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wotoan t1_j15w6v7 wrote

No, a whole house system can (and should) have floor thermostat elements for precisely this reason. Cycling an underfloor heating system on ambient air temperature alone with a naive (non PID) controller leads to these type of issues.

A stable underfloor heating system will have the floor at a constant temperature slightly above the desired ambient air temperature. Heat losses in the house lead to a steady state equilibrium. You can do that with an expensive controller and an ambient air sensor, or a cheap controller and a floor sensor. A cheap controller and an air sensor, like this case, will over and undershoot and be miserable. This can be moderated by high thermal mass systems but is not eliminated.

The problem here is how it’s being controlled, not any fundamental failure of underfloor heating.

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catawampus00 t1_j1619gm wrote

This is 100% accurate. The only other issue to consider is thermal mass. Tile laid over backer board on top of warmboard (aluminum/plywood subfloor) has a low thermal mass but fast thermal response. Tile laid over gypcrete or concrete is the opposite but is much more consistently “warm” to the barefoot.

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evergreensphere t1_j167ss7 wrote

He’s still right - tile at comfortable air temperature (or near it) will feel cold because of the heat transfer coefficient.

Walking barefoot on 74 degree marble will still feel cold, even though it might be heating the air to 72 degrees and the air feels perfectly comfortable.

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wotoan t1_j16nd0o wrote

No that’s not how they actually operate and are perceived. You’re so used to losing a huge amount of heat through your feet warm floors feel amazing.

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