I conducted a pre-bid meeting for a remedial roofing project at an automotive plant in the Midwest last month. The main topic of conversation was centered on the specified requirement for R-20 insulation. All of the participants — contractors and plant personnel — argued that this way much thicker insulation than they ever used at this plant.
On similar projects I have heard the same mantra: “This is not the way we have done things in the past!”
That statement is true — this is not how we have done things in the past. The reason is that the energy requirements in the new ASHRAE standard have increased the R-value requirements for low-slope roof systems in many regions of the country. Some states and local municipalities have adopted this standard as part of their building code.
As a designer, I recommend that you check the codes in the areas you are designing low-slope roofs and make sure they comply with the current energy codes. This is a big deal because added insulation thickness may require raising mechanical equipment, penetrations and flashing details.
Yes, this is not the way we had done things, but it is the way we do things now!