Fresh air!!!!

[Drake]

In designing a new super insulated, passive solar, air tight Winter core addition to our now weekend retreat to retire in I am seeing how important and potentially complex/expensive fresh air exchange can become to the overall design and health of the living space. As the space is only 500 sq' hi tech solutions can quickly become no less expensive as opening a window.

Done a lot of research and am curious what others are/considering doing for fresh air. Workable, reliable, cost effective, maybe DIY solutions. I am not sold on MHVR's(frostup) and am a true disciple of KISS if its an option.

Most ways I have come across so far make claims that appear to be beyond pyhsics, are beyond energy payback(though healthy air itself has to be of value) or has a potential problem that might negate any solution, e.i. frostup, mold.

Things that factor into our solution:
- very low VOC constr/lifesyle(2 people)
- only needed for heating season(many sub freeze days)
- small space
- low heating demand(super INStd, passive solar, Geo HP hydronic radiant heat)

Solutions looked at:
- HRV's, EVR's
- earth to air Hx's(earth tubes)
- earth to h20 to air Hx's
- daytime solar air preheater

[Piwoslaw]

I'd go with a countercurrent HX, with a ground heat exchanger on the intake end and maybe a heat pump on the other. See these two threads for starters:
DIY ventilation heat exchanger
Advice on ventilation ecorenovation
Since this will be designed for only 2 people in a very small building, then the ventilation needs are small and the HX shouldn't be too complicated or expensive to make yourself.

[Drake]

A fairly efficient HRV should be not to difficult to DIY(using low energy fans is must) if intake air can be tempered to prevent frostup problems. I have ideal opportunity for an earth tube, sloping grade away from foundation which will already be trenches for gravity footing drainage. Mold prevention is a concern but I believe if smooth well pitched PVC pipe is used(just in winter, cold air/warm earth) condensation shouldn't happen. Going to save my HP hacking for water/water HP for radiant heat. Am exploring also solar preheating w/DIY panel collector w/ wax PCM storage for extra CFM fresh air in most active period. Night time shouldn't need as much ventilation as daytime??

With an est heat bill of 50./m a lot of tech is hard to payback.

[Jason Morosko]

Try balanced ventilation, especially energy recovery ventilation with good filtration (MERV 10 or better). With this method you are exhausting irritants, pollutants and odors being generated in your home, and replacing this ‘bad air’ with better outdoor air (oxygen), and filtering out triggers like pollen and mold spores. In a matter of hours you will be replacing all of the air in your house, and saving energy in the process.

Check out this product - it will get you started and give you a sense of what you're probably looking for.

[Daox]

Your product seems incredibly efficient (claims 95%). I have yet to see any other HRV/ERVs claim this high of heat reclimation. What makes yours so special?

[Jason Morosko]

Well, for starters, it has the highest energy recovery and highest filtration at the lowest amount of energy used among our competitors.

It has two fans, one fan draws fresh air into the building while the other pushes stale air out. As the two air streams cross, they pass through a patented heat exchanger that transfers both heat and moisture from one air stream to another. In other words, the heat from the air being exhausted is transferred to the fresh inbound air.

Also boasts a MERV rating of 12.

Apologies for the self promotion

[Drake]

FiWi(fine wire) Xchgr's claim similar high recovery. Without some mechanical "extraction" process I don't understand how an air Xchgr can do better than recover to an equilibrium of IN/OUT air temps. Will exit air "frost" up if intake air is subzero for long periods in your unit Jason. Defrosting is the big energy backstep of HRV's that I am looking for a solution too. Is the unit an ERV that extracts humidity(which holds much of the heat energy) also?

[Drake]

Got to inspect a fully automated HRV's system on a "passive house" tour I took today. Very nice but at 10-15K for the whole infrastructure(Air Xchgr, whole house ducting, grnd loop intake tempering and controls it would have to save a lot of heating to pay back.

[Daox]

Well, a lot of people pay $2000 and even $3000 a year for heating. That is easily less than a 10 year ROI. Imagine that that house will stand for 50+ years easily and you're talking TONS of money (and resources, CO2, etc.) saved.

[AC_Hacker]

Originally Posted by Drake

...it would have to save a lot of heating to pay back.

I can see the logic in looking for the least expensive solution to a problem. At the most obvious level, it will leave more personal resources available to apply to the solution of other important problems.

But simultaneously, we are all living in a time where we are suffering the consequences of 'least expensive solutions'.

Just take the example of coal-fired electricity... As long as you keep your perspective fairly narrow, it is a very cheap, reliable way to generate electricity. But on a broader scale, the environment suffers in large-scale global ways and in smaller, more regional ways... to say nothing of alarming increases in instances of asthma, as an example.

I think we need to begin including broader considerations when we make our local decisions.

There is definitely a place for DIY in this...

-AC_Hacker