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)?