Softwood flooring over low temperature radiant?

Teemok

R 1.41 is a standard figure for softwoods. I'd like to have a clearer understanding of the difference between soft and hardwood radiant floor output. My worry is this: with 8-12" spacing and a low supply water temperature, I would get more pronounced heat striping and a certain amount reduced output due to the reduced average floor surface temperature. At 12" spacing the cold center space would be near R7.7 away from the tube. I'm guessing the lower mass might have some effect on temperature stability. I realize raising the water temperature and using aluminum can compensate for this.

I run into the design challenges of tall glass walls and or high windows in high ceiling rooms with little unobstructed heated floor area. The smaller floor areas end up being rug covered or couch covered or built-ins or ….. Output needs for the small uncovered areas might exceed 25BTU/ft add A2WHP temperatures and the areas with the highest heat losses would end up being appreciably cooler than others.

My experience identifying and dealing with radiant output inadequacies is that they were board-line cases that got shrugged off with an "it'll be fine" in design phase and then it turns out worse than expected in reality.

These tall rooms with glass walls surrounded by lots of thermal bridging and small floor areas, toss in some sky lights too and it makes for a heating design challenge. Unproven builder infiltration variability, high humidity and ever present wind and it's not a simple slam dunk.

Supplemental long low radiators under the glass is often refused on design objections and adds complexity and cost to the project.

Where the "No, I won't do that " line is, is a valid question. Is 5/4 or 1" softwood over radiant a red flag for higher BTU output areas with lower supply water temperatures or is that concern over little?

Jamie Hall

I'm not sure that the difference between hardwood and softwood thermal conductivity is going to make much difference — but if I were trying to get anything like an average of 20 BTUh per square foot out of the floor I'd surely use aluminium plates along with the tubing. And make sure that the underside is adequately insulated!

Your other considerations up there… well, yeah. People will put thick carpets down and then wonder why they are cold. Not sure what if anything you can do about that!

hot_rod

The tube spacing has a lot to do with it. Here is a look at a piece of Warmboard and the Uponor suspended tube method, basically joist bay warming. The suspended tube, while lower temperature does have a more even spread.

On the rear 1/2 of these sheets is carpet, no pad. The carpet actually helps spread the temperature profile also.

Realistic, comfortable residential radiant floors, 24- 26 BTU/ sq ft. Above that supplemental heat needs to be considered.

Launstein Hardwood in MI did a lot of studies with various species of wood. They built a test chamber and ran a bunch of different woods. I don't know it that is still available at their site.

Another thing that is not always considered is the heat flux of the room. Furnishings that block the radiation. Couches, cabinets, etc. A couch doesn't necessarily turn into a radiator when placed on a radiant floor heat panel.

From left to right:

Pex in extruded plates 8" OC

Suspended pex, 1" below subfloor

Rubber staple up (with heat transfer staples:)

Copper tube in extruded plates. (notice where I pulled the plate down to make a crinp. The donduction is crucial with plates, so they need to be tightly fastened)

Warmboard

panel #2 copy.bmp

Warmboard IR.bmp

Screenshot 2024-04-29 at 7.39.07 AM.png

Teemok

@Jamie Hall I'd be ineresting to test. I've found that, a firm desire for the irrational is a great contractors red flag. "Oh no, a huge shag rug is going to be right there" Leads to " OK, good luck with that"

Teemok

The differences between masonry and wood is pretty dramatic. I don't think soft vs hard wood would make the same kind of differences but changes in the emitter material will bring some changes in how the system performs. That line between adequate and not quite is hard to define in some cases. Things add up and are always easier to see in hind sight, explaining why there's a problem. Soft wood is just another factor when looking at the whole thing. When all you need is 11BTU/ft and bumping up SWT costs little it's not really an issue. hot_rod, I've seen those thermal shots before. I'll look for others studies. Low temp. water is going to want tighter spacing and good aluminum for highest ouput. I'm leaning toward extruded plates with good insulation over the smaller diameter tubing with 6" spacing. Nails near tubing, cringe.

RascalOrnery

Everywhere I skimped I had to go back and fix or just suffer. Saving money should not have been as high of a priority for me. I built a little box out of my wood flooring and then ran a piece of heated pipe under it just like my floor would be and checked it with an infrared gun and discovered I needed plates. Bad.

Kaos

I believe the Upanor radiant design manual shows the effect of floor R value in terms of heat output at specific SWT.

You definitely want heat spreaders of some kind, I would vote for warmboard (or equivalent) instead of staple up to increase the surface area. The pipes would also be on the top and visible, which makes nails less of an issue.

With anything radiant floor, the key is air sealing. This is especially important at the rim joist bellow and often ignored.

Doesn't matter if all glass or not, an accurate man J will tell you if floor heat will work. If not enough, lot of places nowadays also have cooling, so in that case, you can install a heat pump to get a couple more BTUs into the place to supplement.

BTW, I have a small loft with softwood floor and does not hold up to even light traffic.

hot_rod

you can get deep into the woods exploring the different woods for specific heat, thermal conductivity and thermal resistence. ASHRAE has data on that. Here is a chart of various species.

Of all the “over the top” products I have tried, I found the Roth Radiant panels to be top performers. You can use 6 or 12” oc. The aluminum is not as thick as Warmboard, but the tube does stay in place. The foam helps limit the downward loss, although it is thin under the tubes.

It is light and easy to ship, although it is not a structural panel like Warmboard. Ever lift a piece of Warmboard😟

IMG_1018.jpeg

hot_rod

We had a loft in a barn that converted to living space. It had a long leaf pine t&g floor installed in the 1950s

The hardwood floor finisher used a product that had aluminum oxide blended in urethane. It had a rock hard finish that was very durable. A heavy object would dent the wood if you dropped it, but the finish was extremely tough.

The lower level was a radiant concrete floor with Anderson engineered flooring glued down. It also had an aluminum oxide finish, factory installed that was incredible.

https://forum.heatinghelp.com/discussion/comment/1839650#Comment_1839650

Jamie Hall

The comments about wear on "softwood" floors are rather important — but it's also important to remember the "softwood" in the lumber industry is a term used for lumber derived from trees such as pine, fir, hemlock, and the like — evergreens — while "hardwood" is for deciduous. Within those groups there are radical differences in actual hardness — resistance to denting and wear. Modern plantation grown softwood — mostly southern pine but some Douglas fir — is indeed really soft (I've seen stuff off a rack at Home Depot I could dent with a fingernail!). On the other hand, old growth hard pine, such as might be found in a pre-1920s structure, is just that: amazingly hard. Thermal properties vary all over the map.

Teemok

@Kaos ( it's fun to write @Kaos ) I'll check my Uponor manual. The soft wood choice is not mine. it's an on site material. I get why the owner wants it. No high heals in the woods I guess. The manual J advice is correct; though, you can start to ID questionable cases when you see them with out it. The math is not really proof but the best future telling we have. I won't do it with out a double checked Manual J. The comfort feeling of a lots of glass area is not foretold well by a room manual J. If the north and east walls are mostly glass to 18' and the floor is not able to adequately bath the occupant in radiant heat, it can feel cold near the glass even though 10-12 ft away there's a satisfied thermostat. It looks like Cypress falls between Ceder and S. yellow pine and is less a factor than SWT, spacing, aluminum spreading and the big one, unobstructed floor area. Cypress is fairly stable. R1.1 vs R 0.8 of Oak isn't much. Thanks all for the input. You are a wealth.

Teemok

From Uponor CDAM

Effective floor area (EFA) — The
approximate square footage of a
radiant floor that effectively radiates
heat to satisfy the heat load of a zone.
EFA is the result of multiplying the net
floor area by the effective floor factor.
Effective floor factor (EFF) —
An approximation (expressed in
percentage) used to describe the
amount of net floor area that will
effectively radiate heat. This factor
is used by the designer to take into
consideration intangibles (such as
abnormally large furniture that
covers a large percentage of floor
space) that might interfere with heat
transfer from the floor.

This is at the heart of my concerns, especially when considering A2WHP SW temperatures.

Teemok

I forgot how good the Uponor manual is. This is from the Joist-trak manual. A small increase in floor covering R value requires a greater increase in SWT. My question is: When does the floor assembly R-value (added inches of wood over the joist trak aluminum ) become floor covering R-value? Is the sub floor and finished floor not part of the floor covering R-value? Is a 3/4" sub floor not but the finished floor is?

Kaos

I believe the joist trak manual assumes 3/4" subfloor, so the R value, would be the finished floor only. For something like this I would go with quick trak though as it puts the emitters closer. The small pipes are a bit more work, but not too bad.

In warmer climates you won't be limited by the SWT of AWHP but by how hot you can run the flooring. Of course, it is always better to have lower SWT for efficiency.

If you look at commercial places, walls of glass usually have a high temp emitter or a slot diffuser by the window. The only way not to have cold convective draft there is by supplying extra heat. Going up to triple pane windows makes a world of difference as well, won't need extra heat in most climates.

With the softwood floor, make sure they are not looking it at wide plank. Heating it especially if you need it hot will cause it to gap.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1839728#Comment_1839728

That manual has a lot of goid info

Anyone considering radiant floor heat should own one. There is an online version also.

One thing that concerns me is all the output charts are based on 68 ambient. That is a bit low for older people. Like me.

Alan (California Radiant) Forbes

This came up the other day with a customer in Moraga who had a wall of double-glazed glass and an open floor plan with nowhere to install radiators. He said one of my competitors was feeling nervous about keeping the room warm at design conditions and I agreed. Sometimes you're cornered and don't have an easy solution and what rises to the top may be the only solution which would be to use best quality plates or Ultra-Fin which would keep the area warm on most days and then to fire up the fireplace when it gets very cold. Set up the system for constant circulation as well.