DIY ventilation heat exchanger

[roche]

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.

[Drake]

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.

[Ko_deZ]

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-

[Gasper]

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?

[Piwoslaw]

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

Originally Posted by Gasper

- 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.
[...]
- Here is a nice link to start with DIY: cheap easy living - Air to air heat exchanger

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

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), 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.

Originally Posted by Gasper

- 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

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

[Gasper]

Originally Posted by Piwoslaw

BTW, is that your web site?

No it's not my website.

Originally Posted by Piwoslaw

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), 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.

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.

[Erich_870]

Any updates on these projects?

Erich

[AC_Hacker]

Originally Posted by Erich_870

Any updates on these projects?

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

[Drake]

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).

[lucerne96]

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