Reverted Insulation

GENERAL DESCRIPTION AND COMPARATIVE CHARACTERISTICS

In the inverted insulation, the damp proofing membrane is placed under the thermal insulation membrane in the roof layering series. A necessary condition for constructing a reverted insulation, also due to the fact that the thermal insulation material is in direct contact with the water, is closed cuvettes, therefore the use of extruded polystyrene is the only possible solution. In order to protect and increase the lifespan of the thermal insulation material, a layer for its protection should be applied.

ADVANTAGES:

• The damp proofing membrane is protected from intense thermal fatigue, extreme contractions and expansions, thermal shocks, frost and the negative impact of acid atmospheric precipitation.
• Increasing lifespan of the damp proofing layer functionality.
• Protection from injuries and undesirable perforation due to potential localized loads (eg dropping of sharp objects during maintenance works of air conditioning).
• Limited accessibility and reduced chance of failure due to anthropogenic actions.
• It is not necessary to use a water vapor barrier.
• Moisture creation is avoided due to potential entrapment of water vapor between the barrier and the damp proofing layer.
• The use of anti-root membranes makes it possible to build a planted roof, increasing the feeling of thermal comfort in the underlying space. “

DISADVANTAGES:

• The progressive immersion of the thermal insulation material in water requires the use of a thicker thermal insulation material, in order to balance the reduction of its thermal resistance over time.
• Discharged rainwater causes rapid cooling of the ceiling (rain cooler effect), resulting in the need to use thermal insulation material thicker by 10% than on a conventional roof, in order to achieve the required thermal transmittance coefficient of the roof
• Requires sufficient gradients in order for the drainage at the damp proofing membrane level to be smooth.
• Requires a good preparation of the substrate in order to achieve an even drainage surface (without any points that withhold water)
• The cost of repairing the damp proofing is higher than for a conventional roof.
• The overall construction cost of the inverted roof is higher than that of a conventional roof.
• It is not recommended for old buildings. The roof’s weight, due to the need for a layer of accessibility, is much higher than that of a conventional one and the static resistance measurment is therefore required.”

CONSTRUCTION STEPS:

1. Evenning the surface either by scraping gravel or by filling small cavities with cement mortar.
2. Detailed cleaning of the surface from dust, oil, loose materials etc.
3. Priming the surface that is to be damp proofed with elastomeric bituminous varnish with aqueous base, enriched with synthetic elastomeric additives and anti hydrophilic ingredients for achieving maximum adhesion of the damp proofing layer on the substrate.
4. Coating bituminous type membrane with granulate (if it is the finishing layer). The membrane will rise up to the circumfirencial guardrails by approximately 30cm, where it will be either welded or mechanically supported with a blade.
5. Creation of trench flows (cement mortar or lightweight concrete)
6. Placement of the thermal insulation layer
7. Next is the sealing of the blade with bituminous polyurethane mastic.
8. Placement of a thermal insulation layer with geotextile
9. If required by the technical study, the accessibility layering follows eg a ballast thick enough to rule out any potential drifting of the thermal insulation panels due to the wind. “