cost. I'm going with http://www.tekmarcontrols.com/tn4.html .[/QUOTE]

I just have to ask you why would you use one of these controls in your house? Is it because your a technical junkie or do you like your rooms to be at different temps or am I missing something?


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## SolarGary (Sep 8, 2005)

Hi Kevin,
What you need in the way of PEX spacing and water flow depends on the heat loss for the room(s) served by that loop, the floor covering R value, etc.

I used the free software from IPEX to do the sizing on my loops. Its listed in this section:
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Active
You have to go through a simple registration process to get the package, and it probably does not hurt if they think you are connected with the business. The software is good and easy to use -- it includes doing a heat loss for each room as well as reistance of floor coverings, length of loops, loop temperature drops, and water temps. Its kind of a guess if you don't have this kind of software. 

For my house, the loops are in the 200 to 250 ft range of half inch pex at about 9 inch spacing and with aluminum heat spreader plates made from 0.02 inch material. On my system, 120F water produces enough heat for cold weather -- even 90F water produces useful heat.

The idea of using radiant floor instead of baseboard is better for solar heating, as you can heat with cooler water. Solar collectors produce the lower temperature hot water more efficiently than they do hot water.

The details on my floor are here:
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/House.htm

Gary


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