Will Convection Heat Help Banish Musty Smell? - February 23rd 2009
Convection heat can banish musty smell.
Q: We live in an older rancher (about 40 years old). When we go away for a few weeks, there is a musty smell in the house when we return. It is similar to going into a musty, unfinished basement. The house is on slab and the forced-air heating ducts travel from the furnace either under or in the slab. I can feel the rusted or degraded pieces of duct when I put my hand down as far a possible. We have had an environmental group do tests and there is not any mould.
I was wondering if there is anything to spray or somehow line these ducts? I suspect the smell is from warm/moist air on the cool damp concrete. We only seem to notice it when we have been away and there isn't much air moving in the house. If that is not an option, and I want to seal off all ducts and install electric heat, is there a product to seal them? I suppose there also is the possibility that the odour could be caused by leakage around toilet and bathtub bases and drains. Any help would be much appreciated.
A: The first indication of a moisture problem comes from the description that your home is on a slab. This indicates to me that when the home was built they could not get into the ground deep enough for reasons likely due to water and storm sewer system depth. This is not an unusual problem, especially in some areas of the Lower Mainland -- typically low and marshy areas. You can contact our HouseSmart office for a company that inspects duct systems to see if there is damage and/or deterioration using a cable camera that is inserted into the duct work. In answer to your question about whether the ducts can be lined, to my knowledge this type of process is not available; at least not yet. Perhaps one day someone will develop a system to line under slab or in slab heat duct pipes.
In the past we have sent a drainage company to service the drain tiles around the footings to eliminate the water affecting the under- slab area, thereby stopping water from entering your heating duct system.
You mentioned one choice that has been popular, and that is to convert to electric convection heaters, such as a Convectair unit that uses the current heat ducts for conduit to run wiring to the rooms from the main electric panel. The wiring enters the duct system where the furnace currently sits. After the system has been installed, I suggest plugging the holes with Roxul Rockwool insulation batts and capping off with Polyurethane foam.