UFH in old house

Chickereeeee

I have asked the question before, and Doozergirl came back with pretty definite answer. However, the project is getting close, and I wanted to check. Has anything changed? 

I am looking at heating options for my 1926 house (CWI, suspended wood floor with 100mm pir, currently rads), as I am having an extension built to modern standards. Would  retrofit UFH+ASHP work, or  rads+ASHP or stay with rads+gas boiler?

1. LOTS  of people seem to be refurbishing old houses with UFH (judging by DIY forums)
2. A respected Buildhub contributor says 100mm PIR is not enough for UFH.
3. Builders I have spoken do say they are installing retro UFH all the time now in similar houses
4. Doozergirl and others have said it will not heat the house/be too expensive to run

Very confusing.

Has anybody any more comments? Doozergirl, any new thoughts?

Thanks 

Doozergirl

If you have a well insulated house, put UFH in it, by all means. If you don't, then at least have heat loss calculations down to see what the potential result is.  

What is the motivation for most people to have UFH?  It's usually that they don't want to look at radiators.  The motivation behind that is misplaced if the house isn't well insulated.   You're spending a lot of money on something that gives you nothing, whereas, if you spend upgrading the actual fabric of your home, you will feel the benefit of it physically and financially.  

I sit snugly/smugly in an airtight house with 190mm of solid insulation in the walls and 225mm in the roof of our house.  We have mechanical ventilation with heat recovery and UFH downstairs, no heating upstairs.  I will never be able to live in an older house again.  Our old house had cold areas even when whacking the heat up.  We closed up an open plan house because it was cold.   That improved things no end, but the difference now between that and this house is night and day.    

If someone offered me UFH in my old 1930s house or better insulation and ventilation, I'd snap their hand off at the latter. I want to be comfortable above all else, but also try to keep my bills down.    

We need to upgrade the fabric of our homes before thinking that we can operate them using low temperature

It's referred to as 'fabric first'.  

On ASHP - in 2020 I calculated the cost of gas heating vs electric with ASHP and it still would have cost me double in energy what it costs in gas, before considering the £12,000 ASHP cost vs £1,000 for a gas boiler.  That's in a house that exceeded the building regulations. 

The government has this all backwards, putting money towards grants that no one but the installers see the benefit of, and failing to talk about what else you need with an ASHP - insulation!  

It may be that some builders are doing it, but the builder probably isn't the one specifying it, isn't the one living in it, and they're not paying the bills either. 

I see people with hundreds of thousands of followers on instagram running renovation accounts and people treat them like they're experts, when I can see they're not adding even a mm of insulation to a home, when the opportunity is staring them in the face.  We are so poorly educated, we have the blind leading the blind.  

In my day job now, I deal with many builders who care about their clients and wouldn't advise installing UFH for aesthetic reasons alone.  I also talk with true retrofit specialists who deeply understand buildings and their knowledge leaves me seriously lacking.  There is no change in the conversation - you must insulate your home before considering low temperature heat sources.  

I saw a webinar being advertised yesterday about the minimum insulation needed to run an ASHP, which I thought would be interesting.  https://www.greenregister.org.uk/events/event/fabric-retrofit/

It makes no difference to me what people put in their homes but the potential consequences of just not wanting to look at radiators are pretty high.    We need to think deeper about why we do certain things to our home.   Who are we trying to impress? 

FreeBear

Doozergirl said: I sit snugly/smugly in an airtight house with 190mm of solid insulation in the walls and 225mm in the roof of our house.

I see people with hundreds of thousands of followers on instagram running renovation accounts and people treat them like they're experts, when I can see they're not adding even a mm of insulation to a home, when the opportunity is staring them in the face.  We are so poorly educated, we have the blind leading the blind.

How much insulation did you put in/under the floor slab ?

Agree with you about insulating before doing anything else - Currently in the middle of putting 75mm of Celotex on a bedroom wall, and stuffing another ~100mm of fibreglass in the ceiling. In the process, plugging all those nasty little draughts.

Doozergirl

FreeBear said:

Doozergirl said: I sit snugly/smugly in an airtight house with 190mm of solid insulation in the walls and 225mm in the roof of our house.

I see people with hundreds of thousands of followers on instagram running renovation accounts and people treat them like they're experts, when I can see they're not adding even a mm of insulation to a home, when the opportunity is staring them in the face.  We are so poorly educated, we have the blind leading the blind.

How much insulation did you put in/under the floor slab ?

Agree with you about insulating before doing anything else - Currently in the middle of putting 75mm of Celotex on a bedroom wall, and stuffing another ~100mm of fibreglass in the ceiling. In the process, plugging all those nasty little draughts.

150mm in the floor. 

Chickereeeee

Thanks for reply Doozergirl

Well,,agreed about fabric first. But e.g. my house could (relatively) easily have 100mm EWI added to most walls, but there would be little point in doing that, then stripping it off to build the extension. So, extension first (which would insulate one side of the house.) Two more could be done later, along with other steps. Loft is 300mm mineral wool.

Motivation? I am happy with current rads, but I would not fancy doubling their size, and possibly re-sizingbthe piping, if we have to go ashp  at some time. So, future-proofing. And I don't want to install a new kitchen and find I should have done UFH.

Current house is pretty much draught free, although obviously not air-tight. CH flow temperature has been around 50c all winter, even on the (few) coldest days.

Anyhow, thanks for your thoughts.

Doozergirl

Chickereeeee said:

Thanks for reply Doozergirl

Well,,agreed about fabric first. But e.g. my house could (relatively) easily have 100mm EWI added to most walls, but there would be little point in doing that, then stripping it off to build the extension. So, extension first (which would insulate one side of the house.) Two more could be done later, along with other steps. Loft is 300mm mineral wool.

Motivation? I am happy with current rads, but I would not fancy doubling their size, and possibly re-sizingbthe piping, if we have to go ashp  at some time. So, future-proofing. And I don't want to install a new kitchen and find I should have done UFH.

Current house is pretty much draught free, although obviously not air-tight. CH flow temperature has been around 50c all winter, even on the (few) coldest days.

Anyhow, thanks for your thoughts.

I think you're misunderstanding 'fabric first'.  The extension is part of a fabric first approach because our current building regulations are good.  You want to bring the house up to a standard that complements it.   

Higher output radiators are not necessarily physically much bigger, by the way.   And if you upgrade the fabric, the output required is lower = smaller rads.  

Future proofing makes some sense but there's no point putting your horse before the cart. If your house can't hold the heat, it's not future proof.  

The global motivation is to reduce energy consumption, not simply to move low temperature heating.  That means insulation, not just forcing people onto expensive heat pumps.

ThisIsWeird

Allowing for/disregarding everything else, UFH is surely better matched to ASHPs than any other outputting device, due to its low supply temp?

Then add that it's just comfy - simply the nicest way to heat a room. I've had this confirmed with mil's bungalow which has UFH. With both our rooms stats set at 19oC, her sitting room is just more comfy and pleasant than ours. Hers is heated from the toes upwards, whereas ours is warmed from the ceiling down (ie, via radiators).

And then there's the aesthetics - rads are ugly, take up space, and often dictate furniture positions.

Doozergirl

ThisIsWeird said:

Allowing for/disregarding everything else, UFH is surely better matched to ASHPs than any other outputting device, due to its low supply temp?

Then add that it's just comfy - simply the nicest way to heat a room. I've had this confirmed with mil's bungalow which has UFH. With both our rooms stats set at 19oC, her sitting room is just more comfy and pleasant than ours. Hers is heated from the toes upwards, whereas ours is warmed from the ceiling down (ie, via radiators).

And then there's the aesthetics - rads are ugly, take up space, and often dictate furniture positions.

Yes, but you can't disregard it.  

If the house isn't suited to running heating at lower temps it doesn't matter what you choose to heat it with; it won't work properly is the point.    

It's a lot to spend on less benefit if you don't upgrade the house with it.  

ThisIsWeird

Of course. But that applies equally to oversized rads, surely?
Insulation first, absolutely. 

Chickereeeee

Doozergirl said:

Chickereeeee said:

Thanks for reply Doozergirl

Well,,agreed about fabric first. But e.g. my house could (relatively) easily have 100mm EWI added to most walls, but there would be little point in doing that, then stripping it off to build the extension. So, extension first (which would insulate one side of the house.) Two more could be done later, along with other steps. Loft is 300mm mineral wool.

Motivation? I am happy with current rads, but I would not fancy doubling their size, and possibly re-sizingbthe piping, if we have to go ashp  at some time. So, future-proofing. And I don't want to install a new kitchen and find I should have done UFH.

Current house is pretty much draught free, although obviously not air-tight. CH flow temperature has been around 50c all winter, even on the (few) coldest days.

Anyhow, thanks for your thoughts.

I think you're misunderstanding 'fabric first'.  The extension is part of a fabric first approach because our current building regulations are good.  You want to bring the house up to a standard that complements it.   

Higher output radiators are not necessarily physically much bigger, by the way.   And if you upgrade the fabric, the output required is lower = smaller rads.  

Future proofing makes some sense but there's no point putting your horse before the cart. If your house can't hold the heat, it's not future proof.  

The global motivation is to reduce energy consumption, not simply to move low temperature heating.  That means insulation, not just forcing people onto expensive heat pumps.

No, I am not misunderstanding it.
I know the extension is part of the fabric improvement. BUT i can't do all the fabric at the same time before making a decision on heating.

Re: rad sizes - yes they would be bigger, I can't just add fins etc. (Anyway, if you have a low grade heat source, would not the massive surface area of UFH would be better than larger radiators?)

Finally, are we asking about 'traditional' UFH (imbedded in screed) or retrofit? Retrofit suppliers (and the builders) claim that retrofit overlay systems are much more responsive, can handle higher temperatures, and are much more 'radiator-like' in their performance. Obviously, the floor finish would have to be chosen with care, but if true, they could run at higher temperatures (high 20's?) from a  boiler initially, and lower temperatures from a ASHP later, after insulation improved. 

ThisIsWeird

Chickereeeee said:

(Anyway, if you have a low grade heat source, would not the massive surface area of UFH would be better than larger radiators?)

I think that's surely a 'yes'. UFH is effectively a massive radiator operating at a low water temp.

Whether it'll heat your older house in its current state, well that must surely be simple to calculate as the output from UFH is known, and easy to compare with any other heating method. Clearly, anything driven by an ASHP is going to struggle expensively in a poorly-insulated house regardless of outputting device. If you do not insulate your property adequately, then oversized rads running at 40, 50 or even slightly more degrees will likely output more than UFH which runs as - what? - mid-20's?, but your ASHP will not be very efficient at these 'higher' temps.

No idea about modern retro-fit UFH and whether they can be cranked up to run at higher temps. If they can, then they surely completely win over rads, as rads had nothing else to offer other than their potential higher running temps.