This is an excellent idea, and a small dehumidifier would supply all the required parts.

-AC_Hacker

AC Hacker, Thank you for all your posts here as well as Homemade Heat Pump Manifesto. I have read all of them with great interest. You and all the others have given me so much information. I too will soon start hacking!

Welcome!

I don't know your background, but I usually advise folks to start with small projects and gradually move to more ambitious ones.

Do you have a project in mind already?

-AC_Hacker

small plate heat exchanger with aluminium foil
 

I have been following this thread for a while, and got appetite to start on something myself.

I live in a small 60m2 apartment in an old renovated building. Three rooms in a row, livingroom-kitchencombo, and the last room is my bedroom, with a bathroom semi-attached (no door between them). I renovated this apartment myself, not hindered by much background knowledge, and overlooked a major thermal bridge in my tiled bathroom floor, aggravated by the fact that my neighbor downstairs decided not to use that space at all and does not heat it (he has a larger apartment). Result: lots of condensation on the floor, even when it's just chilly outside (say 6C).

Another source of humidity is cooking: it would have been quite difficult to install a true extractor hood given the setup here, so I'm stuck with a recirculating system. You guessed; there's a lot of humidity, cold spots, I can start to smell mold developing. A seriously bad situation.

A simple extractor fan in my bedroom/bathroom would help a lot, but I’d actually like it to run continuously to improve the air quality throughout the entire place. I’ve been planning to install a HRV unit, and given that its purpose would also be to extract humidity, I’m excluding systems with humidity recovery. Given the price-tag of commercial systems, and an uncontrollable desire to mess around with stuff, I was thinking of getting started on my own HRV.

To cut it short: after quite a bit of reading around, remembering what I liked and ignoring good advice, I thought I’d buy a piece of 4mm or 6mm thick double-sided polycarbonate board, and cut out the individual channels with a cutter (resulting in many thin long pieces of hollow plastic). Then, make flimsily thin empty frames out of this, about 90cmX44cm in size, and then stretch aluminium foil over them, make a stack of them, say 40 pieces, and take an approach somewhat like in the “make” article which was posted above. I would use some silent 120mm fans. I’ve taken up soldering, so I’m looking forward make this run slowly, and somewhat faster when the relative humidity increases.

Questions I have are: does this make any sense whatsoever? Would the fans be able to push the air through (tell me there’s not enough information here to know). Any idea on this surely being so inefficient it cannot be worth it? A specific question I have is: would it make sense to force the flow between the plates to follow an S pattern, using baffles somewhat like in a shell-and-tube heat exchanger. Would such baffles just decrease the capacity? Would they help creating a turbulent flow? In that respect: would it help to try creating a more rugged surface of aluminium?

Lots of questions, not too much structure, long post. Really sorry about that, but any comment is greatly appreciated!

> ...there’s not enough information...

I think your idea will work, and it's not going to be terribly expensive to try it out.

I don't quite get the "S" curve thing... Why not just go with a longer channel?

But the most important thing is to try it out, do some tests...

You got it right the first time when you said that you were, "not hindered by much background knowledge."

I think that is the perfect state of mind with which you should proceed!

Please take photographs of your project, we'll all be very interested to see what you come up with.

Regards,

-AC_Hacker

Here's an addition from Grainger. Energy Recovery Ventilators
http://www.grainger.com/Grainger/ene...rch&sst=subset

Thanks for the feedback. I meant the approach of David L. Meinert, btw, not the `make' article.

do you people know these HRV's, might be inspiring...

http://www.homeventilation.co.uk/retroVent.php

comes at a 400 something GBP price tag, but I find it hard to believe the efficiency of 80-90% given the small surface.

This one, I'm extremely fond of, and there's lots of positive talk on it on German fora
http://www.oekoluefter.de/bilder.htm
http://www.oekoluefter.de/video.htm

It's by a tiny manufacturer. but it's a beautiful thing with magnetic bearings etc.

I had to mess up the urls, hope that works

Yes, we did have some idea... There have been 21 pages of posts on this topic, and 208 posts in those pages.

But the most interesting part is the work that has actually taken place to try to build a useful heat exchange ventilator.

I took a look at the links you left on your previous post. The mechanisms that are being tried look like they may be a challenge to fabricate.


What are your ideas regarding your DIY project approach?

Have you made preliminary sketches yet?

What material will you use for the heat exchanger?

How will you deal with condensation?

-AC_Hacker

At the risk of being somewhat off topic, I have question: Given that running the house at a slightly lower pressure than the ambient atmospheric pressure is desirable, how will that affect say a log burning stove? Will it upset the flue balance unduly, causing it to become smokey?

If it is desirable to run a slight negative pressure (is it?), and if you need to burn wood, then you most likely will need an air-tight stove with an external air supply.

All of the HRVs that I am aware of use balanced in-flow and out-flow fans to ensure zero pressurization.

Is the idea behind slight negative pressure an attempt to avoid moisture condensation in the walls?

-AC_Hacker

Yes - well I have seen it suggested here. Although there are arguments for positive pressure as well; stopping dust/pollen infiltration and so on.

The wood burner is the sole source of heat in my house, so I will need to look at how to feed it with air, especially as the holes in the walls get filled in...Or at least run a balanced pressure system.

AC, where is the thumbnail of the tube HX from? Looks interesting. Also I can't remember where I came across this new direction in commercial Heat HX and I haven't see it referred to in this thread so I am posting it just for FYI. Prototype Breathing Window The idea of decentralizing might help utilize smaller capacity(easier to make) DYI air/air more even though their HX is high tech.

As we have very cold winters here, I have a little insight. With a proper set up ventilation system in Norway, there is a slight negative pressure. The reason is logical when I tell you now =)

If you where to have positive pressure, and very cold outdoors, and one of the inevitable small holes in your humidity block layer (or whatever the plastic on the hot side of the insulation is called), then warm, possibly humid air would be pushed out trough the wall. Moving out the wall, it would be cooled down, the relative humidity going form +20C to -20C would almost guarantee condensation, water damage and rot. It is much better to pull in a little cold air, and keep the building nice and dry. Therefor, all balanced ventilation systems here is not balanced in a pressure type of way, but they are balanced in the way that you do not only force air in or pull air out, but you do both, whereas an unbalanced system would be your bathroom fan going trough the wall to the outside.

To get your wood burning stove burning right, AC is right in saying that you need air supply. Ovens in Norway is trough building regulations codes obligated to have air supply from outdoors to be within the regulated air-tightness that today's buildings should have. My chimney is of this type:
Schiedel : Norway: Solid Vent
Where the air to the oven will come down the chimney on the outside, and the exhaust will go trough the insulated center tube.
The other much used system is just to pull a tube from the outside down to the oven. Be careful with this though, it must be mounted in a way that will not cause condensation on the incoming tube as it will get as cold as the outdoor air.
Feeding the oven with air will give you a much better temperature also btw, since cold air will not be sucked in everywhere, cooling down all rooms that do not have an oven. Mythbusters tested this iirc.

-Ko_deZ-

I have quickly read thru all the posts here are my observations:

- the cheapest recuperator I can find is Mitsubishi Lossnay (1000€ - 250m3/h - humidity exchange - efficeny ~70%)
- No one mentioned cardboard heat exchanger - not the best conductor but it exchanges also humidity. Problem is high outside humidity and warmer temperatures - you need to make a bypass for this situations.
- problem with computer fans (humidity, cold, dust) can be solved by placing them on the inner (house) side of heat exchanger (between used air from the house and heat exchanger and heat exchanger and frash air into the house).
- The problem with Lossnay is rather high electricity use (100 W), some will say not to bother with that, but why to use so much power when you can use only 1/10 of that
- Here is a nice link to start with DIY: http://cheap-easy-living.weebly.com/index.html

What do you think? Is it worth it to go DIY?

Hello Gasper, welcome to EcoRenovator:)
I inserted the link's url in your post. BTW, is that your web site?

I think that using cardboard for testing is a good idea. It's much cheaper and easier to find than coroplast (let alone copper or aluminum:eek:), plus it's easier to cut, glue and then recycle. On the hand, it's not as stiff as coroplast, and is easily ruined by moisture and mold, so I'm not sure if I would trust it in something permanent. And, as you mentioned, it's not a good heat conductor, so in the long run the losses would start to add up.

How true! Many companies cut corners and use cheaper, less efficient fans and pumps in otherwise very nice products.

No it's not my website.

The idea is that all the condesing moisture is taken by the cold outside air as it's getting warmer (thru heat exchange). For spring and autumn time you would use bypass with no heat exchange.

BTW, Lossnay is using paper core.

Any updates on these projects?

Erich

Mike, who lives in Oregon, built a simple corrugated plastic (coroplast) heat exchanger, to increase the ventilation for his too-tight house.


It is a pretty simple device, about 6" x 6" x 24" with a couple of small computer fans driving the incoming and outgoing air. He has it sticking longways through a space in one of his windows, tilted down so that the condensation will drain outside the house.

Details here.

He used it all last winter... minimum cost, minimum hassle... he's satisfied.

Nobody could argue that it's not very elegant... maybe that's your contribution.

-AC

Noticed an interesting thing last winter in that the incoming fresh air required by my forced air furnace running thru an 11' run of4" tube(alum dryer vent) was nearly the same temp as basement by the time it reached return air duct. Meaning it transfered basement heat to cold air pretty well. Most HRV's I've seen to try to stay compact force counter flowing streams of air thru very small,restricted channels to exchange heat as compactly as possible. This long run idea(also used in ground tubes) has me planning an HRV that would just be a long tube in tube counter flow that would be 18'(the length of basement floor joists where it will run parallel between two of them. I will already have a solar air collector that feeds heated fresh outside air thru 4" tube that distance(which if I can aquire them will have 22C/73F PC wax in cooler blocks that can slide into tube to store heat past daylight and create turbulence for better exchange). So running the 4" tube(rigid alum dryer tube) thru a 6" insulated sewer pipe(gives fairly close equal volumes) to counter flow used air out which can be sealed and pitched to provide weepage. 18' should allow for slower less forced air flow and not take up more space than an air duct(could even run cross joists against wall and not waste much space). Finning of 4" tube would be nice if not to difficult but length should balance less efficient exchange. Two separate low volume fans should work. One incoming continuous, the outgoing could be controlled to not run and steal heat from warmer outgoing air. Controls could be tweeked depending on fresh air needed and how tight living space is. Worst case is continuous outgoing would debit heated incoming some. Very simple and inexpensive to construct. This would of coarse be in addition to all other things I could do to minimize fresh air demand within a "healthy" level. A long, slow, low tech HX over a short, fast, hi tech approach. (If I can't find a working PC material I will use a long strip of flexible 4" plastic that I can spin into a helix to better mix air).

Fantec model Buy Fantech Energy Recovery Ventilator Model SER 1504 | Fantech SER 1504 is only $835

@ Drake:
I like the long tube-in-tube contraflow idea, I've thought of doing something similar. How do you plan to suspend the 4" intake tube inside the 6" exhaust?

I have a very coarse rubber coated fiber material that is about 1" thick that is 90% open to air flow that i can cut into rings. Outer tube air will have to pass thru it. I salvaged it from a dumpster.

More HRV
 

Haven't seen much going on here lately.

Garage sales have been good to me.

I picked up a Holmes HAWF3030T window fan.
Dual Centrifugal blowers on one shaft and one can be mechanically reversed to blow out.
Perfect for a new semi-permanent HRV.
Thinking about building a bigger coroplast unit, counterflow, maybe a foot square
and 4 feet long, but haven't been
able to figure out how to support it mechanically without it
sticking out 5 feet from the house or having two right-angle bends
in the air path. One option is to stand the fan on its end, but I'm
concerned about the reliability of the bearings in that configuration.
It's always something.

Oh well, a project for cooler weather.

Also picked up a Dylos DC1100 air particle counter with computer
interface. Should be able to evaluate air filters for next pollen season.

Hi All,

I started reading this thread a few months ago. I came across this while googling for a DIY HRV. There is a lot of information in this thread and even more in all the external links provided over time.

I took some time to think things over for my situation and look around for parts to use.
The ideas condensed, I found my parts, today I ordered sheets of aluminum (Or aluminium as we call it over here) so the building will start next week.

Since this is my 2nd post I'll need a few more posts before I can post pictures, so I'll spread more information over several posts.

Fornax

That sounds great Fornax. We look forward to seeing your build. I'd recommend starting a new thread about the HRV build. This is already a pretty big thread and it'll get buried eventually.

Good to have a new voice!

There is a post you should also look at that contains these pages:

Page #1...

Page #2...

Page #3...

Page #4...

In this post, many of the coroplast issues have been worked out, and also 'dwell time' of the exchanging surfaces has been thought out.

Regarding posting to a different thread, I have a different opinion from Daox, in that I believe that most people come across these threads via Google, just as you did, and I think the information on a topic should stay in one thread, even if it becomes unwieldy.

In fact, the information I am leaving for you in this post came from an 'unrelated' EcoRenovator post on clothes dryer heat recovery. Now I ask you, who would have known?

Best of luck with your new project... we all need a breath of fresh air.

Best,

-AC_Hacker

Hello guys,

I'm following this interesting thread for quite a time now.
Back here in Italy we are also aware about the in-house air quality, so i tried to give it a try on my own.
You can see my work-in-process project here:

cercaenergia.forumcommunity.net/?t=52867443

Sorry, only in Italian for now, if you wish to have some specific info about it I'll be glad to share :)

Why all these spacers between layers of coroplast.......when it can just be turned 90deg. With enough plates the efficiency will be high enough.

this is more interesting though.......It is the LUNOS from Germany. 2 are used per area, one pulls air in for 70sec and the other does the opposite. Exhaust heat is stored in a ceramic or PCM core, then the cycle is reversed. No ductwork needed, just a central controller.

Less material between the hot/cold side will promote faster heat transfer. This allows less material to be used and a cheaper and just as useful product.

Daox, I'll continue posting about my project in this thread. I agree with AC_Hacker that regulars of this site can find it and others using Google can, erm, find it. Also we can easily refer to post #xxx in this thread when needed.

for example, one of the more usefull links for me was the one AC-Hacker posted in post #60, 2.5 years ago (www.fahrenergy.co.uk/FAHR_Installation.pdf).
- Short ducts are good.
- a small HRV covering a part of your house is good, use more if needed to cover other areas.
- A good way to beat radon is ventilation.
- and more

I'll build an HRV that basicaly only covers our groundfloor. I'll connect it to the existing ducting to draw air from the toilet and bathroom but heated fresh air will only be blown into the livingroom.

So FAI will be 100% in the livingroom. OAO will be roughly 80% from the kitchen and the other 20% from the toilet and bathroom.
The exhaust hood above the furnace will be stripped of it's motor etc., exhaust will go via the HRV (yes, with some extra filtering).

Where other houses in my street have a shed in front of the house I have the shed in an odd triangel shape next to my livingroom and kitchen. I can have the HRV in there, out of the way, and connect it with 2 short ducts with 2 relatively simple holes to the kitchen and living. In the kitchen a small duct of about 4m (13') will connect it to the existing ducting to both the toilet and bathroom.

In the lowest setting it will move about 50-75 cubic meters per hour, ACH in the livingroom will be roughly 0.6 which is quite high.

Mikesolar,

Indeed, given enough coroplast the efficiency might be high enough.
When just rotating whole plates 90 degrees you'll have surfaces that are not totaly flat pressed against eachother thus making a lousy contact with eachother. Not only will you have a double amount of coroplast between the cold and warm airstreams, they are separated with a thin layer of insulating air, this is not ideal.

A while back I wondered why use coroplast at all? To me plastics aren't known for their great transfer of heat. But of course if it's a thin sheet with a large surface this is hardly a problem.
Actual numbers: Coroplast 0.20W/m*K, Aluminum 237W/m*K
I found a study where a HRV is build and tested with Coroplast, along with calculations.
I replaced the value for coroplast with the one for aluminum in one of the formulas for -that- heatexchanger-core and the result changed from 12.7 W/m2*K to 13.2 W/m2*K, which is only about 4% higher for aluminum (if used in -that- specific HX).
Link: http://www.ewp.rpi.edu/hartford/user...0Exchanger.pdf

I just checked my email,

The aluminium plates I ordered are send and supposed to be delivered tomorrow.

I ordered 72 plates of 25x50cm (say 10x20 inches), 0.8mm thickness which is, erm, <grabs calculator> 0.03125 inch or exactly 1/32".

The HX-core will be 30 centimeters thick. Using 72 sheets that will separate them by 3.4mm (4.3/32"). So the dimensions will be 25X50X30cm (10x20x15").

When these arive (in good shape) I'll order the 2 fans to be used.
I work in shifts, I plan on starting the build in my next weekend which is about a week from now, I'll be sure to take pictures.

Update, the next day:
Attachment 2730Attachment 2731

Ooooo, this project will be fun!
I think I recall reading that using ECM squirrel cage motors is the most efficient and quietest solution, though not the cheapest. Not sure what kind of airflow you will be needing, but maybe some cheap 140mm computer fans would work for testing?

I'll be needing 2 fans and I have some demands.
They need to be:
- available to me
- somewhat affordable
- able to move the right amount of air
- be reasonably silent while doing that
- economical on energy use.

Airflow in the lowest setting will be around 50-75 m^3/hr (30-44CFM) depending on the resistance in the ducting, filters and HX. I asume this resistance will be quite low. In the middle setting airflow will be up to 150 m^3/hr (88CFM).

With those airvolumes you are in the range of wholehouse ventilators where most types are fairly large, have multiple connections and cost from 200-450 euros. I did find a smaller and cheaper one with only 1 in- and outtake, perfect for me.

It's the Comair Solo 44Y which is of course 230 volt for us in Europe.
Specsheet of the series (in dutch) is at http://www.ventilair.nl/Repository/S...20811A4web.pdf

Specs:
http://ecorenovator.org/forum/attach...2&d=1355397752

http://ecorenovator.org/forum/attach...3&d=1355397752

As you can see in the lowest setting it is stated to use around 8W (times 2) which is conveniently low.
Our current wholehouse ventilator is using around 40W, replacing it with the HRV using about half of that will safe me 40 euros on electricity a year alone.

.

Panasonic Whispergreen bathroom fans are the most energy efficient ways of moving air as long as you are okay with the form factor of the air collector. All sorts of CFM settings and they adjust themselves to speed up to blow the right CFM under pressure.

@ Fornax I'm going to use the Nicotra direct driven motors for my project. Most HRV producers use Nicotra's motors in Europe (at least that's what I was told).
The DDM 120/126 model has a 45W consumption and gives over 400 qm/h at 100Pa
That's more than enough for a 100sqm house.
Have a look:
nicotra-gebhardt.com/front_content.php?idart=106]Catalogues
Maybe you can find a local dealer in the Netherlands, too.

(edit)
Here it is:
NETHERLANDS
Rucon Ventilatoren B.V.
Postbus 263
3840 AG Harderwijk (Netherlands)
Phone 0031 341 439-100
Fax 0031 341 439-190
E-mail verkoop@rucon.nl
wwwrucon.nl

I already ordered the fans I mentioned.

MN Renovator, those Panasonic fans look good indeed and several models on amazon are reasonably priced.

Kostas, that DDM120/126 is rated for a high capacity, more than I need, but did you notice it will make a noise of at least 61dB in the 'low' setting? If the noise is acceptable depends on your situation but for me it would not.

http://ecorenovator.org/forum/attach...4&d=1355422794

Fornax, yes I noticed that, I don't think that this is an issue as I won't need 380 qm/h but only the half of it in daily basis. Also noise insulated ducts will help.
The problem is the price, over €170 each! :(

I see you can buy some EBM Papst DV6424/2TDP fans used from Sun rack-mount computers for around 25 euros. You'll need to supply them with 24v DC. These are mixed flow (i.e. hybrid axial / centrifugal fans). They seem to be a custom high-power version for Sun (either 80w, or 110w depending on model), but are easily PWM controlled. At 40w, the fan curve looks like the below:

Looking for solution
 

Hi,
I have heard that Fantech also makes some very good (quiet) fans. Insulation will definitely help reduce noise, but I think TimSmall may be on to something: If you could use PWM to control the speed- a variable speed motor could easily be adjusted to an acceptable level that meets both noise and efficiency requirements. A lot of the noise will depend on the design of the system; large insulated ducts allow more flow at less noise.
I really like the idea of using aluminum plates, they should increase efficiency.

I still have a problem with HRVs. Even at 80% efficiency you are venting warm air and replacing it with cooler air. If the house is at 68*F you would be venting that air and replacing it with 61*F air. You would be cooling your house in the winter.
In link #163 Piwoslaw drew a picture of what I think would be the solution. Some people may say that the HP would use more energy than the HRV alone; however, when you have 61*F air coming into the house something is required to bring that air up to 68* to keep the house warm, either your central heating system or a small auxiliary heater. A small heat pump IMHO would be the best auxiliary heater.
I have some concerns about combining the HRV with a HP (which would be a hacked dehumidifier or AC unit): most HRV are rated at 150-350CFM while an Air Source Heat pump requires a lot of air. My 4 1/2 ton unit flows about 3500CFM. If I design it to make the HRV more efficient (small gap between plates) then the HP won't get much air flow, and if the plates of the HRV are spaced farther apart to increase flow for the HP, then the HRV is less efficient. I read an article on Build it Solar about DIY HRVs and it states that the airflow should be slow to increase heat transfer. Which is the opposite of what a HP needs :confused: I suppose there would have to be a compromise between what they need. Does anybody know how much a small (say 1 ton) dehumidifier flows- CFM?
Every time I think about needing a HRV I come back to this, eventually I will have to make it. :)