Print your own 

 The kits are here: https://www.tindie.com/products/adouglas/kit-3d-print-your-own-energy-recovery-ventilator/

See the community page for source code and guides.

You can also just order the parts directly, some parts are a bother to get, and you will have to buy more than you need, but they are not expensive. 

 If you do this please have a look at the price of a unit like the lunos ego and consider how much money you saved and donate some to help pay for the extensive amount of development work it took to produce a relatively good unit.  See the Support Development page for donation options.  Or you  can at least tell other people about it to help raise funds.

You can easily save more than the cost of a 3d printer by making a single OpenERV! If you make more, you save more.

If you need a project to justify the cost of your printer, this is a good one.  Tangible, utilitarian value and real, direct return on investment is available right here.

I also hope that some people may consider producing and selling units locally.  This would be a rare example of so called cosmo-local production in action.

The source code is linked to from the community page.

It's not trivial to make a unit, but if you can produce quality prints then things fall into place in about a day of work.