ᐅ Insulation of Basement Ceiling with Mineral Wool – How to Install
Created on: 8 Dec 2022 10:16
H
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
Alibert87 schrieb:
sorry if I’m being a nuisance, but with the aluminum-coated version, can I skip the vapor barrier / vapor retarder when insulating the upper floor ceiling?The same applies to a concrete ceiling from above as with the basement ceiling from above. Insulation material doesn’t matter, vapor retarder foil is not necessary. For wooden joists and drywall ceilings, a vapor retarder on the interior side of the room should generally be used.
For vapor-tight insulation materials like PIR (whether with or without aluminum coating doesn’t matter), it can be omitted. The important factor here is airtightness. Drywall construction without any foil usually isn’t airtight, so regardless of the insulation, I would recommend installing an airtight membrane on the room side / interior, in front of the insulation.
To keep it simple, this membrane can also function as a vapor retarder.
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Alibert8715 Jan 2023 08:03dertill schrieb:
The same applies to a concrete ceiling from above as to a basement ceiling from above. The type of insulation does not matter; a vapor retarder is not necessary.
For wooden beams and drywall ceilings, a vapor retarder should generally be used on the interior side of the room.
For vapor-tight insulation materials like PIR (whether with or without aluminum facing does not matter), it can be omitted. The important factor here is airtightness. Drywall construction without any membranes usually is not airtight, so in this case, regardless of the insulation, I would recommend an airtight membrane on the room side, inside, before the insulation.
For simplicity, this membrane should also act as a vapor retarder. I'm a bit confused, so my conclusion is: The house is solidly built with concrete ceilings. For the basement ceiling and the upper floor ceiling, in my case, I don’t need a vapor retarder membrane below the insulation, correct?
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WilderSueden15 Jan 2023 11:03Yes, exactly. Concrete is practically airtight, so you don’t need a vapor barrier if you insulate on the cold side.
Alibert87 schrieb:
I’m a bit confused, so here’s my conclusion. The house is built solidly with concrete ceilings:
for the basement ceiling and the upper floor ceiling, in my case do I not need a vapor barrier under the insulation, right? WilderSüden said:
WilderSueden schrieb:
Exactly. Concrete is (almost) impermeable, so you don’t need a vapor retarder if you insulate on the cold side. Yes, that was already mentioned.
I just wanted to clarify:
dertill schrieb:
The same applies to a concrete ceiling from above as to the basement ceiling from above. That is of course nonsense. The correct statement is:
The same applies to a concrete ceiling from above as to the basement ceiling from BELOW, so on the cold side. Concrete is almost vapor tight. What is important here as well is an airtight connection if there are any penetrations. You should also insulate the chimney flue and other massive thermal bridges for about 1m (3 feet) high to reduce the thermal bridge effect.
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Alibert8724 Feb 2023 12:08dertill schrieb:
WilderSüden already mentioned this.
I just wanted to clarify:
Of course, that’s nonsense. The correct approach:
For a concrete ceiling from above, the same applies as for the basement ceiling from BELOW, so on the cold side. Concrete is basically vapor-tight. What’s important here is an airtight connection, especially if there are penetrations. You should also insulate the chimney flue and other massive thermal bridges about 1 meter (3 feet) high to reduce their thermal bridge effect.Thanks.
I received a good offer for 100mm (4 inch) PIR insulation boards, unfortunately aluminum-faced on both sides. Is it best to fix them to the basement ceiling with plate screws, or do you have a better/more cost-effective idea? Insulation anchors?
Alibert87 schrieb:
Better / cheaper idea? Insulation anchors? 8 mm (0.3 inch) by 155 mm (6 inch) plastic insulation anchors. Plate screws create thermal bridges, are more expensive, and you still need an anchor separately. Use a ceiling or mounting prop to press the panel against the ceiling, drill through it, and push the anchor in. This is sufficient if the substrate is level. Otherwise, apply PUR insulation adhesive to fill in unevenness beneath the panel—you can also use this for corners that are too small or to fill small gaps where using an anchor doesn’t make sense.
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