[Closed] Loft Insulation - Help!

Isn't the junk acting as an insulator?

I would have thought 100mm of insulation with solid board on top with the 'junk' on top of that would be as effective as 150 or 200mm of insulation.

Dont forget to leave the spaces under any water tanks free of insulation though.

I hear that hemp is a great insulator but I only seem to be able to buy it in quarter ounces...

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this is the stuff to use, keep your 100mm of insulation between the rafters and gives you a platform to store your junk

more here
http://www.space-insulation.com/board.html

Recommended depth is 300mm these days. Any less and you're wasting energy.

Space board is expensive, certainly B&Q (don't spit) have a much cheaper basic polystyrene board that does the same thing. It's both in the packs and large sheets, same as Space Board. Laying these across the joists with your chipboard on top will also avoid heat bridging.

The other way is to raise the height of the joists to allow additional insulation to be added between the joists up to the recommended depth.

Cheers guys - tinman the house is steel framed with small metal joists etc. Have looked at building these up but its a right problem frankly.

I'll check out B&Q and ballsofcottonwool I'll check out space-insulation

I've been told that junk is not the best insulator btw

Cheers all

Back again

O.K. This is where I have got to, I've been recommended Kingspan (tp10?) or Celotex or Ecotherm boards - much cheaper than the B&Q/Focus alternatives

Have gathered a list of suppliers, but if anyone has 'seconds' lying around or even boards left over from a build/house conversion then please let me know

cheers all

This is about the cheapest I found for Celotex
http://www.just-insulation.com/index.html

I did the loft a couple of weeks back.

Used 170mm thick insulation between the rafters then put down 18mm thick clip together chip board ontop.

I've just upgraded to the recommended 300mm and today have finished raising the joists in on third of the roof space. I'll then be adding 18mm chipbord floor panels.

SO

I have crappy metal joists - thought about raising them but the insulated kingspan with chipboard on top seems not so much bother

http://www.secondsandco.co.uk/ are great for saving some money. I bought the next thickness up from the spec one because it is "seconds" so the surface finnish can be down a wee fraction on the full price stuff.

we have oodles of crude up there

crude? are you referring to pornography?

Dam Barry! Caught out by my crude crud again!!!

You could use polystyrene sheets, as used under concrete slabs in flooring. Not sure if they present a risk during fires though (fumes etc). They're cheap for 8x4 sheets

[url= http://www.secondsandco.co.uk/shop/page_product/item_344/index.html ]These look good and cheap too![/url]

If you can afford it, use the PU boards such as Kingspan/Celotex as they are fire resistant (don't char easily)
As a guide for roof U values: (just done some quick U value calcs)

300mm mineral wool would have approx U value 0.14
100mm PU board 0.26
100mm Polystyrene 0.30
All allowing for steel bridging form the trusses

I personally would not recommend polystyrene due to the fire implications.

You could look at a foil insulation such as Tri iso super ten which is 35mm thick
Would give you a U value of approx. 0.14

It is a tad dearer.
Can you get any grants off anybody?

Hope this helps

Cheers Teggs

The Kingspan Kooltherm is rated 0.023 W/mK I saw somewhere that phenolic foam of 65mm would be equivalent of over 100mm of conventional. So with the conventional insulation and the Kooltherm that should be +200mm equivalent?

Mmm getting confused now - how do I ensure it comes up to the recommended 270mm-300mm with insulation and boards?

First do not use Polystyrene. Not sure in a domestic situation but insurers get very twitchy in industrial environments. Some very nasty fires.

Celotex and Kingspan both make decent PIR panels, if you want a little more insulation get the foil faced variants, there is a place in mid wales that takes the Kingspan seconds.

Alternatively you could try Rockwool or Knauf rockfibre slabs, but probably a bit pricier, and certainly heavier.

Choice either lay the boards over the ceiling joists or between the roof joists or both.

The PIR foams are far more efficient than glass/rock fibres, thus a roof build of 220mm glass is c 100mm of board.

Ello

To match 270mm Mineral wool you would need approx. 170mm Kingspan/Celotex board allowing for the steel truss bridges.

You could put the PU/PIR insulation under the roof tiles sloping & get a warm roof.
If you kept your 100mm wool & chipboard & then put 100mm PU/PIR board on the slope you'd get a U value of 0.18 as an alternative.

It could be worth having a look at the foils which rely on radiant heat prevention rather than convection & also have no bridging problems.
You could keep your wool as it is now & drape the foil under the roof line which could give you a U value of
0.12 approx & a warm roof space to boot & no problems messing around with what is in place now.

Here is what i have done this year.
Buy some 4"X2" scant timber from Magnet or your local woodyard. (not rip off places like B&Q)
Scant is the timber used for dividing walls.
Then basicily glue it together across the original rafters to give you an extra 8" of depth, then fill it rockwool and put some 4'X2' t&g floor board on top.
That will give you around 300mm of insulation and will make the world of difference to your heating bills.
Also stick some Kingspan on your loft hatch + draft excluder.

Cheers lads

Teggs (teetosugars?) what if there's already 100mm of loft insulation already surely (circa) 100mm of Kingspan would do it?

Bear - That was my original idea. the 4x2 (or 5x2) would go on top of the trusses. My problem is my rafters/roof beams are pressed steel (looks like a Meccano set up there) and attachment could be fun - I have been looking at cable ties and glue to achieve the right effect but it could still be the best/cheapest option

Ta

Try this idea. Place small blocks of your chosen wood onto the rafters. IE cut your 5X2 into 5" peices and glue to steel beams. Then lay the full lenghts os scant along the top of the blocks. Glue or screw to lower together. Offset blocks for overlaps in getting from one end to other. Fit insulation. Lay the t&g onto the top and screw down. The way it works is if you go from wall to wall there will not be any movement in the lower blocks.
Thats how I boarded my centre section of roof space.

Anyone thought of getting a grant?

http://www.government-grants.co.uk/?gclid=CIvRod_ugJ0CFWQB4wod0j6t2A

If you have any left over insulation stick it under the bath. Keeps it nice and toasty!

Grants are a bit hit and miss! We were to get 100% grant for the loft along with all other residents in Powys Mid Wales but what a surprise, they ran out of money the day after the scheme opened!

Now its back to hunting around for anything at all!

Mema - never thought of that one!

We ran two layers of the space board stuff when renovating. Heating bill has plummeted.

Tanks

You would need about 115mm Kingspan to hit a U value of 0.16 together with your existing 100mm of wool.

To save you the cost of using CLS to is it possible to lay the Kingspan in between the rafters under the sarking felt allowing an airgap of 50mm between?

I am presuming that the steel frame roof trusses make up a "trussed roof" lots a diagonal struts between joists & rafters?
B laying your insulation between any CLS you will loose some of the insulations effectiveness thro what is known as Bridging.

Insulation is a funny old thing