ᐅ Insulating a Concrete Ceiling on the Upper Floor / What to Consider?
Created on: 20 Oct 2020 21:57
P
Piotr1981
Hello everyone,
The shell of the house is finished – the windows are still missing but have a delivery time.
In the meantime, I would like to insulate the upper floor ceiling (concrete) and cover it with OSB boards.
Facts:
- 2-story building
- Upper floor ceiling made of concrete – 20 cm (8 inches) thick
- According to the energy saving regulations certificate for KFW 55, the ceiling must be insulated with 18 cm (7 inches) of polystyrene
- The attic will not be used as living space, only for storage
- The purlins rest directly on the concrete ceiling
- The roof will not be insulated, so the floor will be insulated instead.
Questions:
1) What preparatory work do I need to do on the concrete before starting? Deep cleaning? Any ideas?
2) Do I also need to install a vapor barrier foil on the ceiling of the upper floor?
3) I plan to install the XPS panels in two layers of 9 cm (4 inches) each, staggered to ensure closed joints.
4) Then the OSB boards on top (thickness – no idea – any recommendations?)
5) Should I run the necessary electrical cables into the attic first (for lighting, power, and possibly an access point)?
6) Which boards would you recommend? Has anyone had experience with these?
7) Are there any special considerations I might not have thought of yet?
Looking forward to your opinions/ideas/tips and tricks.
Piotr
And one more thing: What exactly are these polystyrene boards? Are there any cheaper alternatives? What is the difference between EPS and XPS?
The shell of the house is finished – the windows are still missing but have a delivery time.
In the meantime, I would like to insulate the upper floor ceiling (concrete) and cover it with OSB boards.
Facts:
- 2-story building
- Upper floor ceiling made of concrete – 20 cm (8 inches) thick
- According to the energy saving regulations certificate for KFW 55, the ceiling must be insulated with 18 cm (7 inches) of polystyrene
- The attic will not be used as living space, only for storage
- The purlins rest directly on the concrete ceiling
- The roof will not be insulated, so the floor will be insulated instead.
Questions:
1) What preparatory work do I need to do on the concrete before starting? Deep cleaning? Any ideas?
2) Do I also need to install a vapor barrier foil on the ceiling of the upper floor?
3) I plan to install the XPS panels in two layers of 9 cm (4 inches) each, staggered to ensure closed joints.
4) Then the OSB boards on top (thickness – no idea – any recommendations?)
5) Should I run the necessary electrical cables into the attic first (for lighting, power, and possibly an access point)?
6) Which boards would you recommend? Has anyone had experience with these?
7) Are there any special considerations I might not have thought of yet?
Looking forward to your opinions/ideas/tips and tricks.
Piotr
And one more thing: What exactly are these polystyrene boards? Are there any cheaper alternatives? What is the difference between EPS and XPS?
P
Piotr198122 Oct 2020 13:19Golfi90 schrieb:
If I were you, I would insulate the roof...
You can't create more storage space!
And the work is (almost) the same, I would say...
Costs might be slightly higher, but not in proportion to the storage space gained.I don't see it that way with a concrete ceiling.
Heat rises, and here I want to retain the energy at the ceiling level, not at the roof.
P
Piotr198122 Oct 2020 13:21sascha-t4-le schrieb:
I wouldn’t put the panels in the roof. If there’s a fire, you don’t want to rely on the fire department.
Suggestion:
Apply 8cm (3 inches) of mineral wool on the concrete slab, then the OSB panels. Additionally, add insulation between the rafters. The panels are now fire-retardant, aren’t they?!
Honestly, before the panels catch fire, the entire wooden roof structure would burn first.
Piotr1981 schrieb:
I don’t see it that way with a concrete ceiling. Heat rises, and here I want to capture the energy at the ceiling, not at the roof.What is your reasoning?
By the way, we did exactly the same: concrete floor slab for the upper floor, insulation between the rafters, and created a comfortably temperate, seemingly endlessly large storage space with minimal additional costs. Of course, you end up heating a few more cubic meters.
Piotr1981 schrieb:
Not if it is a KfW55 house.
That is required by the Energy Saving Ordinance No, it is not. It is not mandatory. We are building a KfW55 house and will also insulate the concrete ceiling, not the roof.
1. Sweeping is sufficient.
2. Lay out the vapor barrier film with excess material to allow for overlaps, covering the entire surface, and fold it up at least 10 cm (4 inches) on the sides to connect to surrounding structural elements such as wall plates and gable walls. Seal the overlaps with suitable tape. Apply an 8 mm (0.3 inch) thick bead of sealant to the surrounding components like wall plates and gable walls, and press the vapor barrier film down smoothly without tension using the flat hand.
3. Install attic insulation boards fully and tightly butted together; avoid cross joints. Minor unevenness in the concrete ceiling will be compensated by the insulation boards. Using multiple layers with staggered joints improves insulation performance and prevents thermal bridges.
4. Lay moisture-resistant particleboard or OSB panels (thickness ≥ 19 mm (0.75 inch)) floating on top of the attic insulation boards and glue the panel joints and seams.
5. Yes, that would be beneficial.
6. Phew, there is quite a bit to consider...
7. The best option is also to insulate the roof, as my predecessors have already mentioned.
2. Lay out the vapor barrier film with excess material to allow for overlaps, covering the entire surface, and fold it up at least 10 cm (4 inches) on the sides to connect to surrounding structural elements such as wall plates and gable walls. Seal the overlaps with suitable tape. Apply an 8 mm (0.3 inch) thick bead of sealant to the surrounding components like wall plates and gable walls, and press the vapor barrier film down smoothly without tension using the flat hand.
3. Install attic insulation boards fully and tightly butted together; avoid cross joints. Minor unevenness in the concrete ceiling will be compensated by the insulation boards. Using multiple layers with staggered joints improves insulation performance and prevents thermal bridges.
4. Lay moisture-resistant particleboard or OSB panels (thickness ≥ 19 mm (0.75 inch)) floating on top of the attic insulation boards and glue the panel joints and seams.
5. Yes, that would be beneficial.
6. Phew, there is quite a bit to consider...
7. The best option is also to insulate the roof, as my predecessors have already mentioned.
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