Should I insulate the wood collar of my keezer?

[tbayav8er]

Hi Everyone,

I've noticed on youtube that most people do not insulate the wood collar of their keezer. Is this something I should do? I know wood itself is a good natural insulator. Just not sure if it's worth the trouble of installing some styrofoam insulation around the inside of the collar to save on electricity/wear on the compressor.

Thanks!

 

[Golddiggie]

I added a layer of 1/2" thick neoprene foam to the inside of my keezer collar early on. It actually helped reduce the temperature swings. I went with adhesive backed foam (from Amazon). I also added a layer of (1" or 1-1/2" wide) thinner foam all around the top (to the lid) and on the underside to create a better seal. Again, all from Amazon.

 

[doug293cz]

Hi Everyone,

I've noticed on youtube that most people do not insulate the wood collar of their keezer. Is this something I should do? I know wood itself is a good natural insulator. Just not sure if it's worth the trouble of installing some styrofoam insulation around the inside of the collar to save on electricity/wear on the compressor.

Thanks!

Yes, you should insulate, and use a moisture barrier between the insulation and the wood. This will save energy and protect the wood.

Brew on

 

[hotbeer]

How much trouble can cutting and installing Styrofoam be? Some of my earliest play power tool sets I got in the 60's when a toddler had Styrofoam sheets to cut out shapes with the play jigsaw they had.

 

[Deadalus]

Hi Everyone,

I've noticed on youtube that most people do not insulate the wood collar of their keezer. Is this something I should do? I know wood itself is a good natural insulator. Just not sure if it's worth the trouble of installing some styrofoam insulation around the inside of the collar to save on electricity/wear on the compressor.

Thanks!

Wood isn't a particularly good insulator, r-value is about 1.25 per inch (softwoods). When compared against concrete, brick, or steel it looks a lot better. Thickness also matters, logs are pretty good, but you aren't using logs here. You can do a lot better as far as r-value with actual insulating materials.

Similar to the collar in a keezer, houses can have a "band joist" on top of the foundation. In the past it was often overlooked as far as insulation but it is a good place to get a some bang for your insulation buck.

 

[beernutz]

I have a couple of keezers with wooden collars. I keep one of them, a 7 cf Magic Chef, in a shed with no AC in a pretty warm part of the US about 10 minutes by boat from the Gulf of Mexico and its collar is just wood with no other insulation.

Just for grins I put a Kill-a-watt energy monitor on that keezer which I keep at 32 (heresy I know but I like my beer cold). It is using about $.80 cents of energy a month.

I could spend some money further insulating the wood but the breakeven period seems like it would occur after I'm dead so I don't.

 

[jseyfert3]

I have a 14 cubic foot kreezer in my house that I used two PVC trim boards back to back (1.5” thick) as the collar, not insulated. If I recall correctly that has roughly the same R-value as wood. Over 102 days, it averaged 0.244 kWh/day, or just under $1 per month at $0.12/kWh.

 

[Deadalus]

Freezers don't use much energy compared to other appliances. I looked at a couple 7cuft models and the yellow stickers were saying $30 a year based on ~250 kWh/year and $0.12 a kWh. Seeing the actual values reported here ($9-$12) got me wondering about how those stickers are calculated. Following that link to Table 16 and a note at the bottom says they haven't changed the "energy factor" used in the calculation since 2003. Usage by a homebrewer could be a lot less than as a freezer too. I don't really open mine except to change out kegs, plus freeze temperature is below freezing generally.

Now you might actually break even though. A 1-inch sheet of polystyrene 4ft x 8ft is listed at ~$18. My keezer is~7 cuft and is ~20 in x 36 in (outside), so the perimeter is 112". I used a 2x8, so height is 7.5 in for a total of 840 square inches or ~6 sq ft. That's about 1/5 of the sheet or $3.60. Save $1 per year in energy costs and it's paid off in just about 3.5 years. If you get just a little bit of life on the freezer, even 5% that'll pay for the insulation too. Depending on how involved your build is, having to replace the keezer sooner than you want to could be a bit time consuming.

Maybe not exactly big bucks though, start with your house if it needs it!

 

[jseyfert3]

Freezers don't use much energy compared to other appliances. I looked at a couple 7cuft models and the yellow stickers were saying $30 a year based on ~250 kWh/year and $0.12 a kWh. Seeing the actual values reported here ($9-$12) got me wondering about how those stickers are calculated. Following that link to Table 16 and a note at the bottom says they haven't changed the "energy factor" used in the calculation since 2003. Usage by a homebrewer could be a lot less than as a freezer too. I don't really open mine except to change out kegs, plus freeze temperature is below freezing generally.

Heat transfer through a material is linearly proportional to the temp difference across the material. So a kreezer at 38 °F in a house at 72 °F has a delta of 34 °F. The highest recommended freezer temp for long term storage is 0 °F. A freezer at 0 °F in a house at 72 °F has a delta of 72 °F. This is 2.1 times higher than a kreezer set at 38 in the same house. This means for standby losses, which means no lid opening or putting warm items inside that need to cool down, and assuming no air leakage, the freezer has 2.1 times the energy requirement of the freezer because the freezer is much colder. I suspect in either the case of the kreezer or freezer, on average, standby losses are the majority of the energy consumption. Though in the case of @bracconiere my gut feeling without doing any math is that cooling his warm kegs likely exceeds his standby losses.

 

[Deadalus]

Heat transfer through a material is linearly proportional to the temp difference across the material. So a kreezer at 38 °F in a house at 72 °F has a delta of 34 °F. The highest recommended freezer temp for long term storage is 0 °F. A freezer at 0 °F in a house at 72 °F has a delta of 72 °F. This is 2.1 times higher than a kreezer set at 38 in the same house. This means for standby losses, which means no lid opening or putting warm items inside that need to cool down, and assuming no air leakage, the freezer has 2.1 times the energy requirement of the freezer because the freezer is much colder. I suspect in either the case of the kreezer or freezer, on average, standby losses are the majority of the energy consumption. Though in the case of @bracconiere my gut feeling without doing any math is that cooling his warm kegs likely exceeds his standby losses.

I don't necessarily disagree with you about the delta difference and it's potential to be a major factor but once a collar is slapped on and taps run the usage is different. Given the linearly proportional relationship though, it's testable by system. One could just maintain the room temperature reasonably constant and change the temperature settings and record the energy used. Adding a collar and taps though changes the material the heat transfers through and there is a surface area change as well. In my situation, the freezer depth was ~28". I have added on a collar that is 7.5", No more than close to 25% more surface area but there's also the top and bottom unchanged and the hump to consider. Frozen food goes in the keezer but kegs of ale go into keezers. How close the freezer energy usage and the converted to keezer energy usage are is somewhat muddled. Seems a good guess though that the delta is very important.

I was mistaken about that link being the calculation behind the yellow sticker. That link is for the Home Energy Saver Calculator. I looked a little more and it appears the Department of Energy is responsible for Standards and Test Procedures. Then skipping forward, freezer test procedures are in Appendix B, which is way more complex than that first link I posted and too lengthy to puzzle through. It seemed pretty disparate though that the 2 reported energy usages were only about 1/3 of a typical sized freezer. I am not doubting the Kill-o-watt readings. I happen to have one and will be plugging it in to see what it says for my unit.

 

[crazyjake19]

Wood is a particularly poor insulator, so I figured why not insulate my collar for minimal cost. I used 2" thick polyisocyanurate foil-lined rigid foam insulation, which made the thickness of foam + wood equal to the original thickness of my chest freezer walls.

 

[bracconiere]

Though in the case of @bracconiere my gut feeling without doing any math is that cooling his warm kegs likely exceeds his standby losses.

i actually have a mini fridge for bringing the fermenter down to 40f, before kegging, and putting the kegs in the kegerator. makes burst carbing a lot easier!

 

[jseyfert3]

I don't necessarily disagree with you about the delta difference and it's potential to be a major factor but once a collar is slapped on and taps run the usage is different. Given the linearly proportional relationship though, it's testable by system. One could just maintain the room temperature reasonably constant and change the temperature settings and record the energy used. Adding a collar and taps though changes the material the heat transfers through and there is a surface area change as well. In my situation, the freezer depth was ~28". I have added on a collar that is 7.5", No more than close to 25% more surface area but there's also the top and bottom unchanged and the hump to consider. Frozen food goes in the keezer but kegs of ale go into keezers. How close the freezer energy usage and the converted to keezer energy usage are is somewhat muddled. Seems a good guess though that the delta is very important.

Well I did some math for ballpark numbers. I don't want to drown people in details but when you are calculating heat transfer through a material there are three thermal resistances you need to calculate. First is the air to material, the material itself, then the material to air on the other side. The air to material interfaces are calculated based on convection, conduction, and/or thermal radiation, and get complicated. I seem to recall from my college classes these resistances are typically fairly low, so for ballpark consideration, you can say there is no thermal resistance at the air to material junction. This assumption would be the worst case scenario anyway.

Using my iPhone 12 to measure my collar (I couldn't find a tape measure, but experience has shown this type of measurement is usually good to within an inch) I calculated my 14 ft^3 kreezer with a 3.5" tall collar has 3.96 ft^2 of surface area. Cellular PVC, which is what I built my collar from, has an R value of ~2.1 per inch (wood is ~1.4), and I have 1.5" (R3.15). Assuming a kreezer temp of 38 and a house temp of 70, this calculates to 5.78 BTU/hr, or 1.7 watts. Over a 30 day month, this is 1.2 kWh, or 15 kWh in a year. About $1.80/year in electricity costs. Since my collar is the dimensions of a 2x4, an uninsulated wood collar of the same size would be 1.5x more than these values.

An inch of extruded polystyrene (R5) added to my PVC collar would bump the total R value to 8, dropping the heat lost to 0.296 watts, or 0.21 kWh/month. This is only 2.6 kWh/year, or about $0.31 at $0.12/kWh.

So, at best I'd save $1.50 a year by slapping an inch of foam on my collar. Is that worth the bother to add? Probably not for me. If you are getting condensation on a wood collar though insulation would be worth it purely to avoid wood rot and mold issues, but my PVC collar is not bothered by water (which is why I used PVC and not wood). I've also never notice condensation issues on the collar, may be more of an issue for an outdoor kreezer.

Oh, and it just so happens I have a 14 cubic foot chest freezer in use as an actual freezer, bought about 8-9 years ago. The walls aren't quite as thick as my 14 cubic foot kreezer (insulation thickness has gone up over the years), but I stuck my Kill-A-Watt on that just now to compare for giggles.

The thought also just crossed my mind that it probably would have made more sense to use the brand new Frigidaire freezer I built the kreezer out of as my actual freezer, given the thicker walls, and then converted my 9 year old Whirlpool freezer into the kreezer instead. Ah well.

 

[Homebrew Harry]

An insulated keezer would have a lot less cycles over the years. The result would be less wear on the compressor. It seems that less wear would keep it functioning as desired for a longer period of time.
The hassle of finding warm beer and having to purchase a new freezer and then convert it should be more of a factor than looking at this for a monthly electricity savings IMO.

 

[Deadalus]

Well I did some math for ballpark numbers. I don't want to drown people in details but when you are calculating heat transfer through a material there are three thermal resistances you need to calculate. First is the air to material, the material itself, then the material to air on the other side. The air to material interfaces are calculated based on convection, conduction, and/or thermal radiation, and get complicated. I seem to recall from my college classes these resistances are typically fairly low, so for ballpark consideration, you can say there is no thermal resistance at the air to material junction. This assumption would be the worst case scenario anyway.

Using my iPhone 12 to measure my collar (I couldn't find a tape measure, but experience has shown this type of measurement is usually good to within an inch) I calculated my 14 ft^3 kreezer with a 3.5" tall collar has 3.96 ft^2 of surface area. Cellular PVC, which is what I built my collar from, has an R value of ~2.1 per inch (wood is ~1.4), and I have 1.5" (R3.15). Assuming a kreezer temp of 38 and a house temp of 70, this calculates to 5.78 BTU/hr, or 1.7 watts. Over a 30 day month, this is 1.2 kWh, or 15 kWh in a year. About $1.80/year in electricity costs. Since my collar is the dimensions of a 2x4, an uninsulated wood collar of the same size would be 1.5x more than these values.

An inch of extruded polystyrene (R5) added to my PVC collar would bump the total R value to 8, dropping the heat lost to 0.296 watts, or 0.21 kWh/month. This is only 2.6 kWh/year, or about $0.31 at $0.12/kWh.

So, at best I'd save $1.50 a year by slapping an inch of foam on my collar. Is that worth the bother to add? Probably not for me. If you are getting condensation on a wood collar though insulation would be worth it purely to avoid wood rot and mold issues, but my PVC collar is not bothered by water (which is why I used PVC and not wood). I've also never notice condensation issues on the collar, may be more of an issue for an outdoor kreezer.

Oh, and it just so happens I have a 14 cubic foot chest freezer in use as an actual freezer, bought about 8-9 years ago. The walls aren't quite as thick as my 14 cubic foot kreezer (insulation thickness has gone up over the years), but I stuck my Kill-A-Watt on that just now to compare for giggles.

The thought also just crossed my mind that it probably would have made more sense to use the brand new Frigidaire freezer I built the kreezer out of as my actual freezer, given the thicker walls, and then converted my 9 year old Whirlpool freezer into the kreezer instead. Ah well.

What is the value for the Energy Guide sticker for your keezer model? Something seems potentially off in your calculation. A 14.8 cu ft Frigidaire freezer currently at Lowes is estimated to use 296 kWh yearly ($36). Your estimate is 15 kWh yearly, which us ~1/20th of the possible sticker value. With an insulated collar, your estimate is just 2.6 kWh/year, which is about 1%. Going by what you said previously, you were expecting roughly 1/2 the energy use at 38F vs 0F. I think you may get a different estimate from your Kill-a-watt meter based on what others have reported in this thread. If your calculation is reasonably close, and given what others reported as actual, the disparity between the EnergyGuide values and those reported is still rather large in my opinion, even considering the deltas involved and the collar conversions. I know it all depends on how the appliance is used and real world conditions, and after having my eyes glaze over reading the testing procedures they seemed well described and controlled for and all, but even so I would expect that the EnergyGuide value would be something of an understatement. I say that because manufacturers are always trying to game the system and the winning play on the EnergyGuide would be to go as low as legally possible (perfect conditions). That's what has me intrigued.

Seems so far though that the return on investment would be positive over the life of the keezer. A caulk gun and a utility knife are the basic tools needed. Whether people want to do it or have other competing time interests or specific issues is more of individual concern.

 

[jseyfert3]

A 14.8 cu ft Frigidaire freezer currently at Lowes is estimated to use 296 kWh yearly ($36). Your estimate is 15 kWh yearly, which us ~1/20th of the possible sticker value. With an insulated collar, your estimate is just 2.6 kWh/year, which is about 1%. Going by what you said previously, you were expecting roughly 1/2 the energy use at 38F vs 0F. I think you may get a different estimate from your Kill-a-watt meter based on what others have reported in this thread.

My estimate was the heat gain through an uninsulated collar vs an insulated collar, not the total energy usage of the entire kreezer. That gets complicated, because they run the evaporator and condenser lines through the walls.

Unfortunately when I made my calculation it was only the heat gain into the kreezer through the collar, and I assumed the heat gain was the cost. This is not a correct assumption. In fact generally for heat pumps (which fridges/freezers have) to move 1 kWh of heat from inside the kreezer to the outside takes less than 1 kWh of electricity.

Sorry this probably makes things even more confusing. What it means is my listed savings on insulating a collar, small as they are, are actually even less than that in real life. Again because 1 kWh of heat energy going through the collar may require only 1/2 or 1/3 of a kWh to actually remove from the kreezer. I can explain more tonight if interested but I’m at work right now.

 

[Deadalus]

My estimate was the heat gain through an uninsulated collar vs an insulated collar, not the total energy usage of the entire kreezer. That gets complicated, because they run the evaporator and condenser lines through the walls.

Unfortunately when I made my calculation it was only the heat gain into the kreezer through the collar, and I assumed the heat gain was the cost. This is not a correct assumption. In fact generally for heat pumps (which fridges/freezers have) to move 1 kWh of heat from inside the kreezer to the outside takes less than 1 kWh of electricity.

Sorry this probably makes things even more confusing. What it means is my listed savings on insulating a collar, small as they are, are actually even less than that in real life. Again because 1 kWh of heat energy going through the collar may require only 1/2 or 1/3 of a kWh to actually remove from the kreezer. I can explain more tonight if interested but I’m at work right now.

OK I see what you are doing, I got thrown off when you said you were going to put the KILL-a-watt on it. You would have to run it with and without insulation on the collar to get real data using the Kill-a-watt. Still would be interesting to get some data for the overall usage to compare to the sticker.

Your collar is small BTW, not a judgement just an observation. At ~4 sq ft, an 1/8 of a sheet of polystyrene is only about $2.25. I think you'd still break even.

Not that it matters for your collar, but species of wood matters for r-value. Most softwoods are 1.41/in but most hardwoods are 0.71. People going for a nicer look of specific hardwoods with taps through the collar for instance may want to keep that in mind. Not saying one can't get a nice look using softwoods either. It does matter that your material is 2.1 vs. 1.4 (or 0.7). Seemingly small but that's 50% or 200% better. Since we're only talking a few bucks, the extra pennies matter!

 

[hotbeer]

Insulation isn't just about saving money on the power bill. As some said, it's questionable what the savings might be. However someplace where there is a high moisture content in the air outside the keezer, insulation on the inside should help keep condensation bundling up on the outside surfaces.

If you don't ever have any condensation on the outside, then you don't have a problem.

Besides, if done right it can make your creation look more finished.

 

[jseyfert3]

What is the value for the Energy Guide sticker for your keezer model? Something seems potentially off in your calculation. A 14.8 cu ft Frigidaire freezer currently at Lowes is estimated to use 296 kWh yearly ($36). Your estimate is 15 kWh yearly, which us ~1/20th of the possible sticker value. With an insulated collar, your estimate is just 2.6 kWh/year, which is about 1%. Going by what you said previously, you were expecting roughly 1/2 the energy use at 38F vs 0F. I think you may get a different estimate from your Kill-a-watt meter based on what others have reported in this thread. If your calculation is reasonably close, and given what others reported as actual, the disparity between the EnergyGuide values and those reported is still rather large in my opinion, even considering the deltas involved and the collar conversions.

OK I see what you are doing, I got thrown off when you said you were going to put the KILL-a-watt on it.

So I put the Kill-A-Watt on my freezer to see if my freezer lines up with the sticker values more or less, to help explain that the temp delta is indeed why kreezers have a much lower energy consumption than freezer sticker values, even though the kreezers have a bigger surface area with a collar which may or may not be well insulated.

Since I put that on there, 7.6 kWh in 216 hours, which works out to 25.6 kWh/month or 311 kWh/year. This does indeed line up pretty close to the sticker values you reported earlier. I don’t know what the specific sticker value of that freezer is. If you’re curious I’ll look that up, and also measure the actual temp in the freezer.

This 14 cubic foot Whirlpool model (~10 years old) is in my basement where the ambient temp is currently 67 °F.

Also one thing I’d like to add is I’ve seen people who live off grid use chest freezers as refrigerators. Effectively a kreezer but without the collar. The low powe consumption vs a normal upright fridge freezer is the reason, because of thicker insulation on the chest freezer plus the fact that when you open it the cold air, which is heavier than the ambient air, sits in the chest freezer (fridge), unlike an upright fridge where a lot of it immediately sinks out when the door is opened.

 

[jseyfert3]

Oh, and one thing I forgot earlier is it’s NOT just the temp delta explaining the greatly reduced energy consumption for the kreezers over the sticker value for freezer energy usage. Heat pump efficiency is strongly correlated with temperature delta as well. The large the delta, the lower the efficiency. So being colder not only means more heat gain, but lower efficiency to boot. I haven’t calculated example values but if the say the efficiency is half when you double the temp delta, and doubling the temp delta means twice the heat load, then it will take 4x the energy. Clearly it will take more than that. I should calculate the theoretical maximum efficiency of a heat pump at kreezer vs freezer efficiencies….

 

[JAReeves]

For what it's worth, I figured I'd insulate the collar on mine because I expect it to last years and over the lifespan it will probably save some money and energy; it really took very little to insulate the collar like this.