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Community and Q&A

Cold upstairs of home

pga1811 | Posted in GBA Pro Help on

Last July I purchased a brand new home that is supposed to be an energy efficient house.   The home is about 2400 sq ft and has two constant running bathroom fans.  Both of the fans are located on the upper level in the two bathrooms.  When the weather changed and it got cold the house had issues with the heating system.  The upstairs of the home was about 6 degrees cooler than the main level during the evening and at night.  During the day with when it is sunny it usually is only about a degree or two cooler in the upper level.  The builder has been out twice to review once with the HVAC contractor and once with the Energy auditing contractor.  Neither time could they offer any advice on how to correct the issue except that I should turn up the thermostat so upstairs gets to be a comfortable level the only issue there is than the main level is too hot.  The house has dampers for all the ducts on the main level and the have been adjust in all different positions with no luck.  The only other observation is as you walk up the stairs of the house when you get about 5 steps up (about ceiling level of main floor) you walk into a very cold spot that then continues upstairs.  Is it possible that the constant running exhaust fans are exhausting the warm air from upstairs out the roof and drawing cold air in through the vent holes in the windows and this air is stacking an preventing air flow between the two levels of the house.

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  1. Expert Member
    BILL WICHERS | | #1

    The fans will exhaust some of the warmest air since they’re on the upper level. My guess is those fans are basically operating in place of an HRV, which isn’t the most efficient way to bring in fresh air.

    I would do two, and maybe three things as follows:

    1 - Close the dampers on the upper level, and open the dampers on the lowest level. This will put heat into the colder lower level first and rely on convection to heat the upper level. You can adjust things to “dial it in”, but start with the upper level fully closed or near fully closed, and the lower level fully open.
    2 - set your thermostat to run the blower periodically, even without a call for heat, to help to even out the air temperatures a bit.
    3 - block lower level air returns and keep upper level returns open (this will help to balance air temperatures between the levels too).

    Make sure you don’t close off too many vents at once and cause issues with your furnace. This applies for both the supply vents and the returns.


    1. pga1811 | | #4

      Thanks Bill for the reply. Actually the colder level is the upstairs. The house is a two story with a basement. The furnace is located in the basement. The lower level ducts have dampers but there are two feeds that go upstairs with no dampers. There are two returns in the system one centrally located on the lower level and one centrally located in the upstairs. I have not tried closing all the vents upstairs and opening all the lower dampers rather the complete opposite it is certainly something I will try. The thermostat does have a circulate mode and this has been tried with very little change. Your third suggestion has been tried but I was told by the HVAC contractor not to obstruct the returns as this could damage the furnace. (By the way he is the one that told me to block the lower level to force heat upstairs).

      Thanks for the ideas and any other suggestions would be great.

  2. Expert Member
    Akos | | #2

    Sounds like you have some major air leaks somewhere above your first floor or some leaky duct work in the attic.

    This could be lack of air sealing if it is a 1 1/2 story construction, something with a lot of dormers or you have some 2nd story overhangs. I very often see trades trying to seal up these details by stuffing fluffy insulation in between overhanging joists. Fluffy insulation makes for a great air filter but does nothing for air sealing, all these details need to be sealed up properly with sheet goods and canned foam.

    The constantly running bath fans are also not helping things. You should check what flow they are rated for and if running them constantly is actually needed for the ventilation requirement of your place. A better option would be an H/ERV but that would be expensive to retrofit.

    You can try to see if this is the issue by disabling both bath fans. If the upstairs area gets significantly warmer, you have some major air leaks and you should consider replacing at least one of the bath fans with a pair of Lunos e2 to reduce the amount of cold air being drawn in.

    1. pga1811 | | #5

      Thanks Akos I will see if I can disable the fans and see what happens with the temperature upstairs. The builder did do a second blower door test which the gentleman told me showed that the house was well sealed. The only question I had for him is why he left the two constant running fans on while doing this test his response was they are part of the house.

  3. Expert Member

    A 2400 sf house should need about 100 cfm of continuous ventilation at the most. How big are those bathroom fans? They may be delivering twice that amount.

  4. pga1811 | | #6

    Malcolm I will check to see at what rate they run and also do a measurement of the CFM. Thanks for the link to the article.

  5. Nola_Sweats | | #7

    Is there a thermostat at the top of the stairs? Both houses I have owned had thermostats near the top of the stairs. So warm air would rise up the stairs and warm the thermostat, telling it that heat was not needed. Downstairs and the upstairs thermostat area would remain warm, while the bedrooms around that area stayed cold. NB: I had separate thermostats and heaters for the two floors.

    1. pga1811 | | #9


      There is one thermostat in the house and it is located on an interior wall between the lower level return and the stair case.

    2. pga1811 | | #10

      Peter here are some IR pictures I took

      1. Expert Member
        Akos | | #11

        Without the temperature scale it is hard to tell, but it sure doesn't look like "well sealed".

        In a well sealed house the walls are even and very close to room temperature.

  6. Expert Member
    Peter Engle | | #8

    It sounds like you've got cold air leaks, as mentioned above. It could be that, rather than leakage, you've got cold air running under/behind your insulation, chilling the drywall directly. An infrared camera scan would help to identify cold air leaks and insulation failures. Your energy auditor should have one. You might want to talk to an outside energy auditor - the builder and his guy are the ones who built it wrong in the first place. For this sort of IR scan, you need as much difference between indoors and outdoors as possible, 15 degrees or more is good. Now that Summer's coming, you might have to wait for Fall to get good imaging.

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