Wondering about ERV bang for buck vs. whole house dehumidifier.
Am owner of new build in-progress in hot-humid Austin TX. Contractors spec’d heat pump at first (Carrier Inifinity 25VNA8, 5-stage compressor), with no fresh air intake or separate dehumid. Leading up to build I’ve learned more about dedicated whole house (WH) dehumid, and fresh air intake (besides windows – we love fresh air & open windows below low 80s F).
Contractors mean well & orig. spec was typical practice, but I’m asking to raise the bar. Will pay fairly for that, but don’t want to throw money away either.
They now recommend upgrade to Carrier Greenspeed Infinity (VRF) saying AC will remove enough moisture most of year so no need for WH dehumid. Also they’re concerned about “unintended consequences” adding WH dehumidifier. They recommend Carrier ERV for fresh air.
I decided to go ahead with WH dehumid – tried arguing opposite side with myself, perhaps add later, but devil’s advocate falls short. Rather than keep wondering “what if” and wait a season to get data, do it right from the start. Am not comfortable differing with contractor’s experience either though. (Thought: maybe they never installed WH dehumid – will ask).
Finally the questions:
Q1) Is it worth adding ERV to heat pump/AC with ventilating WH dehumid?
Example Ultra-Aire 70H. It can bring in fresh air, but won’t exchange latent heat & humidity. I do want to "build tight, ventilate right." What about no ERV, just ventilating dehumid + AC?
Q2) Thoughts on saving a little $ - downgrade compressor from Infinity Greenspeed VRF to Inf. 5-stage - if use Ultra Aire dehumid? Pro / con?
Q3) New plan is for 5-ton greenspeed. Does 5-ton seem high?
Worried about short run time, low dehumid. Am told manual J showed a little over 4-ton and they rounded up, partly for heat if had house dehumid…. Hmmm. I said I don’t mind taking an hour to reach temp.
Have more questions but don’t want to overwhelm.
Have read many posts here - great site!
Thanks for your advice.
=== Background info ===
1) 1850 sqft, 3-bed, spray foam 2x4 walls with Zip R-panel & hardiboard. HVAC in spray foamed space below roof (not hot attic).
2) Two-story. Carrier zone control for up vs. down.
3) Minimal windows on hottest sides of house, porch shades SWest. Metal roof.
4) Leaks: Gen. contractor is onboard to seal all big enclosure holes, foam touch-up small holes.
5) Flex-duct. Not my favorite but didn’t put metal ducting in spec or budget early. Working with contractor to add ‘flex-right’ at 90deg bends, support sags, remove kinks. No returns in bed rooms (door gaps only).
6) We (occupants) use AC less than many in Austin. Typical 82F in separate condo even w/o dehumid (but system is old so it runs long enough to dry in summer). We tolerate high humid & windows open early & late summer, but would love ~50-55% rel. humid house to be comfortable, healthy, etc. Esp. when it’s humid out but not hot enough for long AC time.
7) I grew-up in Madison, WI. Stars must be lining up with Ultra-aire coming from Madison!!
8) Recent podcast clinched my WH dehumid. decision: positive energy interview with Teddy Bear – great voice of experience. Podcast: "Faster Horses" & The Future Of HVAC
=======
Am owner of new build in-progress in hot-humid Austin TX. Contractors spec’d heat pump at first (Carrier Inifinity 25VNA8, 5-stage compressor), with no fresh air intake or separate dehumid. Leading up to build I’ve learned more about dedicated whole house (WH) dehumid, and fresh air intake (besides windows – we love fresh air & open windows below low 80s F).
Contractors mean well & orig. spec was typical practice, but I’m asking to raise the bar. Will pay fairly for that, but don’t want to throw money away either.
They now recommend upgrade to Carrier Greenspeed Infinity (VRF) saying AC will remove enough moisture most of year so no need for WH dehumid. Also they’re concerned about “unintended consequences” adding WH dehumidifier. They recommend Carrier ERV for fresh air.
I decided to go ahead with WH dehumid – tried arguing opposite side with myself, perhaps add later, but devil’s advocate falls short. Rather than keep wondering “what if” and wait a season to get data, do it right from the start. Am not comfortable differing with contractor’s experience either though. (Thought: maybe they never installed WH dehumid – will ask).
Finally the questions:
Q1) Is it worth adding ERV to heat pump/AC with ventilating WH dehumid?
Example Ultra-Aire 70H. It can bring in fresh air, but won’t exchange latent heat & humidity. I do want to "build tight, ventilate right." What about no ERV, just ventilating dehumid + AC?
Q2) Thoughts on saving a little $ - downgrade compressor from Infinity Greenspeed VRF to Inf. 5-stage - if use Ultra Aire dehumid? Pro / con?
Q3) New plan is for 5-ton greenspeed. Does 5-ton seem high?
Worried about short run time, low dehumid. Am told manual J showed a little over 4-ton and they rounded up, partly for heat if had house dehumid…. Hmmm. I said I don’t mind taking an hour to reach temp.
Have more questions but don’t want to overwhelm.
Have read many posts here - great site!
Thanks for your advice.
=== Background info ===
1) 1850 sqft, 3-bed, spray foam 2x4 walls with Zip R-panel & hardiboard. HVAC in spray foamed space below roof (not hot attic).
2) Two-story. Carrier zone control for up vs. down.
3) Minimal windows on hottest sides of house, porch shades SWest. Metal roof.
4) Leaks: Gen. contractor is onboard to seal all big enclosure holes, foam touch-up small holes.
5) Flex-duct. Not my favorite but didn’t put metal ducting in spec or budget early. Working with contractor to add ‘flex-right’ at 90deg bends, support sags, remove kinks. No returns in bed rooms (door gaps only).
6) We (occupants) use AC less than many in Austin. Typical 82F in separate condo even w/o dehumid (but system is old so it runs long enough to dry in summer). We tolerate high humid & windows open early & late summer, but would love ~50-55% rel. humid house to be comfortable, healthy, etc. Esp. when it’s humid out but not hot enough for long AC time.
7) I grew-up in Madison, WI. Stars must be lining up with Ultra-aire coming from Madison!!
8) Recent podcast clinched my WH dehumid. decision: positive energy interview with Teddy Bear – great voice of experience. Podcast: "Faster Horses" & The Future Of HVAC
=======
source https://hvac-talk.com/vbb/showthread.php?2223320-ERV-vs-Ultra-Aire-house-dehumidifier-in-Austin-TX&goto=newpost
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