ᐅ Insulation on Upper Floor Concrete Slab / Roof as DIY Work – Vapor Retarder?
Created on: 14 Aug 2014 11:24
H
Harald1982
Hello dear members,
I want to insulate my upper floor ceiling / attic space as a DIY project.
Construction: 2 layers of 10 cm (4 inches) EPS insulation with a thermal conductivity of 0.035 W/(m·K) and on top of that 1.5 cm (0.6 inch) OSB boards for walking on.
Around the outer edge, I will leave out the first row of OSB boards.
Now the question: Do I need a vapor barrier?
I keep reading very different opinions and recommendations.
I want to insulate my upper floor ceiling / attic space as a DIY project.
Construction: 2 layers of 10 cm (4 inches) EPS insulation with a thermal conductivity of 0.035 W/(m·K) and on top of that 1.5 cm (0.6 inch) OSB boards for walking on.
Around the outer edge, I will leave out the first row of OSB boards.
Now the question: Do I need a vapor barrier?
I keep reading very different opinions and recommendations.
Bauexperte schrieb:
Hello,
Since when?
WU stands for WaterProof; this property is generally inherent in all concrete
Regards, BauexperteI’m not sure exactly since when, but to some extent concrete is vapor-permeable, otherwise how would it dry out?
WU concrete is a specific type of concrete – there are so many different compositions...
In general, a vapor retarder should at least be installed between the cold (roof) and the warm upper floor ceiling.
As far as I know, in concrete, the critical factor is not vapor diffusion but transport through capillary action. By the way, even waterproof concrete is not immune to this. It provides protection because, with proper execution, the cracks remain small, preventing water under pressure from penetrating. However, moisture is still transported through the material. Depending on the thickness, it may not be a large amount, but if it cannot dry out from above and instead accumulates in the insulation, that is problematic. So, use a vapor barrier! If you’re skeptical, remember that screed dries as well, even when the surface already appears finished.
B
Bauexperte19 Aug 2014 11:03Hello,
WU Concrete:
*Waterproof (WU) structures refer to concrete constructions that are made without additional external membrane-like waterproofing and prevent the passage of liquid water solely due to the material itself and special structural measures such as joint sealing and crack width limitation.
Moisture transport
Moisture transport and diffusion within an undisturbed cross-section of waterproof concrete can be summarized according to recent research as follows. Capillary water uptake on the side facing the water occurs independently of hydrostatic water pressure to a maximum depth of about 7 cm (3 inches). On the air-facing side, the component dries out slowly. This diffusion zone describes the area where the excess water in the concrete is released to the indoor air (drying out construction moisture). The drying depth in the diffusion zone is at most about 8 cm (3 inches), because the diffusion resistance increases with depth in the concrete. In addition, the amount of moisture emitted by occupants on the room side counteracts drying through diffusion. As long as the capillary and diffusion zones do not overlap (e.g., component thicknesses > 20 cm (8 inches)), there appears to be no moisture transport in the core area. This means that indoor moisture release behaves almost independently of the external boundary conditions and moisture situation when the thickness is sufficient. In buildings with high-quality use, diffusion in the drying zone slows over time and reaches an equilibrium state, as the temperature gradient from inside (approx. 20°C (68°F)) to outside (approx. 8°C (46°F)) counteracts the outward release of water vapor.
*Source: Regulations and recommendations for WU concrete
I am gradually beginning to understand why WU concrete is nowadays often referred to as a "white bathtub," even though the regulations themselves—at least from my subjective perspective—misuse this term at every opportunity. I learned it quite differently a long time ago...
**On the topic of insulating the top floor ceiling:
Basically, two approaches must be distinguished for insulating the top floor ceiling. On one hand, you can have an open (non-walkable) attic insulation if the attic is not used as storage space, or you can opt for walkable attic insulation in order to maintain storage space or room for a drying rack in the future.
Process and construction for a concrete ceiling:
1. As a vapor retarder, a vapor barrier foil should be applied over the entire existing concrete floor and carefully fastened and sealed all around. At the purlins and wall connections, be sure to allow a 10 cm (4 inch) overlap and seal it with special adhesive. Ensure the foil is tension-free to avoid cracks and damage. The existing concrete slab should be very carefully cleaned (swept, vacuumed, and ideally also wiped damp) before applying the foil.
2. Now the insulation can be laid. Suitable materials include glass wool mats, stone wool, or natural insulation materials such as wood fiber insulation boards. Always start installing the insulation in the rear, outermost corner and work your way forward toward the stairs or access point. When insulating the top floor ceiling, ensure the insulation is sufficiently thick. Ideally, 240 mm+ (9½ inches) of WLG 035 insulation should be installed. To avoid thermal bridges between insulation mats, it makes sense to lay them in two layers (e.g., 2 x 120 mm (2 x 5 inches)) with staggered joints.
Walkable attic insulation (concrete ceiling)
If the attic insulation is to be walkable, the insulation of a concrete ceiling differs only slightly from non-walkable attic insulation. Foot traffic-resistant insulation material must be used instead of mats. Suitable are rigid XPS or PUR boards with continuous tongue-and-groove edges. These insulation boards usually have better insulation values (WLG 032 or even 028) and can therefore be dimensioned somewhat thinner (approximately 160-180 mm (6½-7 inches)) than the mats mentioned above.
To compensate for unevenness of the attic ceiling, a thin (10-20 mm (½ inch)) impact sound insulation mat can be laid under the actual insulation layer to facilitate installation of the rigid XPS/PUR boards. To reduce thermal bridges at connections to the purlins, a two-layer arrangement can again be used here.
As a floor covering for walkable attic insulation, OSB boards or chipboard panels are installed floating directly on the insulation. The boards are glued at the tongue and groove joints. This results in a load-bearing floor that also retains heat in the house from now on.
Alternatively, the edge areas of the floor, which are non-walkable due to the roof slope, can be insulated simply with glass wool mats as described above. This helps save some money and facilitates connection to the roof purlins to avoid thermal bridges.
**Source: from the depths of my information on house construction
Regards, Bauexperte
Saruss schrieb:That is correct... I realize once again that I shouldn’t always try to be brief
As far as I know, with concrete, vapor diffusion is not the decisive factor, but rather transport through capillary action. Incidentally, even waterproof concrete (WU concrete) is not immune to this.
WU Concrete:
*Waterproof (WU) structures refer to concrete constructions that are made without additional external membrane-like waterproofing and prevent the passage of liquid water solely due to the material itself and special structural measures such as joint sealing and crack width limitation.
Moisture transport
Moisture transport and diffusion within an undisturbed cross-section of waterproof concrete can be summarized according to recent research as follows. Capillary water uptake on the side facing the water occurs independently of hydrostatic water pressure to a maximum depth of about 7 cm (3 inches). On the air-facing side, the component dries out slowly. This diffusion zone describes the area where the excess water in the concrete is released to the indoor air (drying out construction moisture). The drying depth in the diffusion zone is at most about 8 cm (3 inches), because the diffusion resistance increases with depth in the concrete. In addition, the amount of moisture emitted by occupants on the room side counteracts drying through diffusion. As long as the capillary and diffusion zones do not overlap (e.g., component thicknesses > 20 cm (8 inches)), there appears to be no moisture transport in the core area. This means that indoor moisture release behaves almost independently of the external boundary conditions and moisture situation when the thickness is sufficient. In buildings with high-quality use, diffusion in the drying zone slows over time and reaches an equilibrium state, as the temperature gradient from inside (approx. 20°C (68°F)) to outside (approx. 8°C (46°F)) counteracts the outward release of water vapor.
*Source: Regulations and recommendations for WU concrete
Saruss schrieb:However, the term "pressurized water" is not correctly used in this case, since for protection against this load case a special waterproof tape according to DIN "18-haumichtot" must be applied.
It does protect, because with proper execution the cracks are small, against pressurized water, but moisture is nevertheless transported through.
I am gradually beginning to understand why WU concrete is nowadays often referred to as a "white bathtub," even though the regulations themselves—at least from my subjective perspective—misuse this term at every opportunity. I learned it quite differently a long time ago...
**On the topic of insulating the top floor ceiling:
Basically, two approaches must be distinguished for insulating the top floor ceiling. On one hand, you can have an open (non-walkable) attic insulation if the attic is not used as storage space, or you can opt for walkable attic insulation in order to maintain storage space or room for a drying rack in the future.
Process and construction for a concrete ceiling:
1. As a vapor retarder, a vapor barrier foil should be applied over the entire existing concrete floor and carefully fastened and sealed all around. At the purlins and wall connections, be sure to allow a 10 cm (4 inch) overlap and seal it with special adhesive. Ensure the foil is tension-free to avoid cracks and damage. The existing concrete slab should be very carefully cleaned (swept, vacuumed, and ideally also wiped damp) before applying the foil.
2. Now the insulation can be laid. Suitable materials include glass wool mats, stone wool, or natural insulation materials such as wood fiber insulation boards. Always start installing the insulation in the rear, outermost corner and work your way forward toward the stairs or access point. When insulating the top floor ceiling, ensure the insulation is sufficiently thick. Ideally, 240 mm+ (9½ inches) of WLG 035 insulation should be installed. To avoid thermal bridges between insulation mats, it makes sense to lay them in two layers (e.g., 2 x 120 mm (2 x 5 inches)) with staggered joints.
Walkable attic insulation (concrete ceiling)
If the attic insulation is to be walkable, the insulation of a concrete ceiling differs only slightly from non-walkable attic insulation. Foot traffic-resistant insulation material must be used instead of mats. Suitable are rigid XPS or PUR boards with continuous tongue-and-groove edges. These insulation boards usually have better insulation values (WLG 032 or even 028) and can therefore be dimensioned somewhat thinner (approximately 160-180 mm (6½-7 inches)) than the mats mentioned above.
To compensate for unevenness of the attic ceiling, a thin (10-20 mm (½ inch)) impact sound insulation mat can be laid under the actual insulation layer to facilitate installation of the rigid XPS/PUR boards. To reduce thermal bridges at connections to the purlins, a two-layer arrangement can again be used here.
As a floor covering for walkable attic insulation, OSB boards or chipboard panels are installed floating directly on the insulation. The boards are glued at the tongue and groove joints. This results in a load-bearing floor that also retains heat in the house from now on.
Alternatively, the edge areas of the floor, which are non-walkable due to the roof slope, can be insulated simply with glass wool mats as described above. This helps save some money and facilitates connection to the roof purlins to avoid thermal bridges.
**Source: from the depths of my information on house construction
Regards, Bauexperte
H
Harald198221 Aug 2014 08:32Since we are copying instructions from the internet anyway, I found the following:
"Make sure the ceiling construction has a sufficient vapor resistance to prevent condensation and, consequently, mold growth. Especially with wooden beam ceilings, it is often necessary to install a vapor barrier film, whereas solid concrete ceilings usually do not require an additional vapor-retarding layer."
Installation of the walking surface* made of wood chip panels V100...
"Make sure the ceiling construction has a sufficient vapor resistance to prevent condensation and, consequently, mold growth. Especially with wooden beam ceilings, it is often necessary to install a vapor barrier film, whereas solid concrete ceilings usually do not require an additional vapor-retarding layer."
Installation of the walking surface* made of wood chip panels V100...
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