Comments on: 4 Ways to Do Balanced Ventilation

By: Gaetan

Gaetan — Sat, 17 Oct 2020 10:17:04 +0000

I am putting my hrv unit in a
I am putting my hrv unit in a heated crawlspace my outside vent will be only 8 " off ground i know it is suppose to be 18" is there any person had that problem? I there a snorkel kit a can build on they outside of wall to bring it higher?

By: JJ

JJ — Wed, 05 Aug 2020 17:24:57 +0000

Allison, first time poster of
Allison, first time poster of comments, but been a longtime lurker of your excellent posts. I was wondering if you could share some results/thoughts/experiences with the CERV and/or Minotair units. Perhaps something to consider for a future blog post :)

By: John Dobmeyer

John Dobmeyer — Wed, 04 Sep 2019 02:15:09 +0000

I am using the ERV for
I am using the ERV for bathroom ventilation. I am using the manufacturer wall timers 20/40/60 minute. The ERV allows me to pull the air out of the the toilet room, the bathroom and Laundry room. The problem I am having now is one of the municipalities is wanting proof that installation is ICC approved in place of the traditional bath fans. The reason I use the ERV in encapsulation is to prevent migration of humidity from the outside down into the living space. At this point I cannot find any manufacturer literature for the ICC approval.

By: Yuri Sagdatov

Yuri Sagdatov — Thu, 04 Apr 2019 14:29:53 +0000

Im a design+build firm just
Im a design+build firm just outside Washington DC. We utilize ERV’s but Ive found we have consistant humidity issues in slack spring/fall months and in summer. In response Im going to try your “3a” approach. One question in regards to the ERV + exhaust fan approach. How is this balanced? In a super tight house, the ERV will bring in and exhaust but in conjunction with this the exhaust fans are exhausting – still creating the “suck”. Or in the case of a tight house simply not working correctly.

By: Clay

Clay — Wed, 08 Aug 2018 16:08:10 +0000

Thanks for posting this
Thanks for posting this article. I have built a home with an exhaust only ventilation design (using WhisperGreen bath fans), but the house has turned out to be too tight for this to work like I planned. I am now looking to retrofit a #3 strategy. I have full basement access, so I plan to mount the fan there and run ducts as needed. I also have a far bedroom that gets a bit stuffy. We are using ductless minisplits and the air isn't getting down to that room when there are occupants. Can I run a duct out of that room and add that to the duct coming in from outside (before the fan) to use the fan to circulate a little air, or would that not provide enough circulation to make a difference?

By: abailes

abailes — Wed, 01 Nov 2017 14:25:34 +0000

In reply to Jay. That's a great question, Jay.

That's a great question, Jay. In the early days of green building, that was a common way to add mechanical ventilation to a home. Now it's not allowed by most green building and energy efficiency programs because of the the problems with doing it that way:

You have no control over how much you're ventilating. With most systems being oversized, you may not get enough air even in the really hot and cold parts of the year. When the weather is mild, you may get little to none that way.
A duct to the outdoors with no damper in the run is really just duct leakage.
When the system isn't running, that duct adds to a home's infiltration.

I wrote an article about this topic three years ago. Here's the link:

Why Is This Obsolete Supply-Only Ventilation Method Still Used?

By: Jay

Jay — Wed, 01 Nov 2017 14:05:38 +0000

Would there be any issue with
Would there be any issue with just adding a small duct from outside connected to the air return so that whenever the air comes on it sucks in some from outside? That way it would pass through the whole house filter and the coil to control pollen and humidity. Is there something I'm missing that would make this a bad idea?

By: Wayne Dean

Wayne Dean — Tue, 19 Sep 2017 11:54:53 +0000

It seems that there are
It seems that there are considerable new reports from recognized authorities relating Alzheimer’s to exposure to PM2.5 exposure.
Google Alzheimer’s and PM2.5
For a video demonstrating installation, see https://www.youtube.com/watch?v=qn7NKRuGVlg
All controllers described in the earlier comment are available.
A prototype controller automatically and dynamically adjusting air delivery rates is expected to be in production soon. It incorporates a PIR occupancy sensor with push button selectable delay off of 8, 24, or 60 hours. It also includes a RH controller that will temporarily terminate operation in the event indoor relative humidity goes above an adjustable 50% to 60% upper limit. Integral Carbon Dioxide, VOC, temperature and RH controllers reveal present exposures on screen and may be easily set to control air delivery rates, 0-70 cfm.
Certainly not perfection, but an immediately available fresh air system with considerable benefits and that can be installed quickly with little trauma or expense.

By: David Schreiber

David Schreiber — Mon, 18 Sep 2017 00:16:29 +0000

That's pretty scary. What is
That's pretty scary. What is the technology you speak of that would solve this problem?

By: Wayne Dean

Wayne Dean — Sun, 17 Sep 2017 20:49:48 +0000

There is an easy, quick way
There is an easy, quick way to provide precise amounts/rates of fresh air that has been cleaned by a MERV 14-15 filter and is delivered in amounts appropriate to the actual number of occupants, automatically. An installation can be completed through an exterior wall from indoors in two hours or less and does not require any restoration, even with faux finish and custom papered walls. No outdoor access necessary. (A skilled installer can complete the installation in and out the door in less than one hour.) A CO2 controller can automatically and precisely adjust fan speed/air delivery rate for the number of occupants and to maintain indoor carbon dioxide levels of 600 ppm, which is the level recommended by LBNL and HSPH to provide substantially increased cognitive function and improved sleep. Google: LBNL and HSPH cognitive function CO2. It is my belief that most ventilation systems are grossly underrated and will deliver a much greater heat and moisture load than expected. It is my further belief that a CO2 controller operating a variable speed fan is the best way to avoid over ventilation while providing excellent and precise ventilation even with changing occupancy. With no one home, no CO2 is generated, no ventilation occurs.
It is my carefully considered belief that by avoiding over ventilation and using very low energy consumption air movers, 15-30 watts, instead of HVAC fans, a “Smart” supply only system can deliver an energy savings result superior to HRVs and ERVs in many climates. And it will operate according to occupancy (Smart) instead of being controlled by a thermostat or a fixed timer (Dumb.) Additionally an existing temperature/humidity preferred bandwidth controller (Smart) is able to sense indoor environments outside the comfort bands and will temporarily suspend ventilator operation or reduce flow in such event. Satisfactory results have been achieved in over 130 installations in South Florida.
(It also seems to fix radon issues in energy efficient structures as a bonus)
An interesting and informative read: https://medium.com/@joeljean/im-living-in-a-carbon-bubble-literally-b7c391e8ab6