Underfloor cooling with ASHP?

B2468

As part of a renovation, we're going to be installing UFH with an ASHP.

We're also considering air conditioning for the bedrooms, but I'm wondering about using a reversable ASHP for cooling instead. I mentioned this to some of the ASHP people we've been getting quotes from, and their comments have basically been that it works, but it's not nearly as good as air conditioning and that when they do install it that way people end up disappointed.

Does anyone have experience with this to share? Mostly what I find is UFH suppliers talking it up, but no actual users giving feedback. Since it'll end up with us buying a less-expensive heating-only ASHP, I'm leaning away from it. But I haven't got a quote for the aircon yet, and 'basically free and ok' may beat 'expensive but better'.

Does anyone have any experience/feedback on the underfloor UFH for colling?

This in London - a semi-detatched 4-story property. Floor coverings would be a mixture of wood and carpet, but the carpetted bedroom floors are where we want the cooling (and the only floors we'd put aircon on), which I appreciate may make it less useful too.

I know that using the ASHP for cooling would no longer be permitted development, but we need planning permission for the other work anyway.

Reed_Richards

Are heating only ASHPs really less expensive?  Mine (LG Therma V) is perfectly capable of cooling but I don't have planning permission to use it that way.

Netexporter

 but it's not nearly as good as air conditioning and that when they do install it that way people end up disappointed.

Cooling isn't the same thing as air-conditioning. A/C reduces the humidity of the air, as well as cooling it.

matelodave

The problem with cooling is condensation - cooler air holds less moisture which condenses on cold surfaces, that's how dehumidifiers work. Air conditioning units have drains to get rid of the water, how do you propose to dispose of the condensate that will form on your floor?

Cooling your floor means you probably end up with it being wet and TBH covering it with wood or carpet seems like a pointless thing to do with the possibility of damp & mould under the carpet or wood covering due to condensation.

Reed_Richards

This it true but possibly a bit pessimistic.  I have a wood floor which is not particularly well-insulated from the concrete directly underneath, which is not well insulated from the earth underneath that.  So the floor is the coldest surface in the house in summer.  But it doesn't suffer from condensation because it's not that cold.  I think you should be able to get mild cooling by circulating cool water through your UFH but in order to avoid condensation you must only make the floor a little cooler than the room so it won't be very effective.  

matelodave

If you aren't going to cool it by much then there's not a lot of point in doing it and, as cool air sits on the floor rather than rising like heat, then all you'll probably get is cold feet and a hot head. 

But I'd be interested to find out how effective it is if the OP decides to go ahead 

Netexporter

Personally, I'd go for the ASHP for heating and have MVHR to deal with excess moisture without significant heat loss or high energy consumption.

tacpot12

Setting up a heat pump to do cooling properly is a major undertaking. There is a lot to consider, especially the same heat pump is going to be used for heating your domestic hot water. It's not just condensation issues with the floor, but also with the all the pipe works. It needs a very switched on designer and installer. If either of these aren't there, you won't be happy with the result.

It's often as cheap to have a second ASHP for DHW if you are going to use the main one for cooling or to have a mini-split system for summer cooling as reserve the main ashp for winter heating and all-year hot water production. 

QrizB

I think @Mstty (sadly no longer a board user) did exactly this with his ASHP and UFH last summer when it was exceptionally warm.

I can find a post where he was discussing it here, but not the post where he stated it actually worked. I think it did. though.

B2468

Thanks for this. Sicne we're getting a heat pump anyway, I suspect that we'll install it (assuming that the different in cost for the heat pump is minimal), and if it doesn't help then it hasn't really cost us anything

matelodave

If you are hoping to get the government grant for installing your heat pump it would be worth checking whether your chosen device will qualify.

If you aren't bothered then go ahead