Humidifier/Dehumidifier Sizing for Any Home (Gal/Day and Pints/Day) 

Crazy how much chemistry is involved in understanding this.

You’re a very good teacher. I would highly recommend everyone oversize dehumidifier/humidifier by 20% minimum. The new systems will automatically actuate when needed.

Great info Corbett! As a follow-up video, could you address the expense associated with humidity control and how much energy is saved by a) building air tight in both hot/humid and cold climates, and b) using an ERV vs an HRV in both climates as well? I did some math in a GBA forum post and I’d like to see if my calculations are anywhere close to what you come up with (I would trust you more than me). Thanks!!!

Great video! Appreciate the myth busting at the beginning, and showing the math throughout!

Great video. Wish you guys were on SI units already rather than half way. :) Principal factor determining Δg/kg in a tight house: * with HRV are external loads. This is equivalent to 0% efficient ERV, or a leaky house * with no ventilation (suffocation) are internal loads. Equivalent to 100% efficient ERV. * with typical ERV, external load >> internal load. Therefore sized based on ventilation rate based on delta grams of water / kg of air method, upsized for realistic capacity. And noting ERV halves the ventilation impact on latent heat or humidity. ERV Latent heat efficiency typically ~60% Zehnder ComfoAir Q600 ERV ~ 68%. BROAN ERV250 ECM ~ 55% As latent efficiency improves I assume the principal factor will eventually shift from external to internal loads.

Great info! I enjoyed this thanks!

Fantastic info coming from an engineer in TX!!

Good info, agree with your math. With your sizing though, you may want to reconsider. Sizing both to the extremes when neither are the primary. HVAC isn't sized to the extremes either. Oversizing is going to happen, this may not matter with humidifier. Dehumidifier, unless it modulates will cause issues.

One little point about humidifiers. There are several types in the market. My experience is that when you actually want to control humidity, you need an electrode humidifier, like the aprilaire model referenced in the video. Other types either require heat to operating to add moisture the air or are drastically less effective when the heat is not running. Bypass, fan assist, mist type, might take the edge off but really not gonna work very well. Disclaimer: My design day is like 8degrees if you live in a place where your design day is in the 20s then maybe you can get away with crappy humidifiers.

Great video especially explaining the delta grains method of sizing. This works great in a home like yours. 1. I will say that pressure driven infiltration due to duct leakage and improper room pressure balancing will increase the amount of humidity and dehumidification needed. These problems need to be addressed if possible at the same time. But for those reasons, it’s ok to aim a little high in sizing hums and dehus as long as you don’t go crazy. 2. In my volunteer work designing high occupancy places of worship with lots of ventilation I created a worksheet to calculate the unmet latent load in order to size the dehu needed during full load and part load conditions and it even takes into account the de-rating of the dehu due to actual indoor conditions and duct friction. You might like it, I can send it to you. 3. If you need help installing that Aprilaire, I’ve put several in. With your low crawl, there might not be a natural steam tube rise between the humidifier and the duct connector and you might need to do a funky p trap. As always, thank you Corbett!

Thanks for the video. I have a dehumidifier that dumps into my return to the air handler. Where would be best to add an ERV? In-line with the dehumidifier, or before the dehumidifier, or after the dehumidifier in your opinion? My dehumidifier only moves about 140cfm (sante fe Ultra 70). It is currently set up to pull in inside and outside air, mix it, and push it into the return. I'm going to be planning for an ERV and was wanting your fact based opinions. Thank you so much!!!

Do ERVs also transfer some humidity, and if so, would this affect the delta target during the winter? And where do considerations like moisture from showers, cooking, breathing, etc come in, or are these sufficiently negligible so as not to be a concern?

Love the channel, another very informative video. Is my understanding correct that as a whole house dehumidifier cannot be oversized? In other words if it helps arrive at the desired level of humidity fast, then that relative humidity is consistent throughout the entire building (assuming we'll sealed). Thanks

Fantastic video mate. Can a portable dehumidifier placed in the hallway work for multiple rooms simultaneously whose doors are open and connected to the hallway? Will it work that way? Assuming the four or five connected rooms are ranging from 8 to 16 sq.m and it can dehumidify multiple rooms at the same, how large a dehumidifier do I need?

Would you say that most homes in the south have some sort of mold growth in them, since many families have their thermostat temperature set below the outdoor dewpoint temperature, during the summertime?

Thanks for the info! There is a lot of different types of humidifier. What are the differences in them?

How did you calculate the 120 Gr/Lb (outside) number? You stated this number right after determining the outdoor temperature of 80.4 & dew point of 73.3. There is another number on the chart (HR 128.5). Do you convert this number? Thanks!

ok corbett- whats better in the summer for getting your 150 com per hour you need in your house - dehumidification- a ventilating dehumidifier OR an ERV ??

Maybe I missed that but how to you account for your ERV? Should nt you add a delta to external humidity due to ERV for your calculations? Say external humidity is 20 RH but ERV brings in air at 25 RH. This should allow to decrease and maybe eliminate the need for humidifier in a super tight home.

Have you ever consulted on HVAC design for let’s say a Greenhouse or Indoor Vertical farm?

Note that the video talks about other videos that are being linked, but no such links are actually showing up.

Dear Sir, how can I contact you regarding a solution for our house in Barcelona by the sea? The house has been built in 1900, we made a complete refurbishment, 2 years after we are having massive issues with humidity. Looking forward to hearing from you, sincerely yours, H

🤣🤣🤣 Sometimes I'm an idiot." 🤣🤣🤣

One liquid pint equals 16 fluid ounces.

At first glance I read *humanity control* was gonna say you can’t even trust your friendly building science guy anymore these days smh

This would be so much easier in metric 😂

Wait. What if all my rooms are zoned And tightly foamed. Exterior and interior walls all foamed. As if each room is a separate house. Each with thier own thermostat. each a return and supply. I want to keep some rooms at 80 with just a ceiling fan. And maybe install the in wall dehumidifier units. Has anyone explored that route? For larger homes. 4/5000sqft