Hello,
I didn’t find anything in the search. My architect initially planned to use cellular glass gravel under the slab-on-grade (without a basement) on strip foundations. However, he now suggests that, for cost reasons, this could be omitted and instead the insulation installed below the screed, since the clay soil beneath shouldn’t freeze in winter.
This would save me about 5,000 euros (approximately $5,000). From his perspective, this is acceptable, but he asked me if I think it’s okay. I’ve been researching for two days now but haven’t found any useful information.
What do you think?
I didn’t find anything in the search. My architect initially planned to use cellular glass gravel under the slab-on-grade (without a basement) on strip foundations. However, he now suggests that, for cost reasons, this could be omitted and instead the insulation installed below the screed, since the clay soil beneath shouldn’t freeze in winter.
This would save me about 5,000 euros (approximately $5,000). From his perspective, this is acceptable, but he asked me if I think it’s okay. I’ve been researching for two days now but haven’t found any useful information.
What do you think?
It's all a matter of belief... I didn’t do it and I don’t feel bad about it. Why? Because I also spoke with former energy consultants, and they all agreed it mostly serves as a calculation proof rather than providing practical benefit.
You won’t get a clear answer here... I also have strip foundations—of course, protected against frost. Beneath them is gravel and a thick moisture barrier that doesn’t rot after 5 years. The barrier prevents moisture, and inside I have 12cm EPS (5 inches) insulation without a basement—however, the pipes are protected separately. Electrical conduits don’t get extra protection because they already have very good insulation themselves (see Fraunhofer study).
You have thermal bridges in both cases... that can’t be avoided, only reduced.
That's it.
You won’t get a clear answer here... I also have strip foundations—of course, protected against frost. Beneath them is gravel and a thick moisture barrier that doesn’t rot after 5 years. The barrier prevents moisture, and inside I have 12cm EPS (5 inches) insulation without a basement—however, the pipes are protected separately. Electrical conduits don’t get extra protection because they already have very good insulation themselves (see Fraunhofer study).
You have thermal bridges in both cases... that can’t be avoided, only reduced.
That's it.
E
elVincent24 Mar 2016 09:30We chose the exterior insulation option, mainly due to moisture protection. Condensation always occurs where it is cold, and with interior insulation, this is on the inside of the slab, meaning that, to put it simply, condensation forms under the insulation. Additionally, there is a thermal bridge in the area of the exterior walls extending downward, creating cold spots where condensation can potentially develop. From my perspective, exterior insulation that fully surrounds the slab and continues into the perimeter insulation of the exterior walls is the better solution.
Regarding the compressive strength of XPS: XPS 3035 CS has an allowable compressive stress under permanent load of 13 tons per m², so a house with a 100m² (1,076 sq ft) footprint could weigh 1,300 tons. Even if you filled an average house completely with water, this still would not exceed that value.
Regarding the compressive strength of XPS: XPS 3035 CS has an allowable compressive stress under permanent load of 13 tons per m², so a house with a 100m² (1,076 sq ft) footprint could weigh 1,300 tons. Even if you filled an average house completely with water, this still would not exceed that value.
S
Sebastian7924 Mar 2016 09:37However, condensation does not occur in this case... and with the perimeter insulation, you cover the entire walls down to the floor – the thermal bridge is minimal due to the interior insulation combined with the exterior perimeter insulation and can be safely disregarded regarding condensation.
Not to forget (although often overlooked) is the other type of equipotential bonding in a fully encapsulated slab.
Not to forget (although often overlooked) is the other type of equipotential bonding in a fully encapsulated slab.
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elVincent26 Mar 2016 19:41Sebastian79 schrieb:
Calculated like that, no condensation occurs...What should the construction be like to prevent any condensation? In my understanding, it mainly depends on the temperature gradient. And the area near the slab-on-grade usually has the lowest temperature, resulting in the highest relative humidity.
The modified equipotential bonding is, I believe, also necessary when using foam glass, right?
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