A Dow (fabricante de painéis XPS) recomenda seus painéis sobre a impermeabilização do telhado plano . Você tem que cobrir com um agregado ou um telhado verde. A prática é chamada de " telhado invertido "
Os painéis PIR são classificados de maneira semelhante para uso em telhado invertido .
PIR é "melhor" do que lã de rocha em valor-U vs. espessura:
Mineral wool fibre loft insulation (sold as Rockwool), would also need to be 270mm deep to achieve a U-value of 0.16. Mineral wool fibre is claimed to be less irritating to the installer’s skin than fibreglass, although my own experience is actually the opposite. It is also more expensive than fibreglass, and would cost around £8.20 per sq m. ... The most thermally efficient insulation material is polyisocyanurate, or PIR, sold as lightweight rigid foam boards – Kingspan, Celotex, and some other brand names. The 0.16 U-value could be achieved using a PIR board 175mm (6¾in) thick. excerpted from Jeff Howells article in The Telegraph