Dormer roof/bedroom insulation/air leak issues.

Jeepers_Creepers

paulcam said:

A red heron indeed. :-)

Ok, that orange rectangle is a flat ceiling over the bedroom? Cool. That probably explains why it was easy to insulate. Is there a loft hatch to it? It also explains why they couldn't add insulation to the lower section, outlined in blue - it slopes and there's no access. That's fine. 

Two approaches to getting your bedroom warmer; one is to get in to the lower void and insulate the walls from behind and, whilst you are at it, insulate the ceiling of the rooms below - the hallway and that front room.

The other method is to line the bedroom walls with insulated plasterboard. I can tell you that even the thinnest - which is only around 35mm total thickness (20mm polyurethane foam and 9.5mm p'board - will make a huge and noticeable difference, but going a bit thicker will obviously be better.

Then find and block off all sources of draught! Do this regardless - there should NOT be draughts coming in to that room other than via an open window...

The first method is better - it means no work or mess inside the bedroom other than the access panel through the wall, and it also allows you to insulate part of the ceiling below. 

I think that's worth a try. You could just make a small hatch first - enough to stick yer head and a torch through - before judging whether to go further. 

Jeepers_Creepers

paulcam said:

reading back through those posts it seems they may have been referring to the flat roof alone getting completely sealed up and thus rotting the rafters/joists in the roof... not the dormer itself.  S

Yes, that does make sense; flat roofs are of two types, 'warm' and 'cold'. Unless the sandwich of boards and insulation are literally sealed tight to prevent moisture from penetrating them (and possibly condensing out, causing the risk of rot as you say) then they need to be ventilated instead to keep them dry.

However, this has nothing to do with the room below - in this case a the bedroom. If the dormer's roof has been built properly, then it'll be fine. If it hasn't, then it might develop problems over time - or it might not. But this has nothing to do with vent gaps in the actual bedroom - the bedroom should be draught-free and cosy.

In case the flat roof has not been insulted very well - which seems pretty likely - I personally would want to add a layer of insulated p'board to its underside. I'd go for the thinnest - 35mm - so as not to lower the ceiling height further, and this will make a huge difference. 

Sheets are simply cut to fit neatly and screwed with the right length of p'board screws (70+mm-ish) through the existing ceiling and in to the joists above (which, of course, you'll need to locate). Tape-and-skim or tape-and-fill if DIYing. Seal any gaps in the perimeter using foam. 

Is the dormer ceiling the exact same height as the rest of the bedroom? 

Finally check fro draughts at floor level, usually from under the skirtings. I presume it's a chipboard floor, so that should be air-tight. Use anything to seal gaps under the skirting - cartridges of sealant (eg 'Frame' sealant is cheap and will do the job), or strips of draught-excluder foam pushed in using a filling knife. 

Petriix

Modern flat roofs *should* be warm. A lot of builders seem to be stuck in the 90s but it makes so much more sense to create a solid slab of insulation with no thermal bridging and no danger of moist air meeting a cold surface.

The inside of the loft room should be fully insulated and completely sealed from cold air getting in and moist, warm air getting to the timbers. If it was built recently then the builder has been negligent. It certainly doesn't meet current regs.

Le_Kirk

paulcam said:

Sorry to spam, but... the sill might be a red heron caused by my assumptions.  

Well at least it won't be anything fishy as it should be a red herring!

Jeepers_Creepers

Nope - Paul was right.

(I really spend too much time on here)

paulcam

Yea the bedroom ceiling is the same height as the dormer throughout and goes back to the chimney, the rear of the upstairs has 2 more "bedrooms" and a bathroom.  The only access hatch is into the upper peaked section.

The floor is tongue and grove, but I don't know how many times it's been lifted.

The right side of the roof which slopes is literally the stairway ceiling and it's cold to touch, a candidate for insulated plasterboard I think.

I think I'll call a local insulation company and get a quote to add the rear side insulation on the bedroom stud wall under the window, hopefully there is enough space to crawl right access in there.  They should have access to seal off the downstairs ceiling/bedroom floor space as well.  Maybe they can leave an access hatch in the wall.

I still think opening up the ventilated slates in the top roof has made things worse than they were.  I walked in there earlier, about 2 hours after I got up and it felt like walking out side.  The sound of the street outside very clear and a cold wind blew past me out the door.  Something is wide open to the outside and I can't see anything other than that gap in the sill.  It does sound like a window it open.  I might just see if I can run a bead of silicon down it as contractors seem to have a long wait list at the minute.

Jeepers_Creepers

paulcam said:

I still think opening up the ventilated slates in the top roof has made things worse than they were.  I walked in there earlier, about 2 hours after I got up and it felt like walking out side.  The sound of the street outside very clear and a cold wind blew past me out the door.  Something is wide open to the outside and I can't see anything other than that gap in the sill.  It does sound like a window it open.  I might just see if I can run a bead of silicon down it as contractors seem to have a long wait list at the minute.

It's important that the roof voids are well ventilated, so the addition of vent slates was good; the draughty bedroom is a completely separate issue.

The main bedroom ceiling - with the pitched roof above it - has loft insulation on top, then? So the only part you don't know whether it's insulated is the flat dormer roof? It's a hard one to call, but do you think there is insulation in that flat roof? Is it stone cold freezing to touch? Does mould form on any part of it?

If you were to add insulated p'board to that part of the ceiling, then you'd either have to continue it across the whole ceiling, or else have a step at the dormer. Your call - but it isn't actually unusual to have a step there. 

By all means seal up that sill gap as a temp measure, but really the sill needs removing as part of the larger job and insulation put down there.

Simplest way to draught-proof the floor is to cover it with insulated sheets such as - for example - low-density fibreboards you can get for under some laminate flooring (I got some from Wickes - it was 6 or 8mm thick). Glue them down right on to the floorboards so's they don't move, and seal between each staggered sheet using frame sealant. Importantly, also seal them against the skirting boards. That will stop all draughts and add a useful further layer of insulation. There are probably other systems too - rolls of foil blanket, etc.

That leaves the walls - where you can, insulate them from behind. Where you cannot - and if they really don't have any insulation in them - add insulted p'board. Very effective stuff. 

You clearly have a major issue in that room! It should be a sealed, insulated box and not be affected by the cold roof voids.