Adding to loft insulation.

[Orby1]

Hiya,
Our new place is about 15yrs old and only has 10cm of loft insulation, squashed down to 8cm on one side by loft boards. I need to add to this.
My plan is to just put some 6x2 inch timber across the rafters, fasten it down and fill with 6" (15cm) of roll-out insulation. Then I can put the loft boards down on top again on the one side and away we go.
My question is this.
Should I lay the new timber across the old rafters, or lay them on top of the old ones running the same direction? Does it make any difference with weight distribution?
Also, is this recycled plastic insulation, the stuff you don't need gloves for, any good?
Any advice would be really welcome!
Ta!

 

[Symptoms]

Orby - why bother lifting loft boards as these have insulating properties themselves (probably equal to additional layer of insulation). Just overlay the new stuff on the old.

 

[ModernMaterials]

why bother lifting loft boards?quote]

I think he wants to use the boards again after he has added height to the joists.

My gut feeling is to go across the current rafters.

Be aware that you are adding weight to those joists- I dont know if it matters. I am interested in this subject myself so i hope someone puts in a proper answer.

 

[MasterAbacus]

I really would not bother lifting the boards to add more insulation. The properties of the boards them self will be enough.

The Recycled stuff your on about, does it have a name? there are many proucts out thier....

Cross batterning just adds wieght to the whole job... How big are the joists already?

Have you thaught about insulating the actual Rafters area of your loft space? this is as good as doing the floor area. And makes you loft area Warmer too...

Dont for get to lay any new insulation under any stray cabling that might be about in your loft....

If you have a browse through this forum topic you will find many simlar questions with answers.....Loft insulation if very popular at this time of year....

Feel free to reply, or add more here, ill come along later, unless someone else beats me to it...

 

[Orby1]

Hiya, thanks for your advice, people.
Yes I do need to use the loft boards afterwards to put stuff on, so I can't just lay more insulation on the top.
As I said, the current rafters are 8cm high. I would prefer to raise the height of these by 15-20cm by adding extra timbers on top (cross battening?) but was worried about the extra weight.
As for insulating the actual rafters in the loft space - I understand your point, but I want to keep the heat in the house below, not let it get up into the loft then keep it there, so I'd rather insulate the loft floor.
The name of the recycled plastic stuff I don't recall - I saw an advert in the paper that B&Q were selling rolls of it BOGOF this weekend - it's meant to be made from recycled plastic bottles and stuff, but I've not heard a lot about it.
I will take a look through other threads about the same problem, thanks everyone for your help.

 

[Symptoms]

Orby - why do you want to lift the boards, is it so you can get more insulation under them? Or is it to strengthen the floor so you can pack more stuff up there? I realise that you want to retain a floored section for storage purposes. My point is that if your only purpose is to pack more insulation under the boards in the belief that you are going to gain added insulation values, then don't bother. The chipboard has good insulating properties; by all means beaf-up the insulation where there are no boards.