My HRV design

[angstrom]

Hello Ecorenovators, I'm new to this forum and it's my first post.

I'm reading this forum for a while, was looking for ideas for my HRV project.
But finally ended up with my own design, as I'm a bit sceptical about using plastic for heat exchanger.
My inspiration for HRV is ecorenovator's forum, so I wanted to share with you what I came up with.
The heat exchanger is made from 0,5mm aluminium sheets, 1 meter x 0,33 meter. It's around 13 square meters of usefull surface area. Spacers between sheets are made from sheet rubber, 1 cm width, 4mm thick. One usually used for gaskets.
HRV housing is made from moisture resistant medium density fibreboard. Every inner corner is sealed with silicone.
In pictures you can see two white fans, it's simple, AC type, 70 W each, plastic housing fans with affordable price tag. I decided to mount them outside HRV housing as it is too big to fit inside.
As controls for unit I temporary use two speed regulators for fans and a simple timer. It turns on and off my HRV few times a day. As I said it's temporary, I really really wanted to test how my unit is performing.
And finally, performance. A few days ago it was -16 degrees C outside, and I got +8 degrees C air blowing into my living room and it the result AT FULL POWER. So, I'm quite happy. I'm planning to measure all four IN and OUT temperatures soon and calculate COP. If I only find a formula for it...
And I have a few questions for you guys.
How should I set the fans to work, a slight pressure or vacuum in house is better? As it's hard to make neutral.
I'm thinking in making some electronics with PWM and differential pressure sensor to control the fans work. But is it worth doing it? To have a moisture sensor in house would be nice too.