INSULATION FOR EXISTING UNINSULATED CONCRETE FLOOR SLAB

[claire2011]

Hi

I would be very grateful for any help with this.

We want to put down underfloor heating through our hall and kitchen/ dining area.

The floor is concrete slab which is not insulated - the house was built in the 1980s.

We dont want the heat from the underfloor heating to be lost through the existing concrete floor and so we want to put down insulation under the underfloor heating to stop the heat escaping into the concrete.

We dont have high ceilings so we need the insullation to be as thin as possible - ideally a maximum 10mm. Can anyone please recommend a suitable insulation product?

I have looked into 'warmup' 10mm board but its very expensive - are there any good alternatives?

In the lounge we would like to insulate the concrete floor with a 10mm board and then lay wooden flooring, with no underfloor heating - can anyone suggest a suitable product for this?

Many thanks, Claire.

 

[mointainwalker]

You must realise that there are real-world limitations to things, no matter how much we would like it to be otherwise.

New regs require 270 mm of insulation ( R value 5.7 ) in a roof, so it is impossible to expect any reasonable degree of insulation from 10 mm, especially if you are also looking for it to be cheap.

If you are going to install electric UFH and want to save money on the insulation, you could use polystyrene ceiling-tiles - about 8 - 10 mm I think, but you are only saving installation costs and not really running costs..

As far as the wooden flooring is concerned, it would be useful to say if 100% wood, engineered-wood etc before asking about what goes under it.

 

[noyk]

I used floorheater for my bathroom, 12 months on so far so good.

http://www.floorheater.co.uk/the_box_techspec.php

 

[mointainwalker]

Looks like 90% *******s to con gullible people taken in by science -speak and a couple of formulae with values for reflective foil.

 

[claire2011]

Hi
thanks for your help.

not sure if i have explained v well - we are not trying to insulate the loft. we are trying to insulate a concrete floor as have been told that if we dont, half the heat from the underfloor htg will be lost through the cold exisiting concrete floor. so we want to put insulation over the concrete floor, then underfloor heating, and then tiles / wooden flooring. we dont want to raise the floor height too much so want a very thin insulating board to go over the concrete floor.

if this changes anything / wasnt clear before please let me know!

Claire.

 

[freddiemercurystwin]

What you're looking for does not exist. Only things that are effective that thin are for the aviation or military industries and they're megabucks.

 

[mointainwalker]

not sure if i have explained v well - we are not trying to insulate the loft

I did not think you were trying to insulate the loft . I gave you that as a COMPARISON to highlight the total inadequacy of the insulation you are thinking of using.

I think that an estimate of 50 % wasted energy is about right..

You should also bear in mind that with a very thin heated -floor, you are always going to be using peak-rate electricity and your effective costs ( taking into account the 50% waste) will approach 20 p kW/h.

 

[ajrobb]

Forget underfloor heating. Your house was built for fitted carpets.

Heat is lost at the edges. A large warehouse needs no insulation under the floor as the ground just warms up. If you must have underfloor heating, keep it away from external walls. Even with an insulated floor you should expect less than 100W/m² so you may need other forms of heating.

 

[freddiemercurystwin]

I knew what you meant mointainwalker.

 

[RedHerring2]

Me too, but sometimes wasted energy is...... well, wasted. But it keeps you cool.

 

[noyk]

Looks like 90% **** to con gullible people taken in by science -speak and a couple of formulae with values for reflective foil.

Is that in reply to me? Thanks for the vote of confidence dude. Anyway, i'm simply posting a reply to the question, a question which i had asked in the past and no one I asked then (or now it seems) had a solution so i searched for my own.

If you try finding an option for web ufh that doesn't involve digging out and insulating, rescreeding etc it is virtually impossible, this company along with one other that i found provides a solution. It provides insulation, heat spreader and underfloor heating in one package and i was simply reporting that it works for me. It's not very cheap, but the alternatives worked out far more expensive.

As the system uses Wet UHF it is more flexible not to mention cheaper than electric. I realise it's not the best in terms of insulation values but something is better than nothing in insulation terms and more importantly turns the room into one in which you can enjoy rather dread in the winter.

 

[mointainwalker]

@ noyx

I've no idea if you are one of those or not , however my comment was not aimed at you.

I hate this type of selling. It deliberately loads the spec with tons of information useless to anyone except an expert industrial buyer/engineer writing a contract or tender - see below - which is intended to clog people's thought processes so that they skip over and get onto nice understandable words like unique and reliable and cosy comfort. to aid the selling process.

Strangely enough, in spite of their love of confusing formulae/numbers, the only ones they miss out are the actual insulating rating for the insulation mat

Dimensions of straight panel: 1175 x 768 mm.
Dimensions of U-turn panel: 768 x 192 mm.
Groove’s center-center spacing: 192 mm.
Insulation material: Compressed expanded polystyrene (EPS)
EPS density: 40 kg/m³
Max short-term load: 300 kPa (~300 kg/dm²)
Max long-term load: 120 kg/dm² (12 tons/m² distributed load)
Heat diffusion material: Aluminium foil
Thermal conductivity of aluminium: 200 W/(m °C)
Foil thickness: 0.1 mm
The foil is laminated onto the EPS with thermally activated adhesive.

Since there are no running costs quoted, people have to invest to find out and are likely to have no realistic hope of a successful complaint if subsequently disappointed.

It was interesting to read that you find the system isn't cheap - ( presumably means running costs ?)

 

[noyk]

.

It was interesting to read that you find the system isn't cheap - ( presumably means running costs ?)

No, i meant not cheap to buy, to run it's cheap (relatively with increasing gas prices) as it's water based rather than electric and gives a much more uniform heat than a radiator would plus as i mentioned gets rid of the cold floor problems. However, the expensive component, the pump, scales well to larger systems so it's proportion of the cost will drop with increasing system size.