Overlay UFH boards
Discussion
I can see there have been numerous overlay UFH threads over the years, but I have a very specific question which I'm struggling to find information on. That question is, what is the best material for the boards? From what I have read the choices are gypsum board or XPS. I've discounted EPS as the cost saving doesn't seem significant enough to justify the heat loss and potential problems. As I understand it:
XPS is a better insulator, meaning reduced heat loss into the slab and heats up quicker.
Gypsum Board has greater thermal mass meaning it stores heat and dissipates it evenly into the room, but will lose more downwards.
The house is old, but relatively well insulated in the walls and roof. The slab won't be insulated given the age of the house. It will be powered by an oil boiler. We have relatively generous ceilings so losing 25mm wouldn't be a problem. Floor coverings will probably be tiles in the kitchen and bathroom, engineered wood in the living and dining rooms, carpet in the bedrooms. This will be our main source of heat, we also have a log burner in the living room.
I'm leaning towards gypsum board as it seems the most solid, and I like the idea of heating up the floor then maintaining that with low input, but I don't really like the idea of heating up worms.
XPS is a better insulator, meaning reduced heat loss into the slab and heats up quicker.
Gypsum Board has greater thermal mass meaning it stores heat and dissipates it evenly into the room, but will lose more downwards.
The house is old, but relatively well insulated in the walls and roof. The slab won't be insulated given the age of the house. It will be powered by an oil boiler. We have relatively generous ceilings so losing 25mm wouldn't be a problem. Floor coverings will probably be tiles in the kitchen and bathroom, engineered wood in the living and dining rooms, carpet in the bedrooms. This will be our main source of heat, we also have a log burner in the living room.
I'm leaning towards gypsum board as it seems the most solid, and I like the idea of heating up the floor then maintaining that with low input, but I don't really like the idea of heating up worms.
We used this: https://baseufh.co.uk/system/12-ultra-low-panel-sy... as we had limited height available and didn't want a big rise from the small front door lobby into the lounge.
LMV said:
I think that is castellated panels which you then put levelling compound over? Looks good but significantly more to install. How do you find it?
It's been in for three winters now and found that the UFH is surprisingly cheap to run, we have three zones as we are largely open plan apart from the small lobby at the front door. We have Heatmiser stats and controller connected to a Viessman Vitodens Combi boiler with rads upstairs (that never get turned on). I like that I can turn the heating off/on remotely when we are away so when it's very cold we can warm the house before we arrive. Yes, we did put self-levelling latex type compound over the top as recommended by Base (found some Polish chaps through a builder friend and they had a machine that mixed the compound and pumped it in) we supplied the materials they did the work.LMV said:
Do you know or have a theory whether you were losing heat specifically into the ground or just generally through poor insulation?
Our house is quite well insulated above ground but I'm presuming the slab is just concrete.
Lounge and hall were old and straight to slab….cold, kitchen and Cinema room were new and insulated…toasty. When it snowed half the house had snow up to the walls and half had a melted path around the outside!!!Our house is quite well insulated above ground but I'm presuming the slab is just concrete.
Huge difference!
Happy Jim said:
UFH is a radiating heat, ie as much down as up. If you have it straight to slab (zero insulation) then you are heating up the garden and it will cost a load to maintain a happy temperature - the more insulation under the UFH the better
Jim
There are two approaches to UFH in slabsJim
Lots of insulation
or
None
None doesn't mean horrific costs theory starts at 11:15
Underfloor heating with limited or no insulation doesn't have to be a problem.
If pipes are kept away from the edge, (say 600mm), there won't be any significant loss to the outside. Losses downwards aren't losses - energy doesn't disappear - heating the ground is just a larger thermal mass.
Generally speaking, it's best to have thermal mass with underfloor heating - an overlay system tends to restrict this - just think about doors, toilets, wardrobes, kitchen units etc etc and determine how much thermal mass there is going to be.
100mm of concrete is great, 50 mm is OK. Grooving an existing floor is a good solution, grooving concrete isn't easy - screed is easy, see https://www.jk-gb.com/
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