Hello all,

 

I am doing internal wall insulation on a solid wall house (built about 80 years ago). I have fixed 50mm pir (38mm insulation/12mm plasterboard) directly to the interior of the walls using the  'mushroom head' metal fixings. I fixed the boards directly to the wall to conserve room space and not doing internal walls.

I now need to do the same in an upstairs bedroom. I want as thin an insulation board as possible, as the room is only 2600mm wide. The only thin insulation board I've found is stormdry EP (this is a system using adhesive and not readily available).   Stormdry EP Board - Energy Performance Board (safeguardeurope.com)

Are there any better options? 

I don't mind the cost, within reason, given the small area. The room needs a new radiator and aside from being 'cool' the room is good as a bedroom as is.

My other options are

1. Moving the radiator so it doesn't reduce the 2600mm width (its against the main wall to be insulated). This would mean taking up a good quality floor. 

2. Removing the top 10mm of plaster (not much benefit) . I'm not keen to do this, as concerned about 'mess' and disturbing the integrity of the render underneath, although I'm probably just being paranoid. 

3. Leaving the wall as is.- The 'flat' ceiling/attic above this particular room has no insulation! If I can insulate better around the dormer window and 'sloping' part of the ceiling/roof alongside the dormer- has anyone done this? Not sure if I can get any access to this sloping roof space.

4. Modern radiator and ceiling insulation only.

 

The room is only 3500mm long by 2600mm wide and has a dormer window so there is a slope over the final third of the 3500mm wall. Thanks

If you are really, really tight for space (and your budget does not run to aerogel), you can get 12mm PIR (online - the carriage will probably cost you almost twice the £14+ price, but a bird in the hand...). 9mm plasterboard over that, joint-filled with no skimming will lose you under 25mm and halve the U value ( rough calc says about 0.88W/m2K, copared with around 1.7 for the 'base-case' wall).

 

Insulating sloping ceilings by 'poking things down' is usually a lost cause, as there's usually a joist in the way, nailed to one of each pair of rafters, and keeping an even vent gap *and* getting air-tightness is really hard.