GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Confused about ventilation: balanced vs. exhaust-only vs. ERV vs HRV etc.

DavidDrake | Posted in Energy Efficiency and Durability on

Hello all,
I believe I’ve read most of the article on GBA concerning ventilation and am still somewhat confused about which strategy makes most sense for my project.

Project is detached ADU, studio and single car garage on ground floor, with 600 SF apartment above. Located in climate zone 5 (N. Idaho), 6900 HDD, R40-ish walls, R60 roof, R20 under the slab. Aiming for airtightness of ≤1 ACH. Dried in last year, plan to have ready for occupancy by this fall.

ADU is all electric, with 2000W of baseboard heating in the upstairs apartment, and another 1000W in the studio. I plan to install a PV array next year that should meet all electrical needs for the building.

My budget for the project has been relatively modest, and I expect construction costs to ultimately be in the $100-125/SF range (I’ve been doing a lot of the labor myself). Keeping costs low has involved a lot of ‘pretty good’ rather than ‘best’ thinking; for example: buying decent double pane casement windows (~U 0.25), and putting the savings toward more insulation and PV. 

From what I’ve read here, given the scale of the project and my approach so far, there doesn’t seem to be a compelling argument for either HRV or ERV. The expense, in particular, seems difficult to justify.

The system described in Michael Chandler’s blog post “Exhaust Only Ventilation Systems” is attractive for it’s simplicity and cost, and I’ve been happy with Panasonic Whisper series fans I’ve installed in the main house. However, I realize the post is from 2010, and may be outdated.

Is a similar approach possible, perhaps using two Panasonic fans, one for exhaust and one for intake? Or is exhaust-only (with or without passive intake vents) still considered a viable option?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. user-2310254 | | #1


    A Panasonic WhisperComfort spot ERV would probably be sufficient and only require one wall penetration. It would probably be better than exhaust-only ventilation in conserving energy and preventing the interior air from becoming too dry during the winter.

    1. charlie_sullivan | | #2

      With exhaust only you rest drawing air from the garage. So I think Steve's suggestion is the way to go for that reason as well as the reasons he gives.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |