My neighbour built a dormer window and loft extension that went above
the height of my chimneys. Thier dormer is about five feet from our
chimney. We have two gas fires and the fumes are extracted via
chimneys. Now what is happening is that on the prevalling wind (SW)
the air is going over their roof and dormer and over our chimeny (as
the roof is now heigher) and causing a change in air pressure and
forcing the fumes back down our chimney. I found some information
about this issue a while ago which showed diagrams etc of what happens
to the air circulation and extraction and when a construction goes
above a chimney level. Does this come under building regs? Can anybody
point me in the right direction please or offer advice. Thanks.