The unpredictable harsh weather conditions often result in power outages in most of the country. You can ensure that your home still has power by investing in a generator of your choice. However, most models are very loud and even though you can by a silencing/soundproof box for it, it is very expensive. Luckily, it is possible to build your own at home using simple tools.
It'd be cheaper.

Here is a 4-steps guide on how to building a silencing box for a generator.

Supplies

Wood is the best material for a silencing box and it does not have to be much – 2x4’s or 2x2’s will be enough. Purchase a flexible material such as fiberboard (MDF) for paneling.
You can also decide to use plywood but its stiffer and heavier so moving the box will be cumbersome.

Avoid metals for the frames or walls as they will rattle and create more noise when its on. If you do, use spectrum or damplifier pro to reduce the rattling.

Step 1: Determine the Dimensions and Size

Generators come in different sizes and dimensions. So the first thing that you need to do is take measurements of your generator and note it down in a piece of paper. Because generators produce a lot of heat, you need to account for adequate airflow by adding extra weight and height. Otherwise, the generator will be too close to the walls of the box. You should also factor in additional soundproofing and insulation layers. Don’t forget to measure the cutouts for the rub cables and exhaust.

Step 2: Insulation

As mentioned earlier, generators produce a lot of heat. Insulate the box by creating panels with a space in between them. These panels will act as walls of the silencing box. In the space, insert Class A fire rated insulation material such as Mega Zorbe or Heat Wave Pro.

Both can be purchased online at Amazon or any other reputable store.

Step 3: Soundproofing

You definitely don’t want to hear the rattling noise when you turn the generator on. Use mass loaded vinyl material to soundproof the box. It is recommendable to install the material on the outer walls of the box to effectively block the sound. Make sure that the walls are covered firmly with vinyl contact cement, screws, nails, or staples. The edges can be taped using acoustic caulk or foil tape to make the box completely airtight.

Step 4: Ventilation and Exhaust

Lack of adequate ventilation will not only ruin the brand-new silencing box you just built, but also affect the performance of the generator. If the box is big and has more airspace, you don’t need to worry about ventilation, but if its small, install an extended exhaust pipe that runs outside the box.

You can purchase the specific exhaust pipe designed for your generator online (for latest models, it wouldn't be a problem). Alternatively, you can build one yourself (as I did for my Champion) by first measuring the size of your exhaust then using a copper piping that can withstand the heat from the exhaust. Make sure that this pipe completely seals the generator exhaust to prevent fumes from leaking.

You can also decide to cut sections of the box to act as additional ventilation windows but this is dependent on the size of the generator and amount of heat it produces.

Step 5: Cooling

Though optional, you can add a fan inside the silencing box to enhance airflow and cooling. If you decide to install one, consider the amount of space available in the box when shopping. Use caulk to seal the fan and fill the gaps and make sure the cord is pointing inward so that can easily plug it into the generator when its running.