Seeking window mounted (or DIY) ERV or HRV solution
 

Hello - I live in a rental, so i am not allowed to do duct work or wall work.

Does anyone know of an HRV or ERV system that can be window mounted, like an a/c? Or is there a 'workaround' DIY solution where i could take one of the 'duct-work required' units and just sit it on a table, running ducts through a window?

My goal is to keep the Co2 ppm in the low 400s in a 300 sq ft apt, does anyone know the CFM rating that would be needed for this?

Thanks!

Welcome to the site Bill.

Have you measured your CO2 levels and see them exceeding them? If so I'd say you're pretty lucky to rent a place that is that efficiently built!

Daox - thank you! Glad to be here!

Yes, the Co2 ppm gets as high as 600 (there are other people in the house in other rooms). I can keep the ppm at about 425 with the windows open all summer, but obviously that's going to be a problem come fall and winter.

Do you actually have a CO2 measuring device?

I built a CO2 detecting HRV controller, and I know what CO2 levels actually look like in an urban environment.

Your target level is pretty optimistic, but it is doable. Your air exchange rates will be pretty high.

There is a DIY HRV thread that features lots of brave and creative HRVs that could be window adapted.

Wishing you success with your project, and take loads of photos!

Best Luck,

-AC_Hacker

Thank you so much! I will check out those threads.

The ambient Co2 where i am is at 400ppm during the day. So i would love to mimic that as close as possible.

I used the ASHRAE formula for Co2 ppm. Here: b3mn dot org/guidelines/archive/version2_1/downloads_v2_1/5IEQ_App-I-2_V2-1.pdf

According to this, if i want 420 ppm, i will need about 550 CFM. Does that sound about right?

Thanks!

ps - yes, i have a Co2 meter

My CO2 controller is built and working, but the HRV is still parts at this point.

I looked at your paper, and to be honest, the cfm doesn't mean too much to me at this point, since I am counting on my HRV controller to supply air at what ever rate rate is required give me my target CO2 range.

I have noticed that if your winter air is fairly still, CO2 'bubbles' will form where you may be sitting, or working.

Gas cooking is a CO2 crime scene, and I have gone to induction cooking when possible (almost always).

My gas dryer is also bad as is my gas water heater, and they're all hooked up OK.

Last time I looked closely at ASHRE CO2 acceptable levels, I thought they were way too high. So I'm not sure if you paper will get you what you want or not.

I also found some great research from Germany, citing better school performance when CO2 levels were below 800 ppm. Makes sense to me.

Here is a link to an Irish Passive House HRV, that was my inspitation for building my CO2 controller, and I plan to closely model my HRV on their product, which they will not sell into the US.

[QUOTE]
The system will always run itself to maintain the highest level of efficiency while ensuring CO2 and humidity levels are regulated using sensors for each. When CO2 reaches 650ppm or humidity reaches 45%, the unit automatically slows down to trickle speed until levels become higher again.
[/QIOTE]

By the way, how is your indoor plant situation? (no joke)


Best,

-AC

Thanks, but i looked into plants, and they dont really lower Co2 any meaningful amount. See page 2 here: sweets.construction dot com/swts_content_files/152845/713268.pdf

I agree that the ASHRAE levels are way too high. I was more using that paper to figure out what CFM i need in an HRV/ERV unit, for a given Co2 ppm target.

Just curious - why wont they sell that HRV into the US? (not that i could use it anyway as it is an 'in-wall' unit)

Thanks

They claim that the 120v/60 Hz is not compatible with their controller. Hard for me to imagine, I mean China can do it, maybe they can, too.

You should contact them, maybe they changed their mind(s).

-AC

Thanks, i will contact them. But that is a thru-wall unit, no? My Landlord wont allow me to make those types of changes.

Interesting on the controller, i would think an adapter would work.

You were talking about even setting the thing on the floor & making some kind of window-adapter... their HRV will run in any position, but there is an condensation issue with any HRV and theirs relies on gravity, so it does need to be upright.

BTW, there are other window mounted units, but they don't have anything close to the same efficiency.

Study the drawing really closely, you're not so far away from your goal.

-AC