Worth Adding Wall Insulation?

[MadDesigner]

Hi, currently doing up the spare room we have to become our daughter's bedroom. It currently is a darkroom. It has two external walls - longest N facing, shortest W facing and is the back room of a typical Victorian terraced house, so notorious for being cold.

Current loft space above boarded over and full of boxes! I probably will remove all boxes, remove boarding and add more insulation above. Currently cross braced with joists at right angles to originals to add strength to hold boxes. I can add an additional 75-100mm to existing.

I was thinking about hacking out all the original plaster and drylining with either insul-plasterboard or battens, batts, membrane and plasterboard to a depth of 50mm. Original plaster is old so at least 30-40mm thick. I'll lose minimal space this way in what is a smallish room. Will be both external walls so only one window frame to worry about. This will be replaced with a new double glazed unit as the 60's single glazed aluminium frame is ~@%&!

What are the pros and cons of both methods and more importantly - is it worth doing?

Thanks

Nick

 

[Deluks]

If the old plaster is sound, you could just dot n dab insulated plasterboard straight to it. Or use fixing foam. Defo worth doing if you are refurbing/redecorating anyway.

 

[mointainwalker]

Very much worthwhile doing. The initial insualting layer gives the greatest pro-rata benefit, although 50 mm is very little. Can't you run to 100 mm total ?

 

[theoldun]

As the two posts above say its three yeses, how ever in our opinion, you must do it right. Current U values for walls is 0.28W/m2k
To achieve this value you need 65mm plus 12.5mm laminated plasterboard (total thickness 72.5mm) of Celotex PL4000 on 15mm dot and dab. If old plaster suspect in any way then hack of and work of exposed brickwork. You may not achieve 0.28 on the north facing wall. It could be .029 or .even 0.30.
Try and get total 0f 300mm fibreglass in roof space to compensate.
Regards oldun