UFH fed by Solar and ASHP, zone design policy?

[brancusi]

Hello everyone! First post, so apologies if this should be elsewhere...

First - some context:

I'm starting to specify the heating solution for a 230 square metre new build farmhouse in central Italy. Because the existing property is a ruin, we have the opportunity to rebuild from scratch so we should be able to ensure it is well insulated, has double glazed windows etc and with out going OTT, hopefully the heat losses will be modest.

The plan is to have heat bank fed from a 8.5Kw Mitsubishi Ecodan ASHP and suitable wet solar capacity (probably around 8 square metres, angle optimised for winter sun) to run DHW and UFH in all areas. We'll have a wood burning stove for spot heat in cold winters and we may or may not have a back boiler for it so we can top up the system that way too (I'd prefer to run it without the boiler, but we may be slightly under capacity in cold weather - need to do more calculations).

There are 12 UFH zones, 4 of which would be open flow.

It seems mad to have a thermostat per zone (room) as you would be forever running around fiddling with them and in any case I would expect the heat to gradually spread over the concrete floor making lots of small zones a bit daft.

My thinking is that it is better to have as few thermostats as possible and am currently looking at a solution that has one thermostat for each of;

a) The Annex (30 sqm, single storey, open plan, adjoins main house)
b) The Ground Floor (open plan living / dining / kitchen / downstairs wc which are actually 2 actuator controlled zones)
c) The Upper Floor (4 actuator controlled zones plus 4 open flow zones)
d) The Basement (for frost protection if it gets really cold)

Does this sound like a sensible approach - ie to reduce the number of thermostats?

When it comes closer to the project going ahead, I'll obviously discuss all this with the selected installer, but I'd like to know as much as possible myself before we start so I know what makes sense and what doesn't.

Thanks!
Roger

[Bodidly]

Hi brancusi and welcome

We live in a converted barn with UFH driven by a GSHP. We also have a wood burning stove which is not directly connected to the underfloor heating circuit. All the UFH is open flow and we tend to leave most of the doors open. At the moment the GSHP is not on but the circulation pump on the UFH is running the stove is on and at one end of our long thin barn, we find that the circulation of water around the UFH  circuit distributes the heat quite well .

Current temperature readings from around the house.

The floor by the stove 30C
Sitting area near stove 21.5C (double hight room with balcony)
Balcony 24c
Upstairs bedroom 20c
Upstairs bathroom on north end wall 18.5c
Down stairs bedroom, bathroom and utility (this is 18m from the fire) 18c

Beau

[rt29781]

Hi Roger,

We live in the south of France.  From our experience I would say that it is best to put the heat into the floor rather than store it.  We do have a stors of 500lts but in retrospect I would say put the heat into the floor.  We have 150 tubes and that will heat baot 40m2 in winter. We have a 12kW Activair heat pump.  That is capable of heating 80m2 I would say in winter with an air temperature of 5C.  You will need to insulate your house well.  The underfllor slabs are concrete and range from 8cm to a2cm thick (a 5:1 sand :cement screed).  The air source heat pump works well in the same circuit as the solar.  The ASHP has a bypass of 40cm PVC pipe so that it doesn't overheat but after this the heat goes to the floor.  See our blog for details or send us a pm if you have questions.