So. As some might know I've been helping my sister do up her first house. (Bungalow) 1 large issue is, where a few of the windows are 50 years old, the wood is obviously rotten. The water has got in the cavity where the window sill has shrunk. It has the fluff style insulation that is now wet where the windows are. My thought was to remove it where wet when I take the windows out. After talking to a insulation pro, he said that you can't just remove some or you will get condensation. My next plan was to maybe replace what I remove with the polystyrene bead type ? My next thought was how would I stop the whole street not looking like a winter wonderland ? I made the house look like Santa's grotto just trying to fill a kids outside bean bag.
Your man is spot on, with that advice. What sort of windows are you fitting now ? Don’t leave gaps in the insulation or you will have serious cold spot issues because of the magnetic way that heat gravitates to cold spots. Easiest way on the proviso that it’s a total cavity fill is to cut out the damp stuff as squarely as you can and refill with dry cavity fibreglass insulation not loft insulation. Loft insulation was fine when it was all pumped in under pressure and may or may not be good enough depending on your cavity wall surface finish. If it’s a waterproof finish (render) you have a good shout. When you insert new insulation, you won’t be able to marry the new to the old so cut it as squarely as you can possibly with diagonal undercuts if possible to allow water passage. When filling use much thicker than required and compress before fitting using any mean’s possible including pieces of ply then dragging them out once fitted. If it’s a face brickwork property, the only thing that’ll help once fillled is Thompson’s or similar clear silicone to waterproof the exterior every five years or so or blue circle stabilisers then sandtex paint re mewed every four or five years. If it’s not a total fill but only a partial fill, disregard ^^^^ and run like hell. Ozziedog,,,,,,,,,, just kiddin
Old stuff is like wool. There would be no cutting it out. Hoover out the cavity was my plan. Refill with polystyrene bead type stuff
Ah , so you are replacing the windows , misread that. Lots of companies , 1970’s onwards pushed cavity insulation…beads or blown, claiming it was non - conductive/ impermeable to water. Turned out to be incorrect. Forgetting the problems of beads dropping below DPC level the damp came through via the brick ties ( assisted by the beads/insulation) and caused mayhem. Done loads of claims, seen the results etc. Even today with greatly increased cavity gaps it still relies a lot on focus, ie good brickies, properly inserted insulation etc. It’s a nightmare if done incorrectly. As an aside I once visited a seminar ( involved in claims at the time) The presenter had a bucket full of so called non osmotic ( whatever) polystyrene beads . He said they had been submerged for a few hours… picked up a handful and squeezed them out .. I was acting for a product insurance co at the time…..they paid out all claims
This is why I worry about insulating my non insulated house. I think the answer is insulate the inside or outside but not the cavity.
I’m sure they all come with downsides , but insulating a small cavity ( which may already be breached by tie wires, mortar from brickies not using trays etc) is IMO far more risky. My dad was a builder and I studied building and Civil Engineering to HND so not green. Two 1970’s large estates near where I live suffered shocking “ rising damp”. Local DPC contractors had a field day with their “ insurance backed” injection products. In brief I / we arranged for bricks to be taken out randomly in the first and second course above dpc. Surprise, surprise the whole cavity was filled randomly up to 12 “ above dpc with mortar, due to lazy/incompetent brickies. My house has 2inch kingspan internally, installed 12 years ago, no problem and toasty warm. . Read lots of opinions about risks of condensation etc but , as my walls were dry, no problems.
