Hello all,

I'm working out the design of my addition which is based on a 32x40 barn I reclaimed and relocated to my property for reassembly.

The roof details are: pitch=8/12, rafters = 2x5 @ 24" o.c., major purlins (6x6") at mid rafter span, no ridge beam.

My dilema is how to meet code on the roofing insulation, achieve the look I am after and afford it. Western MA code says I need R37 minumum in my roof.

I wish to keep a vaulted ceilings with all the original barn roof structure exposed. I wish to add whatever insulation I need on top of my first layer of roof sheathing so that my roof sheathing, rafters and purlins will remain exposed inside the house.

The two most obvious choices I have come up with are Rigid foam panels (R=7/inch) and fiberglass bats (R3.4/inch) This means I would need 6 inches of rigid foam to meet code or 13 inches of fiberglass to meet code.

Each requires building a second roof structure to secure the insulation into and for attaching the finish roofing too. The rigid foam approach is extremely expensive ($3/ft^2) While the fiberglass approach is a mere .90/lineal foot, it means building up 15" deep cavities over the original roof to fit it in (with air gap). This poses the issue of dealing with how to make a 20" tall facia look unobtrusive.

do any of you have another approach that is cost effective and feasible? Do standard SIP's really meet R-37? How thick are they for roof applications?

thanks,

Shaun