Concrete flat roof insulation

[eifionlangford]

Hi, our bungalow was originally a flat roof building, which has since been extended and had a pitched roof fitted.

All the extended area is insulated. The area with the concrete roof has not been insulated. The concrete roof is six inch thick concrete on top of wooden boards and beams and if course has the pitched roof over it now.

Is it worth insulating the area covered by the concrete flat roof? I would have thought the concrete would be enough but of course I don't know enough about it. In the summer on really hot days it stays nice and cool so I assume the opposite in winter?

Thanks.

 

[motorbiking]

Concrete U values aren't easy to calculate as it depends on the mix. It could be between 0.75 and 3 depending on the mix. Is it very cold to the touch?

 

[eifionlangford]

Thanks, not cold really, but it does still have a layer of bitumen in top as well.

 

[motorbiking]

You could look at the roof to see if its not covered in frost during a cold spell, that is a give away of a poorly insulated loft.

 

[catlad]

If I'm understanding you correctly and you have built a pitched roof over a concrete flat roof? then you can lay Celotex/Kingspan on the top of the flat roof and just weigh it down with a few old bricks.