Insulation slab concrete crawlspace under on face

[jamesdo]

Hello,

my house dates from the 50s, the basement consists of a semi-underground garage on 1/3 of the surface, the remaining 2/3 are a crawl space accessible by bending the spine. The total surface is 50m².

I intend to insulate on the underside of a concrete slab, i.e. the ceiling of my basement.
For the moment, my renovation is geared towards local and / or ecological products (cellulose wadding, organic paint, VMC hygro, etc.).

The gain of a soil insulation is around 10% in the best of cases (source ADEME), is it relevant to move towards natural products, often expensive?

Is a good old styrodur economically viable without damaging my ecological morale?

for a thickness of 6 to 10 centimeters, which 'green' product can compete with conventional materials?

last question, how to fix the insulations in rigid plate on this famous concrete ceiling?

please

[Obamot]

I did not understand, if the garage slab is on crawl space and can be accessed ... Why not isolate the crawl space instead?

Now we need photos, because otherwise we can't say anything.

[Woodcutter]

[...] The gain of an insulation of the ground is approximately 10% in the best of the cases (source ADEME), is it relevant to move towards natural products, often expensive? [...]

Is your crawl space ventilated? Basically, does it cool in winter or not?
If the answer is no, or at least if it does not stray from the temperature of a cellar, do not bother you too much, the delta T ° is not interesting enough to gain something (or so when you did everything else ...)

[...]
for a thickness of 6 to 10 centimeters, which 'green' product can compete with conventional materials?

If you compare to styrodur or polyurethanes, under these conditions (SS concrete underside) the answer is NOTHING ... (unfortunately)
Otherwise, accepting lower performance, semi-rigid wood / hemp panels at 40 or 45 kg / m3 will work fairly well, fixing with plastic flange screws:
http://csimg.webmarchand.com/srv/FR/290 ... -cb-ep.jpg
http://www.acr-dedie.com/spiderbatiment ... olants.png

[jamesdo]

thank you Lumberjack.

yes it is rather well ventilated, since in addition to the traditional small opening (10cm * 10cm) there is a large opening (60 * 60) which overlooks a semi buried garage. I do not know if I am clear, but roughly part of the crawl space was disbursed to make a garage workshop space with a garage door. so yes it curdles in winter, and the tiling of the living room above is freezing, unbearable barefoot and I'm not chilly ...

I think it's worth it, even if the eternal thermal bridges will spoil the evening

[Woodcutter]

thank you Lumberjack.

yes it is rather well ventilated, since in addition to the traditional small opening (10cm * 10cm) there is a large opening (60 * 60) which overlooks a semi buried garage. I do not know if I am clear, but roughly part of the crawl space was disbursed to make a garage workshop space with a garage door. so yes it curdles in winter, and the tiling of the living room above is freezing, unbearable barefoot and I'm not chilly ... [...]

So you can earn much more than the 10% of the ADEME, which relates to an exchange with soil at temperature ... of soil! (average of 10 ° C all year around ...)

[Obamot]

This is possibly a delicate case with a cold bridge. Surely other points to isolate.

Would have to see on site all the "details" amha.

[jamesdo]

yes Obamot, the details are very important:

a view of the VS from the garage:

[Obamot]

This is the Lascaux cave this VS!

Yes, well, it would be better to see the detail of the façade all the way around ... Etc. Because cold bridges are also (and above all) at the slab / wall joint.

Apparently the soil seems very dry. It's a pretty good sign!

Should we condemn the issues and clean up? In this case, no need to insulate, if not the exterior walls ?! Simple guess. (And just keep ventilation between the garage and the VS). I let others say what they think of the idea. Of course it would require ad hoc finishes!

[Forhorse]

Difficult to answer without knowing the exact situation ...
But at first would it not be easier to condemn the air intakes temporarily during the cold season?
Especially since the floor has dry air, ventilation all year round may not be essential.
The gain may already be significant.

Then I would say that depending on the situation, the most important thing to deal with would be the thermal bridges with the outside (the junction between slab and exterior walls).
But that generally requires the use of exterior thermal insulation.
Anyway, if there are indeed thermal bridges, it is not the insulation of the underside that will change much.

[jamesdo]

yes there are thermal slab-wall bridges all over the ground floor. But I don't yet have the budget for exterior insulation and I may never have it ...

To return to my basement, it is semi buried, that is to say that the level of earth that we see in the photo is roughly merdo the level of the ground outside. There is therefore approximately 1m of wall in contact with the outside air on 20m linear, that is 20m² of exchange surface. We can then consider that my basement is cold.
In addition, on 1/3 of the basement, a garage was disbursed dug and closed by a beautiful garage door. so here again i think my garage temperature is very close to the outside temperature. Consequently, I think that the insulation on the underside of the slab allows a gain but which will necessarily be reduced by the thermal slab-wall bridges.

Considering that this basement is an unheated room, we recommend an R of around 2 to 3W / m².K.

For a thickness of insulation of 10cm and a simple implementation (by myself) for a low price and approximately 50m² of surface, which materials and implementation do you recommend?

subsidiary question: is it possible to spray cellulose wadding under a horizontal surface?