Riverside Cottage 4 (I think)

Underfloor heating.

Insulation thoughts... the existing ground floor has 25mm Jablite topped with 22mm chip. Recommendation is to over fit 25mm of pre-grooved insulation and a further set of flooring: chip + Vinyl or engineered hardwood.

Downside is loss of height in doorways.

What is the real energy loss in heating a relatively uninsulated floor slab in a roughly square building? For 24 hour occupation, doesn't it come down to what is lost at the edges?

Reply to
Tim Lamb
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Nowhere near what is lost through the roof and walls before insulation. I would guess at less than 10% before any insulation for a solid floor. With 25mm of insulation that will take it down to about 2% another 25mm will take it down to about 1%. Unless the insulation is really cheap and labour free it will never pay for itself.

Reply to
dennis

Mm. Its a very very complicated calculation as you have to take the mean path through a variable soil conductivity to the outside air.

And it isn't dominated by edge effects at all.

Plus remember that the hotter the floor is in comparison to the room the worse will be the heat loss through it.

Don't think 25mm poly is anywhere near enough.

You must have that extra 25mm, and even then Id say its gonna be lossy.

Reply to
The Natural Philosopher

Confirming once again that Denise cant read a post before replying.

And has no understanding of heat loss in buildings or why its different with UFH.

And this is the calibre of mind that thinks staying in the EU is the right thing to do.

For him it probably is. Unable to think coherently for himself, and must always buy 'microwave ready' pre-cooked opinion from the Guardian...

Reply to
The Natural Philosopher

You really don't understand physics do you! If you put pipes onto and they are at 55C that will only about double the heat loss through the floor and that loss is only the 1% so at best adding another 25 mm will take it to the same level as a normal room without UFH.

Just for the understanding.. if you double the temperature difference you double the loss. If you double the insulation you halve the loss.

Whats the Guardian? ;-)

Reply to
dennis

You might, but you've overlooked one thing - see below:

No - because you've incorrectly assumed the substrate temperature under the subfloor remains the same (your assumption appearing to be about 0c )

This is true of walls and roofs. But the general mass of earth under the house will rise in temperature with an increased floor surface temperature, so it is far from obvious how much difference an extra 25mm of insulation will make.

I've never understood the details, but I can see enough to know your argument has an error.

Reply to
Tim Watts

I do understand physics

No, its noth8ng like as low as that

so at best

Reply to
The Natural Philosopher

Yes but the error is in favour of the insulation making less difference.

You can work it out but its not easy so most people just take the figures published.

Reply to
dennis

Of course it is, just read what I said and think about it.

Reply to
dennis

Firstly are we talking about a solid floor, or suspended - I suspect the former, but its worth checking since it can make a big difference in these situations.

The next thing to consider is the overall area of the floor - larger floors are disproportionately more efficient than smaller ones, and the centre of the floor better than the edges.

The actual calculation method required is described in BS EN ISO 13370, and BS EN ISO 6946 will give you appropriate data to play with for U values of the soil type etc. (I can't find the BSI link on my local library page the moment to get the docs - your's may be better)

There is also a BRE doc, number 443 that gives some more info on the process.

Reply to
John Rumm

Oh. I was rather thinking dry soil might be a reasonable insulator and, once the slab temperature stabilised, most of the losses would be from the edge though the brickwork.

I suppose I could ditch the intermediate chip.

Reply to
Tim Lamb

Solid.

Roughly 8mx9m

Right. I had a poke around. Installed Silverlight as requested and then failed to make head or tail of the options offered. There are free calculators out there but beyond my limited skill to use:-(

Reply to
Tim Lamb

In message , The Natural Philosopher writes

Yebbut. We are discussing losses to subsoil which is not intimately linked to air temperature fluctuations.

Reply to
Tim Lamb

Only a couple of inches makes a big difference in a doorway hieght usagewise. Is there a damp proof membrane under the floor already? If not, it needs to be taken up and remedied along with insulation. Lot of work.

Reply to
harry

Dennis is right on this one. Instead of a temperature difference of say 20 degrees on an outside wall, your talking about a thirty or forty degree difference because its the heat source.

The actual rate of heat transfer varies depending on the nature of the ground and the movement of groundwater. The best being dry sand gravel, the worst being wet clay. You get some of any heat lost back but less then 25% usually

Complex topic.

formatting link

Reply to
harry

Actually they are.

There is just a lot of soil between your floor and the outside air temperature.

If you study the building regulations the way heatloss is calculated is the same as through the walls, but a radically different U value is assigned to a 'slab against the ground', and the form factor of the house is taken into account.

I.e the 'subsoil' is not an infinite sink. It has thermal capacity and thermal resistance and its losing heat to the air all the time. In terms of heatloss calculations the soil looks like a very thick wall.

Of soggy wet clay. Or damp sand. Or rock. Or chalk.

3 meters of rock is about the same insulation value as a standard wall insulation however, and its not that far from the center of the room to the outside, on an average hose, let alone the edges.

And the floor area is the same as the roof. By and large.

Reply to
The Natural Philosopher

There is an existing membrane.

Simplest is to lay the piping on top of the existing and renew the floor. This will reduce door openings by 67mm.

Reply to
Tim Lamb

Sadly they want money to read that article. Otherwise looks appropriate.

Reply to
Tim Lamb

In message , Tim Lamb writes

Oops! 47mm.

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Reply to
Tim Lamb

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