How to design a 100 mm thick barrier that maximizes thermal and acoustic insulation

insulationsound-proofingweatherstripping

I need to design a thermal and sound barrier – walls of a cuboid-shaped space. Imagine it is a free-standing bike shed in the fields. The walls can not be thicker then about 100 mm (4 inches). The most-internal layer of the wall will be a 2 mm (0.08 in) thick sheet of stainless steel. The most-outer layer of the wall will be a 1 mm (0.04 in) thick sheet of aluminum (fully exposed to weather).

Now, can you suggest what should I put between these two sheets of metal, to achieve the following properties:

  • R-value (thermal resistance) of the walls of at least 2.64 K·m²/W, that is in US units R-15 (15.0 h·ft²·°F/Btu)
  • noise reduction of 50 dB – Sound Transmission Class: STC 50

Are such properties possible to achieve in a 10 cm (4 inch) space wall between two sheets of metal? If not, what are the best possible properties to achieve in that thickness, with the budget of about 70 EUR/m² or 10 USD/ft²?

I have read about materials such as polyisocyanurate (PIR) for thermal insulation and QuietRock 545 for sound (is it available in Europe?), but maybe there are materials which offer thermal and sound insulation combined, with more efficient use of the limited thickness?

Please suggest materials to put inside the wall between the two sheets of metal, preferably materials possible to purchase in Europe. Do I also need to worry about a vapor-barrier in such application (free-standing bike shed with steel walls)?

Best Answer

For thermal, you'll want closed cell foam of some sort. If the wall has to be structural, I'd frame with vertical 2x4s, then on the interior, horizontal 1x1s, spray foam, then your metal panels.

If it doesn't have to be structural, 4" of XPS foam board should work.

That'd be about the best you could do for a thermal barrier.

As for sound proofing, that's a bit of a different goal...especially with interior metal walls...which will reflect a lot of the sound. 4" of insulation and well sealed door openings should get you a decent level of sound deadening, but It definitely won't be sound proof by any means.

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