Please help me improve my home insulation.

[ban-all-sheds]

It's not a case of 'heat radiating onto it....from the cold side'.

The foil is a 'low-emissivity' surface; its purpose is to reduce radiant heat transfer from the insulant and in so doing improves the U-value of the element
of which the board forms a part.

Remember that the foam in the board will attain a certain temperature.

Uniform throughout? No gradient?

If there was no foil on the cold side, the rough surface of the foam would then emit more radiant heat across the void to the colder side.

So from the warm side to the cold side?

its purpose is to reduce radiant heat transfer from the insulant

Will you please just THINK.

The foil on the cold side of the board reduces the emission of radiant heat outwards.

So not "from the insultant" after all.....



BTW - how much radiant energy makes its way through the plasterboard and decorative finishes which typically are placed over the insulation?

 

[tony1851]

It's not a case of 'heat radiating onto it....from the cold side'.

The foil is a 'low-emissivity' surface; its purpose is to reduce radiant heat transfer from the insulant and in so doing improves the U-value of the element
of which the board forms a part.

Remember that the foam in the board will attain a certain temperature.

Uniform throughout? No gradient?

If there was no foil on the cold side, the rough surface of the foam would then emit more radiant heat across the void to the colder side.

So from the warm side to the cold side?

its purpose is to reduce radiant heat transfer from the insulant

Will you please just THINK.

The foil on the cold side of the board reduces the emission of radiant heat outwards.

So not "from the insultant" after all.....



BTW - how much radiant energy makes its way through the plasterboard and decorative finishes which typically are placed over the insulation?

A low-emissivity surface (eg foil) radiates heat less than a rough, matt surface - end of story.
Were you away when they did physics at school?