ᐅ Insulation for the top-floor ceiling – which material to choose?
Created on: 18 Jul 2022 16:02
E
Elias_dee
Hello everyone,
We are building a turnkey house with a general contractor. The contractually agreed scope of work and offer include the following insulation for the top floor ceiling (with an unheated roof above):
“The top floor ceiling will be insulated with EPS 035 polystyrene boards, 240mm (9.5 inches) thick, including 15mm (0.6 inches) OSB boards with tongue and groove all around.”
Since protection against heat is very important to us and summers unfortunately are not getting milder (quite the opposite), we have now discussed options for better heat protection with him.
I should mention that walkability or later finishing of the attic is NOT important to us – there are no windows up there, nothing at all, plus we have a 25° (25°) pitched roof, so not even my wife can stand up there :-) So, we don’t need the attic to be walkable.
We were offered the following options and additional costs:
Option A: Wood fiber boards → these also offer excellent summer heat protection. Additional cost: 4,000 € net
Option B: Keep the polystyrene insulation. Instead of battens and foil on the rafters, use 60mm (2.4 inches) spruce wood panels (for summer heat protection). Additional cost: 3,100 € net
Can anyone tell me which option is better for heat protection and if the prices are reasonable?
Thank you very much!
We are building a turnkey house with a general contractor. The contractually agreed scope of work and offer include the following insulation for the top floor ceiling (with an unheated roof above):
“The top floor ceiling will be insulated with EPS 035 polystyrene boards, 240mm (9.5 inches) thick, including 15mm (0.6 inches) OSB boards with tongue and groove all around.”
Since protection against heat is very important to us and summers unfortunately are not getting milder (quite the opposite), we have now discussed options for better heat protection with him.
I should mention that walkability or later finishing of the attic is NOT important to us – there are no windows up there, nothing at all, plus we have a 25° (25°) pitched roof, so not even my wife can stand up there :-) So, we don’t need the attic to be walkable.
We were offered the following options and additional costs:
Option A: Wood fiber boards → these also offer excellent summer heat protection. Additional cost: 4,000 € net
Option B: Keep the polystyrene insulation. Instead of battens and foil on the rafters, use 60mm (2.4 inches) spruce wood panels (for summer heat protection). Additional cost: 3,100 € net
Can anyone tell me which option is better for heat protection and if the prices are reasonable?
Thank you very much!
Axolotl-neu schrieb:
Yep, because the reinforced concrete ceiling already provides substantial summer heat protection, mineral wool insulation is completely sufficient. And with the savings, you can enjoy a nice garden.I would glue polystyrene foam, then add OSB or plywood on top, as gu suggests. That way, you can at least walk on the cold roof.The idea that wood fiber offers better summer heat protection is simply nonsense. Especially charging an extra 4,000 net for it—how large is the floor area? It has absolutely no effect.
The vapor openness is naturally an advantage, but once the construction moisture has dried out, it probably doesn't matter anymore.
TmMike_2 schrieb:
I would bond Styrofoam, then add OSB or plywood on top, as gu suggests. This way, at least you can walk on the cold roof.
The idea that wood fiber offers better summer heat protection is simply nonsense. Especially charging 4,000 net for it—how large is the floor area? It has no effect at all.
The vapor permeability is naturally an advantage, but once the construction moisture is out, it shouldn’t matter. I have to disagree a bit...
“Wood is the building material with the highest heat storage capacity. Therefore, wood fiber insulation boards offer significantly better summer heat protection compared to conventional insulation materials. They store the absorbed heat energy longer (phase shift) and only transfer small amounts to the interior (amplitude damping). This keeps the indoor space pleasantly cool even during high outdoor temperatures.”
The above statement is from Gutex, and that’s exactly how I understand it (and I believe it works well for us too). Naturally, 1–2 cm (0.4–0.8 inches) is not enough to achieve this effect—we have at least 8 cm (3 inches) on the exterior walls, and more on the roof (I think about 14 cm (5.5 inches)).
i_b_n_a_n schrieb:
I have to disagree a bit...
"Among building materials, wood has the highest heat storage capacity. That’s why insulation boards made from wood fibers offer significantly better protection against heat in summer compared to conventional insulation materials. They store the absorbed heat energy for a longer time (thermal phase shift) and transfer only small amounts of it to the interior (amplitude damping). This keeps the indoor environment comfortably cool even during extreme heat outside."
That’s just marketing talk. Of course, the statement is true on its own: wood does have a high heat capacity. But: how much does the product of mass and heat capacity of the insulation actually contribute relative to a reinforced concrete ceiling? I estimate just under 1%, maybe 2% for wood fiber insulation. That’s 1% more mass—for $5,000.To achieve the same effect, instead of 24 cm (9.5 inches) of EPS insulation, you’d need to increase it by about 0.24 cm (0.1 inches) to 24.24 cm (9.54 inches)...
What really matters is thermal conductivity or the U-value (thermal transmittance). The amount of heat the insulation itself can store plays only a very minor role. The only real advantage is the sustainability aspect.
Similar topics