Heating, Air Conditioning, Fridge, HVAC/High indoor humidity


The past few winters Ive been having a problem with moisture / condensation. We have lived in the house 15 years and as far as we can remember this is just in the past few years. Weve noticed condensation on the windows, pants growing mold. Our house is about 60 years, 1300 sq feet and we have a gas furnace.

 Yesterday I purchased a humidity gauge to measure what we had. Yesterdays (outdoor temperature) was close to 70 degrees with low humidity. When I came into the house the inside temp was about 73 degrees and the humidity was about 61%. Since it was a warm day the furnace did not come on all day. I went into the crawl space and found no signs of leaks (no standing water), the vents were all open and clear. I decided to open a couple of windows and watched as the humidity level quick fell to 51-53 %.  I closed the windows after a couple of hours and although the humidity level rose it stayed at 57% until we went to bed. We did not cook , my wife and I both took short showers and used the exhaust fan. Still the humidity level remained at 57%.

 This morning the first thing I did was check the meter, in the room weve had the most problems in the humidity was 67%, as I walked thru the house some areas were as much at 74%. This morning the outside temp is 57 degrees with 67% humidity. The only thing that changed over night was the furnace was been used.  

Ive read a lot lately about using exhaust fans, venting crawl space. Does the furnace make the air more humid?  Any thoughts would be very helpful.

Hi Frank, Have you replaced the furnace in the last few years? This time of year it is hard to control the humidity. The fact that the humidity is higher inside the house than outside is very unusual.I would do more searching around the house. If you can get me the model and serial number of the furnace that would help.

Running the furnace will reduce the humidity.

Heating, Air Conditioning, Fridge, HVAC

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Jim S.


I can answer questions on gas or electric furnaces, ac units and heat pumps. I don't work on boilers,chillers,or home appliances.


I have been in the HVAC trade for over 35 years. For the past 15 years I have owned my own business. I am semi-retired so I can answer questions in a timely manner.

I attended trade school for 5 years on weekends and evenings. This was very hard to do, but well worth it!

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