When my wife and I relocated from Southern Ontario to the West Coast of British Columbia, we (by-and-large) left cold and snowy winters behind us. While it was easy to adjust to a more temperate, albeit wetter, climate, the occasional coastal windstorm (with winds up to 100 km’s/hour or 60 mph) can easily disrupt your hydro / power supply. Even though the power lines in our area are all underground, we are “fed” from areas where the power lines are above ground. Trees / limbs come down, power is cut. And, while we have experienced some minor earthquakes over the years, if we do experience a significant one, you have to anticipate some major (and prolonged) power outages. One solution: a decent-size generator. Big enough to power household essentials – fridge, freezer, microwave, kettle, tv, radios, heater, few lights, etc. – in the event of a power failure.
Once one has decided to implement this solution, you walk through the related issues of portability versus permanent / stationary (outdoor) installation, method of feeding power into your home, some form of protection from the weather (assuming it is being stored outside), and security (so it cannot easily “disappear” on you). In response to these issues, I designed an outdoor / insulated generator box. What follows is a detailed progression of the build, from basic box construction to final installation.
The size of the box was dictated by the size of the generator – mine includes handlebars and pneumatic tires – and the need / desire to have plenty of clearance top to bottom, side to side and back to front. The box (including base-mounted drip edges) measures 72-inches long, 44-inches deep, 52-inches tall at the back, and 42-inches tall at the front. The box frame (and various doors) is constructed of 2×2, covered by 1/2 –inch exterior plywood. All interior, non-visible surfaces (2×2 and ply) have two coats of primer. The walls and lid are insulated with 1½-inch solid insulation, before being vapour-barriered and skinned with ¼-inch ply. That ¼-inch ply has two coats of primer on the insulated side (non-visible surface) and three coats of exterior, semi-gloss Varathane facing the visible / interior of the box. Same goes for any 2×2 surfaces. The exterior of the box has two coats of primer and two coats of paint (matching the trim of my house).
The base / floor that the box sits on is ¾-inch pressure treated plywood, screwed to a 2×4 pressure-treated frame with multiple cross-members. Each section of the base is insulated by 2-inch solid insulation, vapour barriered and covered with ½-inch exterior sheathing. Wrapped around the base and box is a drip-edge overhang cut from pressure-treated 2×4’s and bevelled appropriately at the corners. All pressure-treated base and overhang surfaces have 4 coats of exterior, semi-gloss Varathane.
The left-hand side of the box features a fully removable door with an integrated vent. The idea here is … in reasonably good weather (when I’m simply running the generator – on a periodic basis – to ensure it will start / run when required), I can fully remove the door and let all the air in I want. In an absolute monsoon situation, I can leave the door secured, keeping the interior of the box dry, while allowing adequate air supply into the box via the 14-inch by 20-inch louvered and screened vent.
The front door is hinged on the left and swings out a full 90-degrees to allow full access to the generator control / start panel. If you are wondering how I start the generator, it is a key start model – no pulling a hefty chord (and dislocating my shoulder). Once started, I partially close the door, sheltering the control panel from the elements but allowing more airflow (versus if I closed it completely). The door and lid overhangs prevent the elements from entering the box.
The rear door unbolts and swings out, directing and allowing the exhaust to escape out the back of the box. Notice (in the final installation pictures) that the door has a sheet of galvanized metal over top the wood to take the exhaust blast / heat from the generator’s exhaust. The exhaust is warm (not really hot), but not enough to heat the metal so it becomes scorched or to cause concerns of catching on fire. Between all the surrounding space, airflow and means of exhaust, I have had no issues with heat / gas / fume build-up.
The lid is sloped for water runoff. It is hinged across the back to allow for full opening. This allows for easy generator inspection and fueling from the top. At the moment, the lid can be held open by hand or a length of 2×2. Given the lid’s weight, I am in the process of securing some lift assists (spring or gas-loaded) to make it easier and hands-free. As a matter of practice, when the generator is running, I do prop the lid up slightly (say, 2-inches or so) to help with airflow and heat dissipation.
Other features of the box include: overhangs above the doors and vents, and drip edges at the bottom of the front door and around the base of the unit. These serve to shed water away and prevent it from entering the box. Aluminum screened vents near the top of the back and right hand side wall. These serve to both enhance air flow through the unit while running but also ensure adequate airflow when the box is closed up. If we happen to experience some extreme cold conditions, I have insulated vent covers ready to insert from the inside.
All doors, vents, and the lid are also wrapped in waterproof gasket material of varying thicknesses and widths, depending on location. The box consumed over 500 stainless steel screws, while the pressure-treated base / floor took about 80 coated deck screws. Most (if not all) hardware is Stanley Exterior / Lifespan or Weathergard series, mounted using stainless steel screws (versus what they come with). The (blue) padlocks are Lee Valley’s “weather-resistant” locks (product number 00F25.01). Most exterior, mating surfaces (e.g. drip edges ./ overhangs) are caulked with either beige or clear silicone.
I did not track the number of hours I put into this project over the 14-months or so that it sat in the middle of my shop. I worked on it between various other projects. The entire unit has to weigh several hundred pounds. To move and install it outside, I had to break it down to the base, 4 walls and lid, and re-assemble in its final resting place. After ensuring it was well-seated into a bed of crushed gravel, level and aligned with the power feed into my crawlspace, the generator was introduced to its new home.
The Effect of Insulating the Box
After installation, we experience several weeks of unusually warm weather here. With the box closed up, I sat one Min-Max thermometer (Lee Valley product number AB803) on the South-facing lid surface and another Min-Max thermometer inside the box. The lid SURFACE temperature hit 50 degrees Celsius (or 120 degrees Fahrenheit), in the mid-afternoon sun. That same (clear) night, the lid surface temperature dropped to 18 degrees C (or 64 degrees F).
Inside the box, the temperature hit a maximum of 33 degrees C (or 92 degrees F), that afternoon. It fell to 26 degrees C (or 74 degrees F) that night.
These results speak to the performance of the insulation and ventilation the box design entails – the interior of the box was approximately 17 degrees C (or 28 degrees F) cooler during the day and 8 degrees C (or 10 degrees F) warmer at night – than the exterior surface temperature of the box.
So far, we have yet to experience any really cold Fall temperatures to do another set of readings. On the West Coast, we only get a few sub-zero days / nights in the average Winter. Temporarily, closing up the vents on those nights should more than ensure the interior of the box / generator does not fall below freezing.
-- Glen - Vancouver, British Columbia, Canada