Any point insulating between rafters?

fatchance

Hello all,

is it worth while using insulation between the rafters in the attic?

I intend using 200mm rockwool or similar over ceiling joists but was curious whether it is good idea or a waste of money to put insulation (like Kingspan's Therma-Pitch10 for eg) between the rafters as well.

Why do people do this? Is it to fight the cold higher up instead of at ceiling level?

Thanks in advance.

Fat chance

311

In our house the roof is insulated and the floor is also.
during the winter months it's the warmest room in the house.

Elfish

Are you actually going to be using the attic as living space?

If so - you need to insulate between rafters under roof.

If not - insulate just between ceiling joists.

whosedaddy?

is it worth doing the rafters in light of the new insulation regulations?
If so, how do things add up? 200 mm over joist == 150mm over joists + 50 mm between rafters? (assuming same materials) Or what is the math here?

Reyman

fatchance wrote:

Hello all,

is it worth while using insulation between the rafters in the attic?

I intend using 200mm rockwool or similar over ceiling joists but was curious whether it is good idea or a waste of money to put insulation (like Kingspan's Therma-Pitch10 for eg) between the rafters as well.

Why do people do this? Is it to fight the cold higher up instead of at ceiling level?
Thanks in advance.

Fat chance

It could be useful in the sense that the heat lost from the upstairs rooms to the attic is not just affected by the amount of insulation on the attic floor. It is also directly proportional to the temperature gradient between the upstairs rooms and the attic.

So if you have an upstairs room temperature of 20C and you keep the attic at 10C vs 0C, you will halve the heat loss to the attic. This is quite a saving

But there's a lot of work involved. So maybe it's better and cheaper to throw down a few more rolls of glass fibre on the attic floor

fatchance

Reyman wrote:

But there's a lot of work involved. So maybe it's better and cheaper to throw down a few more rolls of glass fibre on the attic floor

Straight thinking there, I would agree. Won't ever be living space so I might not bother.

Thanks all

renedescartes

Hi,
Agree with all thats been said except you should consider putting Aluminium foil on the rafters. This is a diy job and is worth doing. This system reflects the radient heat from the house and also stops radient heat from outside. There are various products available on the web. worth looking into. Warmer in the winter and cooler in the summer
Michael