underfloor heating

newtoboilers

I've been studying the underfloor (under the carpet, underlayment, and subflooring) systems, and have been comparing it to the tubing-set-in-concrete system. If the objective is thermal mass heating then the system placed between the joist space is simply heating the 3 or 4 inches of air gap. Air doesn't have such good thermal characteristics (low specific heat). Here's an idea I'd like feedback on...What would happen if you stapple-up the tubing under the subfloor, stapple-up some fine wire mesh, then pack the mesh and tubing with that 'blown-in' concrete you see pool builders use- it's sticky and easily set, even upside down. I figure heating anything other than air would be better. Would that give you more thermal mass under the floor? You also wouldn't need any radiant reflector.

hr

Sounds like fun!

packing overhead concrete

Seriously though, mass works best when you have a conduction connection. Ideally the flooring is in contact with the concrete. Your idea stuill has an air layer to transfer through, the least effective means of conveying radiant energy.

Actually high or medium mass systems are not always the best. Ramp up and cool down time is tied directly to the amount of "weight" or mass you have.

If your climate or building loads dictate frequent temperature swings a low mass system may fit you application better.

Flywheels work great on tractors and heavy trucks. Not so in sports cars and motocrossers.

Which system would fit you application best. Quick responders or slow and steady?

hot rod

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Mike T., Swampeast MO

Gunnite sprayed under a floor

1) Structure would have to be able to handle the added weight.

2) You'd still have to insulate. Radiation from the underside of the concrete would be robbing many BTUs before they get a chance to conduct through the insulating wood above.

3) Concrete is a decent conductor but it has LOTS of mass. It would be much less expensive and ever more simple to use a better conductor with much less mass--like extruded aluminum plates.