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Insulating a chest freezer-worth it?

Post in 'DIY and General non-hearth advice' started by Badfish740, Dec 9, 2009.

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  1. Badfish740

    Badfish740 Minister of Fire

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    I've been meaning to buy a chest freezer for a while now (just missed one for $100 on Craigslist!) as we eat a lot of venison and run out of room in the upstairs freezer pretty quickly. The chest freezer will sit in the utility area of the basement, so as it is I shop the scratch and dent isle at the big box stores because I don't really care what it looks like as long as it works. Energy costs have me thinking though-would it be worth it to attempt to improve upon the insulation of the freezer by supplementing it similar to the idea of a hot water heater blanket in reverse? I was looking at the Reflectix product here and thinking of using it in a similar fashion to the way they insulate HVAC ducts:

    http://www.reflectixinc.com/images/uploads/allpdfs/f62 duct insulation submittal 0107.pdf

    Of course I'd need to take care and not obstruct the ventilation air to the compressor, but it wouldn't be difficult to cover the rest of the outside of the freezer. The average freezer has a surface area (not counting the underside) of about 85 square feet. I can get 400 square feet (48" x 100' roll) of Reflectix for $100, which would essentially allow me to cover each surface four times with airspace in between, which, according to the installation guide, should give me at least an R-8 rating if not more. That still leaves the underside, but I think that would be better served by raising the unit on blocks and placing fiberglass batts underneath as there won't be any real "radiant" heat coming from the floor. I have plenty of fiberglass insulation left over from remodeling my basement as the previous owner even insulated interior partition walls which I ended up tearing out completely. So, if this little project only costs me $100 and a Saturday afternoon and I use the freezer for as long as it lives (15 years at least), is it worth it?

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  2. d.n.f.

    d.n.f. New Member

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    I got a pretty cheap energy star deep freeze at Sears on Sears days. It doesn't use a ton of power and is way better insulated than the ones of old.
    Mine sits in a cold (partially heated) garage at maybe 50 f in the winter.

    Seems like a lot of work and a lot of money. You might want to do the math energy wise per consumption on different models and see if the additional costs are worth it?

    It sounds like a good idea though. Have to keep that motor clear for airflow but you already know that.
  3. peakbagger

    peakbagger Minister of Fire

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    Keep in mind is that many chest freezers have the coils mounted under the outer casing. There are no external coils visible with this type of freezer. Adding insulation to this type of freezer (or refrigerator) has an opposite effect, it uses more energy. I have run into several used freezers that had frozen insulation, they didnt look any different than a standard unit until they were unplugged for a couple of days and a big puddle appeared. Needless to say, not much R value to ice!. If it is a standard unit with external coils, its probably worth a shot once you make sure the door gasket is tight. Most freezers are purchased on price not energy efficiency, so the thermal envelope is probably not a high priority.
  4. Highbeam

    Highbeam Minister of Fire

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    Here's your problem. The modern frost free freezers don't have external coils, they dump the heat through the body of the freezer and do not use a fan. The sides of my frost-free garage freezer get hot. If you insulate the outside of the freezer and the freezer is designed to dump heat through the outside then you are going to stop the required heat exchange and your freezer will thaw.

    If you can find an old style freezer with external coils then this isn't an issue but you'll need to be careful to not block the convective air flow over the coils or if it has a fan then not block the air paths.

    Bottom line, is that this isn't a cooler. The mechanicals need air exchange.
  5. EatenByLimestone

    EatenByLimestone Minister of Fire

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    I looked at insulation in energy saver vs regular freezers. Same make, same size, same insulation between the ES and regular. The energy usage difference must be the compressor or heat exchanger. It isn't in the insulation. That makes me think they are pretty well insulated to start with.

    I ended up with the energy star one because electricity will not become any cheaper over the 20 year life of a freezer. I'll be ahead if it uses less of it.

    Matt
  6. Badfish740

    Badfish740 Minister of Fire

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    Lo and behold, here's what I ended up with:

    http://www.frigidaire.com/products/kitchen-appliances/freezers/ffn15m5hw

    As it turned out the one I saw on Craigslist was still around and I'm picking it up tonight! The owner sent me pictures and it indeed has a louvered vent on the side as in the pictures on Frigidaire's website and it is listed as a manual defrost, not a frost free-I'm assuming that this means the coils are setup conventionally, not within the walls of the freezer correct? If so, any insulation shouldn't cause a problem. As for EatenByLimestone's idea that it's mostly the compressor design, I would tend to agree that compressor design has a lot to do with it, so if you looked at two freezers, one energy star, one not, and the compressors each ran for an identical amount of time, of course the energy star unit is going to come out on top because it's using less energy while running. However, if you could get one of the units to run less (as in place one freezer outside in the shade on a cold day and leave the other in a house heated to 70 degrees) than the other, than clearly the one that runs less will use less electricity. I figure average temperature in my basement is about 60 degrees year round, but in winter it does get pretty warm from the radiant heat thrown by the ESW add-on. I don't want the freezer essentially fighting the furnace to keep my food cold. The bottom line is if I go through with this I'm in a whopping $200 between the freezer and the insulation. Even if it doesn't do much to save energy I'll still have a mysterious box in my basement covered in what looks like shiny bubble wrap-I'll just tell people that I'm storing a Roswell alien because they're remodeling at Area 51 ;)
  7. billb3

    billb3 Minister of Fire

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    I bought an upright manual defrost 2 years ago.
    I haven't had to defrost it yet.
    For frozen vegetables , blueberries, rhubarb and rasberries.
    Actually my sister took half what I managed to put up because I filled this freezer.

    I figure it's full so it's at maximum efficiency.
    Some day I'll put a Killawatt on it to figure exactly what it is costing me.

    What it's not costing me is knowing what pesticides and preservatives I'm not eating. (or less of anyway)
    That's priceless.
  8. benjamin

    benjamin Minister of Fire

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    I'll second the don't bother.

    This thing may use $40 a year, and you may save a couple of bucks meaning if you keep use this for 50 years you'll pay off your investment, less labor and interest of course.

    If it doesn't have the condenser coil and a fan located behind the grille then you have the condenser in the sides of the freezer and you will be defeating or seriously hindering the cooling of the freezer. Even if it does, you're mostly wasting your time, no harm though.
  9. EKLawton

    EKLawton Member

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    you want to save energy, fill jugs with water and keep in the freezer to keep it full. a full freezer runs less than a 3/4 full.
  10. CarbonNeutral

    CarbonNeutral Minister of Fire

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    That's only true if you're opening it on any sort of regular basis. Otherwise you've just paid to freeze a whole load of water.
  11. billb3

    billb3 Minister of Fire

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    That's true for a refrigerator, too.
    H2O mass stores/retains energy a bit better than air.
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