Ducting Systems and Air Ventilation - Looking for better kitchen exhaust vent hood

Hi,

I have a cheap metal kitchen exhaust vent cover (venting form the microwave fan above the stove). It looks similar to this:
http://ec-images.acehardwareoutlet.com/120/products/2130007456_091308_dp.jpg

The problems:
- there is one round flapper that never really closes. I tried to bend it to do so, but it is almost impossible when attached.
- the hooks of the flapper are extremely cheap.
- As the flapper never is 100% shut, the wind can pick it up.
- I also had it stuck in the full open position (stuck in the cover)

So, I want to replace it. What options to I have? Are there code limitations?
I.e. does it have to be metal? Or could I sue one of the louvered types?

http://ec-images.acehardwareoutlet.com/120/products/998021327_092707_jp.jpg

What is the best option out there?

If you go to an HVAC supply house, you should be able to find a better quality vent. Thats where I found mine...much heavier gauge metal, weatherstripped and very lightly spring loaded flapper. Worked great, though I did have to slightly enlarge the cutout in the siding.

In fact, I believe I saw one of these. It even had a gasket. I was not sure if it is for my application - somewhat concerend that the exhaust fan can opne the flapper.

But does it have to be metal?

Doesn't have to be I guess, but I routinely replace the plastic ones, since the vanes and housing get brittle after just a few years...even worse if they get direct sun.

The vanes tend to warp and bend as well, and they don't seal that well even when new.

The better quality metal ones also have a metal mesh bird guard.

JMO