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Rafter insulation

Is polystyrene blocks a good insulation or rubbish ? It’s a lot cheaper than all over insulation.

4 Answers from MyBuilder Insulation Installers

Best Answer

King span is the best or any foiled backed close cell insulation will work.


Answered 5th Jan 2020

Like other organic compounds, polystyrene is flammable. Polystyrene is classified according to DIN4102 as a "B3" product, meaning highly flammable or "Easily Ignited.
The best material to use is 100mm " kingspan" or " celotex" foil backed insulation board, easily cut to size to fit between rafters. 100mm based on 150mm rafters leaving 50mm air flow


Answered 5th Jan 2020

No. Highly flammable and gives off toxic fumes. Use a proprietary insulation eg kingsman or wool


Answered 5th Jan 2020

It depends what you're insulating!?

On walls or on the ground there isn't a better solution.


Answered 17th Jan 2020

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