Wet UFH - insulation advice

[Ben88]

Hi - no doubt this has been done to death, but thought I’d try anyway.

I have a 1960 built bungalow with solid concrete floors. The floors are covered in asbestos tiles but, once removed (carefully and in line with HSE guidance) the concrete is in good condition and dry.

I’d like to install wet UFH in my kitchen / diner which is approximately 34m2. On a rough calculation I need 18-20k BTU to heat it properly. We have a combi boiler which was installed in 2013 so should be okay for the job.

I’d like to know how best to insulate the floor, whilst minimising build up and to avoid a big step into the lounge. Floor covering will be porcelain tiles.

I appreciate that the two may be mutually exclusive, but in need of some advice.

Thanks, Ben.

 

[Nozzle]

You need 50-100mm celotex, don't waste your money with the thin foil things.

Nozzle

 

[Ben88]

You need 50-100mm celotex, don't waste your money with the thin foil things.

Nozzle

That’s my fear. Nothing else will do it?

 

[Nozzle]

Insulation is all about trapping air and preventing it moving around. If it moves around, it is transporting heat with it. Thin insulation can't trap much air, and squashed insulation with no space for air is even worse, it's just foil against foil with a bit of plastic in between. Foil is metal - A conductor.

I had Wet UFH put in at my place. It involves digging up the concrete floor, digging down through the hardcore, relaying a harcore then concrete with enough space for celotex, ufh pipe and 50mm Screed. The deeper you dig, the thicker the insulation you can use.

Was it worth it? Hell yes.
Would I do the digging and floor laying myself? Hell no!

£££££
Nozzle

 

[Ben88]

Insulation is all about trapping air and preventing it moving around. If it moves around, it is transporting heat with it. Thin insulation can't trap much air, and squashed insulation with no space for air is even worse, it's just foil against foil with a bit of plastic in between. Foil is metal - A conductor.

I had Wet UFH put in at my place. It involves digging up the concrete floor, digging down through the hardcore, relaying a harcore then concrete with enough space for celotex, ufh pipe and 50mm Screed. The deeper you dig, the thicker the insulation you can use.

Was it worth it? Hell yes.
Would I do the digging and floor laying myself? Hell no!

£££££
Nozzle

I’ve had a quote for doing precisely this, including the UFH system at £7.5k.

My concern here is that it doesn’t react that quickly, but is the most effective way of doing it.

The sandwiched system does respond quicker but for that you lose heat through the floor.

 

[Nozzle]

Any system that involves minimal insulation is bound to disappoint.

Nozzle

 

[Ben88]

Any system that involves minimal insulation is bound to disappoint.

Nozzle

Any thoughts on the Kingspan Optim-R solution? Looks high performing but no idea if it can be used.

 

[Nozzle]

My thoughts on Kingspan Optim-R are.. I know nothing about it! Chat with your local architectural technician

 

[Notch7]

Any thoughts on the Kingspan Optim-R solution? Looks high performing but no idea if it can be used.

Best you be sitting when you get a quote for that!

Feedback ive had from customers is UFH is not good retrofitted onto existing concrete floor.

But Ive been involved on jobs where floors have been taken up, then 100mm celetex laid, 25mm perimeter celetex and either liquid screed or mapei top cem -both transmitt heat better than normal screed.

 

[Ben88]

Best you be sitting when you get a quote for that!

I’ll let you know when I get one back!

I appreciate that there is an optimum way of doing this, but I’m also interested is the payback. If I’m losing 10% through the floor on a £800 per year gas bill, then tearing up the concrete and relaying with celotex at a cost of £7k is going to take 100 years to pay back!

 

[Notch7]

I’ll let you know when I get one back!

I appreciate that there is an optimum way of doing this, but I’m also interested is the payback. If I’m losing 10% through the floor on a £800 per year gas bill, then tearing up the concrete and relaying with celotex at a cost of £7k is going to take 100 years to pay back!

UFH isnt a good option for payback calculations.

My advice would be either dig up and insulate or go for radiators.

Think of underfloor heating as a system comprising: insulation, pipes, thermal store.

 

[Ben88]

UFH isnt a good option for payback calculations.

My advice would be either dig up and insulate or go for radiators.

Think of underfloor heating as a system comprising: insulation, pipes, thermal store.

how come it’s not a good candidate for payback calculations?

Radiators likely to cost a lot too - and channelling for pipework etc. will be messy and annoying!

 

[Nozzle]

It all depends what you're starting from - prestine floors with nice carpets. Or shell of a house with nothing to loose.

Nozzle

 

[Ben88]

It all depends what you're starting from - prestine floors with nice carpets. Or shell of a house with nothing to loose.

Nozzle

Far from pristine! Just had the wall separating the kitchen and dining room; bit of a building site. After taking up current flooring, the original concrete slab is covered in asbestos tiles. Concrete is in good nick and dry. Have no reason to dig it up other than for UFH.

If this UFH exercise is futile, I’ll cut channels for radiator pipes, board over the asbestos, and tile on the board.

If the UFH is a goer, I’ll take up the tiles which haven’t already popped and give it a go.

 

[Nozzle]

UFH Work

Nozzle