Hello,
I am currently looking into the topic of floor construction for a new build with a basement. A KfW40 solid wood house with a concrete basement and concrete ceiling is being built. Although the basement is insulated, it is kept cold in practice, meaning it is not heated. My question is, what is the typical thickness of the floor build-up on the ground floor? The entire floor has underfloor heating. The floor covering will be 1.5cm (0.6 inches) natural stone or wood. The architect has planned for 15cm (6 inches) in both the basement and ground floor. However, I have heard from others that I should add a few centimeters more insulation to prevent the floor from getting cold quickly.
How is this typically handled nowadays in this situation?
Thanks in advance
Best regards
I am currently looking into the topic of floor construction for a new build with a basement. A KfW40 solid wood house with a concrete basement and concrete ceiling is being built. Although the basement is insulated, it is kept cold in practice, meaning it is not heated. My question is, what is the typical thickness of the floor build-up on the ground floor? The entire floor has underfloor heating. The floor covering will be 1.5cm (0.6 inches) natural stone or wood. The architect has planned for 15cm (6 inches) in both the basement and ground floor. However, I have heard from others that I should add a few centimeters more insulation to prevent the floor from getting cold quickly.
How is this typically handled nowadays in this situation?
Thanks in advance
Best regards
Not bad, I basically did something similar, just shifted it upwards in parallel. According to the energy saving ordinance / building energy regulations, it should just barely comply with the plan. It should now just barely be sufficient for 55 standard. Since I don’t have any subsidies, it doesn’t really matter.
I installed everything myself up to just below the roller shutter box, that way you know exactly what you have.
I installed everything myself up to just below the roller shutter box, that way you know exactly what you have.
Hi, we also have a solid wood construction and in my apartment (one of four in the building) a wooden floor. However, we don’t have underfloor heating but wall heating instead. Thanks to the passive house standard (including KfW40+...), the floor is never cold despite the lack of underfloor heating; at most, it feels “cooler than the rest.” For me, this is always comfortable since wood never feels as cold as, for example, unheated tiles.
Structure: 8cm (3 inches) of PUR insulation beneath the floor slab (30cm (12 inches) perimeter insulation...), the 30cm (12 inches) thick slab is fully sealed with bitumen. On top of that, I have a 25cm (10 inches) high floor build-up. All cables and pipes (for controlled ventilation, water, etc.) run within the floor. The cross beam joist layer (the top layer spaced about 45cm (18 inches) apart) rests on rubber buffers with simple 032-grade glass wool insulation laid in two crossed layers in between. On top, 18mm (0.7 inches) OSB board plus 1.5mm (0.06 inches) impact sound insulation (an eco-friendly product from Wineo made from castor oil 😉), then 16mm (0.6 inches) oak parquet. Unless someone clumsily opens the main and terrace doors at the same time in winter, letting icy air sweep over the floor, the temperature is perfectly fine. And since I live alone, the only possible clumsy person can be me occasionally 😀
Structure: 8cm (3 inches) of PUR insulation beneath the floor slab (30cm (12 inches) perimeter insulation...), the 30cm (12 inches) thick slab is fully sealed with bitumen. On top of that, I have a 25cm (10 inches) high floor build-up. All cables and pipes (for controlled ventilation, water, etc.) run within the floor. The cross beam joist layer (the top layer spaced about 45cm (18 inches) apart) rests on rubber buffers with simple 032-grade glass wool insulation laid in two crossed layers in between. On top, 18mm (0.7 inches) OSB board plus 1.5mm (0.06 inches) impact sound insulation (an eco-friendly product from Wineo made from castor oil 😉), then 16mm (0.6 inches) oak parquet. Unless someone clumsily opens the main and terrace doors at the same time in winter, letting icy air sweep over the floor, the temperature is perfectly fine. And since I live alone, the only possible clumsy person can be me occasionally 😀
H
Hausbau 5515 Jan 2022 15:02Insulation for the ground slab only counts with a factor of 0.5 in the energy saving regulations or KfW calculation. So, if the U-value is 0.245, the calculation value is 0.123..., which you then compare, for example, with a wall value of 0.12 or similar.
When installing the insulation, do not use a single 120 mm (5 inches) layer, but cross layers of 2 x 60 mm (2.4 inches). This is better to avoid thermal bridges towards unheated rooms or the soil. Electrical installation should be placed in the lowest insulation layer, while water pipes, with simple insulation, should be laid on the first insulation layer, i.e., in the upper insulation layer. The hot water pipe is therefore insulated downward with 70 mm (2.8 inches). Afterwards, only the HB staple roll remains.
When installing the insulation, do not use a single 120 mm (5 inches) layer, but cross layers of 2 x 60 mm (2.4 inches). This is better to avoid thermal bridges towards unheated rooms or the soil. Electrical installation should be placed in the lowest insulation layer, while water pipes, with simple insulation, should be laid on the first insulation layer, i.e., in the upper insulation layer. The hot water pipe is therefore insulated downward with 70 mm (2.8 inches). Afterwards, only the HB staple roll remains.
P
pagoni202015 Jan 2022 17:23In our KfW 40 house, there is 20 cm (8 inches) of insulation under the ground slab (no basement). Originally, 6 cm (2.5 inches) of rigid polyurethane foam (PUR) was planned on top of that (according to the energy consultant), with solid wood floorboards 30 mm (1.2 inches) thick directly above.
In consultation with the energy consultant, we replaced the PUR with wood fiber insulation with a lower performance value underneath the floorboards.
Sometimes I regretted not leaving more space for insulation, but I was convinced otherwise by the general contractor. You tend to think that more insulation is always better or to be more cautious (in this case, I wasn’t).
The current situation is that I don’t feel any difference on the ground floor compared to the upper floor, where the same flooring is installed and we don’t have underfloor heating.
This reminds me of our former house from 1990, where the bedroom was in the ground floor/basement. There was standard insulation with screed and carpet on top, and I never thought it was too cold there.
Still, next time I would choose more than 6 cm (2.5 inches) of insulation height, if only to have more space available for pipes, cables, etc., which caused quite a bit of hassle.
In consultation with the energy consultant, we replaced the PUR with wood fiber insulation with a lower performance value underneath the floorboards.
Sometimes I regretted not leaving more space for insulation, but I was convinced otherwise by the general contractor. You tend to think that more insulation is always better or to be more cautious (in this case, I wasn’t).
The current situation is that I don’t feel any difference on the ground floor compared to the upper floor, where the same flooring is installed and we don’t have underfloor heating.
This reminds me of our former house from 1990, where the bedroom was in the ground floor/basement. There was standard insulation with screed and carpet on top, and I never thought it was too cold there.
Still, next time I would choose more than 6 cm (2.5 inches) of insulation height, if only to have more space available for pipes, cables, etc., which caused quite a bit of hassle.
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