Keepin' the Cold In

by Mike Forbes, from the March 2001 Newsletter

It has been another month, and electricity still flows through the grid. Here is another article in my continuing series on conservation. A bit more theoretical but for the adventuresome a good project: Refrigerators. Almost all of us have them in some form or another. Next to electric hot water or space heaters they are the one of the most consumptive appliances.

It seems that refrigeration has taken steps backward in terms of efficiency. Today's fridges with icemakers, filtered water spigots, 25 cubic feet of space, inadequate insulation, condensers underneath, and frost-free features are becoming less efficient as the years go by. There are some basic concepts that are broken in modern refrigerator design. The frost-free feature actually heats up the inside of the fridge periodically to keep frost build-up down, accounting for over 40% of the total energy consumption. Some refrigerators even have heat tape on the door seals to keep them from freezing, I know I always struggle with doors frozen shut. The compressor being located under the fridge causes heat that is removed from the inside to be radiated up and back into the fridge. You can get a quick idea of the energy consumption by reading the little Energy Guide labels at any appliance store. Most common fridges use about 900-1200 kWh/year. As soon as you eliminate many of the fancy features and reduce your size a little bit you'll be surprised to see the numbers drop to 400-600 kWh. This is still terrible in terms of what is possible. Sunfrost, the most efficient fridge out there actually uses only 204 kWh/year. This isn't a little fridge either, it's the 16-cubic foot model. It does carry a hefty price tag at around $2500. Since I can't afford such an appliance I decided to modify a fridge to make it as efficient as possible.

First I started by analyzing our space needs. We own a chest freezer and owned an upright, 19 cubic foot side-by-side fridge. We found that we didn't need that much freezer space and that the fridge's freezer was more of a convenience than anything. My opinion on fridge size is that you'll fill whatever you have. You should look at what you have in your fridge and compare it to what you've used in the past month and what actually needs to be refrigerated. We settled on a 9.6 cubic foot fridge with a small freezer built-in for ice-cream/juice/fruit. The fridge portion is just a titch smaller than our previous side-by-side fridge. Next we selected a model without the frost-free feature, I think we can manage melting out the ice every once in a while. The model we selected has an off-the-shelf, no modifications energy rating of 398 kWh/year—already we're 60% more efficient than before.

I brought the fridge home and plugged it in. The noise was something that needed to be dealt with. Out came the wall between the kitchen and mudroom. I stuck the fridge through the wall, facing the condenser coils and compressor into the cold mudroom. No more noise in the kitchen. The fridge now only sticks out 13" into the kitchen instead of 22". The kitchen grew. I sealed the fridge with expanding foam where it went through the wall. I then coated the interior portion of the fridge with 6" of rigid foam insulation (Thermax gives the best insulating value at R-7.2/inch). I figured that the factory insulation is about R-7 (very conservative figure) and with my additional insulation I'm up to R-50.2, 7 times more insulation than before. I insulated a portion of the back and the front door with 2" foam. In order to make it look nice I then coated it with oak panels and trim. I'm hoping in the end to reduce the usage down to around 200 kWh/year. At $340 for fridge and insulation I figure it will take 9 years to pay for itself in energy savings and it's a bargain compared to the Sunfrost (the Sunfrost comparable to our fridge costs $1620 and uses 70 kWh/year)

There are a couple of things to be aware of when modifying refrigerators/freezers. You cannot cover the condenser coils. Many fridges without the exposed coils in the back have them located inside all the walls except the door. If you were to add insulation to these the fridge couldn't dissipate heat and would burn itself up.

I have no background in refrigeration. This project came to me because it seemed like these ideas should work. I've spoken with appliance repair shops and they agree (although with many funny looks) that my ideas should increase the efficiency dramatically.

If you don't want to modify your fridge there are a couple of easy things you can do to make yours less of an energy hog. Check the temperature by placing a glass of water in the fridge for 24 hrs. While 35-40° is recommended, many fridges are set much colder. Adjust your thermostat accordingly and allow 24 hrs for changes to happen. All air space, particularly in freezers, is prone to rapid cold loss since air doesn't hold heat well. Replace air space with jugs of water that will hold the cold longer, but freeze them one at a time to avoid a sudden shock to the fridge causing the compressor to work harder. Lastly, the most efficient way to let the cold out of your fridge is through an open front door. Try to avoid standing and looking at the food hoping something you want appears.

If you have any suggestions, I'd love to hear them or if you'd like assistance or more information about this type of stuff don't hesitate to email me at mikeforbes@moscow.com.

Mike Forbes lives in Moscow and pinches kilowatts like an accountant pinches pennies.

 

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