Replies

1. 
   Jon_R | May 18, 2019 08:25pm | #1

   > Does this actually work?

   To meet code or to provide good ventilation to closed door bedrooms? Even many fully ducted systems don't provide the latter. But some people leave all interior doors open making distribution largely a non-issue.

1. 
   jdchess | May 18, 2019 09:57pm | #2

   Jon,

   I'm sure it meets code. The part I'm wondering about is the distribution and/or circulation of the fresh supply air. Seems like even with all interior doors open, it wouldn't be enough to provide hardly any fresh air at all to the bedrooms, unless of course they were directly beside the room where the ERV was located.

1. 
   Jon_R | May 18, 2019 11:01pm | #4

   Open doors move a lot of air. How much depends, but I got 60 and 137 CFM using two different methods. Whether this amount of mixing/exchange provides better or worse bedroom air quality than some much lower CFM delivered directly into a closed door bedroom depends on the specifics. At 20 CFM, the open door will almost certainly outperform.

   "it is clear on a qualitative basis that outside air was fairly well distributed when the doors were open" https://www.buildingscience.com/sites/default/files/migrate/pdf/CP-0802_Field_Test_Room_to_Room.pdf

2. Expert Member
   MALCOLM TAYLOR | May 18, 2019 10:05pm | #3

   Jason,

   As far as I know, the only ways to provide fresh air to bedrooms without ducts, are to either have spot ventilation (something like Lunos) in each room, or have exhaust-only ventilation located somewhere else, and passive fresh-air intakes in the bedrooms. The second option isn't very effective.

3. GBA Editor
   Martin Holladay | May 19, 2019 05:51am | #5

   Jason,
   Matt Risinger's approach probably complies with ASHRAE 62.2. That said, the members of the ASHRAE 62.2 committee have argued for years on the question of whether the standard should include a distribution requirement rather than simply an airflow rate requirement. As far as I know, ASHRAE 62.2 does not require fresh air distribution.

   The best-performing ventilation system will exceed minimum code requirements. I agree with you that installing a spot ventilation system in a laundry room isn't ideal.

4. 
   jdchess | May 19, 2019 10:41am | #6

   Martin and Malcolm,

   Thank you both for the input. What do you think about multiple spot ventilators vs fully ducted, such as one in the laundry room and one in the master bedroom?

1. Expert Member
   MALCOLM TAYLOR | May 19, 2019 10:43am | #7

   Jason,

   I have no direct experience with spot ventilation. From the feedback here people like them. The two downsides appear to be noise and cost.

5. 
   Peter Yost | May 22, 2019 09:10am | #8

   The best single proxy for indoor air quality and distribution in my book is CO2. An engineer for the Vermont Energy Investment Corp (which runs our utility energy program, Efficiency Vermont) has done quite a bit of testing of mechanical ventilation systems using a CO2 monitoring device (https://www.efficiencyvermont.com/Media/Default/docs/white-papers/efficiency-vermont-improving-ventilation-cold-climate-homes-white-paper.pdf ). In this study and in conversations I have had with Brian Just, and my own testing using a CO2 monitor: the distribution system is key, especially with doors closed but even with bedroom doors open, just not enough air movement to adequately distribute without dedicated distribution system.

   Also, not surprisingly, our Martin Holladay has a recent blog on ventilation in which he cites/discusses Just's study: https://www.greenbuildingadvisor.com/article/ensuring-fresh-air-in-bedrooms.

   Peter

1. 
   Jon_R | May 22, 2019 10:27am | #9

   Note that Fig 7B shows that open doors came very close to 1000 ppm - and they would have done better if the homes complied with ASHRAE 62.2 (as Risinger's build does).

   > not enough air movement to adequately distribute without dedicated distribution system.

   It's easy to show that many "best practice" dedicated distribution systems don't provide enough air movement either. For example, with 15 CFM to a closed door, 2 person bedroom, expect ~2000 ppm. Would take more than 30 CFM to beat the Fig 7B results.

   In my opinion, avoid code minimum ventilation and build some type of system that exceeds ASHRAE 62.1 (not just 62.2).