ERV Ducted Into Dehumidifier: Fresh Air Humidity Side Effects

90% of our videos these days are inspired from questions we get in our Patreon group ( / homediagnosistv)or from clients (buildingperformanceworkshop.c.... Here's a great one about the RIGHT way to sequence an ERV and a dehumidifier, if you must sequence them. But there are side effects for the system layout, control options, and other details that should be considered first.
Check out my deep dive into Ventilation Design & Installation: buildingperformanceworkshop.c...

[@Leonidimus59]

I don't get why dehumidifier can't measure both RH and intake temperature and turn on based on these 2 parameters plus the expected room temperature. It's a simple linear equation, any basic controller can calculate this.

[@pupperozucca4994]

not a linear equation, you need a lookup table. Doable IMHO, don't understand that neither

[@jeremyjedynak]

Great video. Would like to see more walkthroughs of your universal designs. Also, you could do a video entitled "What is 'fresh' air?" that talks about what outside air is actually made of (humidity, particles, etc) and the effects that it can have on materials in a house when you just open windows, as compared to passing that air through mechanical systems.

[@HomePerformance]

Thanks and here you go: kzbin.info/www/bejne/rqXYi6ucjtGorNE and kzbin.info/www/bejne/nYvHiHqcjLOXi80

[@hlhl2691]

Dude, what's your background? Why are you so good at explaining this stuff AND knowing about this? Call any HVAC company and ask them about an ERV and they will have no idea about any of this stuff. Smh

[@HomePerformance]

Hey thanks man- I was a musician before. Main thing is remembering what it’s like not to understand any of this stuff. Hang onto that, and then just keep asking dumb questions- they’re the important ones.

[@dustincole2625]

Not all

[@HomePerformance]

‘Why are your panties in the soup’ was crucial for me to know, Dustin you weirdo

[@dustincole2625]

Lol I'm not sure what that means but first that would require me to own panties

[@alexfisher1684]

I have a ventilating dehumidifier in atlanta. It runs the fan 24/7 with a Haven IAQ controlling the Dehumidifier and dehumidifier mode on heat pump. If haven calls for dehumidification they both will run. The dehumidifier makes the temp go up and the heat pump goes cold. Haven also controls the fresh air damper. I ran the wires for an outside temp/humidity lock out but seems good thus far. If I need it I will add it. I will be installing airthings as part of a study. Guess I will see how well we did on design.

[@HomePerformance]

Sounds good Alex

[@davidhoover2446]

The company I use stopped making MERV 16 filters I use for my fresh air. I’d love advice on a filter box to use on the fresh air side of things. I have been looking into a hepa filter box possibly when I run out of filters. I’m just running a ventilating dehumidifier and a 10 speed fan on the fresh air side with filter box so it can be dialed in appropriately. Great video!!!

[@r.j.bedore9884]

I was thinking of a similar setup a few days ago, so this video is well timed. I now understand why you don't want the dehumidifier and its controlling humidity sensor directly after the ERV since the relative humidity will change when the AHU (which I'm assuming includes the heating and cooling systems since they aren't listed separately in your diagram) increases or decreases the temperature. What I don't understand is why the dehumidifier has its own return ducting and outside air supply. Why isn't the dehumidifier just installed in the main supply duct directly after the AHU with its sensor in the duct between the AHU and the dehumidifier, similar to how the humidifier is? Having a dedicated set of return ducts going to the dehumidifier seems like a waste of resources to me, and the outdoor supply makes no sense at all, especially when there appears to be no filtration on it and you are dumping that air into the supply side of the ducting where it can't be heated or cooled to maintain the indoor temperature. On an unrelated note, I understand the need for having a make up air system for the kitchen vent hood, but why doesn't anyone build that into the vent system itself, kind of like a high flow HRV that could blow air into the room out the front of the vent hood that would then get pulled under the hood and back outside so that the hotter or colder outside air isn't mixing with your comfortable inside air as much? Having a make up air vent on the other side of the room like you did in your house seems like you would get cold feet in the winter and hot/humid feet in the summer. Is there a reason for having them on the opposite sides of the room that I'm missing?

[@joeshmoe7899]

Seems a good idea in humid tropical climate. Maybe even a must.

[@coolbydesign]

This is how we typically install ERV - DEHU systems in CZ-1& lower CZ-2. ERV supply ducted into DEHU F/A intake mixed with indoor R/A, DEHU supply ducted into AH supply. After testing different configurations we found this setup to provide the most consistent moisture control in these humid climates.

[@dandaman2226]

CMZ1.. over here!

[@ryansoo4000]

Hi Corbett, I wanted to ask your opinion of the Ephoca AIO which combines a heat pump, erv, merv 13 filter and bathroom exhaust all in one indoor unit (no outdoor unit needed). With houses getting tighter and more insulated I know a lot of people are complaining because they can't find HVAC equipment small enough to handle the low loads. Apparently the AIO can provide heat from about 2700-6700 BTU/hr at 5 degrees F outdoor temperature. Do you think this is the "magic box" that people are looking for in low load homes (their ceiling cassette unit can be ducted to service more than one room)?

[@6stringsandapick]

Any advise on adding dehumidification with a "T" shaped plenum splitting directly above the unit? Do I split the outlet on the dehumidifier into two ducts?

[@ivan.bucher]

Is the diagram at the end an example of decoupling the ERV and DEHU?

[@johnwhite2576]

Corbett what about having an independent return from say a central hallway to the dehum , then connecting supply ie dehum exhaust , into the erv supply ducting (ie a erv skupply duct system independent of hvac ducts)

[@ronm6585]

Thank you.

[@v8zj98]

I have a tiny house that’s built very air tight. I have an adaptive make up air system that pulls in fresh air through a filter into an “HVAC room” with a dehumidifier. It then pipes that air into the house monitoring humidity, temperature, and VPD. We originally used a Panasonic spot ERV, but found our CO2 levels were too high.

[@dustincole2625]

My ERV (oversized core) runs continuously with exhaust from bath and fresh into my dehumidifier FA intake. Bath exhausts have a constant airflow regulators for balancing and dampers to bypass regulators and trigger erv boost mode to activate maximum flow through exhaust when showering, bathing, etc. Dehumidifier fan runs continuously and has HAVEN monitor to boost ventilation through erv on demand from indoor VOC content and activates the Dehu on dew point. Dehu injects supply into HVAC system. Air things activates communicating variable hvac blower based on bedroom Co2 levels. Per my data loggers my dehu & HVAC fan is nearly never activated. My mix of ERV, HVAC, and filtration handle my indoor and outdoor air conditions with the exception of a few times in shoulder season. 3 ton inverter, +/-2800ft2, +/- 3 ACH50, CZ2 coastal Louisiana. Full disclosure most HVAC contractors would cringe at this idea.

[@HomePerformance]

Let’s have you on the channel again via Zoom to show that system off dude

[@dustincole2625]

Let's do it!

[@FirstLast-et3sw]

Ugghh, here we go. Home in MTL. So very cold winters and hot humid summers. I central natural gas furnace and heat pump. I have a passive HRV and humidifier and Ecobee 6 pro thermostat. In the summer, my HRV is set to off so I don’t get any fresh humid air outside (unlike winter where outside air is always fed inside). I can’t get my indoor humidity under 60% at 22 degrees (at least that is what ecobee displays). Do I need a dehumidifier? Should I have an ERV and not HRV? Need help. !!! I’ve been told to run furnace fan 24/7.

[@HomePerformance]

Yes, swap your HRV core with an ERV core, and get a dehu. Here’s how to size it: kzbin.info/www/bejne/o4K3dJ9umJiDotksi=WaabE3tM5EmZRQ5u

[@ZergZfTw]

What you are describing is really close to a commercial DOAS. Just an energy core or wheel followed by a mechanical cooling/heating system. Renew Air has DOAS starting at 375 CFM I think, that's not to oversized for a bigger sized house, especially with ecm fans. Also, thinking in dew point is much more intuitive in my opinion.

[@chaseweeks2708]

Rather than adding the additional complexity of a separate air handler and ducting for the DEHU (if you're running a mini-split system for cooling), I wonder if it wouldn't make more sense to just install one or two in-wall dehumidifiers strategically so that they can handle the load if/when the AC isn't able to.

[@superspeeder]

IDEALLY, we would have a custom dehumidifier (read: small airflow) with the evaporator coil (cooling) located in the ERV fresh airstream into the house, and the condenser coil (heating) located in the stale airstream leaving the house. This ultimate appliance would be an ERV/dehumidifier/AC that tempers incoming air with the ERV core and then cools/dehumidifies that air while rejecting the heat to the outdoors. I understand that appliances like the Minotair operate as an HRV by using a refrigeration circuit, but it has no core to exchange ventilation air energy/moisture without running the compressor. Why is this stuff so darn SLOW to come to market?!?

[@Werdna12345]

1:55 i don’t understand what he was trying to say here about ERVs bathroom and what he doesn’t recommend unless you are replacing bath fans and I’ve seen most of his videos

[@HomePerformance]

kzbin.info/www/bejne/op-ydHSGhbuHa8k

[@r.j.bedore9884]

Basically if you have a really air tight house, traditional bath fans will depressurize the house and will have trouble properly exhausting the stale humid air. If this is the case, then use the exhaust/return air ducts for an ERV in your bathroom instead of a traditional bathroom exhaust fan, since the ERV will also bring in fresh air in a balanced manner to avoid depressurizing the house. The video he linked in his response goes into more detail, but basically place the ERV exhaust/return duct in the corner of the shower ceiling furthest from the door for the best results in removing the humidity. The fresh air supply ducts are typically in nearby bedrooms, so you end up with fresh air coming in under the bathroom door and being pulled across to the upper corner of the shower, taking the stale/humid/hot air with it.

[@BrianBaldridgeC]

The ERV Manufacturers say to let their system do the bulk dehumidification work and supplement with a dehumidifier. Is that what you are saying here?

[@HomePerformance]

Yes, ERV will passively dehumidify, then use energy to take off the rest of the spike.

[@sp1200M3D]

I can’t tell you how many contractors connect dehumidifiers to the return side. Am I missing something? Is it not silly to dump dehumidified air into an air handler!?

[@HomePerformance]

That way steals the AHU cooling coil’s ability to dehumidify. It was actually made illegal to do that in FL building code.

[@sp1200M3D]

@@HomePerformance thank you, Corbett. Honestly, if these companies did proper HVAC installations we wouldn’t need these add on whole home dehumidifiers as much. No? Whether it’s short cycling, or lack of tonnage, people all over the Southern Climate Zone specifically are getting sick from imbalanced indoor fungal ecologies from their HVAC’s. Not to mention duct leakage, duct board getting wet, the list goes on.

[@HomePerformance]

I do think it makes it worse, but actually we need dehus in basically every new home as an insurance policy because of airtightness.

[@sp1200M3D]

@@HomePerformance that will be a great day if it becomes the industry standard that all homes are to be high performance.

[@idontwantachannelimjustcom7745]

Instead of just using rh, why wouldn't you use a temp and rh sensor to get a complete picture instead of just a partial.

[@TheFreedom4you]

Zehnder Q600 ERV = 353 CFM

[@Grace-eq4lr]

Why did the ventilation fan in my house suddenly stop? I set the timer for an hour, but it only worked for a few minutes and then suddenly stopped. I tried it many times and it was the same every time. What is the reason?