Loft insulating help

[MeEsH BaKkA]

Right I currently have about 100mm of fiberglass between the joists and nothing between the roof timbers. I want to insulate the loft space more and have a couple of questions.

1. Should I insulate between the roof beams? If so how to hold it in place, is it worth boarding it over either completely or partialy. Or would using selotex be better?

2. What are the regs on air flow gaps?

3. Is around 250mm enough? The floor is boarded out so I can't go too deep as the boards will end up compressing the insulation.

Erm... Think that's it, oh I'm using rockwool for the flooring and posibly for the roof.

 

[DBT85]

It depends on a a few things. As standard you would insulate the floor of the loft instead of the roof. if you insulate the roof then all that heat from below will also keep the loft warm. do you need the loft to be warm?

compressing the insualtion in any way will negate the insulating effect. its the trapping of air that keeps it warm. Same way wearing 2 thin shirts is warmer than one thicker one.

What I have just ordered (noted in the other insulation thread) is new insulation for the loft using rockwool. A wool kind of material spun out of melted rocks which is also fire retardant (rocks don't burn). usually you will fill in the gap between joists and then lay anything extra over the top at 90 degrees to eliminate any gaps.

The next question then is do you need the entire loft to be boarded? I refuse to put anything in the loft unless its really needed as i've cleared enough out to know that most stuff is junk that people just don't want to throw away and doesnt get touched for 20 years once put up there. As a result we only have 1/4 of our loft boarded out for the odd suitcase and the xmas deccs.

If you do need to board out the entire loft, but dont want to lost heat into an uninhbited loft you can add some height to the floor by laying 6" timbers at 90 degree angles to the existing joists and then board over the top.

if you have enough money then use some kind of foam insulating board which will insualte as well as 270mm of standard insulation but at a thickness probably less than half as thick. No surprises then that its more expensive.

The new insulation to do our entire loft from nothing to the govt recommended 270mm cost £57. bargain.

 

[john_s]

1. Should I insulate between the roof beams? If so how to hold it in place, is it worth boarding it over either completely or partialy. Or would using selotex be better?

2. What are the regs on air flow gaps?

1: It depends how you want to use the loft space. If you're just storing stuff up there, you probably don't need in insulate the roof itself. If you're going to use it as a man cave similar, it would probably make sense to insulate the roof to hold some heat in the loft space.

2: You need a 50mm gap for airflow between the felt and the insulation right over the roof.