Poor insulation above dormer windows and slanted ceilings in bedroom

Turner

House built 2011, ber B3 with pumped cavity wall insulation. 5 bed two story dormer.

Three bedrooms upstairs have dormer windows and slanty ceilings with about foot and a half between bedroom ceiling and roof tiles.

These bedrooms are always colder than the others, significantly colder.

We drilled a peep hole in one of these slanty bedroom ceilings. There is insulation alright but it is not packed tight. The standard yellow roll insulation. And a serious breeze came through the hole.

Above the flat drywall area above the windows there is a 5 inch gap before you hit the insulation, and again a serious breeze coming through the small view hole we drilled.

What are the options for fully insulating this area? There is no attic above obviously. We want to pack it to insulate against the cool breeze thats obviously right behind the dry wall ceiling.

Is it possible to cut out sections of the dry wall ceiling and pack the area tight with insulation? And then replace the dry wall, slab it in and sand and paint etc.

Or is there a way of pumping insulation in?

Any ideas appreciated or recommendations of people to do it.

Baymax2020

You're not supposed to pack your rafters tight with Insulation rafters need to be able to breath. I'm not sure if your budget would allow but best option would be to strip the slabs down and put in 100mm rigid insulation in between your rafters, use an airtight membrane and reslab with an insulated board. There will be a bit of cost and labour involved but there will be a long term gain for comfort and will save on heating costs. Another area where a draft might be getting in is if you have access doors to allow you into the crawl space behind the walls upstairs and it's not sealed properly with draft excluders.

Lumen

Turner, you're conflating insulation and air tightness.

Both are important but you shouldn't try to achieve AT with insulation products because for the most part things which are good insulators have lots of holes in them.

There are probably tens of threads on this subject, maybe start by searching for dormer air tightness in this and the Construction & Planning forum.

Turner

Thanks for the replies.

I just think what's there is wrong.

If I work from the roof tiles to the bedroom ceiling, it goes as follows.

Rooftiles-felt-rockwool insulation-6 inch air gap-plastic membrane-ceiling plasterboard.

When i drilled through this ceiling plasterboard (for a look) the cold wind coming in through this hole is strong and constant and increases with the wind outside. So it is cooling the ceiling plasterboard all the time.

Surely it should be, roof tiles-felt-air gap-insulation-ceiling board.

Do i need to take down the slanted part of the ceiling and replace it with insulated plasterboard?

The horizontal ceiling (where the light hangs from) has attic above it with about 2 foot of insulation behind it.

MicktheMan

Turner wrote: »

Surely it should be, roof tiles-felt-air gap-insulation-ceiling board.

Do i need to take down the slanted part of the ceiling and replace it with insulated plasterboard?

The horizontal ceiling (where the light hangs from) has attic above it with about 2 foot of insulation behind it.

You're correct in that insulation needs to be in contact with what it's supposed to be insulating.
The reason you are noticing the air movement is because there is no airtight barrier present.
Tip: Dormers are notorious for air leakage due to lack of airtight barrier regardless of how well, or not, they're insulated.