08-14-2014, 09:52 AM
Flat Roof: Insulation and Membrane Position
A vented air space is mandatory when using batt insulation in a flat roof!! If you use rigid polystyrene insulation (the blue kind), no air space is necessary as it is waterproof.
Insulation BETWEEN the Deck and the Membrane
Traditional location for insulation:
use low density rigid panels to support the loads on the roof membrane without allowing puncture of membrane
any water vapour trapped in insulation will cause deck to rot so use topside vents to relieve pressure
Insulation ABOVE the Membrane
New concept offering major advantages:
membrane protected from extremes of heat and cold, is on the warm side of the insulation
membrane protected from UV radiation
membrane protected from puncture
insulation must be extruded polystryrene foam board which is water resistant and covered with a filter layer to prevent migration of ballast
A vented air space is mandatory when using batt insulation in a flat roof!! If you use rigid polystyrene insulation (the blue kind), no air space is necessary as it is waterproof.
Insulation BETWEEN the Deck and the Membrane
Traditional location for insulation:
use low density rigid panels to support the loads on the roof membrane without allowing puncture of membrane
any water vapour trapped in insulation will cause deck to rot so use topside vents to relieve pressure
Insulation ABOVE the Membrane
New concept offering major advantages:
membrane protected from extremes of heat and cold, is on the warm side of the insulation
membrane protected from UV radiation
membrane protected from puncture
insulation must be extruded polystryrene foam board which is water resistant and covered with a filter layer to prevent migration of ballast