DIY- Best Generator Shed with noise isolation. Firman generator or other types

This is a generator shed i've made for taking the noise level down a lot. It is really effective and it cost me around 600$.

Size is : 30"x60"x48"approx. Be sure to choose the right muffler extention for your generator model. Mine is a Firman.

Be aware that the shed should be installed at least from a distance of 20 feet minimum from home or any air inlet.

Muffler: Just look on ebay and search for "muffler extension for generator" There are plenty of model available. The link i've used had changed.

Exhaust system: https://www.zombiebox.com/shop/honda-...

Exhaust Fan: https://www.amazon.ca/-/fr/gp/product...
Gas Strut:https://www.amazon.ca/gp/product/B07K...

Inside insulation with Rockwool Safe'n'Sound from HomeDepot and covered it with fireproof cement board in it.