Move the Generator from the Garage to a Generator Shed

The Firman Dual Fuel H08051 is a heck of a generator. It runs on propane or gas. On gasoline, it outputs a 8,000 watt running on a 8 gallon tank that allows for 12 hours of average runtime. It shuts itself off on low oil and has a sweet electric start.

Firman buyers, on the other hand, reported excellent customer service experiences. I chose the Firman H08051, which had everything I wanted: 10,000 starting/8,000 running watts; electric as well as pull-start; very highly-rated; low-oil shutoff; and a dual fuel feature allowing the generator to run on either propane or gasoline.

If you’re buying a generator, using the Amazon Prime credit card on Amazon.com is definitely the way to go. I earned a $43 rebate because I used the credit card at the Amazon.com store. You can learn more about the Amazon Prime credit card here. Plus, there was no lift gate charge, which is the fee truckers charge to get the item from the truck to the house.

How Much Noise Does a Generator Make?

There’s no industry standard for reporting how much noise a generator makes. When you do see a decibel (dB) number, it’s often taken of a sensor positioned 20 ft. away from the running generator. Firman reports that the H08051 outputs 74 decibels. That’s about the noise level of “living room music,” “a flushing toilet.”

I dislike noise enough that even “living room music” level noise has the potential to be annoying. Maybe not blood-curdling awful, but in a long power outage, I don’t need the stress of generator noise of any level adding to my fun.

How to Reduce Generator Noise

I’m always surprised when people subject themselves to rock concerts and motor noise without thinking of what they’re doing to themselves.

I dislike noise as a rule, but everyone should dislike noise if they want to keep hearing!

Sound Experts sent me this cool graphic to share with you.

Everything on the right side will hurt your hearing.

Once it’s gone, you are not going to get that hearing back.

Click the image to see a larger version. Check out Sound Experts so they can help you quiet things down. Link opens in a new window:  Sound Proof Experts

You can place the generator in a noise-insulated, ventilated shed. You can also replace the generator muffler. Painted or coated steel enclosures reduce noise better than wood. Many people have had good luck modifying Suncast or Rubbermaid types of sheds, just keep in mind that cutting vents into blow-moulded plastic is not going to be easy. A wood shed on a concrete patio block floor is a good DIY compromise.

Update Aug 1 2020
Unfortunately my source for this device has no SSL certificate on their website. Here’s the URL in plain text in case you still want to visit their website:
https://www.dieselserviceandsupply.com/Sound_Attenuated_Enclosures_for_Generators.aspx

Noise Absorption Materials

Noise-absorbing materials reduce volume, but they don’t block the noise. Absorption materials are generally much less expensive than noise blocking materials.

Foam egg crates and fiberglass batt insulation are noise-absorbing materials. In my research, I didn’t see any successful egg-crate-foam noise reduction generator sheds. And I did see more than one argument against using that recording studio type of foam.

Fiberglass insulation absorbs about 5 dB. I’m pretty sure that “noise reduction” fiberglass insulation is just regular thermal insulation with a new name. I can’t find noise-reduction ratings for noise reduction insulation, so I’m thinking the manufacturers are not proud of the results.

Noise Blocking Materials

I found a few noise reduction specialty products but they would not have worked in a shed. They were designed to be layered into walls, not to be used by themselves.

Gypsum board and “mass loaded vinyl” block noise. They prevent the noise from passing through the material and out the other side. Mass loaded vinyl blocks about 27 dB. Gypsum board is not suitable for outdoor (generator shed) use. Mass loaded vinyl is OK to use outside. It’s expensive compared to noise absorption materials.

Using Plywood to Deflect Noise into the Ground

If you’re only interested in reducing generator noise (and not protecting the generator from weather and thieves), you can add a better muffler and use plywood to deflect the noise. Ebay seller generatorpartswholesale sells generator-specific mufflers that might be of use. And YouTuber sixtyfiveford offers a brilliant way to use plywood panels to drive generator noise into the ground. It’s not pretty, and it doesn’t protect the generator from weather, but it does reduce the generator noise.

What is the Best Generator Enclosure Shed Material?

Since one of the major goals of this project was to get the generator out of the garage, now it was time to figure out how to create a generator shed. I found three types of shed solutions on YouTube. One was a professional box that cost almost $1,000. Some were plastic blow-moulded pre-cast sheds (like Suncast or Rubbermaid). The third was homemade wooden sheds.

I didn’t want to use steel because I don’t have that kind of skill set. I think it’d be very hard to cut vents into a plastic blow-moulded wall, so that was out as well. The $1,000 box was too expensive. I searched Craigslist and found exactly what I wanted. A used generator shed equipped with wall vents and wire holes. I paid the seller $100 for my new generator shed.

Obtaining the Shed Framework

I found a generator shed on Craigslist. The previous owner had built a box, cut windows into the sides, as well as a port to run the electrical plug. The top was hinged. You used a stick jutting from the front frame to hold the top open the way you’d prop open an old car hood. The front side was just a cover; it had no hardware attaching it to the box frame.

Getting Air to the Generator

A hot generator requires air flow to avoid overheating. If you’re running your generator in a shed in hot weather, you’ll have to put an input fan into your shed structure.

The original owner used an indoor window fan to create an incoming air flow. He plugged the fan into the generator. The shed protected the fan from the weather. There was no water deflection cowl to prevent water from getting into the air vent. So I thought this might be a problem.

I looked for waterproof fans but they were several hundred dollars. I’m not in a hurry to find an input fan solution. The exhaust and noise problems are much more pressing. When I do find a fan, I will protect the input window with a hooded cowl vent cover like this one.

Removing Exhaust from the Generator Enclosure

A generator shed must provide a way to remove exhaust from the running engine. Without an exhaust system the shed will fill with toxic carbon monoxide which will eventually choke off the engine and shut it down.

My new generator shed has vents in the back and left side, but my Firman generator’s exhaust comes out of the front. I considered putting the generator into the shed sideways to accommodate the vents but decided against it because, even though the generator will be in the shed full time I wanted it to be easy to get in and out for maintenance and repairs.

I considered my options. I could use an exhaust fan like this variable speed shutter exhaust fan. I would also have needed to purchase another vent cover. Or I could use an exhaust pipe extension. I opted for the exhaust pipe extension and after some research I chose the Gen Exhaust generator exhaust kit.

Planting the Shed in the Garden

I needed to place the shed within 20 ft. of my front porch. That’s where the generator plugs into the house. So the shed would definitely be placed directly in the front garden, where I had new rhododendrons.

I dug up two rhododendrons positioned in front of the foundation. I put them by the woods on the edge of the front yard. Some mosquitoes decided to eat me for lunch, so I did a half-ass job making sure their new homes were deep enough. Hopefully they’ll blossom from foundation covers to privacy bushes one day. I might need to fix their new homes next spring.

The shed footprint was 4 ft. x 4 ft. Wood on oil will rot, so I got 20 1 ft. x 1 ft. concrete patio blocks from Lowe’s. I used 16 of them to make a 4 ft. x 4 ft. square and had 4 spares. I paid about $32, or $1.60 per block.

Building the Generator Floor (Image Gallery)

I dug out a 4 ft. x 4 ft. landing zone where the plants had been. After I flattened the spot and added the concrete blocks, I brought the extra soil to the woods.

Flattening the Generator Shed Floor

I knew from YouTube videos that I could flatten the ground using a piece straight wood. For reasons I have not figured out, the generator shed I bought on Craigslist had a couple of flat floor boards inside. I used one of these floor boards as a flat skimmed. I kept the bottom parallel to the ground and pushed or pulled. Any soil above the wood height got pushed out of the way.

Sunshine and Moonbeam delayed operations while they inspected my work. Then, being union dogs, they lay down on the job in the cool, freshly dug soil. The ground wasn’t 100% flat. I’ve read that the failure to make a flat floor will hamper my noise reduction efforts. I made it as flat as my stamina allowed.

Painting the Generator Shed (Image Gallery)

Update: See Part II directly below. (In Part II, I’ll explain the sound insulation, generator exhaust and box hardware solutions.)

Moving the Generator from the Garage to a Generator Shed, Part II

When we wheeled the generator into the box, the natural position of the controls was on the left side, not the front where the panel would give us access. If we had built the box for the generator, we would put in two panels: one to wheel the generator into the box, and then a side panel to access the controls. In the pre-built box, neither the panel nor the vents were correct for the generator. The louvers were on the left and the back. For the Firman generator, we needed louvers on the front and right. In the pre-built box, the access panel was in the front. For the Firman generator, we needed acces in the front and the left side.

Creating a Generator Control Access Port

The generator controls landed on the left side of the shed. There was a louver there, so we turned that into a hinged access port. We nailed a 1×2 inch frame around the louver. This boxed in the louver.Then we cut that expanded louver frame out of the box.

Next, we lightly tacked another 1×2 frame around the resulting hole in the box. We didn’t nail it in right away as to allow for adjustments.

Then we dropped the louver and frame back into the framed hole. We attached hinges to connect the left outer frame with the left louver frame; and then we attached a latch from the right inner frame to the right outer frame.

Fixing the Door Panel to the Box

The door was a loose piece of wood that came completely off of and out of the generator box. We attached hinges from the bottom of this door panel to the floor of the box. The front panel swings down to create a ramp for the generator wheels.

We put a  hasp at the top to prevent the panel from falling down. The hasp is on the top right corner of the front panel and connects to the right wall. A padlock joins the two pieces of hasp metal to prevent the front panel from opening.

We still need to add the top left hasp to close up the left side of the front panel.

But the other point of access we still need to address is the top panel. Since it’s unlikely anyone will bring a crane to steal a generator, the top access security is not a priority. To address the lid security, we will attach a hasp from the door to the roof lid. Actually, first we’re going to replace the top lid with a bigger roof overhang. Then we’ll hasp the left side of the front panel to the left front of the new overhang.

Generator Exhaust and Heat Dissipation

To create an exhaust line, we bought a specific assembly compatible with our generator. This connected the exhaust to a flexible line that exits the shed through a double wall exhaust pipe that exits the shed through the right wall.

We were concerned that the plywood of the sidewall wasn’t thick enough to carry the exhaust pipe assembly, so we added a block of wood to the exhaust port. It reinforces the structure by creating enough of a channel so that the exhaust pipe doesn’t wobble around. We put the reinforcement on the outside of the box to maintain clearance inside.

Insulation Sound Reduction Issues

Originally we were going to use batting insulation as well a foam core to muffle the generator noise. But the box interior proved too tight to add interior batting. We still can put the foam core inside the 2×4’s that make up the box interior walls, but the batting was too thick and got very close to the generator.

We will also add a 110v fan to prevent overheating. The fan back will point at the the generator, and push air out the back louver. The fan will plug into a generator port. This fan will be inside the box, so it won’t need to be protected from the rain and snow. The fan is just for heat dissipation. The exhaust ports through the pipe in the front.

Generator Shed Lessons Learned

We started with a box we bought on Craigslist. It didn’t match the generator’s controls or air flow. If we were to do it over again, we would build the box around the generator, taking into account sound deadening and generator size. We were unable to add all of the insulation we bought because the generator was large enough to fill the cavity from left to right. We ran out of room. We would ensure the we had head-on  access to the generator controls. Air vents would line up with generator intake and exhaust.

More Generator Shed Pictures!