GSHP and UFH in thick structural slab. Will I be able to control it?

[dave Mowle]

Hi all,
I am building a 200m2 timber frame home within a 1950’s block barn. We are aiming for 0.1 through the walls, floor and flat internal roof. Due to the poor barn construction we have cast a transfer slab of 120mm over insulation over the original barn floor. The timber frame is then built off of the new slab. We are being careful with all of the usual air tightness and cold bridging issues. We will have MVHR and opening windows in every room.
My question relates to our decision to put UFH into the 120mm slab. We thought carefully about this before hand but where compromised on floor to ceiling heights and the step down to external ground levels. A further screed was not sensible. I am not expecting room by room control of the UFH as the mass is so high and the heat will transfer horizontally. My issue is that I am struggling to understand how the building will perform day to day, week to week when outside temperature rise and fall. Will the building over heat or be to cool as the high thermal mass struggles to keep up? We did consider radiators but with the high levels of insulation and low temperature GSHP feeding the UFH into the high thermal mass slab thought the building should be OK. Am I just having a last minute wobble or will it be OK?
I have tried to research the issue but cannot find information.
Can anybody help?
thanks
Dave

[David Olivier]

I struggle to understand why you’re using UFH in such a heat-tight building. It’s a very expensive method of providing radiant heat compared to radiators.

P.S. Sorry for delay in replying. This forum doesn’t seem to get many users nowadays which risks being a catch-22.

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