ᐅ Is it possible to effectively insulate the basement floor after construction?
Created on: 11 Dec 2018 12:46
N
netzplan
Hello everyone,
we have already consulted an energy advisor and are waiting for a quote, but we still want to gather some information in advance.
We plan to completely renovate our house. As part of the renovation, the exterior facade will receive continuous insulation. In the initial consultation, the energy advisor recommended insulating the basement ceiling with about 8cm (3 inches) of insulation as well.
During the full renovation, we are considering raising the ceiling height in some basement rooms. The architect said this would require underpinning (by 1 or 2 meters, respectively). On the other hand, a construction manager suggested that it might be possible to simply remove the slab foundation and lower it by about 20-30cm (8-12 inches). However, the final decision lies with the structural engineer.
My question now is: Is it feasible to install insulation underneath the slab foundation if it is removed and lowered as planned, as shown in the sketch? Wouldn’t thermal bridges occur as indicated? Or would the insulation become ineffective due to thermal bridging since the strip footings are not covered by continuous insulation?
Note: In the sketch, the slab foundation has not yet been lowered.
we have already consulted an energy advisor and are waiting for a quote, but we still want to gather some information in advance.
We plan to completely renovate our house. As part of the renovation, the exterior facade will receive continuous insulation. In the initial consultation, the energy advisor recommended insulating the basement ceiling with about 8cm (3 inches) of insulation as well.
During the full renovation, we are considering raising the ceiling height in some basement rooms. The architect said this would require underpinning (by 1 or 2 meters, respectively). On the other hand, a construction manager suggested that it might be possible to simply remove the slab foundation and lower it by about 20-30cm (8-12 inches). However, the final decision lies with the structural engineer.
My question now is: Is it feasible to install insulation underneath the slab foundation if it is removed and lowered as planned, as shown in the sketch? Wouldn’t thermal bridges occur as indicated? Or would the insulation become ineffective due to thermal bridging since the strip footings are not covered by continuous insulation?
Note: In the sketch, the slab foundation has not yet been lowered.
I wouldn’t put myself through that. I did something similar, but not because of the ceiling height, rather for insulation. I broke up the screed, added 10 cm (4 inches) of insulation on top, and now the underfloor heating will go on top of that. Just removing the screed was already a huge job. The concrete slab as well... that will be much more difficult. Wouldn’t the frost-proof foundation also need to be made deeper?
If it’s really just about insulation while considering the ceiling height, I would probably just use vacuum insulation panels, which only require about 2 cm (1 inch). They are more expensive, but still much cheaper than breaking up the concrete slab. At most, just remove the screed and install a dry screed layer. If the old screed was, say, 7 cm (3 inches), you would end up with 4 cm (1.5 inches) total (2 cm (1 inch) insulation panel, 2 cm (1 inch) dry screed). As for the ceiling... is insulation there even necessary if the basement floor is going to be heated?
This method would provide better insulation and gain 3 cm (1 inch) in height—at a reasonable cost and effort.
If it’s really just about insulation while considering the ceiling height, I would probably just use vacuum insulation panels, which only require about 2 cm (1 inch). They are more expensive, but still much cheaper than breaking up the concrete slab. At most, just remove the screed and install a dry screed layer. If the old screed was, say, 7 cm (3 inches), you would end up with 4 cm (1.5 inches) total (2 cm (1 inch) insulation panel, 2 cm (1 inch) dry screed). As for the ceiling... is insulation there even necessary if the basement floor is going to be heated?
This method would provide better insulation and gain 3 cm (1 inch) in height—at a reasonable cost and effort.
Hello,
thank you very much for the tips and suggestions. The two rooms that we plan to insulate or increase the ceiling height in have a brick floor (about 7cm (3 inches) high). According to the architect, it can be removed without any problem. We have already done this. The bricks were easy to remove. Below is just red sand for now. Presumably, there is a clean fill layer underneath.
Feedback from the structural engineer is still pending in general. Furthermore, we would involve an energy consultant (who also provides construction supervision) to coordinate the next steps. On one hand, you are of course right that for a guest room in the basement, raising the ceiling height is not absolutely necessary. But another reason why we are also thinking about raising the ceiling height is the following:
An alternative would of course be a step down in the basement extension or to build the extension with a ceiling height of only 2.15m (7 feet). We discussed our preferred extension informally with a builder. He suggested using “WU concrete” for the extension, and in this context, the ceiling height of the two old basement rooms could also be raised by removing the existing floor and applying WU concrete there as well.
However, as mentioned, this must be clarified with the structural engineer, architect, and energy consultant. To avoid being completely out of the loop as a layperson, I came here to the forum to get some tips or suggestions. (For example, I find these vacuum insulation panels interesting, especially if they are easy to install.)
Best regards
thank you very much for the tips and suggestions. The two rooms that we plan to insulate or increase the ceiling height in have a brick floor (about 7cm (3 inches) high). According to the architect, it can be removed without any problem. We have already done this. The bricks were easy to remove. Below is just red sand for now. Presumably, there is a clean fill layer underneath.
Feedback from the structural engineer is still pending in general. Furthermore, we would involve an energy consultant (who also provides construction supervision) to coordinate the next steps. On one hand, you are of course right that for a guest room in the basement, raising the ceiling height is not absolutely necessary. But another reason why we are also thinking about raising the ceiling height is the following:
The house will also have a basement extension. The basement of the extension should have a standard ceiling height since it is a new build. The wish was that the other two basement rooms (guest room and corridor with stair access from the ground floor to the basement), which connect to the extension, would be at the same level as the extension. Hence the desire to raise the ceiling height.
An alternative would of course be a step down in the basement extension or to build the extension with a ceiling height of only 2.15m (7 feet). We discussed our preferred extension informally with a builder. He suggested using “WU concrete” for the extension, and in this context, the ceiling height of the two old basement rooms could also be raised by removing the existing floor and applying WU concrete there as well.
However, as mentioned, this must be clarified with the structural engineer, architect, and energy consultant. To avoid being completely out of the loop as a layperson, I came here to the forum to get some tips or suggestions. (For example, I find these vacuum insulation panels interesting, especially if they are easy to install.)
Best regards
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