Roof Insulation - Cool Homes


Roof Insulation:

The roof emits significant solar radiation and plays an important role in heat gain/losses, day lighting and ventilation. In this system a thermal barrier or insulation is provided over the RCC, so that the heat of the sun is restricted to reach the RCC slab of the roof. In this way we can preserve the RCC from getting heated up. Once the RCC is heated up there is no other way for the heat to escape other than inside the building.


Conventional Roof Insulation with high reflective material like china mosaic / U.V. Reflective Coatings /any insulation material based on Solar Reflective Index (SRI) etc. is not an effective method of insulation as the Solar Reflection gets reduced over a period of time due to accumulation of dust / dirty patches etc.




GIB is a light weight material produced by special process. The material is in the form of glass like bubbles. These are closed cell particles with high mechanical strength, very low water absorption & very high fire resistance characteristic. GIB being chemically inert has excellent heat & acoustic insulation characteristics & once mixed with cement, very high thermal resistance value can be achieved.


GIB is widely used in Building Construction Industry as a light weight aggregate, when combined with Portland cement and water it produces an ultra light weight concrete. GIB is a very unique insulating material especially when studied in comparison with other conventional insulating materials having RValue 2.78.

GIB can also be used in other areas where making a product lighter will be beneficial & a variety of permanent insulating applications.

Popular applications of GIB :-

  • Insulating roof decks
  • Lightweight floor fills / screeds
  • Insulating structural roof decks
  • Curtain wall systems
  • Lightweight pre-cast panels for partitions
  • Lightweight insulating blocks
  • Roof / Ceiling tiles
  • Hollow / Cavity walls


GIB can be mixed with cement, minerals gypsum, fly ash etc. to make variety of finished products. Due to low water absorption property, if GIB is used where water is used to mix the different materials, it will help in reducing water consumption, drying cost and increase productivity etc. More over because of the its low water absorption property the volume of mass remains same after addition of water in the concrete/ mix.


GIB Concrete insulation is the ideal base for built up and single ply roofing system.


Perlcon GIB: Physical Properties



Refractive Index


Free Moisture, Max.




Specific Gravity


Bulk Density

100-250 kg/m3

Grain Size

0-2 mm

Softening Point

871-1093 °C

Fusion Point

1260-1343 °C

Specific Heat

837 J/ kg k

Thermal Conductivity at (24° C)

0.04 -0.06 W/mk



Well insulated roof with the insulation placed on the external side is an effective measure to reduce solar heat gains from the rooftop. The insulated materials should be well protected by water proofing. For air conditioned spaces, Energy Conservation Building Code (ECBC) recommends the thermal performance for external roof for all the five climate zones in India.



Major Benefits:

  • Energy saving upto 35%.
  • Cool and comfortable living.
  • Low carbon emission.
  • Pay back of investment made in Roof Insulation will be 2-3 yrs.
  • In winter it will keep your homes warm also.
  • Very high fire resistance characteristics.


Technical Specifications

Cement to GIB ratio Ideal Thickness Typical Mix Proportion
(by weight)
Area Compressive Strength (28Days) Resultant Dry Density of Mass
By Volume 50 to 100 mm

Cement (Kg)

Perlite (Kg) Water (%) Sq.M. Mpa Kg/m3
1:4 100 mm 2500 1200 65 100 6 550
1:5 100 mm 2087 1250 85 100 5 500
1:6 100 mm 1788 1286 115 100 4 450
"Cement density has been considered 1250 kg/m3 & GIB density 150 kg/m3 for calculations.




How to Apply


  • Clean the dust from floor or roof surface then spray the surface with water.
  • Apply a 5mm (floors) or a 20-25mm (roofs) expansion joint in the perimeter.
  • Mark the levels using laser level and install with aluminum straight edges similar to applyingthe Cement Mortar.
  • First mix Cement with water and mix till a slurry is formed then add GIB and mix manually or using a mixer for 3-4 minutes.
  • Apply GIB lightweight screed in a continuous operation until a section is completed, exactly like applyingthe cement screed.
  • Level the GIB lightweight screed by usingan aluminum straight edge.
  • For large surfaces use construction joints in both directions to avoid expansion cracks.
  • The next day scratch the GIB concrete surface with an aluminum line scratcherto clean and level it. Use a small scratcher for the corners. Spray the surface with water.
  • After 3-4 days, when the GIB lightweight concrete surface is dry, spray it with water and apply mortar then glue directly the floor tiles or apply water proofing solution or material.


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