House Renovation ~ Adding Under Floor Heating & Improving Insulation
Posted 16 March 2014 - 11:10 PM
It is a brick/breeze block construction with a beam & block ground floor but in my case I also have access underneath the whole ground floor as it is built up 1.7m (7 breeze blocks). On top of the block floor is polystyrene sheets, dpm & wyroc. The house is built on traditional concrete strip footings and the 'cellar' floor is soil. I would like to install UFH in a screed on the beam/block throughout the ground floor including a new extension to be built at the rear of the property of approx. 4m x 12m.
I would be grateful if someone could advise me on a preferred approach ? should I be concerned about the floor insulation (beam/block) or the lower ground level (soil) to better insulate - do I have what you refer to as a slab ?
I have considered fixing kingspan insulation on the underside of the floor between the beams and then possibly adding a board to cover the whole underside floor this would allow me to use the gained depth by removing the wyroc & insulation above.
Any comments or suggestions on the most practical approach would be appreciated ~ David
Posted 18 March 2014 - 07:09 AM
Posted 18 March 2014 - 10:55 AM
Posted 18 March 2014 - 08:46 PM
Posted 18 March 2014 - 09:06 PM
I think your property is a perfect candidate for...............
You'll be opening a can of worms to try and fit UFH in a house that simply wasn't intended to accept it.
The overlay systems available may tick enough boxes to give you a token UFH system, but that's about as good as it'll get I'm afraid.
The only realistic ufh option is to bond/support as much rigid insulation as possible to the underside of the b&b floor and then lay UFH pipes in a 30/40mm liquid screed and accept that you'll never be able to turn off the UFH as it would be then, like a big storage heater that would only see real efficiency when heat is maintained.
You will get perimeter heat loss as mentioned, but if the insulation can be fitted to the extremities then that heat loss should be partially reclaimed into the house as useful latent loss.
As Whitney Houston said, "its not right, but its ok".
I still maintain, you'd be better off with rads though.
Posted 18 March 2014 - 11:03 PM
OK what do you think of placing 75mm Kingspan Thermafloor between the beams up to the underside of the blocks and then place boards over the whole area covering beams and blocks ? I presume this must be beneficial.
I guess you picked up on my idea to insulate as well as I can underneath the blocks, and as you say lay a liquid screed with UFH.
I would then have an old fashioned storage heater but in my case no bricks just beam & blocks throughout the floor area.
I haven't worked out how to overcome the perimeter loss but you seem to imply it is "Impossible" but then again "It'll be OK"
Houston we have a problem....
Posted 19 March 2014 - 08:08 AM
Perimeter heat loss would have to be accepted as collateral damage, but can be minimised by leaving a 2/300mm unheated perimeter with the UFH, but only doing this where the UFH abuts an outside or party wall.
I, however, will not "always love you", unless you get a good 200mm of rigid insulation under the slab.
Edited by joiner, 22 March 2014 - 10:00 AM.
Posted 19 March 2014 - 01:05 PM
You haven't said what floor finishes you plan to use? In some rooms we have 80mm of insulation between 80mm battens with 20mm engineered oak on the top. This seems to work better than the screeded and stone/tile floors at tracking varying demand.
We also have some rooms that are carpeted. If you do this it's important to keep the total TOG value as low as possible. I've seen 2-2.5 recommended. Important to use a special low TOG underlay as that will allow a slightly thicker (almost normal) pile carpet. Do not trust carpet salesmen if they say their carpets are suitable for UFH. What they mean is that the UFH won't damage the carpet. Very few have any idea what the TOG value is and that it matter with UFH. Ask to see the manufacturers data sheet. One carpet salesman we asked went off and came back with a post it note. He told us the carpet we were interested in had a TOG of 10! The other thing to watch out for is the small print. Some carpets are available in two versions, one with a hessian back and the other with a foam rubber. The small print of the order form may allow them to supply either when in fact you probably need the hessian backed version to meet the TOG value.
Overall I feel UFH works best for families that have one person at home most days. If both are out at work then I think the faster response time of rads is a better bet.
Edited by temp, 19 March 2014 - 01:06 PM.
Posted 19 March 2014 - 01:08 PM
Posted 19 March 2014 - 04:44 PM
I have solar PV so I have decided on a thermal store of about 500 ltrs. with heat exchangers for heating & DHW , we currently have more piping hot water than we know what to do with except when the 3 grand daughters arrive ~ they seem to use it without any bother.
This refurb is all part of a plan to bring our house, up to or as practically possible near to modern standards. I have been reading all about the self builds going on (jsharris,joiner NickfromWales etc. ) and with the help of your input am starting to get a picture of what is possible and most importantly practical from a financial & achievable point of view. I must remember to let my OH read the advice on carpets it would be easy to fall into that trap.
I want to lift the present wyroc floor and insulation as it wasn't put down in a professional manner some 26 years ago by a National house builder and together with the newly built rear extension have a mainly open plan ground floor using liquid screed.
What is the current or suggested best way to run central heating radiator pipes, within the screed or route them from above and down the walls for the ground floor areas ?
Posted 22 March 2014 - 08:01 AM
No problem running them in screed as long as the pipe is taped up well.
Posted 25 March 2014 - 10:53 AM
I intend to buy a 700 ltrs HTG thermal store and site it in the utility room alongside a wall mounted gas boiler to heat the thermal store only. The two immersion heaters will be supplied from Solar PV via a Solar immersion switch supplying a good deal of my hot water requirements to the thermal store while only using the gas boiler to top up as required.
The present radiator runs come from first floor down the walls to the ground floor radiators so if I decide not to risk UFH in light of my current floor setup I could use these pipe runs especially as they are copper (Nick smiling). I still haven't totally rejected UFH on the ground floor as I would like to improve the makeup of the covering above the blocks, the skirting and door frames etc. will be replaced anyway as part of the refurb.
Posted 29 July 2014 - 09:47 AM
Building regs specify that for my extension 70mm of insulation is needed and in this area I will put 150mm. The rest will all be 75mm (to meet the v value 70mm is needed) I also accept that building regs are the minium. 3 or 4 years ago 50mm was the accepted thicknesf for UFH and over the years its crept up.
A very knowledagable poster on here calculated I would lose approx 100 a year for not increasing the insulation when I calculated the payback I would need to be over 100 years old to get any cost savings so . . . .
In a renovation I would suggest that all aspects need to be considered i.e. yes in an uninsulated floor you lose approx 12 per cent but if you then take the walls and the roof ceilings etc you can offset the losses.
I was lead to belive that UHF is left on therefore when up to temp it ticks over. So I do not understand why it may be more suitable of 1 person at home all day ? its a thermal store so heat is release from a thermal store at a slow rate.
So if you also concentrate on the roof ceilings walls doors windows etc then UFH I think wil work.