Insulation - Retrofit - Dormer House

delta1970

Hi all, firstly I have read a lot of the posts on this here on boards and there is excellent advice so I looking for some assistance with what’s is best and most economic for me.
I've just purchased a dormer house, which was built approx 12 - 13 years ago. Insulation in the walls is pumped polystyrene balls (white) - Believe it or not there was no insulation what so ever in the attic. As it’s a dormer house in the crawl space (storage area) there is 50mm of polystyrene board between the rafters running from the wall plate to the floor joists of the attic. Its rough enough and in a number of places its broken and lots of gaps. The roof consists of slates over black felt over 150mm rafters. The attic floor joists are 120mm. There is no insulation in the crawlspace floor, which is floored with osb. The stud walls, which separate the crawlspace and bedrooms have no insulation either. But there is a stapled multifoil sheeting stapled to the back of the stud wall. (possibly to assist with some form of air tightness as from reading about these products there is not great insulation)
So what I’m thinking of doing is earthwool (300mm min) into the attic space. Remove the multifoil from behind the stud walls in the crawl space and fill the stud walls with earthwool. Staple the multifoil back up to create some form of air tightness. Place eartwool between the 1st floor joists in the crawl space. Ok there is the sloping walls in the bedrooms, which only contain 50mm of polystyrene that is fitted badly in some areas. Do I remove this and try to fit something else instead. The roof trusses are not very evenly spaced so whatever I would fit down would all need to be cut to suit each location. Variations of up to 30mm between rafter. That is why I suspect the polystyrene may be so bad fitting in places, loose or being forced in and cracked and broken. I understand the need for airspace between the rafters so I've discounted the idea of spraying foam. I have attached a drawing of what I'm dealing with. Is placing the earthwool under the floor and at back of the stud wall in the crawlspace ok the way I suggest. So what can I do with the sloping space in the bedrooms? Any suggestions for good insulation and ease of installing. Thanks

gomamochi1

Same setup what did you do in the end?
I am thinking of ripping rigid board insulation 3 " thick sheets and expand foam them in then lapping counter clockwise in the rafters.
Then upgrading the floor insulation like you did too! Dormers are a pain!