Adding underfloor heating to concrete floor

Looking in to much the same thing, conclusion thus far unless anyone can help us otherwise is that we have three choices:

Leccy underfloor mats - minimal uplift in floor height, absolutely no heat output and massive bills due to all the heat leeching into the concrete below.

Wet underfloor with tiny insulation laid on top of slab - bigger uplift in floor height (around 2" being conservative), and better heat output, but still losing a stupid amount of heat into the slab below.

Wet UFH via digging the entire fecking ground floor out and relay slab from earth upwards - perfect UFH operation, optimal conditions, wonderful. And one big fecking mess.



Looks like we're going for option 3 come the spring and moving out whilst it's done!

The thinnest solution would be 6mm solid insulation boards and wire but not a cheap to run option. While thin insulation options exist you can't have too much- I put in 6" of celotex on my (suspended) floors. Wet UFH is always best in the long run.

While breaking up 4 inches or so of concrete floor might seem like a gargantuan job to oneself there's always the option of renting a decent breaker and grinder, chucking em at a pair of cheap labradors for a couple days.

How much did that end up raising the floor by? Boards plus mat, plus screed sounds like quite a bit? What is under the boards?

This is what we've got too - massive

Quality product, economical to run and completely unobtrusive in use - i.e. you could walk round in shorts when there's a foot of snow outside and you don't feel hot - always just right.

We were also recommended to use Ditra matting http://www.schluter.co.uk/produkt.aspx?doc=6-1-dit... under our stone tiles - it reduces thermal shock which can crack some stone (it may sound like BS but ours is fine after 4 years).

No idea what it's made from to be honest. It's pretty heavy so wouldn't be suprised if it's composite with built-in insulation

We're in the same boat.

It's gonna hurt, but we are kinda used to the mess now.

Can you run that off of the existing CH that is all radiators?

Lots of missinformation on here about the amount of heat lost through floors - typically its about 15% compared to 35% through the walls/roof. The reality is that you dont loose much through the floor because the temperature difference accross the floor is normally arround 10-15C in peak winter rather than the 25-30C accross walls, windows, roof. For disbelievers http://www.confusedaboutenergy.co.uk/index.php/hea...

I was commercial HVAC designer for +15years and I installed electric underfloor in my kitchen. Its easy to install, cheap to install, 100% reliable, cheap to run and gives a great level thorough heat.

Do your fag packet calculation and size it correctly and its the way to go.

There is no need to insulate below as the %age of heat lost to the ground is minimal.

Same here.

You fail to understand the information in your link, which clearly states 15% through the floor is for an average house. The average house has gas central heating and convector radiators. Hope this helps you in designing your systems.

Radiant underfloor heating will have completely different heat loss characteristics to the average house due to the floor itself being the radiator. Heat will be conducted away, not gently radiated as per average house. If you don't insulate between an element and a concrete slab, apart from crippling heat conduction losses you'll be looking at several hours for warm-up. I've installed elements or supplies for such in this way as the client/clients builder was to arrogant to take advice and I believe all such systems aren't in use due to the fact you pretty much need to run them 24/7 for them to be warm when you need them.

The only exception will be if the area is a fairly recent build as insulation in incorporated within the floor (if it's done to regs).