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