Talk to me about underfloor heating?

[chroniclard]

Got underfloor wet system in the extension. 10/10 would buy again. (Rest of the house standard rads)

 

[Scam]

The kitchen underfloor is a wet system and runs off the same main boiler. We have no issues with running it on its own or simultaneously with the main house radiator heating. There is a manifold behind one of the kitchen cupboards where the system gets fed and there is a small pump in there like you would see in an airing cupboard. It's inaudible. It has its own digital thermostat and controller in the kitchen and its basic and a bit rubbish. I should update it.

Sounds good. Did you install that? What are we talking for wet UFH throughout the kitchen, ballpark?

If I recall, it worked out about 10-15p per hour, whilst running.

Crikey. My girlfriend's from Yorkshire, that's never gonna fly!

We are completely renovating the kitchen and knocking through into the dining room. So all of the existing flooring will be coming up anyway. It's all very tempting, both types actually!

 

[ShivP]

Wet systems are totally the way to go, electric are ok for a single bathroom but the running costs are far higher. They're pretty efficient and pair really well with the greener heating methods like an air source heat pump as they require lower temps.

The problem you can get is if you can't have it upstairs as well, the downstairs underfloor will needs 35c and if you have rads upstairs will ideally need 65c. So you'd either need to swap out all upstairs rads for bigger volume ones or try and put wet underfloor in there which seems like a bit of a nightmare, underfloor heating doesn't really pair well with carpets either as you'd be essentially insulating the heat in the floor with the carpet and underlay.

I personally don't like it as i don't like the feeling of the floor being warm everywhere but i get that a lot of people like that, it is a huge undertaking to retrofit though, not sure how it works with suspended floors either or if that's even possible with a wet system.

Why? Can't you use a water manifold for the underfloor heating, which will mix the UFH to the correct temperature with cold water

 

[dirtychinchilla]

doing it in my house at the moment, wet UFH downstairs, rads upstairs. the boiler runs at the normal temp for rads( unlike what someone above says) and the blending valve on the manifold controls the underfloor temp. just put the pipes in for the lounge which is a joisted floor, insulated and 25/30 mm screed over the pipes which will have an engineered oak floor over it. my plumber mate who is fitting it did the same at his house but put carpets over it, says it works well as long as your carefull with carpet and underlay choice. fast reacting with such a thin screed but also cools quicker. i think its a better option than spreader plates. kitchen and second lounge are solid floors so after i've dug them up will be in a thicker screed.

See my comments below. Unless you have a combination of UFH and rads, it doesn't make sense to supply your house with very high temperature water.

Does it have any pros Vs a radiator system designed to run at super low temps? Only one I can think of is losing the radiators on the walls. But with underfloor I'd have to have the floor altered is it even possible with suspended floors?

Getting the water up to temperature will require more energy if you want to flow at 70C for radiators vs. maybe 50C for UFH.

Why? Can't you use a water manifold for the underfloor heating, which will mix the UFH to the correct temperature with cold water

Yes, start with high grade heat and mix it down. But with condensing boilers, they run better at lower temperatures because the subsequent low returns ensure that they actually work in condensing mode.

 

[robj20]

See my comments below. Unless you have a combination of UFH and rads, it doesn't make sense to supply your house with very high temperature water.



Getting the water up to temperature will require more energy if you want to flow at 70C for radiators vs. maybe 50C for UFH.



Yes, start with high grade heat and mix it down. But with condensing boilers, they run better at lower temperatures because the subsequent low returns ensure that they actually work in condensing mode.

That's what I asked low flow temps. My radiators generally flow around 35c or less so what benefit of any would UFH have over such a system.

 

[dirtychinchilla]

That's what I asked low flow temps. My radiators generally flow around 35c or less so what benefit of any would UFH have over such a system.

Wow, how big are they? That is a very low flow temp! Good for you

 

[robj20]

Wow, how big are they? That is a very low flow temp! Good for you

As big as I could realistically fit in each room, two in the living room. I think I calculated based around a 30c delta. Opentherm means they run nice and low down to 22c is the lowest I've seen.

Genuinely interested if UFH is worth it, but suspended floors I reckon id lose too much heat through the floor. Evohome can handle UFH so might look at it for the bathroom and just have that on a bypass IE on all the time.

 

[dirtychinchilla]

As big as I could realistically fit in each room, two in the living room. I think I calculated based around a 30c delta. Opentherm means they run nice and low down to 22c is the lowest I've seen.

Genuinely interested if UFH is worth it, but suspended floors I reckon id lose too much heat through the floor. Evohome can handle UFH so might look at it for the bathroom and just have that on a bypass IE on all the time.

That's awesome, very envious. If you would consider an upgrade, you could fit each radiator with a pressure independent TRV (https://www.sav-systems.com/news/savs-new-pt40-valves-help-maintain-low-heating-system-temperatures/). All the radiators would automatically balance themselves based on the flow rates you set, and the Danfoss thermostatic heads are gas so they can go from fully open to fully closed in 8 minutes.

 

[robj20]

That's awesome, very envious. If you would consider an upgrade, you could fit each radiator with a pressure independent TRV (https://www.sav-systems.com/news/savs-new-pt40-valves-help-maintain-low-heating-system-temperatures/). All the radiators would automatically balance themselves based on the flow rates you set, and the Danfoss thermostatic heads are gas so they can go from fully open to fully closed in 8 minutes.

Already have individual thermostats on each radiator, Honeywell Evohome. Each room is therefore completely controllable.

 

[dirtychinchilla]

Already have individual thermostats on each radiator, Honeywell Evohome. Each room is therefore completely controllable.

That's not what the pt40 does - it automatically balances the radiators so that, for example, if one of the TRVs shuts, the other rads in the system will not be flooded by the sudden increase in pressure throughout the system. Essentially, each radiator is fitted with a DPCV.

The heads are about control, but the valve is about automatic balancing and achieving consistently low return temperatures. You can balance these valves in seconds, each independent of the rest of the system.

 

[robj20]

That's not what the pt40 does - it automatically balances the radiators so that, for example, if one of the TRVs shuts, the other rads in the system will not be flooded by the sudden increase in pressure throughout the system. Essentially, each radiator is fitted with a DPCV.

The heads are about control, but the valve is about automatic balancing and achieving consistently low return temperatures. You can balance these valves in seconds, each independent of the rest of the system.

Evohome deals with that as well, it knows how much heat is needed for each room at a given temp, it also knows what every other rad is doing. Does the same thing a different way I feel, took about a week to program itself.

 

[dirtychinchilla]

Evohome deals with that as well, it knows how much heat is needed for each room at a given temp, it also knows what every other rad is doing. Does the same thing a different way I feel, took about a week to program itself.

The Honeywell TRV can't accomplish that. Maybe I'm not explaining myself well enough though. There's no way for it to modulate the pressure at each radiator, only the flow to the system. The pressure control here is completely independent of the temperature control.

Edit: when you installed the TRVs, did you have to balance the radiators?

 

[robj20]

The Honeywell TRV can't accomplish that. Maybe I'm not explaining myself well enough though. There's no way for it to modulate the pressure at each radiator, only the flow to the system. The pressure control here is completely independent of the temperature control.

Edit: when you installed the TRVs, did you have to balance the radiators?

No they self balance all lockshields are fully open. If one rad is on it knows to only open it a certain amount of another rad then opens it knows to open the first one a bit more and so on and so on, when the system is on you can hear the valves constantly adjusting.

 

[Holst1981]

We have underfloor heating (electric) in the upstairs bathroom and kitchen.

We very rarely use it.

I wear slippers or stand on a bathmat.

Nice if it's turned on all the time but it takes ages to warm up and I don't spend enough time in the bathroom to justify the cost.

 

[dirtychinchilla]

No they self balance all lockshields are fully open. If one rad is on it knows to only open it a certain amount of another rad then opens it knows to open the first one a bit more and so on and so on, when the system is on you can hear the valves constantly adjusting.

Hmm OK, that's interesting. I'm going to ask around and ponder what the difference between the pt40s and these might be. Perhaps it's just the automatic mechanical balancing instead of relying on an external electric component.

 

[Deep]

Genuinely interested if UFH is worth it, but suspended floors I reckon id lose too much heat through the floor. Evohome can handle UFH so might look at it for the bathroom and just have that on a bypass IE on all the time.

I was looking into adding UFH into my suspended floor and I've decided against it for the exact same reason.
There is no way to stop heating going downwards unfortunately

 

[bigfoot4616]

I was looking into adding UFH into my suspended floor and I've decided against it for the exact same reason.
There is no way to stop heating going downwards unfortunately

insulation between the joists sorts that, i managed to get 90mm kingspan between mine, yes a solid floor with continuios insulation would be better but it will be good enough. if i hadn't taken up the floor to put in the UFH there would have only been a floorboard between the room and a cold ventilated space, and draughts as it was just bare floorboards.

 

[413x]

If I was getting a forever home and needed a refurb I'd totally want underfloor for the downstairs.

Kitchen here gets damn cold. One radiator in it and you can nearly always feel the gradient across the room. Tiles are cold!

Been in a couple of underfloor heated houses. And have to say they are great

 

[Deep]

insulation between the joists sorts that, i managed to get 90mm kingspan between mine, yes a solid floor with continuios insulation would be better but it will be good enough. if i hadn't taken up the floor to put in the UFH there would have only been a floorboard between the room and a cold ventilated space, and draughts as it was just bare floorboards.

I have 100mm joists, I read online you should keep 25% of your joist exposed to the air so I was planning to get 70-75mm insulation.
I would love to get underfloor heating but I don't want to risk getting it and it not heating up my room.

 

[Simon]

We have underfloor heating (electric) in the upstairs bathroom and kitchen.

We very rarely use it.

I wear slippers or stand on a bathmat.

Nice if it's turned on all the time but it takes ages to warm up and I don't spend enough time in the bathroom to justify the cost.

Similar, got it in my kutchen, 6 sqm 200W/m2 and on 30mm of marmox so as good as you can get really for electric.

It does warm up in 7mins from turning on and takes the edge off, im not sure it will ever warm the room sufficiently in a old house, but its mainly for comfort in the winter but i rarely turn it on anyway, slippers easier, plus the head doesn't spread as far as i hoped and you toes still feel the cold at the sink. Fail!

Deffo the option for wet systems on new builds but retrofits are always going to be compromised.