Glass Fibre versus Foil (loft insulation)

wildmandy

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I've seen foil advertised claiming to have the same inuslating properties of 270mm of fibre. Can this be true? The foil is just 25mm thick.

Anyway, here is my loft insulation plan:

100mm of fibre between joists (joists are 130mm high).
Lay (chipboard) flooring on the joists (there will be 30mm air gap below).
Lay foil over boards.

It's the last part I'm not sure about - maybe I should cross-lay 150mm fibre instead?

Any comments and advice welcomed.
Mandy

DNK

wildmandy wrote: »

Lay foil over boards.

Why would you want to put flooring down and then put the foil on top? Means you can't walk on it which kind of defeats its purpose.
You could put the foil down bewteen the joists first, then the glass fibre, then flooring on top.

I used the insulating foil (thinner one) as a roof liner (to kill two birds with one stone) as I didn't have any there when I moved in.
Like pic below.



I put down the glass fiber insulation between the joists, then floored it.

robv_3

As far as I'm aware none of the foil insulations pass the British standard hot box test. The foil insulation associations claim the tests are out of date but other types of insulation pass, eg Celetox / Kingspan and fibre.

I've used it in a few different places and would never us it in my own house.

wildmandy

DNK wrote: »

Why would you want to put flooring down and then put the foil on top? Means you can't walk on it which kind of defeats its purpose.
You could put the foil down bewteen the joists first, then the glass fibre, then flooring on top.

I used the insulating foil (thinner one) as a roof liner (to kill two birds with one stone) as I didn't have any there when I moved in.
Like pic below.



I put down the glass fiber insulation between the joists, then floored it.

There isn't enough depth between the joists for both, really.
Regarding the foil you stapled to the rafters, I thought this kind of insulation was when the loft was going to be converted, otherwise floor fibre was the way to go?
Mandy

Doozergirl

AFAIK the foil is pretty expensive so unless you really need the space saving qualities of it, you might as well go for the more traditional stuff.

If you do need the U value for a conversion and want it then make sure that you local authority's building control accept it - I was told that not many do but in my area it certainly seems that more do than don't

DNK

wildmandy wrote: »

Regarding the foil you stapled to the rafters, I thought this kind of insulation was when the loft was going to be converted
Mandy

Doesn't have to be, it can be used as an addition.
I managed to source some of this foil fairly cheap so thought I'd use it instead of the paper lining. I wouldn't use it soley for insulating purposes but when I'm up there sorting things out, it definately makes a different (gets warm quickly from my own body heat and not draughty) so it must be assisting with the overall loft insulation to a certain extent. No harm in doing both (especially if you have exposed roof tiles up there.)

If you buy the foil from B&Q etc it is VERY expensive. I bought a huge roll 50m long by 2m wide for a fraction of the price per m². Also bought the Knauf "space blanket" for the floor when it was BOGOF.

mysty60

DNK wrote: »

Doesn't have to be, it can be used as an addition.
I managed to source some of this foil fairly cheap so thought I'd use it instead of the paper lining. I wouldn't use it soley for insulating purposes but when I'm up there sorting things out, it definately makes a different (gets warm quickly from my own body heat and not draughty) so it must be assisting with the overall loft insulation to a certain extent. No harm in doing both (especially if you have exposed roof tiles up there.)

If you buy the foil from B&Q etc it is VERY expensive. I bought a huge roll 50m long by 2m wide for a fraction of the price per m². Also bought the Knauf "space blanket" for the floor when it was BOGOF.

Where did you buy your huge roll from??

Peartree

I spent a lot of time a few months ago trying to sort out what to do with insulation in my loft, combined with some storage space. I posted on various DIY forums and found that the responses I got were pretty much all or nothing and actually people seem to have some VERY strong ideas they want to share about it all which were just bewildering. You and I may not believe it, but there are forums where the mere mention of foil incites intemperate debate.

In the end, I went through the Energysavingtrust http://www.energysavingtrust.org.uk/Contact-us and contacted the local office who gave me very straightforward answers to my queries.

seven1969

We're going to insulate our loft in the next week or two. Ours is already converted and in use but unfortunately, whoever did the conversion (not us) didn't bother to insulate it, if you can believe that? Anyway, we were planning on using the Space Blanket, orange fluffy stuff. My OH was planning on crawling along the eaves and shoving the rolls up into the roof space between the joists. It wouldn't me! Spider heaven. Yuk!

However, after reading this thread, would I be right in thinking that Space Blanket wouldn't be suitable for the roof space? I'm tempted to book a professional but we want it done now and we're on a budget so DIY it is.

Suggestions?