I just purchased a new home in the suburbs of Boston with move in date of November 2017. The home has felt unusually drafty and cold and i've had to increase the heat about 4 degrees above what I usually use. Ordinarily i'm comfortable at 68 but in this house the heat needs to be at 72 for equivalent comfort. In addition to feeling a bit uncomfortable, it has been very dry inside the home for the past 2 weeks. I purchased 2 ThermPro Hygrometers and they have consistently read 10-13 RH for the past 2 weeks. Right now it is 5 degrees outside and the RH is measured at 11% both upstairs and downstairs.
We have 2 exhaust fans that appear to run 24/7. They are both located in bathrooms on each floor. I removed the vent cover and there is a switch that reads they are both operating at 110CFM. This means total venting is 220CFM? Curiously, in our home energy audit packet we received it says the mechanical ventilation rate is 145CFM. I wonder why the difference?
I tried turning both exhaust fans to 50CFM for a total of 100CFM and the home seems a little more comfortable but the very low humidity hasn't changed. These fans are running ALL the time. The wall switch will not turn them off.
I'm worried that even at 100CFM the house is being over ventilated causing cold air to be pulled into the house through the building envelope and exhausting warm moist air too quickly causing the house to dry out. I'm also worried about the opposite problem in the summer - too much humid air being pulled into the house.
Here are the specs on the home:
Basic stats of home: - 2700sq feet - unfinished attic + basement - spray foam in attic + basement - fiberglass batt in exterior walls - forced hot air heat. Dual zone w/ furnaces in Basement and Attic - 8 foot ceilings.
Info from energy audit - Infiltration rate: Htg 688 Clg: 688 CFM50 - Method: blower door test
From 2016 IECC r-406 Confirmed Energy Index Report - R402.4 - Envelope air leakage maximum leakage rate: (3 ACH50 for CZ3-8) PASS
Are indoor RH levels of 10-15% in winter months unusual for a cold climate like Boston?
Could my home be over ventilated?