In-floor Radiant Heating with Air

[debit.servus]

Ive read about the desire for even, in-floor radiant heating and the cost-benefit-risk analysis in several threads here on CRVL. I read about the cons of dedicated water loops, the additional parts to make it work, the risk of leaks; and debating using coolant or not in , automatic drain switch to drain plain water or vigilance to prevent burst pipes in freezing weather. 

I searched "in floor radiant heating using air" and found nothing. People do things 

Why not use air as the working fluid for in-floor radiant heating? You wouldn't be able to store heat in the working fluid, however you eliminate the risk of inaccessible water  leaks, by piping many channels or air under the floor. You have a 12v centrifugal fan at the heater outlet or pipe a Propex-like heater directly underfloor, and pipe the heated air under the floor. You can move the air through PVC pipes, vinyl tubing or even copper tubes. You can get creative with the outlets and pipe them under the mattress or under the sheets, and use the system for ventilation or air conditioning in the summer. More possibilities than with water loops, perhaps. Or you can have a floating floor with a minimum 1/2 inch air gap where air flows underneath, radiating heat like water loops. 

I know air has 1/25th the heat capacity of water and youll still need air & water heating, still the idea shows merit.

 

[John61CT]

There really isn't a strong need to heat the actual floor in any case, just a couple tiny silent fans to keep the warmed air from stratifying is enough.

For a very large rig needing serious distribution, properly sized air ducts to be effective would rob significant space. If you had a lot of excess vertical space I suppose a false floor with a plenum would work.

But the necessary forced air fans would be noisy and use more electric power.

Pumping hot water to a couple baseboard exchangers much less of all three factors.

 

[tx2sturgis]

Air-to-air heat exchangers do exist (ex: intercoolers used on turbo-charged diesel engine intakes) but usually there is some forced movement of air over the coils, tubing, or pipes, and the air in the tubing is under some pressure, much higher than atmospheric. 

So it seems to me that installing all of this in a trailer, motorhome, or van, would be heavy, complex and inefficient. Unless you can figure out a way to make the pipes 'give up' their heat: for example, you would need some forced air pushed thru the channels or passages where the pipes are, with vents to the interior, to aid in heat transfer. Or the entire under-floor area might be one large, hollow, space for trapped, heated air, giving it up slowly to the living space above.

And if you're going to build all of that, why not just force the heated air directly thru ductwork, and forget the pipes.

 

[tx2sturgis]

If I were to begin to design something like this, (which I'm not) I might consider a metal floor, (aluminum deck plating maybe) with square aluminum tubing attached directly underneath and bonded to the metal floor, and pump the heated fluid thru those square tubes, with distributing and collecting manifolds at the forward and rearward ends of the floor.

The 'fluid' could be air, or oil, or some type of safe anti-freeze coolant like the pink RV winterizing stuff. 

Again, cost, complexity, and weight, not to mention serviceability and reliability, would all need to be worked out.

 

[JT646]

The 'fluid' could be air, or oil, or some type of safe anti-freeze coolant like the pink RV winterizing stuff. 

Again, cost, complexity, and weight, not to mention serviceability and reliability, would all need to be worked out.

Whoever figures this out will likely be the envy of fellow van campers.  I've always thought radiant floor heating (correctly done) would be the ultimate way to heat a camper van. 

Advantages:   More comfortable, cleaner, silent...and the heat would NOT be quickly lost to the air/ventilation--as it does for propane/gas type "air heaters".   Newer vans with the "auto start" 48volt alternators could probably be configured to do this electrically....but be prepared for HDR to insult you on how inefficient electrical heating is.

IF money was no object:

*Aerogel or VIP insulation underfloor (R10 to R40)
*Radiant heated floor (electrically or circulating pex-loop)
*"auto start" feature+ 48V alternator+BIG LiFePo4 battery bank

 

[Riverman]

All you need is an RV-type water heater, a Grundfos circulating pump, a closed loop and a thermostat And, lots of patience keeping it working.