I built the best DIY heat recovery ventilator I’ve seen on YouTube
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- Опубликовано: 11 июн 2024
- I built a heat recovery ventilator (HRV) from only sheets of corrugated plastic and adhesive.
EDIT: SEE PINNED COMMENT for some corrected efficiency metrics. To summarize, my HRV is actually 60% efficient (which is still decent!), not 85%.
Even so, it works great! My HRV is powerful enough to deliver fresh air to most of my house, and it’s designed to use 4” thick MERV-13 filters to help keep harmful particulate (PM 2.5 and 10) out. It greatly reduces VOCs and CO2 as well. My indoor air quality has significantly improved. The cherry on top: it cost me less than $300 in materials to build!
Intro - 0:00
What HRVs do - 0:32
The drawbacks of other DIY HRVs I've seen - 1:18
My HRV (THE REVEAL) - 2:58
Its performance data - 5:12
The cost of building it - 7:25
The drawbacks of my design - 7:50
Below are affiliate links, which means I earn a small commission if you make a purchase through them. This helps support the channel at no additional cost to you. Thank you for your support!
The products I used for quantitative testing:
Aranet4 CO2 monitor: amzn.to/4aCvfIA
Dylos DC1100 PRO Particle counter: amzn.to/3V1ssmy
Testo 405i hot wire anemometer: amzn.to/3WYn721
Necessary tools and materials (should cost $200-300 total):
-4 mm coroplast sheets: amzn.to/4aAGmC5
-48" drywall T-square: amzn.to/3ytJ3I7
-Utility knife: amzn.to/3UOsaPO
-X-ACTO knife: amzn.to/4bxG1kZ
-Hot glue gun: amzn.to/44UkyQH
-Hot glue: amzn.to/3UUIfUb
-2 pack of Filtrete MERV 13 filters (I now recommend using a 1" thick filtrete instead of 4" thick filterbuy because filtrete has been shown to be superior even when thinner): amzn.to/450JKFh
-Terrabloom 6" fan (easier to install, but not as powerful): amzn.to/3wZFIQD
-AC infinity 6" fan (harder to install, more powerful): amzn.to/3VgmPSP
-Pen or pencil
Please like, subscribe, and comment if you're compelled to do so. Thanks for watching!
My video about why I now use an ERV instead of this DIY HRV: • HRVs vs. ERVs: Why I D...
My DIY ERV installation (step-by-step build): • DIY Energy Recovery Ve...
Designed by Instinct’s video (this one is most helpful for actually building): • DIY Heat Recovery Vent...
AlexGs Aquarium’s video: • DIY HRV (Heat Recovery...
A few of you have requested CFM measurements for my HRV, so I’ve gone ahead and taken them! So, I measured the CFM at the supply outlet at various fan speeds. Here’s the data:
With an anemometer distance of 6-8 inches from the outlet:
-speed 1 of 8: ~100 cfm
-speed 3 of 8: ~150 cfm
-speed 6 of 8: ~250 cfm
-speed 8 of 8: ~330 cfm 
Хобби
IMPORTANT UPDATE: I did some more efficiency tests in the spring using the outgoing air and it seems that my HRV is actually around 60% efficient (which is still pretty good), not 85%. I wanted to make a video about this but I ended up having to put it on the back burner because I went through the process of selling my house.
When making this video, I made the mistake of testing efficiency using the incoming fresh air. I think that heat generated by the fans skewed the results.
Here’s a formula I used for a corrected efficiency test using the outgoing air instead:
× = (T_room - T_outgoingAir) / (T_room - _outdoors)
An example of one of my test runs (Fahrenheit):
60.5%=(70-44)/(70-27)
So yeah, it is less efficient than I initially thought. That being said, it still worked quite well.
I want to address some questions I’ve seen:
I do think that almost all of the air is flowing through the core. The filters were quite dirty when I dismantled this HRV, and in order for them to have gotten like that, I do believe air must have passed through them/the core.
I don’t think there is very much leakage in the chambers. I sealed them very thoroughly with hot glue and weather stripping, and did leakage tests. I acknowledge that there could be some leakage, but not that I could find.
Next point, to the couple people who quoted Egon Spengler at me: no, I don’t believe I’m “crossing the streams” (intake/exhaust air streams mixing). After this video came out, I installed elbow duct attachments to the indoor supply and outdoor exhaust to the direct the air streams away from the intakes 🙂
Potential reasons I didn’t run into condensation issues: lower HRV efficiency combined with the low dew points in my house (from ventilation with dry, cold air + no humidification).
I only used this HRV during the late fall, winter, and early spring when the air is very dry. I’m too worried about mold growth when it gets humid. Though less efficient than I initially thought, it still worked great!
If you're curious about how this DIY HRV performed long-term, check out this video of mine: ruclips.net/video/LiptsaKmq80/видео.htmlsi=bsEbBQ9pKLKozY4u
60% is good for crossflow HE in these materials. And filters get dirty much faster than we think ;) It's not uncommon to send a reserve filter set with a new AHU.
How would you deal with moisture condensing inside the core? If you turned the box on its side, moisure could run out of the core channels. EDIT: I see you do address this, kinda. However, it’s still true that this is a no-go for any climate that has to deal with condensation.
@@stcredzero great question. I’m also concerned about ventilating using an HRV (even a factory made unit) during humid months. ERVs are better for ventilating humid air. I’m currently making a video explaining how to install an ERV one’s self (even for those who don’t live in a ducted home!). That might prove useful to you when it comes out.
I really love the idea. Things like this have crossed my mind quite some times in the last couple of years.
But please help me as I'm trying to wrap my head around the calculations. Wouldn't it be much more accurate if you measured the temperaturr of the in the four ducts for your calculations? And perhaps als the airflow? (Especially flowing from inside out)
I'm thinking of:
DeltaT_,OutsideIn = T_Inlet_OutsideIn - T_Outlet_OutsideIn
DeltaT_,InsideOut = T_Inlet_InsideOut = T_Outlet_InsideOut =
Delta_T = DeltaT_,InsideOut - DeltaT_,OutsideIn
Gain = Delta_T * Air_HeatCapacity * Airflow_OutsideIn (I'm probably missing some details here 😉)
And then there's this thing about air particles. Do you have any measurements from before then installation of the installation and how do they compare to the new figures?
I'm having some Ikea air quality sensors and about 99% of time they all show no polution or just a little bit.
For better efficiency (if you even need it) you need a bigger and more elongated core.
To all the naysayers, this guy built a system extremely similar to a professionally manufactured one. Many manufacturers also use plastic cores, and even plastic fiber cloth cores (with moisture wicking effect)
As an HVAC guy i can say your design although unconventional and bulky is just fine, your fans you use for circulation would benefit from the coandâ effect to increase air flow. Also those efficiency rating the big companies use are totally skewed so your system is probably working better than off the shelf systems thanks to that massive core you built
I appreciate the encouragement! And thank you for that Coanda effect idea - I’m gonna tweak the locations of my circulating fans to capitalize on it.
How would one deal with condensation for something like this? Curious if this would work as well during Texas summers!!
@@Geoff9001 I’ve only used mine during colder, drier seasons. I definitely would avoid using an HRV in your climate, especially during warmer months. An ERV (combined with a dehumidifier) would be a safer ventilation option for your region.
@@HealthyHomeGuide have you seen any decent homemade ERVs online? This is the first homemade hrv I've seen online and it looks great, although a little big
@macthemec can you elaborate on how one would use box fan to achieve a Coanda effect? Where is the effect happening? Is the idea to get the air flow from the fan to follow to the walls, or floor, and thus travel further than it would had it not? Is it perhaps fashioning a shroud or cowl to affix to the box fan, one which would create a Coanda effect? I really can’t imagine how this would work?
Dude you are brilliant, it never would have occurred to me to use the natural tunnels inside of coroplast board! That's legit mate. You've managed to achieve very near the efficiency of commercial units that cost thousands of dollars. This is such a great idea, you've given me all kinds of ideas for my own apartment.
Aw, that’s very kind! Thank you so much. Feel free to let me know if you have any questions or want to show me your future designs.
what do you think of using corrugated cardboard?@@HealthyHomeGuide
Definitely going to do this now, didn’t know that the diy actually worked so well and with testing to back it up! Thats all I needed! This will definitely help with my parents cold basement and spare second story room if I hooked it up to the previous improperly installed furnace air return. Thanks
Great! You’re super lucky that you have ducts already in place in your house, even if they’re not properly installed. Good luck!
Stunningly simple, cheap and effective. Well done man!
Glad you like it!
Subscribed man. I'm not sure how I've come by your channel, but I am very grateful and have learned so much. Thank you for taking the time to post!
I’m grateful to the algorithm for bringing you here!
Keep it up. Love the facts and your delivery.
Thanks so much! That’s very kind.
Excellent video. Really good build quality and very well explained.
Thanks so much!
Bro, you would put a little greenhouse lean-to against a southern wall of the house outside the window to actually heat your house on sunny winter days.
Also, you could just skip the return fan and suck air in and make your house “positive pressure so that you leak a little air outside rather than allowing dirty air from outside to find its way into the house
Man I'm absolutely blown away. You did an amazing job. Well done on your research and execution. I have a whole new view on heat recovery systems now. In HVAC, these items are extremely expensive. I don't often get to specify these due to clients not having the budget for it. After seeing your results though, I think I can come up with something affordable and efficient on a commercial scale. I feel efficiency can be improved with a quick material study. Thanks for your video. I'm very impressed and appreciative for you helping me see how simple this system can really be.
Man, this is one of the best comments I’ve gotten! I really appreciate that. So glad I was able to inspire you.
This is unbelievably cool, even with the potentially lower efficiency number. I just bought a house and have a 1990s furnace that I want to keep running as long as possible. Currently in the process of cleaning and sealing the duct system and trying to DIY as much as possible. The furnace uses a long insulated flex duct to allow unfiltered cold Canadian air into the furnace room for combustion. I feel it’s very inefficient (and dirty) to have a clear line of outdoor air entering my home. Your system seems like the perfect DIY method to address this problem. Just found your channel and looking forward to seeing what other ideas you have.
Thanks so much! I think you’re smart to pick up on the fact that your furnace situation may not be the best. Most people ignore those things. Not us!
i love this!! thanks soo much for sharing your creation and findings! soo helpful :)
You’re so welcome!
you can make it more "compact" just by placing the vents from the outside in the bottom and the vent inside on the top. then it would cover the window, but at least you'll have floor space. the trubulance from the air turning 90 degrees twice might aid in the heat transfer
Great job!! You SHOULD be proud of it. it looks NO different than the expensive Panasonic one. Thank you for the inspiration!!
That’s very kind! If you end up making it, could you let me know how it turns out?
Wow! Your did great! You did a great job! And so efficient too! I live in a very small home in CT, a 200 yr old home, I renovated 20 yrs ago. Our home is 24x22, with basement, 1st flr, 2nd flr, and walk up attic. It's a post and beam kinda house. I installed ductwork, and Air handlers, one in the attic to service the 2nd flr, and one in basement to service the 1st flr. I have a boiler for heat, so it is a hydronic system. Each AHU has a hot water coil, that way I can also temper the discharge temp. So I think about 5 yrs ago, I added a Fan tech ERV to my 2nd flr setup. I added external filter boxes, with I think Merv 12 filters it came with, cause you need to keep that core clean as well as the air we are gonna be breathing. This was the lowest price unit at the time, and the enthalpy core is same product you used, but not as nice as yours, mine is not very efficient, so on really cold days, I don't use it. But a year later I bought a HRV for the basement I spent a little more and got one a bit more efficient. [I'm not rolling in $] I have seen some really high efficient EVR's but big $. I'm fortunate I inject the "make up" air into my air handling system. I also have UV-C lights in the AHU's. I have my 2nd floor ERV set up so when I run it, a relay turns on the FAN mode on my t-stat, so the AHU is running to distribute the air when the ERV runs. I have a Timer so 2nd floor runs at night [bedrooms all on 2nd flr] but also another timer called an Air cycler. This means it will run say from 6pm to 8am, but the air cycler runs the system 15 mins every hour. Then if someone hits the Exh fan switch for the bathroom, it turns on. [The stale exhaust air, get sucked out through the bathroom registers]. Anyway the results are great! I eventually will improve the ERV with a more efficient one in the future. The indoor air can be so bad, plus I'm try to learn about "static" pressure in the house. So when I turn on the range hood on highest setting 600cfm, where the make up air? or air coming in? Do we pull a negative pressure bringing in more bad stuff through the chimney?? Or cracks around the doors?? So an intentional conditioned make up air system is so important, especially weather when you cannot open windows. So thank you for sharing your project! So cool! [sorry to be so long winded here, but I get excited about this stuff! ] God bless! AL from CT
Thanks for your comment, Al! And thank you for sharing your HVAC experience. It sounds like you’ve had quite the ventilation journey. I’m actually thinking about make-up air a lot right now. And absolutely, if you don’t have a dedicated make-up air system, it’s very likely that the range hood (especially at the highest setting) is pulling air from hazardous places, or at the very least potentially causing moisture to build up in the cracks that the air gets sucked through.
Unfortunately, my kitchen actually doesn’t have an exhaust system at all! I’m now planning on putting one in. My next video is going to be about this! Tune in if you’re interested. It should be out within the next few days.
You are the RUclips MVP on this subject💪🏻
Hahah thank you
Thanks That's a really good design. I've been thinking about how to build something like this for our home. I'd not considering using coroplast, but it's almost made for the job !
Absolutely! Coroplast is an amazing material - polypropylene is the safest plastic, I feel. No BPA, no VOCs. I think that my HRV core is pretty laborious to build though. I’m in the process of trying to find a cheap source for replacement HRV cores, so we DIYers can just build a simple HRV housing for a pre-made core. Stay tuned!
Nicely done!!
Thank you 😊
This is exactly what I was looking for. Thanks.
Glad you found it useful!
Wow! Excellent job, I'm definitely going to build something similar
Thank you! And good luck! Let me know if you have any questions.
@@HealthyHomeGuide do you know how well this would work for hot and humid Texas summers? I know an ERV is what I need, just didn't know if that poly might work well for that or if I needed something like an aluminum core. Thanks!
@@Slipperypuffin Yup, an ERV (as opposed to an HRV) would absolutely be the way to go for the specific reason of ensuring your home didn’t pull in too much moisture from the humid Texas outdoors. If you have the budget and space, I’d recommend buying an ERV, because I’m not sure how to actually build one.
If you want to try an HRV instead (which won’t get rid of humidity) coroplast could certainly work because coroplast is moisture resistant. Based on what I’ve seen, a coroplast core should do fine at cooling the incoming air in the summer, you’d just probably need some sort of condensation drain.
i built one in spokane in 85, using plastic sheeting and bathroom exhaust fans. i like your design.
Damn, you were one of the OGs. Thanks for watching!
Thank you for this wonderful news! :-) Great inspiration! ... And I like your humor! ... lol
I see it as great news as well, thank you! Glad you’re on the wavelength.
Very nice! Hope you have other projects to show off as I just subscribed to your channel.
Such a great design! I may build something like it for my place. Wonderul.
Good luck!
This is really cool!!
Hell yeah! Thanks!
as an actual HVAC Technician i think that is pretty neat. the physics is the right way around and from the numbers i can tell it works. the only way to improve would be a more conductive material to get the usual 90-98% efficiency but apparently its conductive enough.
That’s very kind, thank you! That means even more coming from you, as a legitimate HVAC tech
90-98 is definitely not the “usual” efficiency rating for HRV/ERV’s. That would be on the extremely high end.
@@JordieG8 agreed.
@@JordieG8 i have no explanation for this. i dont remember why i said 90-98 i guess i meant max. just goes to show take everything with a grain of salt or something
@@steffankaizer all good dude, I thought you maybe got it confused with high efficiency furnaces or something. Lol
Awesome! You inspired me to build one. I’ll try brazing aluminum flashing for better conduction.
Glad I inspired you! Hope you build something awesome.
Very nice. Now I want to build an ERV
Glad you enjoyed it! To be clear, this is an HRV, not an ERV. I’m not sure how one would go about making a DIY ERV, but if you find out, do let me know!
Nicely done! Corbett mentioned this video in a video he uploaded today.
Glad you enjoyed it!
this is so rad!
Hell yes! Glad you liked it.
To improve upon your design ; if you suck the air close to the floor in your basement you'll also get Radon out of your home. Intake/exhaust on each side should be seperated by about 6feet.
You could install a ceiling fan instead of the box fan that on the chair.
Great work!
Thanks for the suggestions! You might be interested in seeing my DIY ERV installation (newer video). I made some of the improvements you mentioned.
Dude. You’re an awesome enthusiastic presenter of your creations. I’m thinking of something like this for my large garage. Maybe not quite this big tho
I appreciate that you like my presentation style! If I could do this HRV project again, I’d build it smaller. Maybe with 2” thick filters instead of 4” thick. And with more powerful fans.
@@HealthyHomeGuide In your newer videos you don't seem to be using this design. Is there a reason? Thanks
@@ww-pw6di I appreciate that question. I haven’t used this HRV since the spring because I’m too afraid of mold growth to run it during more warm/humid seasons. During the warmer months this past year, I used my DIY fresh air intake for ventilation, but there were limitations to how much I could use it during warmer, more humid stretches.
I’m now using an ERV for year-round ventilation (+ a whole house dehumidifier in the warmer months). I’m actually working on an ERV installation video (for those of us who don’t have ducted homes).
For the record, I still think my DIY HRV could be a great budget option in colder, drier months.
@@HealthyHomeGuide Thanks for the reply! Was the mold concern in regards to the box or the core getting moldy or rather the humidity causing mold growth elsewhere in the house?
@@ww-pw6di You ask very smart questions. I was concerned about both, to be honest. I’ve learned hard lessons about how careful I have to be with introducing humid air into my living space. Because I’m very sensitive to mold.
Yeah, you earned my subscription. Looking forward to more of your content.
I love to hear it! I’m coming out with some cool stuff soon.
Impressive!
I’m happy you like it!
Well done.
Many thanks!
Fantastic. Great useful information. Thank you. Cheers J
Cheers to you! Thanks 😊
I applaud the initiative. This is certainly the future & I love it. Some things to consider...
1) CO2 "cannot" be affected by the unit, as the CO2 level is whatever you are drawing out of the air coming in from outside (usually about 400 unless something weird is going on. Plants like it when we "talk to them" because we are breathing CO2 at them. CO2 builds up in a house because of "us".
2) I would be greatly concerned about the VOCs coming off all that plastic, adhesive and other chemicals from 3-D printing. It's gonna off-gas, a LOT! Funny your comment, "insane!", right after, cause..., yeh.
3) There is an actual Metric they use, CFM/watt, to quantify how much actual work is being done. It's used to measure performance. Measuring the Factual temps of the airstreams is of great interest also.
4) Tape the edges of the filters or there is bypass (sneaking around the filtration, around corners). HEPA has no "bypass".
5) Measuring the air pressures will tell you the static resistance various parts of the system are causing - core, filters, vents.
Cool experiment, but don't mislead people with hyperbole instead of data. Maintain integrity. Do no harm. Cheers.
There is more things to consider:
1) The heat exchanger is not going to be very efficient, because it does not have perfect counter-flow. In the 2 corners at the border between inside and outside, there will be heat exchange between the hottest part of your system and the coldest part. A simple system of two (long enough) concentric pipes is going to perform better.
2) In winter, condensation in the outstream will boost efficiency even further. In summer, condensation will occur on the instream, making this system unusable.
3) Indoors, it is much better to have air intake and outlet in opposite parts of the house, so the clean air will spread without the need for additional fans. Outdoors, outlet and intake can be closer together, and should probably be pointing in the same direction in order not to get drafts when it's windy.
Very cool. I’d love to see a full build video with parts and dimensions. I’m already wondering if I could fit this in the top of my entry closet. It’d require drilling holes in my exterior wall and the closet wall, but it’d solve the obstruction and looks issues here. Also curious to see the process of changing the filters. If you have to open the top for maintenance then this install location might not work (though I guess you could put it on the floor of the closet instead).
Thanks! I like the idea of putting it in a closet. To give you a rough idea, the housing is 36"x30"x14.25". I do indeed have to open the top cover to change the filters. It's fairly simple; I just secure them in place with a couple strips of tape. I put weather stripping around where the housing contacts the top cover and then secure the top cover down with clear, low VOC tape.
@@HealthyHomeGuide Great idea with the coroplast! Did you use the 4mm or 10mm?
@@Gnavitas thanks! I used 4mm.
Great video, meticulously. explained and delivered. I subscribed and wish you luck. I mainly open a window for fresh air, but a fully running unit would be beneficial no doubt. Btw, those “idiots” you refer to that put pesticides on their lawn probably don’t watch these types of videos!
I’m glad to hear you appreciated my meticulous explanations! Thanks for subscribing. I think you’re absolutely right that pesticide people would have no interest in my content whatsoever haha
Excellent !! Thanks !!
You’re very welcome!
@@HealthyHomeGuide It s so simple and efficient !!!
Great job! I've seen a similar design on "build it solar" website before, but good to actually see a working prototype.
One question: do you get condensation inside your core? Some HRV design includes a heating element to combat the condensation.
Thanks so much! I used this HRV only when it was dry outside in the late fall, winter, and early spring. So I didn’t run into condensation issues. I’m too paranoid about mold growth to use it in the more humid months. But I am working on a DIY ERV installation video for year-round ventilation. To be clear: I’m not making the ERV myself, I’m installing it myself.
I built the unit you saw on Build it Solar back in about 1988 or so. The painted plywood enclosure was around four feet square, as I recall, and about one foot deep. The core was a stack of coroplast sheets siliconed together. I had no way of measuring its performance at the time but it worked very well in our small cottage. All these years later, I'm thinking about doing it again for our off-grid home. Yes, it IS do-able for the do-it-yourselfer!
Great video, could you please go into detail about how you made the Coroplast Square core? Thx for sharing your videos
You’re welcome! The videos I linked in the description are very helpful for demonstrating how to build a core. The one by Designed by Instinct is particularly useful.
You probably want to insulate the intake and exhaust pipes on the outside end of the HRV - those have cold (in winter)/hot (in summer) air that is going to lead to undesirable heat transfer to your indoor air.
I like that suggestion! Thanks.
Love it, considering buiilding one of these for my home too!
You could have used half the correx by using double sided foam tape to create the core, with one channel being formed by taping two sheets together. (using tape with a thickness similar to the height of the plastic sheets) this has the advantage of also reducing the thickness of plastic seperating the air channels, so heat transfer should be more efficient. (as it would be one layer of plastic rather than two layers plus glue)
Also a dual core design could improve efficeny by doubling the surface area for heat transfer.
Please describe differently. The advantage other than more direct contact of the layers is unclear.
@@Mavrik9000 Mainly just because it reduces the amount of material needed for the core, so in theory you could create a dual core confgiuration with the same material plus tape!
@@Chriz.What I mean by "describe differently" is the physical layout. I don't understand how the configuration you have described is assembled.
I have an existing HRV that is starting to show it's age (getting noisy) and replacing the fans would be something like 1200-1500€ so I am thinking about getting a new one. Doing some DIY work on it with third party fans is something I have been thinking about, but the original fans are custom built and I have been unable to find duct fans that I can properly control. The originals are radial fans and built specifically for the HRV...
This is cool content. Subscribed.
Love to hear it! Welcome.
It would so nice to recover moisture also!
Absolutely. I’m actually working on a video where I do a DIY installation of an ERV. I didn’t build the ERV, but I built a system to retrofit it into a window. Stay tuned.
Very cool to see the concept in action. If the plastic transfers heat so well, wouldn't you need another material to insulate the connection to the window?
Great question! I am using weather-sealing tape to ensure that cold air doesn’t blow through small cracks at the edges of the window insert. As for the plastic insert itself, coroplast has a 4 mm layer of air in between its two plastic layers. The air acts as an insulator.
Also, the plastic isn’t actually that fantastic at heat transfer compared to something like aluminum. The coroplast insert doesn’t seem to get that cold.
Thank you for sharing this, truly. Definitely a thumbs up! Sharing knowledge and experience like this this is the internet at its best. Also nice to give credit to your sources at the end.
Question 1: High effective is 85% as compared to a commercial system? I could do my own research of course but in case somebody knows already ...
Question 2: Did you consider alternatives to spray adhesive for laminating the plastic heat exchanger stack? I am thinking it is an unnecessary source of VOC’s? Are there “healthier” adhesive options or am I being overly concerned?
Question 3: Would efficiency increase with a heat exchange filter material of greater thermal conductivity like copper or aluminum?
A am pretty sure moisture build up would be an issue if installed “properly” with outgoing air coming from high air moisture areas like bathroom, kitchen and laundry rooms however. But in any case really cool build!
That’s very kind, thank you! I totally agree: RUclips especially is fantastic in many ways - not only for entertainment, but also for learning and growing.
1: As far as residential HRVs being built and sold commercially in 2023, 85% is considered to be at the low end of the high efficiency range. There are definitely higher efficiency ones than mine available commercially.
2: I did use a low VOC spray, but I understand where you’re coming from. I feel that the spray adhesive is necessary for maximum contact and efficient heat exchange. I’m not too worried about VOC release because once low VOC spray adhesive dries, it solidifies and is less volatile. Air also isn’t flowing in between the coroplast layers, as they’re tightly bonded together. I also personally haven’t smelled any adhesive odor from my HRV after it dried.
3: I’m not sure if efficiency would increase unless the core layers were made of aluminum or copper itself (as opposed to coroplast). I don’t think that putting aluminum in between the coroplast layers would increase heat transfer because the heat still has to go through two layers of coroplast, even if there is aluminum in between. I could be wrong about that, but I believe that more materials would lead to efficiency loss. Also, I don’t see a need for that labor, personally.
4: Absolutely. In the summer, I use a different setup to avoid moisture issues (see my latest video for info about that). This year, I found that this HRV works best in the spring, fall, and winter. Not summer.
Thanks again!
I Would like to see how adding thermal paste in-between the panels would perform...nice video
Freaking love this. Instant sub
Hell yes.
Great project, even if the efficiency did not quite measure up. I would argue however that anybody building one to install in an older home should dive deep into already existing air infiltration issues. Just a few poorly sealed holes in the framing can cause a hidden issue through the entire home, even through interior walls over crawlspace construction. The pocket hole doors originally built into my home permitted an absolute blast of air through them when the house was pressurized, much of it likely coming from the crawlspace. (I sealed the pocket doors in entirely.) Even the catch on the jamb for a door latch became an obvious breach that a little caulk easily fixed.
If your HRV actually is 85% efficient you should get a lot of condensation when outdoor temperature is below freezing. You can figure out the dew point of your indoor air, and unless that is as low or lower than the expected temperature of the exhaust air there should be condensation. The "fresh air" you get is definitely a mix of fresh air and indoor air that leaked into the fresh air stream, possibly not in the core, but definitely in the giga-supersized chambers outside the core. Also you need to make sure the flows doesn't mix outside to get an measurement of the actual efficiency. If you measure the temperature that leaves the house, on the outside, instead of the mixed airflow, and compare that to indoor and outdoor temperatures you can find out the actual efficiency. The actual efficiency is definitely not anywhere near 85%.
Aluminium conducts heat around a thousand times better than most plastics, and you can make aluminium much thinner, which also improves heat transfer compared to plastics. You even have two layers of plastic, and a layer of adhesive, and possibly areas with air too. And no way those fans can force hundreds of CFM through that core, a powerful leaf blower might be able to do that.
Thanks very much for your comment! So, I did some more efficiency tests in the spring using the outgoing air and it seems that my HRV is actually around 60% efficient, not 85%. I wanted to make a video about this but I ended up having to put it on the back burner because I dismantled this HRV when the warmer weather came and went through the process of selling my house.
When making this video, I made the mistake of testing efficiency using the incoming fresh air. I think that heat generated by the fans skewed the results.
Here's a formula I used for a corrected efficiency test using the outgoing air instead:
× = (T_room - T_outgoing Air) / (T_room - _outdoors)
An example of one of my test runs (Fahrenheit):
60.5%=(70-44)/(70-27)
So yeah, it is less efficient than I initially thought.
I want to address some other points:
I do think that almost all of the air is flowing through the core. The filters were quite dirty when I dismantled this HRV, and in order for them to have gotten like that, I do believe air must have passed through them/the core.
I don’t think there is very much leakage in the chambers. I sealed them very thoroughly with hot glue and weather stripping, and conducted leakage tests. I acknowledge that there could be some leakage, but not that I could find.
I also don’t believe the intake/exhaust air streams are mixing very much. I installed elbow duct attachments to the indoor supply and outdoor exhaust to the direct the air streams away from the intakes.
Lastly, dew point in my house is quite low in the winter. I don’t use humidifiers and this HRV brought in plenty of fresh, dry air.
Again, thanks for your insightful comment.
That’s a well regarded reply. Maybe when you get a chance just do an edit update including these findings.
An aluminium heat exchanger can be 'too efficient', you still need the effective insulation factor between the two sides (internal and external), and clarity of where any condensation should (and should not) occur.
The real world heat conduction is also a function of thickness, and in thin material plastic is as good as aluminum in case of HRVs
@@hhkk6155 could still probably get good results with a water loop design. Would also allow you to separate where the intake and exhaust is going. Like one widow has an intake with an aluminum heat exchanger and the other window has an exhaust with a heat exchanger. No mixing of air and probably make it more compact. Hell you could have the exhaust on the other end of the house if you wanted. Could also eliminate the exhaust filter he has and opt for a real heat exchanger cleaner when needed since it isn't plastic.
Good work! What would you recommend for a camper van or RV? Just filtered intake and crank the furnace?
Thanks! That’s a fantastic question. It depends if we’re in a warm season or a cold season. For a small space like that, first and foremost I’d want to ensure that humidity remains below 55%. Not an issue when it’s cold. I personally feel that mold growth is actually more of a health hazard than CO2. Filtered ventilation is still important though, of course. If the weather is cold outside, you may want to build a small HRV. I may attempt one this winter. If you can’t go the HRV route, intake filtered air very sparingly with an intermittent outlet timer.
I’m releasing a video soon about balancing CO2 reduction with humidity/particulate/temperature control. That may further clarifying things for you!
Great vid. Thanks. Do you know how many cfm this unit moves?
Glad you like it! There’s information about the airflow at the bottom of the description
Impressive and inspiring, thank you. For someone interested in trying this, why coroplast, other than it comes pre-corrugated for maximum surface area? Wouldn't metal plates work better at transferring heat? (but much more time-consuming to pleat by hand). Maybe the fins from old A/C and HVAC equipment can be repurposed for this. Amazing effort and spirit, blessings and apprecation.
I appreciate that, thank you for commenting! Good question. I used coroplast because it’s very easy to cut, lightweight, non-toxic (polypropylene is BPA-free and does not off-gas at all), durable, moisture-resistant, recyclable (polypropylene is a thermoplastic that can be recycled), and CHEAP. I wanted to build it all from one cheap material.
Coroplast transfers heat pretty well. Some commercial units built today actually use corrugated plastic for their cores!
I also don’t know how to cut metal, bond it properly, clean it right, and work with it safely in general (especially with old potentially rusty parts). For someone with expertise there, it could be cool!
Thanks again for your great question!
This is great! I wake up every morning and my bedroom smells like crap.. Sinuses and nose at winter are always kinda gunked up ... Every time i get ill in the winter months is always the same symptoms, sinuses , nose and throat full of awful fluids that i have to spit out.....I think all the bad fluids wanting to go out from our lungs and throat is way of our body to clear and flush all that crap out.. Im 100% sure that air quality plays a massive role in that respiratory system. I dont mind opening window for a fresh air multiple times a day but at winter its kind of waste energy and also when it gets cold outside air is crap to! Cause here in Serbia a good bunch of houses still uses wood and coal to heat their homes... here the market is so terrbile that small home HRV's are basicly non existant and the big comercial stuff is to expensive.. Your build rly goot me thinking, looks simple to make and i could put it on my attic and duct it down in the house like a cealing vent. Curious to see whats next .. Would like to see how you tested efficiency , what was the indoor temp and intake temp of the fresh air and stuff like that. Greets from Serbia.
Thank you so much for your comment! My heart goes out to you. I too have woken up many mornings with terrible sinus and throat problems, and even other health problems, especially since I bought the house I'm currently living in. There is something toxic in our homes that I think we don't yet fully understand. So many people are posting online about experiencing these symptoms.
At 6:44 in the video, I shared one of the efficiency test results. Here's another result from a different day: outside temp: 40.0F, Inside room temp: 68.4F, fresh air intake temp: 64.2F = 85% efficiency.
By the way, people burn wood and oil here too, and the byproducts are really unpleasant to breathe. Not coal in the state I live in, fortunately.
I hope you're able to solve your air quality issues! Reach out any time!
Thanks for this!! I’d like to try and build one and was wondering if you published your sketch up design?
Glad you liked it! I didn’t, unfortunately. I now think the housing is a bit too large, so I’d want to redesign it if I shared any sketchup drawings in the future. Thanks for your interest!
@@HealthyHomeGuide oh that’s funny I just got home with my materials and decided to use foam board which comes in 20”x30” pieces and half inch so figured I’d build it that size. I’m other words smaller. Thanks again!!
@@4DDrover Oh nice! Good luck. I salute you for your DIY spirit.
This is amazing. I now think my son should have this in the little room he sleeps in with the door closed all night. He'd be freezing with the window always open, but he has allergies and could use the filter. Plus I can imagine that CO2 levels rise in a tightly-sealed, unventilated small room with someone breathing all night. Hmm. You have me really thinking. I need to get your recommendations for the right instruments to measure air quality.
Oh, and you really are sounding less allergic. Nice!
Thank you so much! You’re spot on with your thinking. Sleeping in a tightly sealed, small room with no ventilation can cause CO2 to rise to unhealthy levels. I slept in a room like that for a while and woke up oddly groggy every day.
Yes, opening a window is a bad solution due to cold of course, but mainly because small particles like car exhaust and byproducts from peoples’ heating systems can drift in in unhealthy quantities. Not to mention allergenic particles, which tend to be larger and less systemically harmful.
If you’re interested in good instruments to measure air quality, check the bottom of the description of this video for the ones I used :) Thanks again!
A known problem with the above coroplast heat exchanger design is it can only transfer heat to the incoming air theoretically maximally by 50% because of Laws of Thermodynamics,. A consequence is room gets chilly, if indeed not quite as cold as as a naked open window would make it.
There are also designs which use a pipe within a pipe, and a different mechanism at the window to exchange heat, I believe by merely mixing and not separating in and out air streams. It can be piped further into the building to the isolated spaces needing air. When it gets there its room temperature warm.
There are small round through wall units for sale, which by principle of operation, when placed across the house or large room from each other will conspire to coordinate taking turns breathing out while other breathes in @ 15 minute intervals (configurable), reducing cold island effect. Don't want little Johnny to miss skool becuz of the sniffles.
Hi, what a great job - well done! I may have to put one in my home. Would you do a design drawings for my house size layout if you could?
Good job, how much the fan motor consume power and where did you buy them
Thanks! Fan: the cloudline pro S6, a good quality duct fan that can handle higher static pressures. 38 W average power usage.
I'm looking into this myself as I'm struggling with keeping the cat litter smell at bay now that I have two cats, and great to see that this design with the plastic actually works well. I would have figured it would not have enough thermal conductivity. I might have to experiment with this and see if it will help. Right now I'm just opening the windows but that won't exactly be an option in the dead of winter!
Thanks for bringing this up! Ventilating is a great way to keep odors like cat litter at bay, but also comes with its risks if not done properly. If you haven’t seen my latest video yet, I think it’d actually be really relevant to your situation:
ruclips.net/video/80r9qwJPcTI/видео.html
The thermal capacity of air is so low compared to most solids that the conductivity is not too much of an issue. Conceptually, if you think of the HRV in a steady state of operation, there is a thermal gradient along each of the channels constantly re-enforced by the air passing through at almost the same temperature. The transfer of heat between the channel wall and the air is likely far more limited than the transfer of heat through the thin plastic wall. I built my own DIY HRV just using a BIG pair of concentric plastic pipes connected up to ducting. Primarily for ventilation, but why wouldn't you want some heat recovery? Capable of higher rates of ventilation as the airflow has little restriction, but better heat recovery at lower speed.
Can you repurpose UFH components to use in a ceiling for cooling, hooked up to a heat dump somewhere?
That’s an intriguing idea, thank you!
Condensation within the unit will be a problem in most climates and when heating or cooling the incoming air. Over time the heat transfer plates will grow a biomass that can (in extreme cases) include dear old Legionella - the bane of commercial air con units. So a unit will need a means to drain condensate to a waste, and a way to periodically (say annually) disinfect / clean the core.
I agree. I only use this HRV in the late fall, winter, and early spring.
Thanks for this video! I think that you could make that box into a vertical version if you used plywood for the largest sides. It would not need to be more than 3/8" thick to support that core. Probably 3/16" would do. I bet masonite or "bath-board" (which has a nice finish on one side) would work very well. Adding some 1/2"x1/2" wood pieces in certain corners to further stiffen the housing would help as well. (even if using your current materials for the walls)
I think that you might get more efficient airflow if you used some internal ducting to reduce turbulence between the air inlets and the filters and the air outlets and the core. (The shape of the chambers the air passes through is probably causing a lot of turbulence) A piece of thin poster board could be formed into a cone that is the diameter of the inlet at one end. The other end could be creased into a square to fit the filter or core. (the circumference of the filter/core end should be equal to or slightly larger than the perimeter of the filter/core in order to fit) That would give you a custom duct for very little in the way of expense and effort. Another good material for this would be a used printing-press plate. They are usually aluminium and can be gotten at any place that prints posters etc on a lithographic press.
A layer of radiant-barrier material (like ArmaFoil from EnergyEfficientSolutions d0t c0m) over the block in the window and on the inside of the walls of the housing of the HRV would insulate the system and increase the efficiency a little more without adding much bulk or weight.
You could also make the core out of the lithographic plates I mentioned above. Just cut out a rectangle whose long side is longer than the short side by twice the distance you want between plates. Then fold the edges of each of the short sides down by the distance you want between plates; so the profile is like a very wide staple or 'u' shape.(if you cut them out and folded them right; they should be square now) Then you stack them alternating the sides that are closed by taping the folded edges to the unfolded edges on the next plate. You could use hvac foil tape for this to get maximum efficiency. This setup has three advantages over the current core design: The first is that aluminium transfers heat much more efficiently than plastic. The second is that the single layer walls would be more efficient. The third is that there would be better airflow through the core because of the undivided center of each layer. (A tip for cutting lithographic plates is to use an xacto knife and a straight edge. You do not need to cut all the way through. Just score it well and then bend it at the score lines and it will snap)
These are great ideas, thank you!
The stale air only needs a dust filter to keep the core clean, not a m13
I disagree. Dust filters are weak. Oddly, they don’t filter out 100% of large particles like dust. According to the EPA, dust filters remove less than 20% of large particles (3-10 microns). A better filter will protect the core more effectively, for longer.
Also, I wanted to use the same filter on the intake and exhaust so the pressures were balanced.
The Panasonic NanoeX does an excellent job of reducing VOCs, if you can get your hands on one.
I’ll check it out, thanks for the suggestion.
U have a 14*14*14 heat exchanger made of coroplast , what should be the size of the heat exchanger should be if i where building with aluminium or copper foils
A build video would be interesting. If you feel like building another one, I'd appreciate that.
I’ve got a room I use for 3d printing. Resin and filament. I’ve been doing research and I think the fastest way to have better air is to replace it rather that strictly filtering the air. Do you think a system like this would be a good use for a room like this? Ultimately I would like to have air intake going through the wall rather than through a window. Also does the height matter? Like would having it lower work better than having it higher closer to the ceiling? Would be so awesome if I could get a response.
I don’t know much about 3D printing, but I do believe that some people use HRVs to carry harmful fumes outside and bring fresh air in. I believe that Designed by Instinct (I linked his video in my description) uses his HRV for something like that.
That being said, if the fumes you’re generating are extremely harmful, it may be risky to use a DIY HRV to ventilate them, given that DIY HRVs are difficult to make perfectly airtight, and the exhaust and intakes are usually fairly close, leading to potential cross contamination.
Again, I’m not an expert on dealing with harmful gases generated from 3D printing so take what I say with a grain of salt. Hope this helps.
Really nice work.
You've mentioned your HRV's size, (07:56), which got me thinking.... the ducts, fans, filters, and heat exchanger must stay about the same size to meet your needs, but eliminating everything except for those essential parts, should reduce its size by at least half, maybe more.
Alternatively, installing your HRV out of sight, like outside, or in the attic, should leave only the intake and output duct holes visible inside the house.
Good luck, and thank you for sharing.
Thanks very much! I definitely could make this design a bit smaller, but only across one axis. The quadrants are just barely big enough for the filters, so I can’t really shrink the quadrants, width-wise, unless I go with smaller filters. However, I can certainly reduce the length of this design without getting rid of any components. For next winter, I’ll probably make a smaller one!
Good job
Thanks!
You have all reasons to be proud. Subsribing.
Nice build. Anyway next time consider brushless centrifugal fans and also damper to allow the unit work in "circulation mode", in mine, is also built-in cheap AC unit, so mu unit can also cool and heat...
Thanks! I’ve tried to find centrifugal fans but I’m not able to find one that is reasonably priced, well-made, and also delivers a good amount of airflow while being speed adjustable (for quiet operation if needed). Let me know if you find one.
The AC infinity fans I use are actually mixed flow fans, so they’re basically a combination of axial and centrifugal, which I find to be great for a DIY application like this.
Is plastic better than metal in that core in some regards? I understand metal is expensive, prone to corrosion..
Nice design! How do you get fresh outdoor air without ducts using a fan?
Thank you! If you're interested in bringing in outdoor air with a fan, this video explains the technique pretty well: ruclips.net/video/1L2ef1CP-yw/видео.html
Although there are some things to be cautious about when bringing in outdoor air that isn't temperature/humidity controlled, and I made a video about that here: ruclips.net/video/80r9qwJPcTI/видео.htmlsi=3iWdVlPH7UjGqXZH
any reason the exhaust channel is getting air pushed instead of pulled like an exhaust fan?
"Never cross the streams." Dr. Egon Spengler
A heat exchanger on the window side output would extract the last bit of heat. It is an energy expense, but heat exchange is more efficient than conventional heating.
The core of this HRV is a heat exchanger. Are you suggesting building a second core, or using a different type of heat exchanger?
Great design bro! This should work damn well for your money! As an engineer, I am pleased to hear competent technical reasoning accompanied by such a simple but ingenious design.Bravo. Physics does not work on the loud brand and price of equipment, but on the principle. You inspired me not only to make a similar device for myself, but also to think about the serial creation of cheaper systems.Where I live, such systems are not financially available at all. Everyone deserves to breathe clean air.
Amen to that, and well said! Everyone does deserve to breathe clean air. Even people who aren’t rich. Even people who don’t live in homes with duct systems, people who rent, or people in areas where HRVs/ERVs aren’t accessible.
What would you suggest if the problem was not heat recovery, but indoor air humidity? only ventilation itself will for sure help, but what if there is also high humidity outside? about 70% when at home should be max60%. What is your air humidity?
Great question! One of my recent videos (“CO2 monitoring and home ventilation”) addresses this. A whole house dehumidifier such as the Santa Fe compact70 is useful for appreciably lowering indoor humidity levels. ERVs also help to ventilate without bringing in too much humidity. So I’d say optimally an ERV and a whole house dehumidifier. I’m in the process of making an ERV installation video so stay tuned.
It would be nice to see examples of external house wall holes that pass permit inspection. Hole covering would include everything needed to simply unplug whatever DIY HRV solution you have in place to easily sell your home.
I like that idea. I think I’ll eventually look into that.
Very interesting, but we need a better way to warm air and cool air in the opposing seasons. Have you had any such thoughts for folks who want/need to have highly efficient homes as far as energy consumption and insulation goes?
As far as year-round ventilation goes, ERVs are the way to go. I’m actually working on a DIY ERV installation video. To be clear: I’m not making the ERV myself, I’m installing it myself.
@@HealthyHomeGuide hmmm, I'm thinking about options that would facilitate a highly flex
Cool.
Thanks!
What about water condensation? Any plans for more detailed steps of constructing this?
See 8:20 for what I said about condensation. It’s a fair concern. It hasn’t been a problem yet, but when it gets warmer, it could be. I may slightly tilt the HRV and put a drainage hole attached to a tube.
Mitsubishi sell these. They are called lossnay units.
Reasonable instantaneous efficiency results, for more reliable figures use loggers and gather more data points at changing operating conditions.
Fascinating! I’ll have to check them out.
Nice design. Do you get a build up of water inside the unit?
Thanks! If you’re interested in knowing how this HRV performed, I made a video on it: ruclips.net/video/LiptsaKmq80/видео.htmlsi=V-saehGltDKRwl6c
@@HealthyHomeGuide thank you 😁
How are you measuring the efficiency of this? Im not convinced by any of this. You have lots of gaps in the coroplast box which will easily allow the pressurized air to exit before they do their expected travels through the merv filters which will bring quite a bit of resistance along the way. Its going to be much easier for the air to just... escape.
His design is very similar to many commercial designs. You can spend $2,000 or $5,000 and get a system that at its core has exactly what his has, something that looks like it was made out of plastic cardboard. If commercial units can get high efficiency in small size, I think he can too. These units have remained a specialty niche item, aka expensive, without widespread adoption yet, prices have not come down. Most people that want fresh air, just open a window an inch, while not as effcient, it is cheaper and easier. Someday, hopefully soon, these units will get cheap, widely incorporated into homes and everyone will have fresher air. The reality of the matter is many people just don't value fresh air. That seems like a harsh statement, but it can be very hard to get people to change the air filter on the HVAC unit every month (one of the main air cleaners in most houses). Many people still smoke in homes, burn incense, and have other air quality issues. There is a market for in home air filters, but that becomes challenging as companies tend to overcharge for the filters.
Chloroplast may work, and you appear to have built this one sufficently large to get fairly good efficency at the rate of air exchange.
But, know this. Plastic is inefficientl at moving heat across a given surface area. Your heat exchanger could get comparable efficency with a smaller design if the core were made of sheets of aluminum seperated by small three or four spacers each layer. Or you could achieve significantly higher efficency with an aluminum core built to to your existing core size.
Thank you for the design on a budget for the DIYer. Would you tell me what brand and model you used to test the CO2 numbers Sir ?? Would you know the CFM of the unit and are you going to make a larger one fella ?? Nice video
You’re very welcome! All the information you requested is in the description. I actually don’t use this HRV anymore - I use an ERV instead. If you’re interested in learning about why, I also have a video on that in the description.
i AM SORRY FOR OVERLOOKING THE INFORMATION SIR. Could you please tell me if you have a super efficient unit inside your mind not built yet ??? Thanks fella too. @@HealthyHomeGuide
@@victoryfirst2878 hahah no problem at all. If you want maximum efficiency, I’d recommend looking into counterflow heat exchanging cores. I don’t have any plans to build any more HRVs though.
Thank you for your response and honesty. Peace to you and Happy New Year a few weeks late. vf@@HealthyHomeGuide
@@victoryfirst2878 You’re very welcome! Good luck.
Hi, good work , whats the size of the fans?
Regards
6 inch fans. Thank you!
Hey mate, that's already on my diy project list, I am evaluating different materials for the heat exchange unit and currently the best choice from my point of view is aluminum as it has the best heat transfer rate and is already available as foil. That should bring the efficiency somewhere around 95%...what's your opinion?
I was very happy if you could provide some statistics about the air quality over time with switched off device and running in different power modes like e.g. being alone in contrast to many party people, cheers and stay healthy 🍻
I wish you luck with your DIY project! I’m intrigued by the idea of using foil for the reasons you mentioned. The issue is that I don’t know of a feasible way to manipulate foil to create a structure with airtight/independent channels for intake and exhaust.
When u say that it reduces the small particulates by like 90%, you mean it reduces it like that on top of the the reductions from your filters?
Could you please post a list of materials used? I have no idea what kind of fans to get.
Thank you for asking! I’ve posted the tools and materials list at the bottom of the video description. The fan is on that list. Let me know if you have further questions.
It would be pretty easy to make that design with slight alterations self-standing on the floor and to act as a window shelf.
Very true!
Filtering the fresh air isn't a bad idea. I apply herbicides all day, but stop near evening because of the inversions carrying the product to unwanted places. I live near the field and wouldn't mind having something like this. Pretty big though.
Yup, temperature inversions are really disconcerting. If I were to build this device again, I’d do it with 2” thick filters instead of 4” thick filters, and I’d make the housing smaller.
Why filter the outgoing air? If there was smoke or something bad outside, are you concerned it may blow in from the output?
I filtered both the intake and exhaust air streams. I filtered the exhaust in order to protect the core from dust buildup, which reduces airflow and efficiency. HRVs sold today for commercial/residential use do this as well. I filtered both streams to balance the intake/exhaust flow rates, though since these filters are 4” thick, they don’t cause much resistance to airflow anyway.
I’m not sure what you mean about air blowing in from the output.
8:52 Condensation needs much less air movement. You always deliver fresh energy, to evaporate the condensate. This is a great factor for efficiency at large temperature differences, but what can you do🤗
Well done and nice and cheap. I well remember last century, pre internet, someone had constructed a very efficient HR unit out of pleated paper! Large pieces of paper, folded about every half inch or centimeter and laid cross ways like your core flute and connected just the same as yours. The paper being thin, had excellent heat transfer properties and low impedance to air flow. Question would be, how would it go in high humidity? Maybe spraying with a mixture of something non toxic but hydrophobic would be the answer. Plant wax?
I'd say your set up would suffer losses because if the poor heat transfer of the double layers of coreflute. I have seen single sided stuff around. That would improve efficiency. Maybe single sided corrugated cardboard would be the go?
Thanks so much! I only use this HRV in the late fall, winter, and early spring when it’s dry enough for me not to worry about mold.
I like your idea about single layer coroplast!
Now add a solar preheater to the inlet and crank that efficiency up.