Mansard Roof Insulation

I have a house with mansard roof in boston.

Mansard roof insulation.

With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same. After having dense pack installed in the building walls the mansard is the next target. The steep roof with windows creates an additional floor of habitable space a garret and reduces the overall height of the roof for a given number of. I recently purchased a home with a mansard roof i had some roofers come to give quotes to replace the top it is finished and they all recommend adding ventilation known issue with mansard s.

Step 1 add a vapor barrier one of the best ways to protect your mansard roof from the problems of ventilation is to use a vapor barrier on the inside. One strategy would be to incorporate the attic into the conditioned space and then use a sandwich of barriers and insulation under a furred vented. Lap the roof underlay over the mansard underlay by minmum 150mm. The mansard roof forms a projection beyond the building wall that creates a concealed space through which fire and products of combustion can travel.

Establish the correct number of courses of mansard tiles to maintain minimum headlap of 65mm. Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation. A mansard or mansard roof also called a french roof or curb roof is a four sided gambrel style hip roof characterized by two slopes on each of its sides with the lower slope punctured by dormer windows at a steeper angle than the upper. To insulate the roof you will need to use a combination of insulation to fully protect the roof.

Originally i was toying with the idea of closed cell spray foam for the whole mansard floor but i do not want to tear down historic plaster.