I didn't do radiant in my basement because it would have added a lot of cost in space that will be mostly used by occasional guests, and to hold my pool and foosball tables.

Be sure you have a radiant barrier below the concrete.

Flooringwise, you have a lot of choices. Carpet, with the right pad-- the sort that allows good heat trasmission-- would be my choice.

We are building a 2400 sq foot rambler in northwestern Minnesota. The entire basement has hot water radiant heat installed beneath the concrete in the basement as well as in the garage. We've been told it will be so toasty our furnace will hardly ever run. It was a spendy venture....

We are putting in some carpet, some tile and possibly just stain the concrete in some areas. I've been in homes with carpet or tile and they've worked well. Punkysmiles, we're in MN too and have been told by friends that the radiant heat really brings down the need to run the furnace also.

oruboris

"Be sure you have a radiant barrier below the concrete."

How would that be constructed and why would it be more effective than insulation?

Our whole house will have hydronic radiant in-floor. The pex tubing will be embedded in lightweight concrete. For floor coverings we will be using a carpet, engineered hardwood, and tile.

Under the carpet we will be using a rubber slab pad. Typical rebond type pads do not conduct heat very well and will not work with in-floor heat.

The engineered hardwood will be a floating installation with a floating underlayment. I prefer solid wood floors, but most of the available wood species do not have enough dimensional stability to withstand expansion and contraction from having heat applied directly to it. Even most engineered flooring will not warranty their product if you install over radiant. We were able to find a few manufactures that specifically include it in their warranty, and chose to use one of them.

The tile will have a roll-on membrane between the lightweight concrete and mortar. This is pretty typical for tile installed over concrete.

Here is a link that might be useful: Kahrs wood flooring

There are several methods of hydro-radiant flooring, with Pex [or similar] tubes usually installed through and beside rafters as for any other level of floor (often in "short" basements where the floor is insulative but not radiant), OR pipes/tubes (of Pex or of many other different materials) are buried in concrete, or a cementious mix, or sand. In all cases that I'm aware of, additional insulative material is considered desirable so as not to waste heat on the surrounding soil while maintaining pipe temperature. When sand is used for the pipe bed, the additional insulative value may be sand or a sand/gravel mix.

Some manufacturers and installation firms do recommend a radiant barrier, apparently considering that an effective co-measure for retaining the heat in pipes. I have not seen any non-affiliated study regarding the actual comparative performance. (If you know of such, please send me a link.)

The flooring over the radiant heating does need to be compatible with radiant-style heat. As is often the case, the fewer natural materials in the flooring, the *more* care must be used for compatibility -- in other words: finished concrete, solid real wood, wool and/or cotton carpeting are least problematic with care needed as to adhesive type, but few other problems with the wood, wool, etc. overcoverings. Whereas laminates and artificial materials can pose difficulties and detailed installation instructions from the manufacturer *must* followed precisely in order to maintain warranties and be preventive to future problems.

I agree about the flooring over radiant hot water heating.

A concrete slab should not be poured directly on a sand bed and any such bed would not effectively act as insulation.

I can't imagine how a radiant barrier would be effective if the heating tubes are in full contact with the floor construction since radiant energy would only exist in this instance in an air space.

We explored radiant heat but were not able to do it. I don't like the idea of carpet below grade. I would choose tile.

M-A commented "A concrete slab should not be poured directly on a sand bed and any such bed would not effectively act as insulation."

I understand that it takes about 18" to 24" of sand to be considered insulative on its own. Among common depth variations in Canada & northern midWest (Minnesota) is 4" sand; 2" insulative material to equal R7 to R15; 4 inches sand with tubing laid on top (and fastened to mesh to prevent movement) and then covered with another 2 inches sand.

I do wonder what concrete is poured on, if not onto packed sand? Oh... directly onto the insulation?

Sand is an unstable surface for pouring a concrete slab and it retains water from the concrete which can cause resilient flooring to not adhere well. Even the ACI no longer recommends it.

Crushed stone should be placed below a slab to create a capillary break and, when appropriate, a layer of rigid insulation. A vapor retarder can go above or below the insulation.

Would you really put hot water heating tubing buried in sand under a concrete slab?

M-A ~ Decades ago, I lived in a house with that method of installation. Very OB designed and built (he was some kind of engineer with the USN). The house was about 15-20 y.o. at that time, with tile flooring over the concrete and the water pipes laid in compacted sand below the concrete. No problems with damp, cracking, losing level, tiles curling, or anything else. I know of 3 other houses with the same method, also no problems. Perhaps I wasn't clear: the weightbearing exterior foundation walls are built as usual but slightly deeper than usual. The dirt within that perimeter was removed (or removed before building the foundation walls) and then vapor barrier/sand/insulation/sand is layered. Maybe everyone using that method has been unusually lucky.

I've only done one radiant heat installation--about 6" of cmpacted crushed gravel followed by a roll-on radiant barrier/insulation, Pex and concrete. The homeowner didn't finish the basement floor other than painting to keep the dust down.

We have radiant heat on both levels of our home (no furnace at all in chilly central Alberta). We have a combination of laminate (living areas), tile (wet/traffic areas) and carpet (bedrooms).

Had I known about it at the time of building, I would have stained the concrete floors throughout the basement. I like the look, it would have been no colder/harder than tile, and we have strategically placed area rugs for "coziness", anyway.

Carrie

The problem with pouring concrete slabs over hot water heating tubes is keeping the tubes within 2 inches of the surface for good heating efficiency. There is also an unusually long heat lag that is not as welcome in some locations as in others.

I am curious how a "roll-on radiant barrier/insulation" would be constructed.

M-A ~ the ones I know about (not the first house, that was pipe) tied the tubing to 6" wire mesh to hold the rows in place. I haven't the vaguest idea if the wire was considered part of the re-inforcement of the concrete. Nah, it couldn't be because it wasn't encased. And it now occurs to me, to wonder how well that wire is holding up and does it matter.

I'm wondering how well that roll-on maintained integrity with all those sharp gravel-edges poking at it?

Worthy ~ Tell us more, please. I haven't heard of an insulated roll-up barrier. What was the R-value? and was the Pex encased in the concrete or set on top of the insulation? Is the barrier warrantied? And how do you know that no holes were poked when the weight of the concrete stretched the material over the gravel?

The material used was Insultarp. It was mentioned in three of the four quotes I got from the most experienced subs I could find.

I'm wondering how well that roll-on maintained integrity with all those sharp gravel-edges poking at it?

Once the gravel is tamped down, there are no points sticking up. How it reacts once the concrete is laid, I can't say.

stained the concrete floors You can also get them embossed and otherwise treated. But finding an experienced contractor may be difficult.

Here is a link that might be useful: Insultarp

You sometimes see aluminum foil laminated to closed cell foam insulation and advertised as a radiant barrier even though the thin foam directly above the polished foil is not an air space that would allow much, if any, infrared energy from the slab to reach the face of the foil. All insulation has air in it but heat moves through it by conduction and convection, not radiation.

This interesting article on radiant floor heating says that typical manufacturer recommendations on insulation are inadequate. To wit:

With slab-on-grade radiant-floor heating systems, there is potential for significant heat loss into the ground. According to Paul Torcellini, Ph.D., P.E., of the National Renewable Energy Laboratory, even with insulation under the slab, 20% of the heat entering the slab can be lost into the ground. This reduces the overall efficiency of the radiant-slab system, offsetting the potential savings described above. Typical manufacturer recommendations for 1" (25 mm) of XPS insulation beneath a radiant slab are clearly inadequate; even 2" (50 mm) may not be enough. Shapiro recommends up to 4" (100 mm) in cold climates. In place of ozone-depleting XPS, one can use high-density expanded polystyrene (minimum 1.5 pcf, 24 kg/m3 foam recommended).

Is MA saying that heat will move through the Insultarp to a greater degree than the suggested board insulations?

Insultarp appears to just be a ½ inch foam insulation with a vapor retarder and a layer of aluminum foil. IMHO itÂs just an expensive vapor retarder. I would use 2" of Styrofoam even under an unheated slab but I once discovered a contractor desperately trying to finish a pour so I wouldnÂt see that he had omitted it so IÂm not sure it has ever gotten into one of my projects.

You donÂt need a PhD to know that more heat will move to the colder side of the slab and that "radiant heat" doesnÂt exist in a concrete slab or the ground or insulation for that matter. Where does this nonsense come from and why does anyone believe it?

On the Insultarp website they claim (twice in two successive paragraphs), "In a heated slab, Radiation is responsible for 93% of the heat traveling downward." Heat energy in a slab doesnÂt know up from down and radiant (infrared) energy needs an air space to exist much less move anywhere so in reality 100% of the heat moving downward through a concrete slab is being "conducted". To slow it down add some insulation.

Sounds right to me. The Building Green article makes the point that in a tight modern house the warm floor effect could actually be better achieved with insulation.

I wish I had known this at the time. But then I told my clients the whole idea didn't make sense to me. Especially with a price tag of $8,000+ in addition to a conventional ducted HVAC system. And, since the radiant floor was a last minute add, there was no time to redesign and downsize the conventional system.