This is a new custom home in the final stages of being finished. Mostly just touch up, fixtures and a good clean up then the homeowner will be moving in.
He called my attention to high humidity levels inside the home. 62-65% RH
A little info about this project:
The AC system has been running for several months now. They have been very good at temporary filters and an inspection by myself last week verified the coils and other bits and pieces are clean.
It is a typical custom home we would see built in our area with workmanship say around 7 or 8 on a scale of 10. The building envelope too is a 7 or 8. Good air sealing, cellulose in the walls and attic. Encapsulated crawlspace with dedicated dehumidifier. Although I do have a supply and return off my HVAC system that is still in play.
Out system is located overhead in a vented attic space. Dark metal roof with techshield sheeting.
Attached is the floorplan of the home. I have it split into four zones: Master bedroom on the left, a main center zone kitchen, dinning, etc., a zone for the two kids bedrooms and a final zone for the bonus room up top.
Also attached is a log of how it performed last Friday. We had a typical warm Kentucky day; sunny with a high of about 90. I took a snapshot about every 10 minutes throughout the day. Note, I had to wrap the animated GIF inside a Microsoft Word document to upload it. The GIF should step through about 46 frames. If it doesn’t work let me know and I will try something else.
Please be aware I programmed a negative 5% offset on the humidity sensor to keep the homeowner from banging on me while I try to resolve this.
Sorry, I know this is a lot info but also keep in mind the ‘cool to dehumidify’ mode is active at the moment. Personally I would like to see that mode go away on thermostats, seems to cause more trouble than it helps. That is why you will see the actual zone temperatures a few degrees below setpoint.
One final thought then I will hit the post button. In the back of my head I think ‘maybe’ that 70 degree indoor temperature is causing a high RH. I haven’t tried setting to 75 degrees but just looking the psychrometric chart if I take that 70 deg air raise it up to 75 deg I drop the RH to around 52% or so.
Anyone want to throw some comments and thoughts at this?
Thanks,
Axis
log.docx