With the arrival of a new year, it is time to evaluate those roofing issues that have recently changed, as well as those that reflect long-term stability and durability.
How Much Insulation is Enough?
The December issue of Roofing Contractor
suggests a systematic approach
to insulating new structures and retrofitting existing roof inventory.
Looking backwards, the oil embargo of 1972-1973 highlighted the sudden demand for energy conservation. A typical roof structure at that time was one with perhaps 3/4 to 1 inch of roof insulation, generally wood fiber, perlite, or glass fiber, with R-values around 3 per inch of thickness. On the West Coast, fiberglass underdeck batts with an R-value of 7 might be used.
Hybrid systems used perlite or glass fiber as a fire barrier, laminated to the desired thickness of newly introduced polyurethane foam. Today, we have reintroduced such systems using cover boards, usually of gypsum board.