Sealing my attic.

bren11

I hope this post is in the correct forum, if not mods, feel free to move. My house is a semidetached with a hipped roof. That means that I have rafters on a wallplate on 3 sides. That means where rafters run down to back of facia/soffit there is gaps where cold air enters attic. There is positive pressure here where this cold air is forced down into house through attic door, conduit down to light switches, and through ceilings at the light pendant roses, and under skirting boards where cold air is forced down behind plaster board, in bedrooms. Attic is only used for storage, and is insulated between and across joists with approx 200mm of rockwool. In the centre is a insulated deckboard area for storage. I know i need some ventilation, but could i block up some of these gaps with a rigid insulation between joists,on top of wallplate say leaving every 4th one open. Roof is tiled with a black felt. Walls are cavity blocks, with a 2inch insulated gap, and foilbacked plaster board. The ventillation to rooms was a hole in plasterboard, with external grill on wall, and sometimes not in line. I used expanding foam to seal draft from attic, and then cut approx a 3 x 3 inch hole between internal and external grills. This has reduced drafts from attic. Also can these cavity block walls be pumped.
Thanks in advance for your help.

tinca

you could run your rockwool right the way across the wallplate and out to the eaves but instead of leaving every fourth space free (which will still allow air into the cavity and around the perimeter of the house), insert a piece of 1 or 2" diameter pipe through the rockwool so that this allows for ventilation from the soffit into the attic but isolates it away from the wall plate... if you get me!