ᐅ Insulation of Basement Ceiling with Mineral Wool – How to Install
Created on: 8 Dec 2022 10:16
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Herbert 80
Hello. I have a house with a full basement.
Currently, there is no insulation applied, so the boards are directly visible.
I have now received quite a few stone wool boards with a thickness of 60mm (2.4 inches) as a gift.
These boards are coated on both sides with a firmer white material to allow the boards to be glued directly to the ceiling.
The problem is the ceiling height.
60mm (2.4 inches) is too thick for me. I would have to cut the boards in half, so to 30mm (1.2 inches), to still be able to walk around (unfortunately, very low ceiling height).
However, after cutting them in half, the white coating would be removed, so I would have to glue the stone wool directly to the ceiling.
I would cut them with a pruning saw with a good guide to keep the cut surface even.
Does anyone have experience with this?
Best regards, Herbert
Currently, there is no insulation applied, so the boards are directly visible.
I have now received quite a few stone wool boards with a thickness of 60mm (2.4 inches) as a gift.
These boards are coated on both sides with a firmer white material to allow the boards to be glued directly to the ceiling.
The problem is the ceiling height.
60mm (2.4 inches) is too thick for me. I would have to cut the boards in half, so to 30mm (1.2 inches), to still be able to walk around (unfortunately, very low ceiling height).
However, after cutting them in half, the white coating would be removed, so I would have to glue the stone wool directly to the ceiling.
I would cut them with a pruning saw with a good guide to keep the cut surface even.
Does anyone have experience with this?
Best regards, Herbert
H
Herbert 808 Dec 2022 16:21@Torti2022neu
Your reply was the same as mine... Yes, because of the basement bar and large room, there are many birthdays, parties, etc. So far, I've removed two panels. Unfortunately, there are no 60mm (2.4 inches) ones available there. But the message is understood. Leaving 60mm (2.4 inches) completely would of course be better.
@everyone
Regarding moisture, I still need to mention something…
I had insulation between the rafters made of mineral wool. At that time, it was installed without any membrane on the outside, so it was visible directly under the roof tiles. After 10 years, the insulation had shrunk to the point that outside air could pass directly between the rafters. I think this caused the moisture issues. I wanted to prevent this in the basement. After all, mineral wool absorbs more moisture than a polystyrene board. Could it cause a musty smell in the basement if the wool absorbs moisture? Should the gaps between the panels and the edges be sealed or plastered? Should the edges be filled with expanding foam?
Your reply was the same as mine... Yes, because of the basement bar and large room, there are many birthdays, parties, etc. So far, I've removed two panels. Unfortunately, there are no 60mm (2.4 inches) ones available there. But the message is understood. Leaving 60mm (2.4 inches) completely would of course be better.
@everyone
Regarding moisture, I still need to mention something…
I had insulation between the rafters made of mineral wool. At that time, it was installed without any membrane on the outside, so it was visible directly under the roof tiles. After 10 years, the insulation had shrunk to the point that outside air could pass directly between the rafters. I think this caused the moisture issues. I wanted to prevent this in the basement. After all, mineral wool absorbs more moisture than a polystyrene board. Could it cause a musty smell in the basement if the wool absorbs moisture? Should the gaps between the panels and the edges be sealed or plastered? Should the edges be filled with expanding foam?
Herbert 80 schrieb:
Are there special anchors and adhesives for insulation boards? Has anyone had good experience with a particular manufacturer or type? Look for insulation fasteners or insulation fixing anchors and choose the smallest size available. Probably around 8mm (0.3 inches) diameter and 80mm (3 inches) length or so.
For adhesive, look for adhesive mortar or use tile adhesive; a flexible type is probably not necessary for the described application.
Herbert 80 schrieb:
I had insulation made of mineral wool between the rafters. At that time, it was installed without any membrane on the outside, so it was directly visible under the roof tiles.Insulating between rafters in the roof is very different from insulating a basement ceiling under a concrete slab. Generally, for basement ceilings: adhesive joints tightly without gaps, and fill any spaces. In the case of mineral wool, do not use foam, but use leftover pieces or loose mineral wool for filling. A vapor retarder, membrane, or anything similar is not necessary: the concrete slab above and the basement below are not exposed to wind or birds (if they are, rebuild the basement walls).A
Alibert8713 Dec 2022 14:20dertill schrieb:
Cutting in half should generally be possible; you can also cut crosswise and glue them together.
The prepared surface will be lost, so I would additionally use dowels to ensure stability.
What year was the house built, or do you have any information about the existing screed?
For any building from 1978 onwards, I wouldn’t worry much about adding more than 3 cm (1.2 inches) of insulation from below.
For older buildings with only 0–2 cm (0–0.8 inches) of insulation thickness (most of which has likely deteriorated after 40+ years), it can help, but obviously 6 cm (2.4 inches) is better. Could you please explain that a bit more? So, does adding insulation to a house built from 1978 onward not really make much sense or isn’t very worthwhile?
And based on your experience, which insulation material and thickness would be sufficient considering cost-effectiveness?
Thank you very much.
Alibert87 schrieb:
Could you explain that a bit? So, does insulating a house built from 1978 onwards not make much sense or isn’t really worth it?
And based on your experience, which insulation material and thickness are sufficient (considering price-performance ratio)? 😉
Thank you very much The first thermal insulation regulation came into effect in November 1977, requiring minimum thermal protection for building components. Since then, at least 6 cm (2.4 inches) of insulation has been installed below the slab. I wouldn’t worry too much about adding more than 3 cm (1.2 inches) on top of that—the first few centimeters matter most. If there’s space for 10 cm (4 inches) of insulation (and the material is as affordable as it was in 2021), adding more is possible.
In terms of price-performance, mineral wool at 10 cm (4 inches) is the most cost-effective choice if there is enough room.
Otherwise, 6 cm (2.4 inches) of rigid polyurethane (PUR) foam achieves a similar effect but is more expensive and thinner.
For underfloor heating systems, 10 cm (4 inches) of PUR or 14 cm (5.5 inches) of mineral wool is recommended.
A
Alibert8713 Dec 2022 15:11dertill schrieb:
Starting November 1977, the first thermal insulation regulations came into effect, requiring a minimum level of insulation for building components. Since then, at least 6 cm (2.4 inches) of insulation have been installed under floor slabs. I wouldn’t worry about adding more than 3 cm (1.2 inches) beyond that—the first few centimeters matter most. If there’s room for 10 cm (4 inches) of insulation (and insulation material is as affordable as it was in 2021), you can add more.
In terms of cost-effectiveness, 10 cm (4 inches) of mineral wool is the best option—if space allows.
Otherwise, 6 cm (2.4 inches) of rigid polyurethane foam (PUR) offers a similar effect but is more expensive and thinner.
For underfloor heating, 10 cm (4 inches) of PUR or 14 cm (5.5 inches) of mineral wool is recommended. Yes, there is underfloor heating. But adding 14 cm (5.5 inches) of insulation on top of that is quite a lot (since I still want to use the basement partially) 🙂
You say 10 cm (4 inches) of mineral wool doesn’t add much, right?
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