Loft and Ceiling space insulation ideas please.

[Udhi]

Hi all,
I have just bought a shed of a house. It is made of 9" solid brick external walls and loses heat like there is no tomorrow. I have created a separate thread on wall insulation. in this forum, current decision is PIR plaster boarding the inside of all external walls.

Now comes the lof and ceiling spaces.

The loft space is ENORMOUS. I can stand up straight in about 40-50% floor area. About 6 foot head space. It is reasonably WARM. Forum knowledge indicates the warmth is a sign of escaping heat. There are remnants of glassfibre insulation on some parts of the floor - maybe 3 or 4 inches, full of dust. The majority is missing. There is NO insulation on the roof at all.

I have considered PIR type boards. My basic maths suggests it is going to be bliddy expensive to install PIR insulation. Reading around, I am aware of "Rockwool" mineral wool or fibreglass wools battens, which look like the easiest and cost efficient to install.

I am also aware that a type of this "wool" comes covered in a plastic cover to prevent water and other poop getting into it and ruining the insulating properties.

so....what is the BEST make of the stuff to use? I have heard of a company KNAUF making the same stuff. I might over board this loft, much later in life. There is room for about 10" maximum depth in between the wooden rafters or whatever the current plasterboards are fixed to.

Thank You for any ideas you can give.

Before anyone suggests it - please no wool or cotton alternatives which seem almost as expensive as PIR type solid insulation by CELOTEX or KINGSPAN.

 

[mointainwalker]

1) AFAIK all mineral wools at the bottom end of the price range cost much the same although Rockwool is often a little more expensive.

2) Where you have space these materials give the most economical insulation solution.

3) The plastic wrapped stuff will cost more for the convenience without any major advantage. The dirt and dust don't matter very much and you shouldn't be getting water ingress anyway !

This would , in any case only be advantageous if it fits well between your joists, so if you want to consider it, you should measure the distance between joists and see if it is available in that width.

There are grants available for this from energy suppliers but they would want their contractors to lay it, not your builder.

Before any work is done I would say lift the existing wool remnants and sweep up all the dust etc. The existing wool could be kept after shaking out dust but up to you.

Check and note what wiring there is and if it is attached to joists where it is likely to be covered by insulation .

Reason for this is wiring is not supposed to be covered by insulation because that reduces its load-carrying capacity and increases fire-risk, so the advice is to put it on top of the insulation.

In real life this is usually not possible because there is no slack, so you should leave a void around wires.

Once you have done all that roll out thin plastic sheeting loosely over the whole surface taping joints where necessary between sheets - this is your very important VB. I use thin plastic sheets sold as floor protection whilst decorating - buy from sheds.

Unroll your 200/250 mm rolls ( cut or bought to size )between the joists ( paper-side up to keep out dust ) but ensure that you -or your builder - does not roll to the very edge of ceiling under the eaves because this need to be left clear to allow ventilation into roof to prevent condensation, damp etc.

This is the single easiest, cheapest very effective insulation improvement you can carry out and should bring about a noticeable cut in your heating costs

Best of luck with the other works.

 

[dave_sch]

Im curious about the comment about putting the plastic over the insulation. Wouldn't that trap moisture which could rot the joists ?

 

[mointainwalker]

Can you quote - or explain - which bit you are referring to ?

 

[igotalake]

anything below the insulation should be 'warm' and therefore not subject to condensation...therefore no great need for ventilation

 

[PrenticeBoyofDerry]

Rock wool is normally the cheapest and not that difficult to install. You will need a vapour check barrier, to stop condensation this will be placed between the ceiling board and the insulation.
This maybe already in place as you have mention remains of an old insulation, it could come in the form of plastic sheeting or could well be part of your plasterboard system, if they are foil backed boards (known as duplex boards) this will be vapour checked and okay to isulate straight over, so worth having a little look in the loft to see.
http://www.energysavingtrust.org.uk...ducts/Home-insulation-glazing/Loft-insulation