best loft insulation?

Doglover88

of the 3 types i know of (fibreglass rolls, foam type with foil backing comes as boards or vermiculite granules) is there a best one to use?
looking to do the loft next week and wondered best to use, what if theres already some down (think its the crappy fibreglass rolls) do i go over the top of it or pull it up and start again?

And is it a case of the more the better with insulation?

many thanks in advance
glen

robnye

if the existing fibreglass insulation is pretty clean , ie not a dirty grey colour, then just lay new fibreglass over the top. as the recommended level is now 250mm (i think,) then the more the better

make sure you use gloves and have a face mask.........

for more info. try giving your local council a call

adr0ck

new bldg regs require 270mm of insulation

this is for new build (england & wales)

100mm between rafters

170mm across rafters

this is fibreglass insulation

it is by far the easiest and quickest to install and is also the cheapest by approx £15/m2 (over rigid board kingspan, celotex etc) which over a 100m2 roof = £1,500 cheaper!!!!!!!!!!!

if youve got approx 100mm existing already between rafters just get 170mm and lay across

alanobrien

As they say the glass fibre is the cheapest if you already have some. Bagged stuff is better and less of an irritant but more costly.

I topped up mine recently, wickes and some other DIY sheds do a buy 2 get 1 free on rolls so give them a look.

dodgy_gooner

This might be a daft question but how do you put loft boards down if you have 250mm of insulation ?

adr0ck

either just sqaush it down

or remove part of the thickness (just rip it)

or increase height of joist/truss things

twobob_2

If your putting boards down or considering a conversion at some point I would consider rockwool, as it's fire retardant properties are superior.

economiser

As I wanted board out our loft space for usable storage I insulated under the tiles with kingspan. This was cheaper than raising the rafters which would also have restricted headroom

gromituk

adr0ck wrote:

either just sqaush it down

Absolutely not, I'm afraid. Insulation works by trapping air. If you squash it, you squash the air out, and it will be a worse insulator than you would get by using a thickness appropriate for the space you want to put it into.

If you want to board the loft you will need to raise the height of the rafters. This is best done by laying new ones at right angles to the old, so that you minimise the "cold bridging" of a continuous thickness of wood.

Rockwool (mineral wool) is a slightly better insulator than fibreglass. Both are non-combustible.

gromituk

economiser wrote:

As I wanted board out our loft space for usable storage I insulated under the tiles with kingspan. This was cheaper than raising the rafters which would also have restricted headroom

If you do this, you must be very careful to allow air to be able to circulate around the timbers. Otherwise you will get mildew, or even risk dry rot.

If I remember correctly, building regs require the equivalent of a 10mm air gap all the way around the eaves, if the underside of the slates/tiles is blocked by felt and/or insulation.

adr0ck

gromituks rights....if u do squash insulation down...or rip it...it wont obvioulsy be as good.......but if your only boarding a small part of your loft out....then i really wouldn't worry about it...the energy savings would be so negliable it wouldnt really matter....don't forget that wahetever you store on your boards will have an insulating effect anyway!!!!!!!!

with regards to rigid board.....does anyone fit this correctly??????