Cooling a green-raft slab with UFH

[Steve247]

Hi all, So we are about to start ground works for an insulated green-raft slab (and ICF polarwall) with UFH within the slab linked to ASHP and some PV panels.

 

Obviously (with recent hot weather) I am keen to have cooling with the UFH.  

 

I contacted Wunda but they said cooling with their system isn't possible!  

I remember seeing on here that someone purchased Wunda pipework and a different manifold.  Was this the reason? 

 

Can anyone recommend UFH company for supply only with good product/warranty and cooling is possible and perhaps also an ASHP that compliments the UFH when cooling.

 

Many thanks 

Steve 

 

[Conor]

The UFH system you use has nothing to do with whether you can cool or not. It's all about the heat pump. You just need the right type of control valve setup to allow the UFH to circulate with cold water and not go through the hot water cylinder.

[jack]

@Steve247, there was an event posting that mirrored the wording above. I assume it was unintentional, so I've hidden it.

 

On the topic of underfloor cooling, there's nothing in the standard Wunda setup that will prevent its use for use with an ASHP in cooling mode. They just don't want to be responsible for someone running their cooling at well below the dew point under wooden floors, and being sued a few years for water damage caused by condensation.

 

I have a standard Wunda manifold and pump set (admittedly from about 6 or 7 years ago) and it works perfectly fine to cool our insulated slab with polished concrete overlay.  

 

[JohnMo]

It all about control out with the UFH pump and mixer.  UFH mixer sets the min flow temp.  So can almost be ignored in cooling mode.

 

There are several threads on here that discuss the details with drawings, but you will have to have search to find them.

[Steve247]

Thanks for responses. I'll search further on here particularly for drawings which will be very useful. 

[jack]

1 hour ago, Steve247 said:

Thanks for responses. I'll search further on here particularly for drawings which will be very useful. 

 

I wouldn't worry about looking for drawings to set up underfloor cooling. It's literally exactly the same as UFH.

 

The only differences when cooling instead of heating are:

 - You need to figure out how to enable cooling mode on the ASHP. Varies by manufacturer and model. 

 - If you want to have the cooling controlled by a thermostat, I seem to recall that you may need a second thermostat for cooling operation, or at least a thermostat with both normally open and normally closed outputs. One output is connected to call for heat, the other is connected to call for cooling.

 

I personally don't bother with a thermostat in cooling mode. I have the ASHP outlet temp set to about 15° C in cooling mode, and that seems to result in the (polished concrete) floor settling at around 19° C. 

 

During long warm periods, I run it during the day when the sun is up so it gets assistance from our PV. During the worst of the recent heatwave I left it on 24 hours a day for about five days, including a couple of days before the really high heat hit. Worked really well.

[mike2016]

Would I be right in saying that the flooring choice has a bearing here? 

If you have a polished concrete / screen floor you're ok?

Tiled Floor is ok?

Wooden/laminate/bamboo floor with underlayment would present a condensation risk?

Carpet???

I'm considering an air to air system with a separate heat pump for the hot water but still debating if I should put in the underfloor heating loop or not just in case. Would prefer tile/bamboo mix downstairs if that can support cooling effectively. 

[jack]

12 minutes ago, mike2016 said:

Would I be right in saying that the flooring choice has a bearing here? 

If you have a polished concrete / screen floor you're ok?

Tiled Floor is ok?

Wooden/laminate/bamboo floor with underlayment would present a condensation risk?

Carpet???

I'm considering an air to air system with a separate heat pump for the hot water but still debating if I should put in the underfloor heating loop or not just in case. Would prefer tile/bamboo mix downstairs if that can support cooling effectively. 

 

Concrete or tiles should be fine (assuming no chipboard or OSB underneath). I suppose if there was enough condensation within grout for a long enough period you could get some mould growth, but at the sorts of temperatures we're talking about that doesn't seem likely.

 

There's an increasing risk the more mould prone the final surface or substrate is.

 

Also, the more insulating the substrate, the less effective the cooling. We have one carpeted room downstairs, for example, and it's the hottest room in summer and the coldest in winter, as a result of the carpet and underlay (not low-TOG) insulating the underlying slab from the room. 

[NSS]

We have Karndean flooring throughout and run the cooling input temp at around 12-14C which allowed us to maintain a floor temp around 18/19C through the recent hot spell. We were running it for 4 hours in the night and 8 hours during the day. As in Jack's experience, we've had no issues with condensation here.