Q. I value your opinion very much and need it for the debate that is presently going on with my parents. It is about how necessary it is to have a humidifier on the gas furnace in our house. They say it is not but I say it is as necessary as the furnace itself. We used to have one back in the 1970s and 80s. The house felt so much better in winter. That humidifier is still attached but not working because it just stopped working and needed too much maintenance. We now have problems with out sinuses an d dry eyes. It never seems to feel warm enough even though the thermostat is set at 75ºF. Are there humidifiers that don’t need as much maintenance and do we actually need one? Are they expensive to run and which one is best?

A.If you have been a long time reader of my column you may know that my relationship with duct-mounted whole-house humidifiers and me have been at odds historically. Sure, warm moist air feels better than warm dry air and you don’t spark when you reach f or a door knob. Folks do live in dry climates and when it comes to freezing I think the furnace is much more necessary than any humidifier, or combination thereof. As a builder, remodeler and then home inspector, I have encountered humidifiers in all s tates of malfunction and disrepair and have been aware of medical studies that date back to the early 1970’s documenting ailments then called “humidifier fever” long before such things as Legionnaires Disease ever came into the language. I have torn apa rt ductwork downstream of an old humidifier to find all sorts of wierd things growing in the ductwork perpetually hydrated by a malfunctioning humidifier. I have seen the undersides of roofs soaking wet during winter attributable to a humidifier pumping moisture into the household air-stream that ultimately migrated into the attic where it found the cool surface of the underside of the roof’s plywood to condense upon-- and cause mildew and rot. Even the best of the humidifier designs tend to ultimate ly succumb to mineral deposits from the water supply and leakage that goes unnoticed or repaired and the humidifier stops working-- probably as yours did.

When I wrote negatively about humidifiers during the early days of my column I got lots of angry mail from homeowners who claimed their humidifiers were purer than Caesar's wife and I was an idiot for attacking them. I tried to convince these gentle rea ders that my complaint really wasn’t with the humidifier itself but what happens three, five or ten feet down the ductwork where the humidified air encounters a metal surface that’s below the condensation temperature of the newly humidified air and depos its water on the metal surface inside the duct. Then along comes a living microbial, a bio-aerosol that lands there in the warm wet after some infected human or animal launches it into the air-stream via a cough or sneeze. Now this bug is in a real world petri dish and procreates and proliferates and makes those susceptible in the house sick or sicker. That was my complaint. Not surprisingly I received only one letter from a disgruntled humidifier purveyor who cited a study showing that they were just f ine-- funded by a humidifier manufacturer. Somewhat like those studies paid for by the tobacco companies in the 70s and 80s proving how harmless smoking was for us.

But after about 30 plus years of installing humidifiers on heating systems that were little more than, as one doctor said during an inspection when I pointed to the humidifier and said,”Do you know that is?” and he replied “A disease distribution system” , the industry has arrived at a partial solution. The solution is the addition of a UVC sanitizer light system that installs in the plenum-- the main ductwork by the furnace or heat pump air-handler-- and kills 99.9% of the living germs that fly past it. They cost about as much as the humidifier itself and the bulbs do need to be replaced from time to time but they are worth it. After doing that the thing you should be concerned about will be the quality of the water going to the humidifier itself to pr event the works from getting gummed up with minerals. There are all sorts and types of humidifiers out there but as long as you can control basic water quality and kill off the germs-- one’s good as the other. After installation they cost about as much as a couple of 60 watt light bulbs to operate and they only work when the furnace is on.