ROOF INSULATION WITH KOOLSHEETS
Overdeck insulation is recommended for flat roofs
Flat roof insulation can be done both “Overdeck” (Over the roof deck) or “Underdeck”. However, all the energy saving rating systems advocate the “Overdeck”. The overdeck system gives an insulating exterior skin to the building thereby protecting it from daily expansion-contractions due to day-night temperature variance and thus protecting the underlying layers (waterproofing & the concrete deck) from thermal stress cracks due to the same. Moreover, it uses the underlying high mass (high thermal inertia) concrete layer as a storage for ambience (heat/cold) thus improving the insulation effect. Underdeck insulation in flat conventional roofs is recommended only when there are space ownership constraints or short duration space conditioning is required. Technically speaking, over deck insulation should be monolithic i.e. without joints or staggered, as joints may act as thermal bridges leading to differential thermal zones and consequent localized thermal stresses and resultant cracks in underlying layers.