Room in Roof - Advice needed

[Energywise]

I have a Persimmon 2 1/2 storey 5-bed town house with the master suite being in the roof - as a room-in-the-roof.
This room has always seemed to be freezing cold in the winter and baking hot in the summer - rather odd I thought?
I removed one of the inspection panels to the roof void, after finding it was nailed in place despite removing the capped screws!
To my horror, I noticed that there was NO insulation whatsoever between the joists (ceiling of first floor) and nothing on the back of any of the room-in-roof walls...just plasterboard.
Consequently, cold air can travel in through soffit vents and immediately cool the plasterboard, which is usually cold to touch from the inside, especially on frosty nights!
They have put rafter insulation up (held in place with bowed strips of plasterboard!!!) but I believe this has absolutely zero benefit to us in the room at night! The Local Building Control checked the void above the RIR and made Persimmon put an extra layer of insulation over it to bring it to about 250mm. The pitched parts of the ceiling were reinsukated with Spantex or Celotex rigid foam but when this was installed, it pushed out the rafter insulation to leave it in heaps in the void areas! Duh!
So, I have asked Persimmon to return and insulate the joists and plasterboard rears....thy said no, they would only do what was the original spec and that was rafter insulation.
My point is tha the original house designs can't have met design approval as the RIR would always be cold with that arrangement.
Am I correct in my thoughts on this?? The house was built in 2003 and Persimmon are saying it met regulations at that time. I think regaulations would have stated to insulate the joists and plasterboard (with possibly a vapour barrier).
Can anyone clarify what the regs would have stated in 2003 and do I have a case to complain???
Thanks for your help with this.
Peter

[willyj]

Hi

There are 2 acceptable ways to insulate a roof both of which conform to current and previous Building Regulations:-

1. Lay the insulation over the ceiling joists ('cold roof') so the roof space is unheated.

2. Fix the insulation to the roof rafters ('warm roof') in which the roof space becomes part of the heated area of the house.

From your description it is apparent that you have the second form of construction which would be the norm for a house with a room in the roof. The roof does need ventilation but in both 'cold roof' and 'warm roof' construction the ventilation should be provided above the level of the insulation.

In your case there should be a gap between the top of the insulation board in the rafters and the underside of the roofing felt (or vapour permeable underlay these days )and it is that gap that should be ventilated. The insulation in the rafters should overlap with the insulation in the walls at roof plate level, to effectively seal the warm roof space and prevent air leakage.

Quite clearly in your case the soffit vents have introduced air leakage in to a heated part of your house, so while the form of construction used complies with The Building Regulations Part L, the way in which it has been executed does not.

This is a fundamental error by the builder and the easy fix would be to do as you say and insulate the ceiling joists and dwarf walls of the room in the roof.

Hope this is clear:unsure: