The later is used in new construction as the interior board serves as an inner wall.
Roof decking with insulation.
Insulation above the roof deck or air vapor impermeable insulation below the roof deck is needed for condensation control in an unvented roof.
Hot roofs are insulated above the rafters.
It typically has 3 variations.
For standard steel deck construction this approach has many advantages such as.
Bare foam board one sided sheathing board or double sided which is also reference as structural insulated panels.
For such constructions the principles and benefits of unvented attic construction are similar to that occurring in a single family residence.
Rigid foam board is just above the roof deck or an exterior insulation option.
Insulation for condensation control.
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The ratio of insulation above the roof deck or air permeable insulation below the roof deck is a matter of climate and interior conditions.
The dew point is typically within the insulation layer lowering condensation risks.
But spray foam insulation used at the underside of the roof deck would need to be covered by a thermal barrier and intumescent coatings are commonly used.
Because the insulation is so close to the roof and you want to avoid unwanted moisture buildup these roofs will need to be completely sealed off.
Explore owens corning commercial roof and roof deck insulation products to help with your next building project.
Install baffles or make sure there s 1 minimum of airspace between the roof deck and insulation.
For most of us in the low slope roofing industry it s considered to be absolutely standard to have insulation placed above the roof deck.