Last few weeks are experiencing a very strong mildew smell in home. We have a water source furnace. (The furnace fan runs continuously throughout the year.) We have a dehumidifying system in basement. We have sump pump that runs year round. Odour is so strong on entering house that we blocked off register at entrance last week as it seemed to be blowing out the smell. I lifted furnace last week and put it on blocks so that air could circulate under as odour was noticeably strong near floor in furnace room. I have even removed old insulation in the furnace. We have never had this problem before.
Answer:
Your problem has more to do with ventilation than anything else. As long as there is moisture, in whatever form, down there you'll get the mildew odour.
