Hi,

I was wondering if anyone had an idea about insulation that can be placed on top of poured concrete flooring?

Some kind of thin but high U-value material would be preferable - also should be easy to lay.

Carpet tiles will be placed on top of the insulation/ concrete as well to form the actual floor.

Is there any issue with dust fires?

Thanks,
Finbar

Posted By: Finbar MWilliamsCarpet tiles will be placed on top of the insulation/ concrete as well to form the actual floor.

Most insulation needs to be protected with a wearing surface. It's usual to use a screed or floorboards over the insulation or put the insulation under the concrete slab.

How thick can the insulation be? There's a huge price difference between Aerogel & extruded polystyrene. Have you thought about using cork tiles instead?

David

Just as a guide... I think the Building Regs these days require something like 70mm of Celotex in a new floor. Aerogel is the best insulator know to man but it's still only about twice as good as Celotex - so I suspect that even with Aerogel you would still be looking at something like 35-40mm plus the wearing surface (typically 18-21mm minimium for a wood floor) if aiming to meet the current building regs.

ANY thinner solution will be proportionatly worse. For example Cork is worse then Celotex so 10mm cork will be at least seven times worse than the buildings regs require for a new floor....BUT that might still be many times better than what you currently have. The whole world is looking for some kind of thin LOW U-value material -It doesn't really exist.

How much total thickness can you afford to add?

Thanks - yes, this is problematic - does anyone whether aerogel can be walked on?

The main issue seems to be that it is better to insulate under the concrete...

Thanks!

Posted By: brig001Some good info here (about half way down):http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9&page=3" rel="nofollow" >http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9&page=3
I am also looking into something like this for my house. The thing I am not sure of is how much colder the slab will be when I add the insulation. Currently, the slab will end up close to room temperature (in the middle anyway). When you add insulation above it, it will cool, partially negating the insulation you have added. Anyone know how big this effect will be?

Sure the slab will get colder but that doesn't negate any of the insulation you add. The insulating properties of most materials aren't significantly effected by the temperature drop across them.

Consider an electrical resistor... If you connect it in series with a light bulb the voltage at the light bulb is reduced but the resistance of the resistor stays the same. The current flowing from the battery is reduced.

Posted By: brig001The main issue seems to be that it is better to insulate under the concrete...

The important thing is that thickness matters wherever it is.

The thermal conductivity of a material is a measure of how good an insulator is it is. It's normally specified for a nominal 1 meter thickness so you can easily scale the numbers to work out how good it is at whatever thickness you want or can afford.

Some examples show that most common insulating materials have broadly similar thermal conductivity so only the thickness really matters. Ok so I'll admit that some are two or three times as good as others but none are 20 or 100 times better. This explains why there is no magic super thin insulator..

Straw insulation 0.09
Cork 0.070
Rock Wool insulation 0.045
Styrofoam 0.033
Air 0.024 (without convection)
Urethane foam 0.021
Aerogel 0.013

Source:
http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

CWatters, all true, but as I understand it, solid floors can already have very low U values when the building has been occupied for a while and the ground is "full" of heat. This is especially true in commercial buildings when the floor area is large. The thermal comfort should be better for the feet if the floor is insulated, but I suspect that the energy savings will be nearly zero.

Mike,
Unfortunate news on the trial of aerogel as an underlay. Dust is an issue that needs to be managed.
I did hear this week of someone using it and reputedly successfully in that application with the aerogel sandwiched between two layers of breather membrane...you know the one, T***k the much beloved catalyst for conspiracy theorists

Joe,

As far as I recall the research suggests that some insulation (about the current BR level) is beneficial its just that the diminishing returns kick in much quicker. No matter the amount of heat in the ground and wing insulation etc the heat is still only flowing one way...

J

...both... its just a matter of extent...



J

Posted By: joe90brig001,

I agree and plan to have NO insulation beneath my concrete floor in my new build but to have vertical insulation extending the wall insulation down to the footings level. Solar gain with house usage will create a heat bank (thermal mass) to even out temperature fluctuations within the house. This is IF I can get it past the BCO.

Make sure you use an insulation that's doesn't loose it's properties when wet. I think Celotex say to put a DPM under it when used under a slab so presumably that absorbs water?

http://www.tonyshouse.info/interseasonal.htm

So how worthwhile is internally insulating a solid floor, bearing in mind that thickness is likely to be very limited?
Finbar MWilliams: The main issue seems to be that it is better to insulate under the concrete...
CWatters: A thin layer of almost any insulation will make the floor feel warmer to the touch (compared to say bare concrete) but probably won't make a big difference to overall heat losses or room temperature...
and: The important thing is that thickness matters wherever it is.
Tony: Ah yea but is the ground an insulator or a conductor?

So, there doesn't seem to be an answer, I guess because we don't know the initial U value for the floor. I am considering something simple and cheap like the green boards for underneath laminate flooring, a layer of ply on top then fit the carpets as normal. This would only take up 15mm or so, and would improve comfort, but wouldn't really make any difference to heat loss unless the room temperature can be dropped because the floor feels warmer.

What do we think?
Finbar, would something like that achieve what you want?

Posted By: brig001So, there doesn't seem to be an answer, I

see below...

Posted By: James Nortonsome insulation (about the current BR level) is beneficial

Saint,

If you read my thread you will see that I am not against insulation, quite the opposite, my house will be insulated to passive house standards. I was trying to move the insulation to another location, wings or vertical, to improve the thermal capacity of the ground below the slab.

There have been many threads before this talking about the ability to have an interseasonal store using the ground below ones house and no-one is against insulation.