Underfloor heating in a passive house?

BigGeorge

Am looking to understand the implication of installing underfloor heating in a passive house. I've heard a range of opinions ranging
(1) it will give a lower background heat if the thermostat is kept turned down...to
(2) the lag in the heating process, will mean that the 'hot' slab will overheat the room once the thermostat shuts off due to very low heat losses and the nature of the controller

Anyone any specific experience using UFH in a low energy house?

exaisle

The lag in the heating process is variable and is hugely dependent on the depth of the slab and its composition. It's possible to get modern screeds poured that only need to cover the UFH pipes by 25-30mm which also are easier to heat because of the materials used (ie not concrete).

What heat source are you considering?

BigGeorge

50mm ez screed, with rigid insulation below is the buildup, individual zoned rooms

Heating is from stratified buffer tank, ca 1500lt, with a large solar thermal panel & 10kw condensing gas boiler

heinbloed

Anyone any specific experience using UFH in a low energy house?

Check the home page of the PHI.

As exaisle said, the delay in thermal transfer can be calculated and adjusted by optimizing the design of the slab/heat emitting surface.
The lower the flow temperature and the lower the thermal capacity of the slab is the less it influences the heat resp. the cooling load.

Most PH ( at least in the 1-household range) have such a low energy demand that there isn't any need for an UFH. But in a retrofit situation with an already existing UFH system why not making use of it.

If going for a wet thermal distribution system in the very low flow temperature range for a new build check also the www. for the "Solarhaus" ( for example Jenni in Switzerland) or the term " solar house" in general.
Try also " thermal activation " of building structures.

If you have the drawings details contact a civil engineer, such a calculation is standard.

Good luck!