Advice on loft insulation

ronant2019

Hi there

I was looking for some advance on loft insulation (between joists) and specifically for reducing traffic noise from outside property.

I have read that sheep wool insulation is the best for acoustic performance but obviously comes at quite a cost so I was wondering is it possible to use sheep wool as a base layer (100mm depth) and then top up with standard, cheaper insulation you can get from B&Q etc? The sheep wool insulation has a good sound rating at 100mm but does anyone know if the fact that I would be using another insulation type above it would reduce the sound proofing qualities?
Many thanks!
Ronan

loyalstokie

You would be using on sort of insulation as acoustic insulation and another ad thermal insulation, but both will have some amount of the insulation of both.

You could insulate your ceiling with one and your roof with the other if you really wanted to keep them separate.



If you know anyone who has food deliveries in boxes (Hello fresh is a definite) you could ask them for the packaging as they use lamb's wool to protect to food and expect it to go in the compost bin afterwards.

Davesnave

loyalstokie wrote: »

You could insulate your ceiling with one and your roof with the other if you really wanted to keep them separate.

I'm doubtful this would be good practice, unless you mean 270mm between the joists and then more under the roof itself, but even then the required air flow would mean the loft was cold, so any roof insulation would give little benefit regarding heat loss.

mnbvcxz

I don't know about the acoustic properties of sheeps wool but I do know it can attract bugs.

The manufacturers are on about the third pest proofing process which this time they say definitely works. But they said that that the first two times as well.

It may be true that it is now pest proof but as I deal with a house full of clothes moths I would not trust them again, its just not worth it.

loyalstokie

Davesnave wrote: »

I'm doubtful this would be good practice, unless you mean 270mm between the joists and then more under the roof itself, but even then the required air flow would mean the loft was cold, so any roof insulation would give little benefit regarding heat loss.

Yes, I was think of the required amount between the ceiling joists then extra between the roof joists.

However, the requirement if to have a minimum r-value rather than a minimum thickness. Back in 2016 the co-op was saying an r-value of 7, the havelockwool sites say wool has an r-value 3.6 per-inch - at those numbers 2 inches meet the requirements.



https://havelockwool.com/fiberglass-insulation-vs-wool-insulation/

https://www.cooperativeenergy.coop/news-and-views/how-to-insulate-your-loft/


Ronant2019, the only way I can think that additional insulation would reduce the effectiveness is if it compresses the wool.

ed110220

What about something like rockwool sound insulation batts between the joists and then ordinary loft insulation over the top? Definitely don't try to insulate the roof as well as the ceiling as a traditional loft needs good ventilation so insulating the roof would be at best pointless and at worst harmful.

Green_hopeful

If you research sound transmission on google a lot of it’s about cracks that let sound through. I can tell our windows are not well sealed because I can hear birds despite the double glazed windows being shut. You might find that draught proofing helps with noise transmission too.