attic/roof insulation

[vblanche]

Hi,

I know, nothing to do with cars, but I thought I would ask you as some (or most) of you have certainly encounter this problem.
What is best? ceiling insulation with glass fiber or polyurethane panel between rafters below tiles?

many thanks for your help.
vincent

[ALPB1033]

Usually a layer of glass fibre between the rafters in the attic but I always lays 2 layers of them. Then you can broad them up and use as a store room in the attic. But be careful not to put too much on. Otherwise the ceiling will collapse.

[ade and liz flint]

Usually a layer of glass fibre between the rafters in the attic but I always lays 2 layers of them.

IMO, the best option too. Saw an advertisement in Saturdays' paper for B&Q selling 5.5m2 rolls at £3 each. Can't remember its thickness though. Bargain price, and the non-itch version too. Current spec appears to be 270mm (about 10-11") of this (we topped up earlier this year and have got 10"now ).....

http://www.energysavingtrust.org.uk/Hom ... insulation

Shop around as there are a lot of grant-supported products out there atm!

[Chas]

This year I installed glass-fibre (double layer) in the loft floor and Kingspan PU panels in the roof. The PU panels are expensive and can be a bu99er to cut and fit, but it's worth it. We've also built an extension this year which is fully insulated with PU panels - roof, walls and under the concrete floor!! It's like having an insulated jacket on the front of the house.

[vblanche]

thanks everybody for your replies. Our council is offering us the glass fiber, but we need to change the joits, so I was looking at alternative, like Kingspan panels to do a under-roof insulation instead of floor insulation.

This year I installed glass-fibre (double layer) in the loft floor and Kingspan PU panels in the roof. The PU panels are expensive and can be a bu99er to cut and fit, but it's worth it. We've also built an extension this year which is fully insulated with PU panels - roof, walls and under the concrete floor!! It's like having an insulated jacket on the front of the house.

I was considering these panels but if they are too expensive...hmmm
Would these panels not be enough? do I need glass fiber floor insulation? which one performs best?

thanks
vincent

[Bruce M]

Why do you need to change the joists?

I did my in-laws loft early this year with plenty of rockwool type blankets. It is not the nicest job diy but worth doing.

I bought the material via an Npower deal and the rolls cost about £20 all in for a good sized loft (inc delivery).

Currently they are doing the rolls for £3 each but I'm sure I paid about £2 each

[vblanche]

Why do you need to change the joists?

Well, I need to extend them not replace them. they asked us to extend them by 6in because they are fitting much higher glass fiber rolls. and then we want to put floor boards to use the attic.

thanks
vincent

[ade and liz flint]

Why do you need to change the joists?

Well, I need to extend them not replace them. they asked us to extend them by 6in because they are fitting much higher glass fiber rolls. and then we want to put floor boards to use the attic.

thanks
vincent

The usual problem with the current regs...the insulation (10-11" thick) is much thicker than the original joists (usually 3-4"), which IS a bugger if you want to use the floorspace for something else. Be aware if you insulate the roof space in your loft instead of the floor, you're effectively paying to heat that as another room as the heat loss through the floor into the attic is vast. Increasing joist height is very easy, but obviously has a cost implication.

We cheated a bit as we've got the 10" insulation over 70% of the loft, and 4" insulation plus boarding in the storage area...did it myself so no issue with the council saying you have to do it all or not at all (daft rule IMO).

[vblanche]

Be aware if you insulate the roof space in your loft instead of the floor, you're effectively paying to heat that as another room as the heat loss through the floor into the attic is vast.

hmmm good point, thanks.

[Bruce M]

Ah, makes sense.

With the in-laws not using the loft for storage (too old to be running up a ladder), I filled the gaps between the joists and then cross layed another blanket over the top. I did this in the sections with low head room (access not an issue) and kept some joists visible in the center area where access was needed (to water tank etc).

If you are doing it yourself, you could do part 'n' part and extend the joists only where you need the storage area.

[Chas]

I was looking at alternative, like Kingspan panels to do a under-roof insulation instead of floor insulation. Would these panels not be enough? do I need glass fiber floor insulation? which one performs best?

The glass fibre / rockwool is relatively cheap and easy to lay, as Bruce has said. The non-irritant stuff is good but don't take it literally - you should still use gloves and a mask but it's certainly less irritant

If you need to increase rafter depth as much as 6", a better alternative would be to use Kingspan for the floor rather than rockwool. It comes in several depths to suit rafter depth and will far outperform rockwool by a factor of 3 or more. Given the performance of Kingspan, the additional cost may actually be a saving if it avoids the expense of raising the rafters, and you save the 6" in height if you intend using the loft!

We spent about £2k on insulation - £1700 on Kingspan in the roof panels and £300 for rockwool under the loft floor. Bear in mind we have 3 lofts totalling around 200sqm of floor space so that cost is excessive compared to most properties. The rockwool went in first, doubling up on the original glassfibre rolls. Then I floored the lofts. We noticed quite a difference with that alone. The Kingspan went in for good measure and because I intend to use the main loft for a home cinema and the annexe loft for a kids play area with scalextrix or a train set. No need to ask which kid will play with it most

[vblanche]

Which kingspan panels can I use to put on the floor between the joists?

Also, on this webpage, they seem to say that glassfiber is better?

[ade and liz flint]

Which kingspan panels can I use to put on the floor between the joists?

Also, on this webpage, they seem to say that glassfiber is better?

You need to get, and compare, the thermal resistance figure for all available option materials to come to a conclusion which may suit your application the best. These should be readily available online. Would have thought glass fibre is best, but happy to be proved wrong!

[Chas]

Which kingspan panels can I use to put on the floor between the joists?

Also, on this webpage, they seem to say that glassfiber is better?

Kingspan comes in "sheets" which are 2400x1200xNNmm in size. "NN" is the depth and I believe there are several depths available to suit different rafter sizes. You simply cut the sheets to the size required with a saw. They are very easy to cut, but you must measure and cut carefully; they are made of solid foam and don't compress so if you cut too large they won't fit and will need to be trimmed.

I don't see where that webpage suggests glassfiber is better. I'd happy lie naked inside a box made of Kingspan at the North Pole - it's thermal efficiency is that good. I wouldn't consider doing that with any of the alternative materials

[Mickl]

Why do you need to change the joists?

Well, I need to extend them not replace them. they asked us to extend them by 6in because they are fitting much higher glass fiber rolls. and then we want to put floor boards to use the attic.

thanks
vincent

Hi Vincent
I come up against this problem quite often and what I do is lay 100mm glass fibre between existing ceiling joists and then where storage area is required lay 150mm joists at 90deg to existing joists, fill with 150mm glass fibre and then overboard with t&g chipboard floor, of course this is only adequate for storage. the remaining loft area not used for storage can just be overlaid with the 150mm glass fibre at 90 deg to original ceiling joists, a cheaper and easier option than cutting kingspan/celotex between rafters.
Good luck

Mick l