Under-roof heat insulation: really worth it? Which type keeps your house cool against the Thai sun

Under-roof insulation: really worth it, or just a trend?

Thailand's sun is famously fierce, and the part of the house that builds up the most heat is the Roofing Installing heat insulation under the roof is therefore an investment that is very worthwhile in the long term , because it reduces heat transfer into the house, can lower the temperature built up above the ceiling by 3-5°C, makes the air-conditioning work less and can save as much as 20-30% on your monthly electricity bill. It typically pays back the cost of materials and installation within the first 1-3 years.

Popular heat insulation compared: which suits your home

There are many types of heat-insulating materials on the market, each with different properties and installation methods:

• Fibreglass insulation: excellent heat insulation, wrapped in moisture-proof aluminium foil and easy to lay on the ceiling; suits ordinary homes
• PE foam insulation: lightweight, tough, very flexible and impact-resistant at an affordable price; used both under roofs and in extensions
• PU foam insulation: comes as sheets or spray foam with no joints, and dampens the noise of rain well, but costs more than other types
• Reflective foil (aluminium foil): reflects radiant heat before it enters the house; usually fixed under the roof battens before tiling

Checklist to prepare before buying and installing

• Check the R-value (thermal resistance): choose insulation with a high R-value — the higher the R-value, the better it resists heat
• Check the ceiling structure: if you use insulation laid on top of the ceiling, make sure the gypsum or SmartBoard and its frame can safely carry the weight
• Measure the area accurately: calculate the square metres under the roof and allow about 5-10% for cutting and overlaps

Safety precautions: The space under the roof is cramped and very hot, and may hide old wiring. If you need to check the load-bearing structure or there's electrical work near the installation area, we recommend that you consult and hire a specialist to prevent short circuits and the ceiling collapsing.