"Imagine you could open a window to get fresh air into your house and stale air out, but when you did so, most of the heat/humidity would stay in during the winter, or stay out during the summer, leaving you just the fresh air".
In terms of the effect on environment inside a house, I usually say:
"Imagine it's always a fresh-air spring day inside your house"
This is a great project. One problem with ERV/HRV systems right now is that they are very expensive niche products. While this system doesn't achieve the extremely high heat recovery efficiencies of counter-flow units, the perfect is the enemy of the good, and this seems like it could be orders of magnitude cheaper.
My entire "medium sized European suburban house" runs on a $2.5k 400m3/h unit with HEPA filters made in Lithuania - and that was the more expensive model that I can directly control over MODBUS / 0-10V signal (even turning it into a "dumb" unit). Most of the expenses were running the ducts. YMMV
It's just awesome. Every single room has fresh-smelling air and after fine tuning all my heating systems with algos implemented in Home Assistant - I'm getting ~60-100ppm over outdoor CO2, perfectly clean air, temperature within 1C of the set value, on-demand humidity extraction after showers etc. All it needs to be properly overengineered now is a bunch of dampers and per-room CO2/humidity feedback :)
I'd be very interested in hearing the details of this.
That is just the HRV, not the design of the system, the ductwork, and the installation. All those add up. In new construction those costs can be shared with the regular HVAC system design, but in a retrofit its far more expensive
Most building codes in US/CA mandate them since about 2015, so I'm not sure how niche they are (at least in new construction).
Depending on the (air) volumes involved, ERVs can be had for under CA$ 2000:
* https://gasexperts.ca/product-category/air-exchangers/lifebr...
* https://bphsales.ca/collections/high-quality-erv-air-exchang...
HRVs for less, but it's probably worth the extra few hundred for better humidity management.
Outdoors °C -23 -15 -10 -5 0 25 30 35
After unit, °C 12,9 14,5 15,5 16,5 17,5 22,6 23,6 24,6The downside of this is that the high efficiency is limited to small spaces (based on the mass of your core), where counter flow units are great for entire homes.
One point often overlooked with counter flow units, is that you can place exhaust ducts in spaces that you want to purposefully remove air, like bathrooms and kitchens, while providing fresh air to places with little air movement, like closets, basements.
Regenerative core ERVs do little for fresh air circulation.
Naively allowing the air columns to thermally mix would result in the average of the inside and outside temp. So how does this do better?
Heat exchanger there is usually an extruded ceramic grid (ERV) or rolled corrugated aluminum (functions closer to HRV than ERV)
CO2 scrubbing would be better than nothing, but it's really expensive and won't improve other metrics like TVOC
If you are doing that level of renovation is is probably better to just tear down the house and rebuild. The costs will be similar and there are a lot of other things people demand of a new house layout that cannot be retrofitted in the old shell. Often the law will not allow this and so you are forced to renovate just to keep some now illegal feature that is worth keeping, but otherwise a tear down would be better.
There's only so much temperature gradient these setups can handle economically, and it's quite possible that the hot LA summers combined with the cool AC air are too much for such an installation not to leak energy at an unacceptable rate.
Then again, just like with ACs that also serve as heat pumps, it could just be a matter of not enough people (or professionals) knowing about these installations to make it viable to build a business around them.
If you call a random HVAC company, they may not want to deal with "fussy clients" that want something "fancy" like an HRV/ERV. Best to look at folks that perhaps try to adhere to building science more. A quick search for the LA area:
* https://www.jmsacandheating.com/indoor-air-quality/heat-ener...
* https://www.aircomfortexperts.com/additional-products/ervs/
* https://www.azaircond.com/indoor-air-quality/energy-recovery...
* https://www.socalclimatecontrol.com/ervs-and-hrvs-energy-eff...
Or do a dealer search from a manufacturer, e.g.,:
* https://broan-nutone.com/en-us/home/dealer-locator
> Is there a particular climate these are suited for?
Any climate. Modern ones can even handle IECC Zones 6 and 7:
Getting rid of humidity in winter is the main reason why you want to bring fresh air in a house though!
Bringing in cold air at 50% humidity, then warming it up to room temp makes the humidity fall, leading to dryer air indoors than comfortable.
Possibly just different terms used in different countries where the humidity is a bigger problem (very hot and/or very cold outside air).
This current OpenERV product appears to use dessicants for this purpose but might be an optional add-on?
Really a lot of our older homes shoud be retrofitted with a MVHR unit to help things as ventelation is awful in most houses. I'm actually quite surprised a lot of landlords in the UK don't do it as theres always a fight between them and their tenants who don't necesserily want to leave a window open all day in the winter to stop mold.
I'm sorry I don't have a bunch of units ready to ship out, as the site says it's still in beta, I am to be honest kind of taking my time because I have another project, the big quiet fan, which is actually funded a little better, and thus I've been directing most of my time to that. But I do advance this a bit most days. I have a twitter where I tweet my progress : @open_erv, and also I'm on bluesky.
I have shipped a few units to other engineers who have/will test the units so I can share third party confirmation for any skeptics.
To clarify some of the discussion, it is not a counterflow heat exhanger, it is a regenerative type. https://en.wikipedia.org/wiki/Regenerative_heat_exchanger. I prefer this type because they can recover latent heat more effectively than recouperative (such as counterflow) type, and latent heat is 40-50% of the total energy content of the air, seasonal average in Ottawa or Toronto.
I am hoping to get the machine tested by the PassiveHaus institute to show beyond doubt how good the efficiency is with a third party test. I have no doubt, I have tested it myself, though.
These can theoretically handy any temperature differential, but the TW4 and WM12 are currently made of a polymer that I wouldn't trust in an extremely hot climate combined with direct sunlight. For that reason, I am focussed on cold climate scenarios. I am pretty sure it will not frost up even in extremely cold weather like -30. I used it last year in my window and had no problem, and it did get to like -25 at least iirc.
Anyway, I've tried to turn the very temporary influx of interest into something positive and lasting by searching for 2 people who can install and document the install of a pair of TW4 energy recovery ventilators, so anyone who wishes to buy thereafter can know what they are in for on that count. There is another guy Alex who will test flow and efficiency, I've already sent him the stuff.
So we get things tested and verified, and I will continue getting a jump on producing units by running the printers and assembling in between when I am doing the more respectably paid work in my life. The kits are on the back burner because even I am still stabilizing the assembly methodology. I even added a new component just recently, a flow straightener that boosts flow by about 10% while allowing noise to be reduced even further.
So stabilize, verify, produce, and then after that, within a couple months, I sell in a more or less ordinary way to anyone who wants them. I'm sorry it's not in time for the cold weather, but we have to remember ERV is about the big picture and long term. Like the rest of a building, it's an investment, and the machines are made for (very) good return and long lifespan.
I will prepare some WM12 units for those who have asked for them. To be clear I only got 12 emails expressing interest, not an absolute flood, but it's encouraging to know some people "get it" at least. I knew there would only ever be a small trickle of relatively wise people from around the world that appreciate good performance and return on investment. I only need to sell a few pairs per month to make it worthwhile, at the eventual $1300 CAD price tag.
I am open to scaling up production with more efficient production methodologies, but I am actually fairly well acquainted with injection molding, machining and other conventional approaches, and they aren't magic. They would help for sure but they wouldn't radically change the price, or the rate of return on investment, and they also take a lot of investment not just for tooling but also re-testing and re-design. I've also changed the design so, so many times after I thought it was done I am highly wary of being locked in.
Small note: the older single-room unit we have with the fan on the outside can ice up and make horrible noises then stall at a few degrees below zero (here in London UK)... B^>
Also: as the creator of a project called OpenTRV, I cannot but help admire your taste in naming! B^> B^>
I’m excited for more competition in this space. Beyond the hardware I’ve found that HVAC installers are way behind the curve on air quality. I hope education and awareness increases in the industry.
Can someone expand of this?
intuition tells me that a regenerative design can be no better than 50% efficient, and would be worse at recovering latent heat
I would consider installing this in my open finished attic even though I already have a whole house ERV. The problem with a whole house ERV, particularly in a multi story house is that it doesn’t necessarily produce a lot of fresh air where you are in the house.
However, reading the docs, they seem written more to discourage any kind of DIY attempt by saying things A, B or C are difficult, than actually explaining how to do them correctly. I'd love to contribute to the project, but it feels like it's not set-up to foster community contribution.
If I'm mistaken, I'd love to donate some of my time on this!
IMO, this feels like a more marketing project than anything open. ERVs are already very simple (a recovery core + blowers/fans). Commercial units last an extremely long time (some with 10 year warranties) and have comprehensive parts availability.
Also a long term window install is a bit janky and is likely to lose out on efficiency due to glass being a poor insulator.
In the photos it seems to be a bunch of nested single-perimeter cylinders that are joined at a few points to maintain spacing. Easy enough to model, but I agree the documentation is horrible and there's no way to contribute.
Commercial units are not comparable because they're way more expensive despite being so simple
It looks like a fun project. I don’t want to discount what has been designed and built. It is confusing to start reading about the project and discover that it’s more of a business than a community project while simultaneously being unavailable for purchase. The person who built it commented on HN that they’re focused on a 3rd different fan project right now, which brings the future of this project into question.
It would be great if a community effort could fork this project and work on making it easier to DIY so the community could push it forward.
EDIT: After exploring the files I’m not sure I’d even call this open source. I either can’t find some key files or they’re deliberately excluded. True open source projects would also include the CAD source, not only .STLs so others could adapt and modify the source. I think the open angle on this project is more marketing than substance.
The most likely scenario for longer term is that people may submit minor patches or suggestions, which I roll into the hardware or firmware. In reality, hardware is not like software. You can't make changes easily. Some wizards may take it upon themselves to spruce up the firmware with fancy features and release something, which anyone is free to do. There would then be multiple compatible versions of the firmware, one which I curate for reliability with minimal features, and others which others can provide. Same as for 3d printer firmware.
The firmware is Micropython, which is extremely easy to understand and modify.I also have this DIY bookmarked: https://www.youtube.com/watch?v=wJB3dyHDa-8
Naively, if on average the same amount of air goes in and out, I'd expect the temperature of the heat exchanger (on average in space and time, eventually) to be the average of the outside and inside temperatures. If the outside is hotter, the air coming in would be cooler than the outside air (which is a win), but it couldn't be cooler than the average of the temperatures. So, it would still not be anywhere as cool as the inside air, which doesn't sound like 90% heat retention.
Is the heat exchanger attached to a heater or a cooler? The linked video, https://www.youtube.com/watch?v=CDCu0IbEn8Q , would suggest not, as it talks about saving the energy needed for cooling or heating. Is there another clever trick?
You can improve this by exchanging heat across a continuous length along opposing flows. Imagine two parallel pipes thermally bonded where fluids flow in opposite directions. Each point still averages the temperatures, but the average temperature varies across the length and approaches the interior temperature on the interior side and the exterior temperature on the exterior side.
Thanks!
Imagine a pipe filled with 3 metallic grid sections (such that the air temperature in the section will equalize with the metal temperature) separated by plastic grids (such that the heat isn't conducted through the metal), and you push air alternatively from one hot side at 20°C to a cold side at 0°C for 30s and in the other direction for 30s.
For symmetry reason, the pipe will passively (we don't count the energy required to move the air) have a gradient of temperature from the hot side to the cold side. The first section will be ~15°C, the second ~ 10°C, the third ~5°C. (Each section temperature is the temporal average of the temperature of the air flowing from previous sections : so because air switch direction, it means it's the average of left and right sections.)
From the point of view of the house, you only lose energy from the first section of the pipe which will be more like 15°C rather than 0°C.
(I've seen ERVs with heaters attached; but for the purpose of avoiding frost buildup when it's below freezing outside.)
Imagine two air streams counter-flowing. They "swap places" within your heat exchanger, so you can (theoretically) get 100% heat recovery.
This principle is used by animals to minimize the heat waste, by counter-flowing warm and cold blood: https://en.wikipedia.org/wiki/Rete_mirabile
Countercurrent-flow heat exchangers (where the two channels of the fluid/gas) move in opposite directions on both sides of the heat-transfer mechanism maintain a heat flow gradient over the entire length of the heat exchanger. This can result in an almost complete transfer of heat from one current to another.
High efficiency HRV/ERVs use counter-current flow heat exchangers.
EDIT: It does, if you click on "learn more", you'll learn more: "The OpenERV TW4 modules are made to always work in pairs. One always sucks air while the other blows air, synchronized over WiFi. This should be done, or hot air would be pushed out from the building through the walls during the ingress phase, causing heat loss." ...Perfect!
Currently I have two holes in my wall for ventilation, when it is windy it's too much (feel the wind blowing inside), when some people visit and there is no wind, boom, >3000 ppm CO2 in 20 minutes.
I just really hope it is very quiet, although it says ~37 dBa (which is quite a lot imho), I replaced my bathroom ventilator recently, it produces 25 db! [1]). The previous one [2] produced 52 dB (cheapest around), that was pretty annoying, you'd hear it in the bedrooms above the room it was used in. Maybe 37 dB it isn't so bad, especially since you can wind it down and mostly need it when it's busy/noisy (many people) anyway.
Btw, don't buy a CO2 sensor, pretty soon you're a ventilation nerd, or as my wife would call it, a ventilation curmudgeon.
[0] https://blaubergventilatoren.de/en/series/vento-expert-a50-1...
[1] https://www.filterfabriek.nl/ventilatoren/badkamerventilator...
[2] https://www.hornbach.nl/p/rotheigner-toilet-badkamerventilat...
Absolutely.
> A room is not heated by increasing its internal energy but by decreasing its entropy due to the fact that during heating, the volume and pressure remain constant and air is expelled.
https://pubs.aip.org/aapt/ajp/article-abstract/79/1/74/10418...
The point about balancing airflow is crucial, but I think underappreciated by non-professionals. Thermodynamics is highly non-intuitive in places, and the enclosed climate-controlled spaces we love to inhabit are certainly included in that.
Don't get me started on the idea that you can cool a closed room by running a fan or opening a fridge.
Oh man I had this discussion with my wife yesterday, we have a small electric heater in a room where a pipe burst and I still need to fix that (no heating means instant fungus problems). It keeps its fan rotating always, that way it determines the input temp for its thermostat more accurately. But wife insists it is sometimes blowing cold air and thus very very bad... I explain what a thermostat is (bimetals and all) and that she experiences "coldness" because a layer of warm air is blown from her skin, it's not blowing cold air... she doesn't follow... I even measure the energy usage and the thing only uses 20 W or so when just blowing, not heating. Even when just blowing it's moving cold moist air from the walls so overall good. It's difficult dealing with her like this.
I'll pay someone to tell me how to deal with someone like this and maintain a positive atmosphere. The thing is, I also do it for things that really are probably not worth discussing... I should pick my battles better, is there ever a good time for some mansplaining? Or should I say... Nerdsplaining?
On that note, I'm curious if hybrid heating/cooling solutions will ever take off. Other than this OpenERV product I mean, which I guess technically counts!
Low Tech Magazine mentioned some experiments in their article on compressed air energy storage (CAES). Instead of trying to make that form of energy storage an adiabatic process, the idea is to use the heat produced/required in the compression/decompression steps in the household to improve the energy efficiency (e.g. use heat produced during compression to heat water; do the decompression in a space that should be cold anyway like a basement used for food storage).
[0] https://solar.lowtechmagazine.com/2018/05/ditch-the-batterie...
I was surprised when I saw they're mostly made of thin plastic and don't depend on thermal capacity at all (unlike, say, HX espresso machines). The way they work is quite simple:
c
w o
a │ │ l
r └─────────────────────────────────────────────────────┘ d
m
air at 50 deg ────────────────────────► air now 5 deg o
i u
d ───┬──┬──┬──── heat exchanging surface─────┬──┬──┬───── t
o ── ▼ ▼ ▼ ─────────────────────────────── ▼ ▼ ▼ ──── d
o o
r air now 45 deg ◄─────────────────────────air at 0 deg o
r
a ┌─────────────────────────────────────────────────────┐
i │ │ a
r i
r
The lightweight plastic walls are advantageous here - while plastic isn't particularly conductive, the walls are so thin that heat transfers readily. It's how these heat exchangers can achieve 80-90% efficiency without needing any expensive materials or thermal mass. The warm exhaust air leaves only slightly warmer than the incoming cold air, having transferred most of its heat to the incoming stream.
Clever design.
They should be made of high thermal conductivity material like resin or ceramic.
The hardest part is finding a good spot for the ventilation unit, which is about the size of a large, old CRT TV. You have to run ducting from there to multiple rooms, but their ducting system is easy to install.
Mine draws about 20W/hour at its typical setting, and it greatly improves comfort. Keeps some of the humidity out when it's humid out, keeps some moisture in when it's dry out. Fresh air year round. Keeps mosquitos out. Keeps some dust/particulates out.
Worth the effort, even in my small house.
A decentralized unit would be a lot easier to install, but I imagine it's less efficient, less suitable for larger dwellings, and probably louder. YMMV.
Paraphrased:
- push-pull ventilation is easy to install and comparatively cheap
- it's prone to hygiene issues like blowing dirt out of the filters back into the air and providing a moist environment for microorganisms in some operational conditions
- it's prone to windy conditions
- the numbers stated by commercial vendors seem to have no basis in reality, there seems to be no vendor providing data based on the relevant testing standard for these systems. OPenERV states they want to get it tested by Passivehause institute but also say no lab data measured yet.
Might be just my counter-factual gut-feeling, maybe a mechanical window opener based on EspHome for short pulsed passive ventilation intervals is actually more efficient, easier to implement and need less maintenance? Not aware of any comparisons though and last time I checked I could only find some finicky 3d printed actors that might not survive a guest opening the window.
I am super happy with them. We now always have air that feels fresh and warm in winter, and the humidity has dropped significantly.
There are two types of such ERV devices:
1. Those with only one air channel that switches directions periodically. They use a heat storage element in the airflow. OpenERV belongs to this group.
2. Those with two separate air channels for intake and exhaust at the same time. The air does not mix but passes through a heat exchanger. Bayernlüfter works like this.
The only thing I don't like about Bayernlüfter is that it is not open source. It is controlled by a Raspberry Pi (or a similar clone), and I don't have access to it.
I've personally been looking at installing such a system [1]. However since houses in the Netherlands are almost all made out of concrete installing such a system in an existing house is pretty hard.
[1] https://www.duco.eu/uk-ie/products/mechanical-ventilation/ve...
The old-and-trusted brand here is https://www.genvex.com/en (ours was supplied by Ecovent though https://ecovent.dk/?lang=en )
Unfortunately, the gDrive files are not providing enough information for me to build one of these in a DIY manner. I didn't find enough information on the hardware side, no BOM, no hardware documentation. I think that, if the author would like to actually boost DIY adoption, it'd be worth having a step by step assembly guide. At the same time, when reading the page, I had a feeling like it's more supposed to be a way of advertising a future commercial product, not really focusing on the FOSS/DIY side.
The software is provided, but from my experience with such projects, it's maybe half of the minimum information needed to build a full fledged device.
I like the project and would love to build it in the near future though.
These are licensed CC BY-NC-SA 4.0, so depending on your personal definitions, they may or may not be "open source" (IMO they're open source but not FOSS but I've seen others equate open source with FOSS).
The purpose of the source code is to enable maintenance, not cloning, I say that on the website. That is this context, there are many others. It improves the economics because the machine lasts longer and there is no planned obsolescence. People are welcome to make their own units from the source if they have the skill, but although it would be fun, I don't really have time to make it easy. Some day there may be a kit which is very economical but it will still take a whole day of work to assemble, probably.
When i saw this I immediately thought of studying it and reuse some of its designs for my custom use case, which does not appear to be currently possible.
At first glance it appears to be "open source" in the sense that you can buy it, but if and when something breaks you can print/reorder it easily.
Correct me if i'm wrong
Have looked in this kind of systems, for my parents. The use case was basically, not about energy efficiency, but rather noise protection - to be able to sleep with a closed windows. I think so far I always had two issues (in that usecase).
- First the device by itself - produces a bit noise like 42db might be too much for some people if you want to sleep. Especially some of the devices are using one ventilator, which switches directions and won't produce homogeneous noise.
- Second 60 CFM is fine, but if you want to have the feeling of an open window - it should be much more and most devices can't deliver that. Also the heat exchange thing is kind of cool in the winter for sure. In the summer, you often have the case that in the evening you house is much warmer than the air outside - so you would like to turn the heat exchange off in the winter.
PS: Actually, maybe looking for a complete different use case. But I think what would be very cool, would be some idea to make at least one room 100% quite (with fresh air ) in a cheap way. Guess this would be a huge life changer for a lot of people, who suffer from noise pollution.
I would love some sort of intelligent house ventilation system which could do all that. Heat recovery when it makes sense, normal ventilation when it doesn't. All automated based on dT and relative humidities.
Normal (heat recovery mode) you have them reverse flow every 60 seconds or so to swap heat.
In cooling mode you just run then continually. One is bringing in fresh air and the other is removing stale air.
The heat store in the intake will soon cool to the outside temp and the heat store in the output is irrelevant (apart from maybe slowing the air flow and creating noise).
If you manually control the system you could combine with a few open windows to create cross breezes even on still evenings.
The alternative design is a counter-flow heat exchanger. Using 3d printing and gyroids it seems possible to build quite compact ones. (metal 3d printed heat exchanger for helicopter https://www.youtube.com/watch?v=1qifd3yn9S0 )
3d-printing a counter-flowing heat-exchanger seems interesting but maybe there are some molding issues that need to be taken care of (maybe HEPA filters on the inside in/outlet are sufficient).
The main advantage of the heat-exchanger solution is that you won't need specific electronic control and can reuse the standard fans for controlled ventilation, but there is more thermally isolated piping required (and the pipes are quite big (~10cm diameter) because they need to move a lot of air even if the fans are weak).
The push-pull system is harder to DIY because most of the off-the shelf fans can't be reversed easily (and 3d printed fans are noisy and inefficient).
I live in a place where supposedly the air is of good quality, and yet, when I open the windows, the all place gets a thin film of black dust on all surfaces - most probably due to the particle emissions and tire degradation dust from vehicles from the highway nearby.
The solution I've found is to open the windows every day for about half an hour and then put an air purifier to work.
It effectively heats the fins slightly in one direction, then cools them again slightly in the opposite direction.
Same with wetting and drying for recovering moisture.
I am surprised that the fins appear to be plastic - one would imagine that steel fins would have far better thermal capacity
Prices there start at $150 + shipping.
Has anyone tested these?
> Recuperative types are what most people think of, consisting of a thin layer of material that separates two gas streams. Regenerative heat exchangers are different. They briefly store the energy while air flows in one direction, then release it when the air flow reverses.
I have to admit I am slightly more dubious about this type as they are new to me, though I did see a YouTube video about a commercial one recently and they seem to be a hot new thing.
Possibly this is something sensible that only becomes practical with software and wireless communication? Rather than running ducts to a central location.
Though then fitting two side by side in a window seems odd. Why not use the traditional type in that case?
They are rated 90% recovery at low speed. Today it's 11C 75%RH outside, 18C 65%RH inside, at low speed (15m3/h rated at 1.2W) there's barely a difference: 17.8-17.9C air intake temperature. They keep the air noticeably fresh, drier and also keep the CO2 down (<600ppm right now). I'm running them below the "recommended" 50% air-change per hour (ACH about 35%), and boost when needed.
There's a recuperative ducted type in the attic for the first floor, when I checked last month it was 4C outside, 18C at the outlet vent, and 17C at the inlet vents. That runs at 50% ACH.
The reasoning for the paired up window model isn't obvious, maybe a simple increase in capacity. The website is quite clear you need a push/pull pair to be efficient, and an immediately adjacent such pair is not going to work so well.
Great work.
I cannot help to wonder what brings the total cost to $600, the price of a modern, powerful computer.
And yes, I am familiar with the economy of scale :)
The whole thing, designed and made in China could probably come to a BOM under $4, and retail in the USA for $12.
What does really inflate the BOM ?
And this is in no way to discount your effort or your results, I'm genuinely curious.
There's lots of text on that web-site, but details of the actual design of the thing are pretty scant.
The worst scenario is during high wildfire smoke events... trying to keep the house sealed enough to keep the smoke out often requires taping door seams, etc. and the CO2 skyrockets.
My home was most likely 'retrofit' in the '90s to make it airtight for efficiency, and even with the windows cracked is too airtight to be healthy, and still more so than it was probably designed for in the ~1950s.
We have a fireplace, which is not efficient at all, in part because it sucks cold air in from the outside. I was thinking it would be great it we could use an ERV to condition the air that gets brought in.
However, as far as I can tell, the moment you exhaust air from your house in any way except through the ERV itself, the ERV cannot help you with the replacement air that comes in.
Is that correct?
This product cost around 500$ and also has heat exchange. A friend of mine has installed it and is very happy with it.
This model is available in Europe for about 900 EUR: https://www.international.zehnder-systems.com/en/comfortable...
Unfortunately, due to cars and dirty heating systems around where I live, outdoor air tends to be not great.
Hope they used a throwaway google account with absolutely no link to his domains or main email address.
How did you get the fans to run backwards? They look like standard PC fans
This isn't something to even consider without some expert reviews. The projects are also work in progress and overall incomplete with many details missing.
Be careful when you do anything involving ERV and HRV. It's very easy to cause serious damage to the property you live in, harm yourself and others in an irreversible way, or even both.
You could glue a fan to an air filter and then position the thing in a window, to bring in outside air that then gets scrubbed by the filter. But now you're bringing in cold air in the winter, or hot air in the summer.
An ERV brings in fresh air and mostly solves the problem of having cold air rushing in on a winter day, or hot air rushing in on a summer day.
Is the air outdoor or clean? It can't be both!
Marketing bullshit aside, this looks great!
Low-CO2 outdoor air vs high-CO2 indoor air, if you prefer. Important for how air-tight modern energy-efficient construction is.
Unfortunately, outdoor air has particulate and ozone pollution. Filtering it gives you "clean" air.
In winter and summer, you also heat or cool the indoor air for comfort. If you just pump in outside air, you effectively also pump out the indoor air. This wastes the energy that had gone into heating or cooling it.
These systems save that energy by transfering heat between the air that's getting pumped in and the air that's getting pumped out.
But this is actually treating indoor air, that's very confusing.
Fresh outdoor air is easy to find: just go outside!
In the summer it's not a problem for me, I leave my windows partially open all the time but in the winter especially when working from home this would be quite neat. Also, I live in a small town in germany so the air quality here is comparatively good to many of the city folks here.