underfloor heating & insulation

sansnom

sansnom

sansnom

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Hello chaps

I'm putting together a scope of works for the complete refurbishment of a 1900's victorian mid-terrace which is going back to brick (so new everything) and I'm curious about two things: underfloor heating and complete re-insulation.

The contractors I've met with have recommended I do not bother reinsulating under floor boards or external walls as the cost wouldn't justify the benefit (being solid wall, brick built house).

Now I've also been looking into underfloor heating, partly as a way to keep things clean and neat without the need for radiators, partly because I've heard it gives a more uniform temperature around the house.

So questions I need answered:

1. If you were going with underfloor heating, would you go with a wet system connected to your new system boiler or a dry electric system? Whole house or only some parts?
How would it work and how much is it likely upfront cost and typical running costs? I hear UF heating is kept on 24/7 which sounds a bit mental to me and if electric I'm probably looking at what, 5k per year in running costs?

2. Would you reinsulate the entire house including external brick walls (this will shave off about 4cm of internal space in each room, and add about 15k to the cost of the refurb which is a lot considering the entire budget is 75k however I cannot help but feel that without insulating the house properly any benefit achieved from UF heating would be offset by the poor thermal retention of the house)

Thanks in advance
 
I wouldn't touch UFH however I've seen a very tidy system of

Log burner
Wet UFH
Solor HW
Gas boiler

All connected to one megaflow, seems to work very well all be it very expensive install.

If you're going UFH at the very minimum you'd want to insulate the floor I'd guess. Have a look here http://www.bordersunderfloor.co.uk/images/diagbj.jpg which will involve ripping every floor board up.
 
Jez said:
Out of interest - why? :)
Click to expand...

I don't know, maybe it's the amount of smashing out it takes to repair them and floor replacements, sorry I see it on every site we do, someone doesn't do something properly and the grief is massive to fix , yes it's bad workmanship but I can't help thinking it's a massive liability.

Bit like modern diesel cars, ultra efficient until they break then all the savings are flushed.

Saying that we have electric UFH in our bathroom and it's fantastic however if it breaks I'll just take out the control box and plaster over it no loss.
 
I wouldn't bother with underfloor heating in a terrace, only useful in big floor area houses like bungalows.

I would dry line the walls though if you are going back to brick.
£15K is way off the mark though, I used timber framing and glass fibre batts and it was dirt cheap. With a bigger budget I'd use plasterboard with celotex? bonded on the back.

Not so much for the u value, the rooms just heated up faster. Even in winter and unheated they felt OK.
It also made wiring easier, no channelling required.
 
I'm putting in wet ufh in my 6mx8m extension, seems the best type, if its new build although there are products out there for wet systems if you don't have the depth to sink it in new pad or screed.

All connections above ground. Runs at a low temp compared to rad's so makes it cheaper.


Insulating existing solid walls/unfilled cavities is tricky as it can lead to damp problems in cases.
 
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We have a wet system in the extension and electric in the bathroom.
The extension and the 2 rooms adjoining are by far the warmest in the house.
This is despite the underfloor zone being on for a fraction of the time the radiator zone is.
If it wasnt for the hassle of tearing up the floors in the other rooms in the house I would install it there in an instant.
If I was starting from scratch it would be a no brainer.
 
My current house is UFH and its rubbish, its a 2 year old system in a bran new house and the attic rooms are always cold and cant get up to temp, this is because the pump fitted is not good enough. It is off at the moment and not working so a heating engineer will be here tomorrow.

It can take 48 hrs form cold to get warm. I miss central heating and would only have ufh in a bathroom now.
 
what kind of installation do you have? in screed downstairs and some form of insulating board upstairs?

if it's just the pump should be a quick fix. good luck
 
Its a solid floor downstairs (takes 24 hours to warm up) upper two floors are floorboard and insulation, i have easy access to everything, but its not my house, but would like a fix if its easy.
 
dsb said:
It can take 48 hrs form cold to get warm.
Click to expand...

That sounds a nightmare :( we went out to someone with a similar problem a few weeks back, the whole house was UFH and one of the bedrooms would never get warm. Was a combination of pump and balance. Once working correctly, UFH really is fantastic tho.
 
Thanks guys, there's some helpful input here.

Seems a bit of a mixed-bag so far and nobody really went into great detail about relative costs between electricity and gas UFH (both initial installation and running costs)

Can someone shed some light on this? Typical 4 bed mid-terrace with a loft conversion.

Current options are:
1. 100% UFH either electric or wet
2. UFH in kitchen and 3 bathrooms, normal radiators everywhere else
3. Any combination of the above with re-insulating external walls only and all floor boards (the drylining is not the same thing, drylining with insulation is a different board that's either 40mm thick (as opposed to normal 12.5mm) or a reduced 25mm thick. The extra thickness comes from the built-in insulation foam so basically the usual 12.5mm + insulation foam.

I suppose what I am confused about is, if I bother doing all the UFH in the house and incurring an extra £x in cost, is it a waste of time without insulating the house? I'm assuming such low temps in the UFH would be easily overcome by poor insulation or end up costing a fortune
 
In a terrace all the rooms are fairly small so radiator heating works quite well, in a large bungalow/barn then it sucks because of the huge open plan area to heat, hence OFH is a good choice in that situation. It's popular now partly because of all the people doing huge barn conversions.

I'm not sure it is worth the expense, the only room that needs to be warm all the time is the bathroom, bedrooms/kitchens can be heated as required and radiators are better for that kind of instant heat.

If you have money to burn in running it then great (buy an Aga too), but I don't see it being massively better than radiator heating.
It is good for rugrats and if you are home all day, otherwise, meh.
Electric UFH ? only heard of that for bathrooms, sounds very expensive for a whole house.

You won't notice 4cm from an external wall, you will definitely notice how much warmer it is.
I lost 7cm, didn't notice, and I quite liked the wider windowsills.
 
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The insulation will save you money, without it you will be throwing away the same amount of heat out the building regardless of how you distribute its supply. (I would prioritise sorting out insulation and look into the heat recovery systems, but that is just my 2p).
 
(No experience in this, these are just my thoughts)

Afaik, electric is the most expensive fuel source in raw terms of £/BTU and natural gas is the cheapest. If you have electric ufh, you would need to have a generator to reclaim energy from different sources. If you have water ufh, you can easily heat the water in the system from multiple sources.

Thus, if it was me, I would have wet ufh with a wood burner, gas burner and electric immersion with suitable heat exchangers, allowing for flexible freedom of fuel source decisions.

Insulation is obviously very important, but so long as you are aware of it I am sure it can be worked around. For example, making sure your thermal mass flooring isnt just leaking heat out the bottom of the house.
 
Have you thought about an air source heat pump?

We are just installing one to a new build, we are being sold 1kw electric in gets you 5kw heat out however the installation is £ x 2 minimum.
 
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Our heat pump (ground source) was running at 2.3p per kWh up until last week, not calculated the numbers this week yet but it wont be far off, thats cheaper than gas. Of course the installation cost is a lot higher but once you factor in the RHI payments, it really is a no brainer.
 
We fitted a wet underfloor system when we did our extension and then a couple of years later when we did the kitchen and dining room ripped up the floor boards and fitted wet ufh into there aswell.

Took off the floor boards and nailed them under the joists to support the kingspan.

P1080059.jpg


Clipped in the ufh pipe so it finished level with the top of the joists.

P1080067.jpg


Filled in with a dry mix level with the top of the joists, then used ply sheets over the top and tiled.

P1080066.jpg
 
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