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Community and Q&A

HVAC planning for central TX

Merlin M | Posted in Mechanicals on

We’re in the planning stages for two 4000 ft^2 SFRs in central Texas (between Austin & San Antonio). It’s a cooling-dominated hot and humid climate. Air-sealing and insulation will be well beyond code. 

Wants for both structures include VFR-based systems, ERVs for fresh air, and supplemental dehumidification.

Questions:

Would ducted systems be best? Thinking of AC-provided humidity control provided by the AC during the cooling system and then the dehumidifier during the shoulder seasons.  

Could one duct system be used for heat/cooling + ERV + dehumidifier? Or, would a separate duct system for the ERV be advised? 

Thanks for thoughts and opinions.

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Replies

  1. Daniel Powell | | #1

    Most of the examples I have seen for an ERV have their own duct system. I would think it to be difficult for the erv to push fresh air into the Hvac duct work while the Hvac is running so you may not get as much fresh air into the house as you had planned. My dehumidifier manual show the first option is to duct it into the Hvac supply however. Good luck.

  2. Jon R | | #2

    > one duct system be used for heat/cooling + ERV + dehumidifier

    There are a variety of issues which make any sharing of ducts difficult to do right. If you do, use a self-balancing ERV (like the Panasonic Intelli Balance).

  3. Merlin M | | #3

    Thanks Daniel & Jon. When we've done ERVs, it's always been with a dedicated ducting system. ERV ducting is smaller (in diameter) than what the HVAC would use. Using the same ducts would also preclude the balancing feature as well.

  4. Walter Ahlgrim | | #4

    The first thing to do in Texas is to keep all your ductwork and equipment inside the conditioned space. Do not be a lemming and jump off the cliff just because that is how we build houses in Texas.

    You may find Matt Risinger YouTube channel interesting as he is in Texas and see how he deals with your conditions.
    https://www.youtube.com/channel/UCFCTrfb1JUJjs3Im8OZDtBw

    I am not sold on every house needs an EVR system. Unless there I see a blower test under 1 ACH50 and a population over 1 person per thousand square feet I do not see the point, from I need an EVR to provide fresh breathable air point of view. From I need an ERV to remove the excess moisture point of view. I doubt in Texas an EVR will remove any moisture from the house on most days as the air in the house is dryer than the outdoor air the EVR will bring into the house. From I need an ERV to recover the energy from the exhaust point of view on the worst day it may be 115° outside and 80° inside with a difference of 35° and many days it will be close to zero in Texas. Seems like small potatoes given the costs.

    Walta

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