Underfloor heating in period houses

[Lostgardensof]

I am just about to start renovating a grade II listed building which currently has no heating system. We have been in contact with the CO and she is happy for us to put in underfloor heating or radiators. I have a preference for underfloor as there will be no visible heat source however I am not sure that it will be able to heat the house up enough to make it bearable.

The construction is a stone vaulted basement with timber joists supporting the ground floor floorboards. We hope to lift the boards, install the heating and replace the original floor.

Does anyone have underfloor heating in a period house with a suspended floor? Does it work?

Does anyone think the timbers/floor might warp with the heat? (it should be low ~50oC so should be OK I think)

Has anyone used the metal spreading devices which sit directly under the floorboards to spread the heat?

If we fill our underfloor space with concrete screed and insulation is it likely to cause damp issues?

All advice gladly received.

 

[Kearn]

however I am not sure that it will be able to heat the house up enough to make it bearable.

I haven't personal experience, but advice from those more experienced than myself when recently digging up a concrete floor and relaying in limecrete, who really didn't think it worth the expense for the minimal heat transferred from the room. In my example, on a solid floor, the heat loss/transfer is minimal via the floor vs walls/roofspace and the transference of heat from the floor to the room is a nice way to take the edge of of a hard cold floor underfoot, but not considered a primary heating source for a room into the air itself. You heat a mass of floor not a room full of air. Also, if I understand your situation correctly, you're more likely to keep the chill off of your basement with this method than the rooms intended.

We hope to lift the boards, install the heating and replace the original floor.

If the boards are indeed original, then there is a school of thought that says really don't lift them unless absolutely necessary. Damage will be done regardless of care and skill applied, iron brads will be bonded to the wood making removal somewhat destructive, boards will never go down again as tightly as they once were. I would have also thought that a CO wouldn't be keen on this in a listed building, but you never know...

If we fill our underfloor space with concrete screed and insulation is it likely to cause damp issues?

Highly probable. That space is there for a reason - airflow. And as we all know with old buildings, airflow is essential.

 

[88v8]

The idea of having no anachronistic heating units is a worthy one.

But wood is an insulator.
Underfloor heating beneath a suspended floor, sorry, no.

In a concrete or limecrete floor, the whole mass eventually heats through and acts as a massive storage heater.
But under a suspended floor, it simply won't work, wood does not store heat, and as K says the necessary airflow will remove the heat anyway.

Be glad that you have original features and a house which is not damp as so many are. Don't start tampering with the design to shoehorn in a heating system which is simply inappropriate.
And yes, it is impossible to lift old boards without damage, although I'm sure you would find any number of couldn't-care-less tradesmen who will pretend otherwise. And yes, it would split and shrink the boards.

Cast-iron radiators.... are more available new and old, than they have been for fifty years, and will look well in your period home.

Ivor

 

[Kearn]

Cast-iron radiators.... are more available new and old, than they have been for fifty years, and will look well in your period home.

I'm not saying they are the best out there, but I have previously bought rads from here which I am very pleased with https://www.ukaa.com/ and I will buy again once I have got round to laying my brick floor in our entrance hall (old animal shelter) which needs some serious heat.
Not necessarily to all tastes (but there are lots of styles and great options to have new rads built to room volume spec and size which look the part, alternatively refurbish originals, but this is not easy!).

Sounds like you have found an interesting project, sans heating!! hopefully the rest of the property is similarly unmolested - any photos?

 

[Flyfisher]

I have a preference for underfloor as there will be no visible heat source however I am not sure that it will be able to heat the house up enough to make it bearable.

Nor am I, though that will depend on what you mean by 'bearable'.

I've no experience of underfloor heating with a suspended wooden floor but I think you're wise to be wary of it, for most of the reasons already mentioned. I do, however, have experience of (wet) UFH with a solid floor as, although I was in two minds about it at the time, we decided to give it a try when we had our kitchen extension built. Being a new build, we had no existing constraints, so that made it fairly easy, particularly in respect of properly insulating underneath the UFH to ensure that heat is not wasted trying to heat up the ground!. It's also ideal for a kitchen as wall space for conventional radiators is often at a premium.

As mentioned above, UFH acts as a storage heater and is not very responsive, so if you're after fast heating (and cooling) times then forget it. In operation it acts as a very large, low temperature radiator. Our kitchen floor area is adjacent to our suspended floor sitting room and both areas are open to each other and although the sitting room also has a large cast iron radiator the UFH kitchen floor area is large enough to provide enough heating for both rooms.

But, in practice, we find that the UFH alone is rarely enough to heat both rooms to above about 17/18C and if the weather is really cold then it's more likely to be 15/16C. Personally I find that 'bearable' - especially when I've just walked through some of the totally unheated rooms we've not finished yet - but would admit it's not exactly shorts and Tee-shirts comfortable. But with a good set of 'thermals' and a decent pullover it's ok. Fortunately, the sitting room houses our boiler stove and this will easily make the room bearable, nay comfortable, even without a thick pullover, and we also have the radiator as a backup option. When the boiler stove is alight it also provides enough hot water to run the UFH as well as our bedroom radiator and the gas boiler switches itself off - which is good for the wallet

The really good thing about UFH is that it provides a gentle background heat that seeps into the entire fabric of the building - something that is very noticeable when compared with our unheated rooms.

Overall, I'm very pleased with our UFH and would definitely choose it again. I think it would be more effective in a totally new build house with up to date insulation, though in a 400 year old timber frame building with large SG sash windows and draughty doors my experience is that UFH alone would struggle to keep things 'comfortable' (20/21/22C ??) and for that sort of temperature an additional source of heat is very likely to be required.

Having said all that, I also think that anyone with a suspended wooden floor is starting at a disadvantage as far as UFH is concerned - though that's just conjecture on my part. it would be good to find someone with first hand experience of living with suspended floor UFH.

 

[livias]

My experience has been similar. We put in a well insulated limecrete floor with underfloor heating last summer and the recent weather has given it the first good test. At the same time the timber framed house was insulated as much as we could manage (roof excellent, gable ends reasonable, side walls no more than the original wattle daub and lime plaster) We are finding draughts and blocking them and apart from one elusive hole in the kitchen we are now reasonably well sealed up.

Our thermostats are set to 20 degrees throughout the house and 24 hours a day. There is no point in fine tuning the adjustment of temperatures as the response time is so slow. In average weather, like now, we find it very comfortable. In the very cold weather the house sat at 19 degrees and failed to get up to 20 degrees at any time, which was OK but not wonderful. We are due to get a woodburner put in the sitting room fireplace during the next month and my experience of woodburners says that will provide more than enough toasty warm heat for the whole house in the coldest of weather.

In fact I would not want to be without it in winter. It has the added advantage that it is not dependent on electricity which everything else is. We are wondering about buying a backup generator for the house and wondering how to link it in. Has anyone else gone that route?

 

[MikeG]

Don't do it. Really, really, don't do it.

It won't work. Underfloor heating is great in solid floors, set in screed. It is useless, and I mean useless, in timber suspended floors. There is no thermal mass, and there is marginal contact between heat source and flooring. The air takes the heat away. I have been involved in a number of cases where homeowners insisted on UFH in suspended timber floors, and have then whinged when it didn't work. I now absolutely refuse point blank to specify it in these circumstances (I'm an architect). My own house has UFH downstairs in the screed, and radiators upstairs.

On one job (ground floor suspended floor) we had to lift the flooring and pug the entire void with kiln dried sand, filling to the very top of the joists before replacing the floor. Now, you can imagine the pain involved with that procedure. One grain of sand on a joist and the boards wouldn't sit back down, and you try walking around on joists surrounded by sand without disturbing a grain. All because the owner insisted on UFH......and then couldn't feel any warmth at all when it came on, just exactly as I predicted.

Please, please reconsider.

 

[Flyfisher]

Our thermostats are set to 20 degrees throughout the house and 24 hours a day. There is no point in fine tuning the adjustment of temperatures as the response time is so slow. In average weather, like now, we find it very comfortable. In the very cold weather the house sat at 19 degrees and failed to get up to 20 degrees at any time, which was OK but not wonderful.

Yes, that sounds very familiar. We don't usually leave the UFH heating on 24/7 though and find that if its on at 6am then things are warm enough by 9pm (we don't get up very early ), though its not starting from totally cold though as it takes a long time to cool down completely. We did have it switched on all day in the recent cold weather though.

We are due to get a woodburner put in the sitting room fireplace during the next month and my experience of woodburners says that will provide more than enough toasty warm heat for the whole house in the coldest of weather.

Agreed. I wouldn't want to be without ours, especially as it also heats our water and bedroom radiator meaning that we use no gas when it's alight.

Having recently been playing with a remote temperature sensing system, I can confirm the following temperatures at the time of this post:

Outdoors : 8.2C
Boiler Room (a small utility room next to kitchen housing the gas boiler and DHW system) : 19.2C
Kitchen: 18.1C
Sitting Room (open to the UFH kitchen and with a wood burner currently alight): 23.6C
Dressing Room (a small bedroom only heated in the mornings): 12.9C
Master bedroom (radiator-heated by the boiler stove): 18.4C
Spare Bedroom (curently unheated): 8.9C
Drawing Room (currently unheated): 9.4C

In fact I would not want to be without it in winter. It has the added advantage that it is not dependent on electricity which everything else is. We are wondering about buying a backup generator for the house and wondering how to link it in. Has anyone else gone that route?

I've have a friend in USA who connected a backup generator to his house in Virginia because their snowy winters frequently bring down power cables. I don't know the precise connection or switchover details but he said it was quite easy (he is an electronic engineer though!). It only powers 'essential' circuits as it's not large enough for the whole house. I imagine such a system would have to be connected by a qualified electrician in the UK and the work duly signed off. I've toyed with the idea but we have so few power cuts that it hardly seems worth it (perhaps I shouldn't have said that!!).

If you're really keen though, it's possible to implement a fairly authentic 'period' solution for local generation:
https://www.youtube.com/watch?v=XNswRamTy2U

 

[Flyfisher]

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[Lostgardensof]

Sorry for not popping back earlier, i didn't realise this had been approved yet.

Right Firstly thank you everyone for taking the time to reply.

I suspected that the underfloor heating was not workable so I am glad we found out before installing it! It just won't work if you need to conserve the air flow I assume and having spent days reading old posts from here I really point want any damp issues. Much easier to make a decision when there is consensus.

We would have lifted the Floor ourselves as there is no way I would trust builders to do it.

So period radiators, a wood burner and thick curtains then?

Here are a couple of pics to whet everyone's interest, plus the garden was once part of a botanical garden, although now very overgrown, hence the username.

 

[fernicarry]

We put UFH in our kitchen refurb in a suspended floor. Wool insulation hung between the joists, Polypipe overlay cement boards cut down to fit between the joists so that they were flush with the top, then a new plywood deck over that. We were looking to minimise build up to keep the FFS similar to the dining room.

Two things I'd do differently, the insulation between the joists needs to be more carefully packed in to avoid air circulation, its noticeably cooler on windy days. I've done it with wood fibre bats in the upstairs bathroom. I'd use a cement board as the deck to improve heat transfer. The surface will eventually be tiled so we didn't need to worry about keeping the original floor covering (which was long gone anyways). As many have said almost certainly won't work under floorboards but reasonably viable if you don't need to keep the original floor covering.

Its perfect for Spring/Autumn use but in winter we need a secondary heat source which is the Aga. We run it close to maximum circulation temperature and its on its own circulating pump which probably runs just about continuously.

-AL

 

[Feltwell]

If you're really keen though, it's possible to implement a fairly authentic 'period' solution for local generation:
https://www.youtube.com/watch?v=XNswRamTy2U

Blimey, that takes me back. As a kid I remember going out on a reasonably regular basis with my Dad (who knows about such things) to the rather wonderfully named Muriel's Farm to fix their ancient Lister Start-o-matic. It was very old and not that reliable, but for a Norfolk farmhouse about 3 miles away from the nearest National Grid connection it was the only option. You used to walk into a room, flick the Bakelite switch and wait about 6 seconds before the light bulb flickered into life as the generator started. I seemed to remember that in exchange for keeping it going we got free sacks of spuds and the occasional joint of pork.

I made the mistake of looking on Google Street View a while ago to see if the old farmhouse was still there. No, it's been replaced by a couple of modern bland boxes, and the old barns where I happily played as a kid all over the ancient machinery within them (probably highly dangerous but I'm still here!) have all gone

 

[Flyfisher]

We're going a bit off-topic now (what's new? :lol: ) but these sort of 'stationary engines' were once quite commonplace and used for all manner of agricultural and light-industrial jobs. Lister was one of the major manufacturers and many of their engines are still running. I've read that one problem with the Start-o-Matic (which sounds like something straight out of Wallace & Gromit :lol: ) was the start/stop operation depending on the electricity demand such that the engine would not get up to running temperature, exacerbating waer and tear. Conversely, engines that were run for long periods of time, e.g. for pumping water, were highly reliable and still work well today.

On my 'playtime to-do list' is to install an automatic watering system for the garden using stored rainwater and topped up during the summer months by pumping water from our adjacent river, using a 'Lister D' stationary engine and suitable pump. Something like this https://www.youtube.com/watch?v=Un5WwjgdM7s

 

[Feltwell]

If I'd known that about 5 years ago you could have had the very nice Lister-engined water pump that my Dad got rid of when he moved house. 1920's / 30's, all mounted on an wheelbarrow type frame. Ran very quietly with a gentle chuff chuff. Went to an enthusiast for not a lot of money.

 

[Flyfisher]

Sounds exactly like the sort of thing I'm looking for. I'm aiming for a Lister D precisely because they are quite widely available for very reasonable prices, probably because they were manufactured in such large volumes and are fairly easy to maintain, with spare parts still being quite easily available. Time is the thing I really need . . . :wink:

 

[Feltwell]

Here are a couple of pics to whet everyone's interest, plus the garden was once part of a botanical garden, although now very overgrown, hence the username.

Oooo - very nice - more details, lots of, and pictures please! How long has it been empty for? I'm presuming one of your first jobs is roofing repairs.

 

[Flyfisher]

Yes, very nice way to be dragged back on topic - very interesting looking house.

 

[Bathman]

Not disagreeing with any views but thought I would offer a differing view based on my own experience of installing UFH on timber floors - may be a slightly different application to the OPs situation as this is a first floor rather than ground floor but may be useful for anyone else who comes across this thread.

I installed electric foil UFH in my first floor bathroom, so not the air flow problems like you might get on the ground floor (although perhaps that could be addressed by some close-fitting insulation between joists?). I have a layer of ply on top of the original floorboards, then a thin layer of soft insulation on top. followed by the foil heating mats. I then have waterproof laminate tiles directly on top of these (no underlay). With this setup there is nothing to act as a heatsink, and tiles warm up very quickly.

I have this turned on for a couple of hours in the morning and evening and makes a significant improvement compared to when I just had the heated towel rail in there (unheated porch directly underneath and 2 external wall)

Perhaps not a very period solution, but for my bathroom I wanted things functional (the only period features were the original architraves, cill and door which I have kept).

 

[MikeG]

The electric under-tile heating is a very different thing. It isn't for space heating so much as warming the floor. It is effective in doing that job, and as a bonus can take the edge off the cool of a small room such as a bathroom, but it absolutely cannot heat a house. Fundamentally it differs in sitting on top of the floor, rather than underneath it.

 

[Feltwell]

I fitted electric UFH in a previous house in the bathroom on a suspended floor - I wouldn't really regard it as heating as such, it was more a comfort thing to make the cold floor tiles nice and toasty in the morning. I plumbed a towel rail in to the usual central heating circuit to act as a radiator to actually heat the room.