i am doing the bedroom up , have ended up having to remove all the plaster on the window wall , on the inside skin of bricks there is a wooden lintel across the length of the window opening , then the cavity then the outside skin of bricks on the window . Can I shove some loft insulation between the wood lintel and the bricks ? I have cavity wall insulation but there is none in this part of the cavity, will it cause any problems?