Help Loft/Attic Insulation Roof or Walls

[crhynes]

I have a bungalow which when I moved in had the attic converted. I now have 2 bedrooms with a small hatch door on one of the walls which provides access to the rest of the roof space. These rooms are freezing and as its an older property there doesn't seem to be any insulation. There has been some insulation laid on the floor space but that appears to be it. I was looking to purchase and install some airtec double insulation as I thought it the easiest and most effective for me but after reading up on it there is a lot of focus on vapour and condensation...im now clueless. Initially I was going to cover the slopes of the roof but given I don't intend to use the space other than for storage I thought best to do the walls of the bedrooms. As you stand in attic and look towards wall there is just the joists with the plasterboard from the room walls there at the moment. If I install this airtec over the joist leaving the gap would this be sufficient enough? I'm concerned that as I have no clue what I'm doing this airtec will reflect heat and create condensation onto the plasterboard. Can anyone help please and recommend suggestions

 

[^woody^]

I would use a foil backed insulation board (Celotex / Kingspan) between the timbers on the walls 100mm or two layers of 50mm. That will bring the wall up to today's external wall standard. Fill small gaps with expanding foam or cut some slivers.

Or use a mineral wool insulation bat (again 100mm) which won't be as good, but you could then supplement it with your Airtec idea.

I would not use any foil roll insulation on its own.

Then lay quilt insulation on the ceiling. 300mm if you can.

Do not insulate the rafters.

 

[crhynes]

Thanks woody. Any suggestions on what to use if I can't access ceilings, I had wall insulation blown into the wall cavities on the downstairs walls, could I use a similar technique and try insulate the roof that way rather than have to take down ceiling plasterboard.

 

[^woody^]

The problem is, if you don't insulate all the ceiling equally, then cold spots could cause condensation mould on the ceiling or worse, condensation rot in the roof void. This is a possibility with any attempt at blown-in insulation.

The insulation may tend to settle and compact, so blown fibre may not be feasible. Which leaves polystyrene beads, but you can't have that in contact with electric cables. I don't know if vermiculite is still used.

But you may like to check with an installer.

Would a layer below the ceiling and new plaster board make it too low?