Radiant staple-up system under my hardwood floor?

[Sawyer]

I was planning to install a radiant staple-up system under my living room floor. I did it under the master bath which has tile and it seems to be working fine. Our living room floor will have hardwood. I am doing this because we previously used the fireplace or the propane boiler and a coil in the plenum. With the Garn now operating I want to be able to use the lower temps that are working so well in the lower level and upper bath in the living room also. I intend it to buffer the high heat loss of 60’ of windows in this room as I either overheat the front of the house (the forced air in the house is zoned front and back) to satisfy the thermostat of the living room or leave the living room slightly cooler (operating on the kitchen thermostat) and have a comfortable atmosphere in the rest of the house.

In the thread “Theoretical†Question https://www.hearth.com/talk/threads/68790/ comments seem to leave me with the opinion that this is not a good choice or at least a substandard installation.

Nine years ago when I installed the staple up radiant in the joists I stapled the hepex to the sub floor, covered with foil-faced bubble wrap, and the insulated with R11 insulation. It seems to work fine but I have no way of knowing how much better it could be. (If you catch one pound bass all your life and never know there are 5 pounders you are happy! ;-)) The space below the living room is heated so any escaping energy would not be lost to the outside or earth.

Are radiant panels a necessary expense? Will I loose so many BTU’s to other areas than up through the floor to make me wish I had done things differently? Going over the top of the sub floor is not an option. Any idea how many BTU’s I will be able to get through the hardwood floor?

Please direct me in a direction if you think I should be reading more information before making my decision. I will gladly read any information or articles.

 

[in hot water]

As you can see there are plenty of ways to install radiant from the top or bottom. They all have plus and minuses. The better methods cost more and take more time, like most things. If the floor has nails sticking through, a plate installation can be a real hassle.

The plates just make for a better connection and transfer surface. It allows better response and lower operating temperatures. If it is worth the extra $$ for you, for sure use the heavier gauge extruded plates, not the thin flashing gauge, as those can be noisy and will not move the energy laterally as well as heavier plates.

How large of an area are you planning?

Here is an article explaining a bit about plates vs staple up. www.pmmag.com/Articles/Column/c3f68c312dfc7010VgnVCM100000f932a8c0____

hr

 

[Sawyer]

Thanks hr,

I will read the article tonight.

We have 500 sq/ft. heat loss calculation for the room max 36,000btu/hr

 

[bigburner]

read the article - My first thought was he a wholesaler and my second one was he's an engineer. Work with both all the time, they are like pilots or doctors - good ones and not some good ones. I have done all the types of installations mentioned. We have never used under floor for the primary heat source, and for that reason we mostly use staple up -with insulation & without plates. It does a good job with most floor coverings -hard wood floor, failing is more of a humidity issue, then any thing else, but because a contractor is not in control of the operation, we are very cautious when going under hard wood floors.

 

[Hunderliggur]

I have under floor PEX with Al plates souced from the Radiant Company. I am very pleased with the installation. I get about 30,000 btuh (3gpm x 20 deltaT x 500) out of 2100 feet (7x300) for a 1400 sf area. Works great. We have 3/4 bamboo over 5/8" Advantec subfloor. There are two zones like this (1st and 2nd floor) plus an additional 1000SF (5x300) in-law zone ;-) I have not insulated the 1st floor joist bays (yet). They are accesible from the basement. The joist bays under the 2nd floor are insulated with R-11 denim batts. I normally run a max temp of 130F (mixing valve) and run it as low as 100F.

 

[Floydian]

Hey George,

Any chance of a miscalculation or typo? Maybe the room is all glass?
what heat loss calc did you use?
36,000 btuh is quite a load for 500 sq ft. 72 btu/sq ft is way beyond any radiant floor.

Panel rads sized for lower temps with TRVs would give great comfort and control and be a heck of lot easier to install than staple up.
Of course your room layout and furniture placement would be a factor as well.

Noah

 

[Reggie Dunlap]

I've retrofitted staple up radiant a bunch of times, with and without the aluminum plates. It's hard to say if the plates are worth the added expense, but I doubt it. Flooring nails protruding through the sub floor are an issue, but a pair of end nippers and a six pack will solve the problem.

Your wood flooring will probably shrink a little more than it ever has since heat is going to be directly applied to it. How much will depend on wood species and water temp. I'd keep the water temp low to start with and add a humidifier to the room.

 

[ISeeDeadBTUs]

All my radient is staple-up, except the cc slabs. Conventional wisdom said hard wood and radient don't mix. My observation is that tile 'works' better than laminant. A client of mine had 'engineered hardwood' put in, and he's happy with that.

Jimbo

 

[Sawyer]

Thanks for all the input. If many of you are like me, pick and choosing keys on the keyboard, you are using your valuable free time to reply. I appreciate your effort!

I will not order any radiant supplies today, it is obvious that I need to do more homework before moving ahead with this project so I do it right the first time. Fortunately at -4* the living room is still 68* after firing the Garn at 10pm last night.

“Panel rads sized for lower temps with TRVs would give great comfort and control and be a heck of lot easier to install than staple up. Of course your room layout and furniture placement would be a factor as well.â€
Noah, could you direct me to a source/manufacturer you have used and would recommend?

I do want to have yellow birch hardwood floors if at all possible, the boards are already in the pole building. I will look at radiant panels though I would rather not look at them along the walls and would prefer a warm floor. I could sticker my flooring in the boiler room before installation, the temperature averages 85 degrees with humidity level of 12%.

I am also glad it was mentioned that nails may be a problem when trying to get a good contact with plates to the sub floor. I also would not want to have had “staple up†in place and then installed the hardwood floor from above! If lower temps are required for the hardwood, I may have a problem benefiting from radiant floor even with an 8†spacing.

I reran my heat loss calculations with Slant Fin and got similar BTU losses at -30. Is there a better program available to an amateur? This was using the factor of a heated ceiling as the other choices were limited to a maximum of 12†of insulation. Yes, three walls in the upper level are primarily glass to take advantage of the lake view.

 

[in hot water]

Nice home, I like the siding. Yes, that is a lot of glass, and the -30F design makes for big load numbers. The radiant would be a floor warming a BigB mentioned. There is no way to cover that load with floor radiant, alone. Many contractors use a two stage thermostat, as there will be some days where the radiant will meet the load. If the radiant cannot keep up, a second stage heat kicks in.

I'd like to see second stage be another hydronic system not a forced air as FA will just stratify that tall room., Honeywell and tekmar are a couple favorites for t-stats. I like the tekmar as it can limit floor temperatures to prevent stressing the hardwood.

It is the moisture level that causes hardwood to move around. Acclimate the wood to the jobsite and try to maintain a humidity level. Engineered hardwoods are more stable, usually a plywood backer with hardwood venner. I like the brands with a hardwood ply as the backer. You can also buy them with a baked on finish. Aluminum oxide is often used and it is a rock hard, long lasting finish.

Launstein Hardwoods is great site to see actual test data on various hardwoods in radiant applications.

hr

 

[4acrefarm]

I have radiant staple-up with the thin aluninum sheets they sell at radiantec. I never have the water temp obove 130*. It is the sole heat source for a large part of the house till around 0*. At 0* with some wind I need to fire up wood stove for a couple of hours. I have 1200ft of 7/8 pex under 880 sf of insulated, well windowed cape. My insulation job under the floor is sub-standard but the boiler is under it.

 

[Fred61]

I have about 300 sq. ft. of Brazilian cherry with 7/8 staple up and annealed aluminum plates from Radiant company beneath (one run per bay). Run 140* maximum temp. and haven't seen any problems. This will be my fourth year with the radiant. I also haven't heard one click from the plates.

 

[4acrefarm]

I also have not heard one click from mine, I have a nother section with diferent plates that do click. Not a big deal either you hear it when the heat goes on for 1 minute. Beats steaming radiators or forced hot air. That sounds like a freight train in comparison.

 

[ISeeDeadBTUs]

ADK siding. . .in Wisconsin??? :wow:

 

[Reggie Dunlap]

Since the flooring is not installed yet just snap lines roughly where the tubing will be, and keep your nails a couple of inches either side of the line. You're still going to have to nip a few nails off when you install the pex, but it shouldn't be too many.

Humidification and acclimatization will be the key to the birch flooring not shrinking or cracking. Birch is relatively stable and I've had good luck with installing it over radiant.

 

[in hot water]

Some hardwood installing tricks, for 3/4" T&G flooring.

A local hardwood installer showed me options for nailing over our radiant installs. One option is a shorter, 1-1/2 fastener. I believe they call these cleats not nails and they are the best way to install hardwood. Some installers use pin nailer or staplers but these cleats were designed for flooring installation. The shape, serrations and L shaped head are all part of the holding power.

All wood will move a bit as the moisture level changes, wider boards much more of course. A cleat will allow some movement without coming loose or allowing the floor to squeak. Yes, cleats they do cost more then nails or staples and it is where some installers cut costs.

The installer would use the short nail at the typical 45 angle or a 2" nail at a 35 degree. He would just modify the angle of the nailer. He explained there is no need for the cleat to penetrate below the subfloor, that portion of the fastener really is not doing any work.

Certainly they should avoid the tube if they have lines snapped, but with short pieces of hardwood you need to nail according to the piece.

hr

 

[woodsmaster]

Nothing to do with heat, but I recomend using wide planks for flooring. I put 400 sq' of 3/4 x 2" in my living room and it took me a long time. 4" would be twice as fast.

 

[Reggie Dunlap]

Wide flooring lays quicker per square foot, but it leaves much bigger gaps when it shrinks over the radiant heat. I usually try to avoid anything wider than 4" over radiant.

 

[Sawyer]

Thanks for the comments on the siding, cut the tress on the woodlot and sawed on my Woodmizer. Lots of work sorting to maintain elevations.

I will look at thermostats/controllers to give priority to radiant but after that I will have to use the coil. Launstein Hardwoods does have a lot of information!

Thanks for the installation tips and references to different panels and staple up installations. I have used the cleats previously, I did not know they had a 2†cleat, sounds like a good fastener for my application. I like the fact there are more than one way to accomplish this project. Guess I will be reading right up to the Packer/Bears game. ;-)

 

[Sawyer]

ADK siding. . .in Wisconsin??? :wow:

You Betcha!

 

[sgrenier35]

When I built my house 7 years ago, I put radiant under the whole first floor. I used clic hangers to space the tubing +/- 3/8" off the subfloor, and insulated under that with foil faced fiberglass. The entire 1,000 sf is covered with cherry hardwood. I have never had any problems heating the house and have a max water temp of 130 running the system. I don't have windows as big as yours but I do have substantial glass area. There are many ways to do a radiant installthat will work. You just need to pick the one that will work best for you. Remember you have a garn, that will supply plenty of BTU's for what ever you use, and will probably use less btu's than your current system. If you really want to heat with the least amount of btu's look into the differen't control schemes available to control the water temp in your radient tubing, ie outdoor reset, mixing valve vs tempering valve vs injection pumping.

 

[Sawyer]

When I built my house 7 years ago, I put radiant under the whole first floor. I used clic hangers to space the tubing +/- 3/8" off the subfloor, and insulated under that with foil faced fiberglass. The entire 1,000 sf is covered with cherry hardwood. I have never had any problems heating the house and have a max water temp of 130 running the system. I don't have windows as big as yours but I do have substantial glass area. There are many ways to do a radiant installthat will work. You just need to pick the one that will work best for you. Remember you have a garn, that will supply plenty of BTU's for what ever you use, and will probably use less btu's than your current system. If you really want to heat with the least amount of btu's look into the differen't control schemes available to control the water temp in your radient tubing, ie outdoor reset, mixing valve vs tempering valve vs injection pumping.

Clic hangers?

I am anxious to get this zone installed. I can see by the recent electric bill that the coil fan running 24/7 will justify doing the install the appropriate way.

I certainly did not like firing the Garn at 5 this morning with 160* water present just to get the coil warmer water when I had 730,000 BTU still usable for radiant. Kinda defeats the purpose of the large storage capacity.

 

[Floydian]

George,

My take on the Slantfin software is that it runs a bit high. I ran all my numbers by hand(U-valuexAreaxDelta T or Area/R-valuexDelta T)and cross checked them with the free software that came with Modern Hydronic Heating. These numbers were very similar whereas Slantfin was at least 25% higher. I think the only real guess work in the calculation should be air changes per hour.

I made a few assumptions based on your numbers and put these into Room Heat Load Estimator and hear is what I came up with:

Indoor temp 65*F, Outside design temp -30*F
windows: 360 sq ft, R 2.7 = 12,667 btuh
exposed wall:528 sq ft, R17(thermal bridging)=2,951 btuh
exposed ceiling:600? sq ft, R30?=1,900 btuh
exposed floor:none?

So your conductive heat loss should be around 17,518 btuh

That leaves guessing you air leakage.
Hopefully someone more knowledgeable can give a better idea of ACH with your construction. Looks nice and tight.
volume:6400 cu ft?
@ 1 air change per hour =10,944 btuh
@.5 ACH = 5,472 btuh

So total heat loss 22,990 btuh to 28,461 btuh with a bit guessing involved.
Still 46+btuh/sq ft is beyond radiant floor alone.

I am not a heating pro but I have read enough discussion from pros to know that heat loads are the foundation of any properly designed radiant system. In your case I would definitely strive for the lowest possible temps but as you know greater efficiency/convenience costs more up front.

I went with an above the subfloor installation for my radiant floor. 3/4" infill,9.5"x 24' lightweight aluminum plates with omega shape for a tight fit to the 1/2" tubing. 3/8" AC plywood as my finish floor for now(<1$ a sq ft with Emulsion finish, not counting my time) so I could afford this radiant system.

Not sure if this type of install would work for you as you would be adding an additional 3/4" but the less wood you have to push that heat though means lower supply water temps.

Also not sure this post really helps you much but good luck with your project.
Noah

 

[woodsmaster]

Wide flooring lays quicker per square foot, but it leaves much bigger gaps when it shrinks over the radiant heat. I usually try to avoid anything wider than 4" over radiant.

Didn't realize that. Good point.

 

[sgrenier35]

Clic hanger similar to these, available at your local plumbing supply house

http://www.sunsourceproducts.com/catalog/productdetail.asp?cat=PZ&part=0200

When I did mine this was the recommended "staple up" technique by uponor/wirsbo.