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Message
new house - humid upstairs
Posted on 8/17/20 at 5:16 pm
Posted on 8/17/20 at 5:16 pm
Background: We moved in the end of June. House has 3 bed/2ba upstairs, right under 1000 sf upstairs, 12 ft ceilings, 8 ft doors. Upstairs has a 1.5 ton unit. Typical blown-in insulation in attic.
Issue: upstairs has remained very humid since moving in. One water closet in particular had condensation on the walls (there was no a/c vent in this room with just a toiled in it). Contractor has been back several times, performed a humidity test to confirm our claims, added an A/C vent over this toilet (fixed the condensation), re-sealed all the vents in the attic, slowed the upstairs blower speed, checked the bathroom ventilation fans for back flow issues...and the shite is still 80-90% humidity during day and mid 70s at night per our smart thermostat. When you walk upstairs, you can feel the change in air.
I am about out of ideas as to where this moisture is coming from? I have damp-rip and a dehumidifier pulling a lot of water out the air and also put weather stripping on our attic door this weekend.
Issue: upstairs has remained very humid since moving in. One water closet in particular had condensation on the walls (there was no a/c vent in this room with just a toiled in it). Contractor has been back several times, performed a humidity test to confirm our claims, added an A/C vent over this toilet (fixed the condensation), re-sealed all the vents in the attic, slowed the upstairs blower speed, checked the bathroom ventilation fans for back flow issues...and the shite is still 80-90% humidity during day and mid 70s at night per our smart thermostat. When you walk upstairs, you can feel the change in air.
I am about out of ideas as to where this moisture is coming from? I have damp-rip and a dehumidifier pulling a lot of water out the air and also put weather stripping on our attic door this weekend.
5
Posted on 8/17/20 at 5:24 pm to man in the stadium
1.5 tons for 1k sf and 12’ ceilings with blown insulation sounds really undersized. Has a load calculation been performed?
This post was edited on 8/17/20 at 5:32 pm
Posted on 8/17/20 at 5:31 pm to wickowick
quote:
1.5 tons for 1k sf and 12’ ceilings with blown insulation sounds really undersized.
thats what i was thinking
Posted on 8/17/20 at 5:32 pm to man in the stadium
You’ll never remove humidity
Posted on 8/17/20 at 6:54 pm to wickowick
If it was undersized there wouldn't be a humidity issue.
Does the unit ever kick off during peak afternoon heat on hot days?
Does the unit ever kick off during peak afternoon heat on hot days?
Posted on 8/17/20 at 7:34 pm to man in the stadium
How many return vents on second floor, and their size? Air flow, or lack thereof, could an issue.
Can you measure the air temperature at both the return air vent/plenum and the supply grill closest to the air handler and post that here in your thread?
Also have they measured the refrigeratant charge in the HVAC and verified it’s within specifications? I know one would assume so, but one should not assume anything at this point.
Can you measure the air temperature at both the return air vent/plenum and the supply grill closest to the air handler and post that here in your thread?
Also have they measured the refrigeratant charge in the HVAC and verified it’s within specifications? I know one would assume so, but one should not assume anything at this point.
Posted on 8/17/20 at 8:19 pm to man in the stadium
I had this problem on my last house. It was solved by adjusting the settings on the air handler in the attic.
It comes from the factory set at the mid setting. For my application, it was set too high and did not run long enough to remove the excess humidity. The setting was changed to low and the problem was solved.
Try this.
It comes from the factory set at the mid setting. For my application, it was set too high and did not run long enough to remove the excess humidity. The setting was changed to low and the problem was solved.
Try this.
Posted on 8/18/20 at 7:59 am to ruzil
quote:
I had this problem on my last house. It was solved by adjusting the settings on the air handler in the attic.
It comes from the factory set at the mid setting. For my application, it was set too high and did not run long enough to remove the excess humidity. The setting was changed to low and the problem was solved.
Try this.
This is certainly something that should be looked into as well and is often the solution with over-sized HVACs that short-cycle, but if you currently have long run times of your AC In the afternoon, like running non-stop for most of the afternoon, in this current heat wave I wouldn’t think you’d be having the humidity issue you are describing if the equipment is functioning properly.
It may not be a single issue causing the high humidity issue but 2 or more issues working in concert with each other - an equipment issue, ducts (airflow) issue, outside air infiltration, etc.
Posted on 8/18/20 at 2:06 pm to man in the stadium
I assume single stage unit? How long does the unit run? Two stage and especially variable speed units are much better at removing humidity. If your unit isnt short cycling it sounds like humid attic air might be infiltrating the living space. Find someone that does blower door test in your area and they can help.
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