Our house originally had eight fireplaces but six are long gone so we had the chimneys capped with mushroom shaped vents. However there are still two fireplaces which we don't use but don't want to permanently disable for future owners. I was thus searching for some sort of cap thay would sit on an existing chimney pot securely enough not to blow off so protecting it from rain but providing a little ventilation.
But I can't find one. Does such a thing exist ?