Results 1 to 6 of 6
  1. #1
    Join Date
    Mar 2019
    Posts
    4
    Post Likes

    Foam Insulation and Stat Settings

    Hello All!

    Long-time lurker of this site. Tons of great info on here. It has helped immensely in diagnosing some of the pitfalls in the design of my system. If only i knew then what i know now,...

    Here's some specs for y'all:

    New build 02/2018
    2 story
    2700 sq ft (1500 downstairs)
    3 ton Trane XR-16 single stage heat pump
    Trane Variable AH with 2 different zones. (downstairs and upstairs)
    Spray foam insulated walls and attic. Sealed attic, no vented soffits.

    I had serious humidity problems when i first moved in. We have mild winters in the Texas hill country and for my first two weeks after moving in the heat never came on. Had Airtron come out a solid half dozen times because of it and they said "that's just the way foam houses are". In hindsight they didn't set up the ventilation correctly and the valve wasn't actually opening. But that was discovered AFTER i dropped some serious coin on a Aprilaire 1850 dehum unit. That made a HUGE difference. My RH is a steady 40-50% now all the time, even when the heat or ac doesn't cycle for over a week.

    There's the backstory, here's my question:

    Does foam insulation negate the benefits of thermostat setbacks? Since it's so tight, would it be better to set it and forget it?

    Thankfully, our master is downstairs, so i've been keeping the upstairs set quite a bit higher. For example in the summer i set it at 81* while downstairs is at 75*. I know there are some "standards" for 2 story thermostat differentials but to me, logic says: "if no one is upstairs (no kids yet) then why would i cool it?".

    My thought process is probably flawed and I'm very open to your suggestions - thanks!

  2. #2
    Join Date
    Mar 2019
    Posts
    4
    Post Likes
    Thread Starter
    I think i need to move this to the AOP: Residential section

  3. #3
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    8,971
    Post Likes
    Sounds like a success story to me. Fresh air when occupied. Maintain <60%RH all the time. As you know low humidity make higher temperature possible.
    I am no sure more rules than that.
    Keep posted on you long term.
    When your dehu quits keep Ultra-Aire in mind.
    Well done.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  4. #4
    Join Date
    Mar 2019
    Posts
    4
    Post Likes
    Thread Starter
    Quote Originally Posted by teddy bear View Post
    Sounds like a success story to me. Fresh air when occupied. Maintain <60%RH all the time. As you know low humidity make higher temperature possible.
    I am no sure more rules than that.
    Keep posted on you long term.
    When your dehu quits keep Ultra-Aire in mind.
    Well done.
    Regards Teddy Bear
    Thanks Teddy! Yes, I have noticed that i can get away with a higher setpoint because of the low RH. The HVAC company my builder works with could only source Aprilaire products - believe me, I really wanted Ultra-Aire. Especially the SD12

  5. #5
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    16,991
    Post Likes
    Sounds like you’ve got it figured out.

    I’d just set it and forget it, your utility bills should be pretty low regardless since you’re basically living in a walk in cooler right?

    As long as humidity is in check via the dehumidifier then you can set it at whatever temp you like. Only problem I see is excessive wear and tear on the hvac system since it is zoned and will be running on an undersized duct system when one zone is calling more often.

  6. #6
    Join Date
    Jan 2004
    Location
    PA
    Posts
    77,029
    Post Likes
    Moved to AOP.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.