ᐅ Interior insulation with extruded polystyrene (XPS) in the basement
Created on: 19 May 2015 21:01
H
Hausmeister72H
Hausmeister7219 May 2015 21:01Hello everyone,
a basement room is going to be insulated from the inside.
With the U-value calculation, I came to the following result:
Under these conditions, mold growth should not be expected.
Moisture Protection
During the winter thaw period of 90 days, a total of 0.175 kg of condensation water per square meter occurs in this building component. This amount dries out during the summer within 81 days (drying period according to DIN 4108-3:2014-11).
# Material sd-value Condensation Drying time Weight
m kg/m² % days kg/m²
1 1.5 cm (0.6 inch) Knauf Rotband bonding plaster gypsum 0.08 - 0.0 14.3
2 5 cm (2 inch) XPS rigid foam 4.00 0.15 8.6 1.8
... on outside 0.15
3 1.5 cm (0.6 inch) lime-cement plaster 0.52 0.17 0.6 27.0
... on inside 0.15 70
... on outside 0.023
4 25 cm (10 inch) reinforced concrete (1% reinforcement) 32.50 0.026 0.0 575.0
... on inside 0.023 81
... on outside 0.0024
5 0.3 cm (0.1 inch) bituminous thick coating 150.00 - 0.0 3.2
... on inside 0.0024 42
33.3 cm (13 inch) total building component 187.10 0.18 81 621.2
The calculation from the online tool states: "No mold is to be expected."
However, condensation does occur, which makes me uncertain.
Is this acceptable if constructed as described above?
I do not want to have to tear everything down again...
a basement room is going to be insulated from the inside.
With the U-value calculation, I came to the following result:
Under these conditions, mold growth should not be expected.
Moisture Protection
During the winter thaw period of 90 days, a total of 0.175 kg of condensation water per square meter occurs in this building component. This amount dries out during the summer within 81 days (drying period according to DIN 4108-3:2014-11).
# Material sd-value Condensation Drying time Weight
m kg/m² % days kg/m²
1 1.5 cm (0.6 inch) Knauf Rotband bonding plaster gypsum 0.08 - 0.0 14.3
2 5 cm (2 inch) XPS rigid foam 4.00 0.15 8.6 1.8
... on outside 0.15
3 1.5 cm (0.6 inch) lime-cement plaster 0.52 0.17 0.6 27.0
... on inside 0.15 70
... on outside 0.023
4 25 cm (10 inch) reinforced concrete (1% reinforcement) 32.50 0.026 0.0 575.0
... on inside 0.023 81
... on outside 0.0024
5 0.3 cm (0.1 inch) bituminous thick coating 150.00 - 0.0 3.2
... on inside 0.0024 42
33.3 cm (13 inch) total building component 187.10 0.18 81 621.2
The calculation from the online tool states: "No mold is to be expected."
However, condensation does occur, which makes me uncertain.
Is this acceptable if constructed as described above?
I do not want to have to tear everything down again...
Internal insulation is always problematic, and in my opinion, XPS (extruded polystyrene) is the worst option you can choose. It may look good in calculations because it is extremely airtight (so the numbers add up), but in practice, it is not feasible.
Additionally, you need to heat significantly more (higher temperature) to feel comfortable warmth.
A better approach is to use a vapor-permeable material and ventilate regularly.
Additionally, you need to heat significantly more (higher temperature) to feel comfortable warmth.
A better approach is to use a vapor-permeable material and ventilate regularly.
H
Hausmeister7220 May 2015 19:57Hmm... that sounds like it would rather be inadvisable...?
Internal insulation is not always bad and is sometimes unavoidable. The important thing is that the insulation is not bypassed by air, meaning no air should get behind it. This can be ensured, for example, by full-surface adhesion (instead of patchwise application). But what can 2.5 cm (1 inch) of insulation really achieve? The cost and effort clearly outweigh any benefit. In our timber construction upstairs, we have 6 cm (2.4 inches) of internal insulation (flexible mineral wool between battens, with a climate membrane above and rigid plasterboards). External insulation was not possible at the required thickness because we do not have a roof overhang. Yes, rooms become narrower with internal insulation, but 2.5 cm (1 inch) really doesn’t help at all.
H
Hausmeister7221 May 2015 23:13Well... at least it’s 5 cm XPS, and for a room that’s 3.5 x 4.5 m (11.5 x 14.8 ft) in size, the “reduction” hardly makes a difference. Excavating from the outside is simply much more complicated.
The only thing is... the mold worries me when using XPS.
The only thing is... the mold worries me when using XPS.
On the lower floor, we have composite panels on the inside of the exterior walls – that is, expanded polystyrene (EPS) and drywall. There has been no mold anywhere. Mold can only develop if air circulates behind the insulation. Otherwise, the wall is warmer than without insulation. The 5 cm (2 inches) is correct; I had overlooked that item 2 comes before it and thought it was a decimal point. Yes, 5 cm (2 inches) is definitely better.
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