Using UFH circuits for cooling

[Nick1c]

Not sure if this is the right place for this but:

A significant issue in very well insulated houses seems to be overheating. Is there any merit in the idea of putting some UFH pipes under the hardcore of a passive slab and pumping the UFH water through them in the summer to cool the slab, or will the pipe be damaged by what is above it?

[joe90]

@Nick1c you need to read @JSHarris blog about getting his ASHP to cool his slab, it’s what I will do IF we suffer from over heating.

[Jeremy Harris]

@Nick1c, the UFH pipes run inside the concrete of the slab, not underneath the insulation in the hardcore of a passive slab.  We find that the cooling effect of running water at around 12 deg C through the floor in very hot weather works extremely well at mitigating overheating.  It seems a bit counter-intuitive that cooling the floor works as well as it does, as there's no doubting that it does.

 

If you have PV then this cooling is free, as whenever you need it there is a very good chance that you're generating more electricity than you're using.

[Nick1c]

I realise that the UFH is in the slab, I was just wondering if a second 'circuit' below the slab would have the potential to provide a low tech form of cooling as the ground would be at circa 10C. 

[joe90]

3 minutes ago, Nick1c said:

I realise that the UFH is in the slab, I was just wondering if a second 'circuit' below the slab would have the potential to provide a low tech form of cooling as the ground would be at circa 10C. 

 

Wrong side of the insulation as @JSHarris says, why have two loops when one will do both even from the same source if you use an ASHP.

[Jeremy Harris]

6 minutes ago, Nick1c said:

I realise that the UFH is in the slab, I was just wondering if a second 'circuit' below the slab would have the potential to provide a low tech form of cooling as the ground would be at circa 10C. 

 

Not sure how well that would work, TBH, as in the well-drained layer under the house heat conduction is likely to be fairly poor.  I think the pipes would need to be arranged like a conventional GSHP collector, and buried more deeply in reasonably well conducting soil.

 

If you  have an ASHP, it's dead easy to just run it in cooling mode to keep the floor cool in very hot weather,

 

 

[Nick1c]

I see what you mean about the poor conductivity. Oh well, it was just an idle thought. If we get an ASHP I'll look into using it for cooling. 

[Vijay]

Is there any way of cooling if you're not using an ASHP?

[Jeremy Harris]

10 minutes ago, Vijay said:

Is there any way of cooling if you're not using an ASHP?

 

Yes, you can run a buried brine loop, essentially the same as a ground source heat pump collector, deep into the ground around the plot.  This will typically deliver brine at around 8 to 10 deg C all year around, so would work well for summer cooling.  The downside is the expense and disruption of burying a lot of pipe in the ground, and overall it may well be more cost effective to just install an ASHP and use that for heating and cooling.