Roof Insulation Period Property

Old 07-11-13, 05:09 AM
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Roof Insulation Period Property

Hi, the roof of my house is being retiled and felted with a breathable membrane.

The house is a period property with yorkshire stone roof, however it has suffered from dry rot in parts.

Now seems the perfect time to add insulation as it has none.

I measured the roof trusses gap and it is around 5.8 - 7 cm. in parts.
I ordered 45mm kingspan insulation and left a gap to allow airflow to prevent any condensation.

As I understand I will need a vapour barrier before installing the insulation on the warmer side.

Would I see any benefit in installing multi layer foil insulation and using as the vapour barrier instead of a plastic roll?

I have looked on the internet and it appears that single foil / bubble wrap causes condensation whereas multi foil does not?
Also I notice it is questionable as to how well it works, however surely it should work well for reflecting radiant heat?

The price of the foil is 120 so it does not appear too expensive.
SFTV - SuperFOIL Multi Foil Insulation - Radiant Barrier (Multifoil)

Any advise would be great.
Old 07-11-13, 07:31 AM
Join Date: Oct 2008
Location: New England
Posts: 9,460
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Hi Tom,
* Your location is outside the US so codes and local requirements will be different.
* Tell us what climate you are in, heating, air conditioning, or mixed.
* The 45 mm insulation (not familiar with kingspan) is not very thick, although anything is better than nothing.
* The bubble wrap radiant barriers often exaggerate their performance and have lost the respect of the building industry. There may be a place for them at times, but even a low cost is hard to justify. In very hot climates, maybe, otherwise more insulation is better.

Tell us about your climate, temperatures and humidity.


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