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Returns and chimney breasts


Two points I can't find covered on the website / forum / internet are:

1.  How much of an internal wall should be insulated with IWI to prevent a thermal bridge?  The whole wall or X mm into the room?

2.  Should I use IWI to insulate a chimney breast, or leave it un-insulated (as technically the breast isn't actually an external wall)?  If the former, do I need to be concerned of the insulating catching fire / the insulated chimney breast being damaged if the fireplace is in use? 



Topic starter Posted : 29/03/2021 1:25 pm
Chris Brookman
Member Admin

Hi Ben

When returning insulation along internal walls we'd typically suggest coming at least 500mm along or to something that will hide the edge of the insulation. You can use the UdiIN 2CM wood fibre boards for this as you can normally install it and plaster it and then taper the plaster back to the level of the surrounding plaster without it being particularly visible.

I would suggest always insulating a chimney breast but also blanking off the opening and back filling with an insulating, non-combustible, aggregate. There would not be any risk of the insulation on the surface of the chimney catching fire as it would need to be at 250 degrees C or more to do so and you'd be in a lot of trouble if this actually occurred!

Hope that helps

Posted : 29/03/2021 6:14 pm

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