Wet underfloor heating, how should I use it?
Wet underfloor heating, how should I use it?
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Quattr04.

Original Poster:

663 posts

8 months

Just moved into a house which has a electric boiler (unfortunately) which runs underfloor heating in the hall, kitchen and living room

Previously I’ve lived in houses with gas boilers and radiators so you just set up the schedule and as it was a new build it retained heat and didn’t take long to heat up when it had been off a while

With underfloor heating, which is a wet system in the screed, what is the best way to use it? I’m thinking just leaving it at a constant 18 degrees, then having a schedule so it’s constant 20 in the day at the weekends, to come on at 6am when we get up at 8?

We both work from home on a Friday but apart from that we are at work Monday - Thursday 8-5 so I guess set it to 18, then set it to come up to 20 about a hour before we arrive home? Then just constant 20 on the Friday?

Probably not worth having on in the morning if we’re getting up at 7 and leaving at 8? I can’t see it dropping much over night

The new house is a converted barn, which is well insulated and had a B EPC rating

Any advice?


LaserTam

2,176 posts

236 months

Because it takes a while to warm up (and cool down) because it warms the slab, if you turn the temp up at say 6am, you won't notice a difference until dinner time (maybe exaggeration). So probably just leave it at your desired temp 24x7.

Arrivalist

1,672 posts

16 months

There’s a bit of a myth about leaving wet UFH on constantly. It’s a little nuanced …

Most manuals suggest:

Find your comfort heat for the room and have that set as your ‘on’ setting during the day.

Then have a setback temp around 2-3 degrees less to run overnight.

But it really depends on the slab the pipes are in and how quickly it warms up and cools down.

Snow and Rocks

2,900 posts

44 months

It'll take some experimentation to see how quickly it responds to heat inputs which is largely dependent on the thickness of the slab/screed.

My parent's system has the pipes set deep in a thick concrete slab and so it takes many hours or even days to heat up and cool back down. They generally just leave it set at the desired temperature all the time which mostly works OK with a couple of exceptions.

1) if the weather suddenly warms up or there's lots of sunshine - the house rapidly overheats and there's little you can do but open the windows and wait for the slab to stop belting out the heat.

2) if the opposite happens and there's a sudden cold snap it takes a long time for the slab to warm up and so the house gets pretty cold. They've solved it with a woodburner but previously resorted to jumpers and thick socks.

Your system might be set in a much thinner, and thus more responsive slab but something to bear in mind.

Deep Thought

38,012 posts

214 months

LaserTam said:
Because it takes a while to warm up (and cool down) because it warms the slab, if you turn the temp up at say 6am, you won't notice a difference until dinner time (maybe exaggeration). So probably just leave it at your desired temp 24x7.
We've wet underfloor throughout our house.

You should be feeling a difference within an hour, maybe two, tops.

We keep rooms we are using at a fallback temp of 18 degrees, then boost to 21 degrees a couple of hours ahead of using the space.

Snow and Rocks

2,900 posts

44 months

Deep Thought said:
You should be feeling a difference within an hour, maybe two, tops.
As I said above, you can't generalise, the response time is largely dependent on the thickness of the slab and the depth of the pipes.

8-P

3,053 posts

277 months

I hope it’s more cost effective to run than my electric underfloor heating that we never use.

Arrivalist

1,672 posts

16 months

Snow and Rocks said:
Deep Thought said:
You should be feeling a difference within an hour, maybe two, tops.
As I said above, you can't generalise, the response time is largely dependent on the thickness of the slab and the depth of the pipes.
Indeed.

I’ve had wet systems that have taken hours to warm up so are able to be turned off for hours once up to temp and others that operated much more like radiators and could be used more reactively to heat requirements.

OutInTheShed

12,021 posts

43 months

Depends on the mass of the slab and how well insulated the house is.
Also how tightly the slab is linked to the air temp, e.g. is it covered in carpet or ceramic tiles.

Possibly there is mileage in heating the slab on economy 7 cheap rate or zummat?