Loft Insulation .... Again

[danw]

Apologies if this has been done to death but I would be grateful for another opinion.

My 1930s house (no cavity walls, no felt under roof tiles) has about

100mm of oldish loft insulation (fibreglass I think - don't know how old). Currently little of the loft is boarded and what is, is not really usable.

I need to board a fair percentage of the loft for storage purposes.

What I am wondering is whether it is worth getting the loft reinsulated before I board. As the new guidelines specify 250mm or so of insulation depth I would have the problem of losing my joists for attaching the boards to.

Should I leave the insulation as it is and just put my boards down. Saving the £199[*] it will cost to reinsulate?

or

Should I reinsulate fully then negotiate (ie remove) the insulation where I need to board?

or

Should I look for another insulation material to go under the boards that won't rise above the joists?

At present, my instinct tells me to leave it as it is. Though maybe add a little more insulation around the edges. Will what I store in the loft help insulate?

It seems that good loft insulation and using the loft as storage space don't necessarily go hand in hand.

Thanks, Dan

[* - A flat fee I have been quoted]

[Pete Verdon]

Possibly. I did this, though, before realising that my insulation is probably inadequate, and now I regret it.

I don't see how this would help. Squashing 200mm of insulation into

100mm of space gives it the effectiveness of 100mm. So sweeping it away from the joists into the gaps, and then pressing the boards down on top, makes the whole lot a waste.

That's a possibility, though the material will almost certainly be more expensive.

Not to any real extent, unless you're storing loft insulation :-).

Another option might be to extend the joists upwards, by putting another timber strip on top. Don't rely on these for added strength without some serious thought (though they'd probably add some if well-fixed to the joists) but they'd put your boards higher up with room for more insulation.

Pete

[Phil L]

It doesn't....200mm of insulation squashed down to 100mm still has a lot more insulating properties than 100mm

To the OP: add another 70 or 80mm of insulation (you can use any kind of fibreglass for this, cavity batts will suffice and they are availible in these thicknesses) and then board over.

Add another 200mm to the remainder of the loft if you feel like it

[Pete Verdon]

Really? I was under the impression that the purpose of the insulation was simply to hold air in one place, with the actual inhibition of heat transfer provided by the air. After all, glass isn't a particularly good insulator (cold window-panes?) itself.

Pete

[Phil L]

That's what I thought too, but we had to visit the factory where it's made (which is incidentally only a mile away from where I live) when we were installing CWI...the factory makes all kinds of insulation and on this particular day, a FG mat was coming off the conveyor belt which must have been easily 500mm thick, and it went through a compressing machine which spat out rigid boards at the other side. I mentioned about the air being the insulant and was informed that the FG would retain '70 to 80% of it's original insulating properties'...this meant that the boards, which were about 40mm, had the insulation properties of at least 300mm matting

[The Medway Handyman]

I guess 18mm chipboard must have some insulating properties anyway?

[The Natural Philosopher]

At current fuel prices I'd go celotex and FULL boarding. Floor grade chip.

[The Natural Philosopher]

You would be surpised.

I have found te UFH floor under the sofa to be some 4-5 C warmer tha te floor that just has a rug on it..inference being the sofa is doing some insulation.

Piles of old newpaperes probably are as good as 60mm celotex.

[Mogga]

And there's no undue pressure on the ceiling below?

[Doctor Drivel]

Fill between the joists with rockwool, or what you already have. Then put over the joists rigid foam insulation. Over that chipboard. Screw right through the chipboard and foam. Thos eliminated cold bridging.

Seal with silicon all holes in the ceiling and fit an insulated sealed hatch.

[Doctor Drivel]

You made that up. And what a fire hazzard.

[The Natural Philosopher]

Not as much as your polystyrene.

Newspapers are surprisingly good insulators.

A foot of newspaper is - if dry - a substantial layer.

[Edward W. Thompson]

That's because they contain a lot of 'hot air'!

[Doctor Drivel]

Figures please?

[jal]

:-D Outstanding.

A foot of newspapers weighs an _awful_ lot! My neighbour's roof (outside) has discernible dips in it: he was told by an architect friend that this was because he's got so much crap stored here there and everywhere in his loft (carpets, furniture, etc.), and the weight is dragging on the roof trusses.

[danw]

Thanks for all the replies. If I were to buy something such as Celotex where should I go for it? And should I stick to 90mm?

Thanks, Dan

[Doctor Drivel]

Figures please.

[The Natural Philosopher]

Would you understand them If I wrote them?

You never have before.

[Doctor Drivel]

Not with your crayon.