Reflectix Insulation for Kettle - Disappointing Results

I have a 3000W E-kettle. Faster heating is always nicer, and I wanted to obtain a more vigorous boil, so I picked up a roll of Reflectix and metal tape. Total cost was under $20 at Lowes.

Spent about an hour wrapping two layers around the various gadgets that stick out of my kettle.



I was pretty happy with the aesthetics and assumed I would be with the performance. I did before and after testing of heating 5.8 gallons of tap water from room temperature to a boil. Here are the results-



Both kettles got to the full (just short of rolling) boil within 5 minutes after that last temperature reading.

If we were doing real science here, my error bars would be 5F (well, and I'd be using Kelvin, but that's a separate issue) which makes this a completely null result. No change demonstrated by the intervention.

I will say that the insulation is warm, but I can rest my hand on it. That was definitely not the case with the bare kettle. So I do believe that less heat is being radiated away, but it just must not be that big a deal. Evaporative cooling must be the major force for heat loss.

Now I need to decide if I want to just toss the insulation, or go on with my plan to get the whole thing coated in truck bed liner.

I would not think that the insulation would help in the heating process as your heat source will be putting out much more of a substantial impact vs the amount of loss during the heating process in such a relatively small volume. I would like to see the chart during the mashing process as in how much does the temperature vary and how often does your element have to kick on to reheat with and without the insulation.

I have the same insulation on all my kettles. For me, it does make a difference in heat retention and also helps a lot when brewing in cool/cold weather.

Edit: I have the same pots as you show in the OP

Do you use a lid? I would think the bulk of the heat loss is from the top.

That's funny, I had the same experience this weekend on my last brew. Wrapped my whole kettle (sides and a piece for the lid) with a single layer of reflectix, noticed absolutely no difference in heating times. I do single vessel electric BIAB and I suppose my mash held a bit steadier, maybe one less degree drop during the hour...maybe. But really not enough to justify it.

I did enjoy being able to accidentally brush the side of the kettle without yelling. Overall the kettle looks nicer with it off though, so I think I'll scrap mine.

Cpt_Kirks said:

Do you use a lid? I would think the bulk of the heat loss is from the top.

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I did these tests without a lid. In retrospect, adding the lid would have potentially helped to isolate the effect of the insulation, as we do all agree that the majority of heat loss is through the top. My original thought was to see if I could obtain a stronger boil (maybe...a little) and a secondary gain was speeding up the heating.

I've decided to keep it. I'll add a layer on the bottom, and then see how the guys at the local Line-X place react when I bring it by for an estimate. You can apparently DIY this with a product from Herculiner, though it's supposed to be pretty messy.

But can I get some more details on the tool box in the pic? Never mind I found it.

the point is moot though, as you did this on the boil kettle instead of the mash tun where it would actually matter. 95% of the energy lost in your boil kettle is due to evaporation. the only way to get it to boil faster is to apply more energy more quickly.

i added this same insulation (3 layers) to my mash tun (converted half keg) and decreased the time it takes to heat a given amount of water to mash temp by about 15%, and my PID spends around 35% less time "on" to maintain that temperature (on a 70*F ambient day with low wind). i dont have a pretty graph of it though.

Do you brew indoors? Even the slightest breeze can have very negative effects on heat retention of an unisulated vessel, which any insulation at all will remedy. Two layers of reflectix made a world of difference for my MLT keggle, but I brew outside. I wouldn't expect insulation to have much effect on an electric rig used indoors though.

I split time between inside and outside brewing. I do think this will help if I happen to be outdoors on a colder day, especially with the wind blowing like JuanMoore mentions.

I mash in a beverage cooler, but like audger says, this is a modification that's likely to be very helpful for anyone who mashes in a bare metal vessel.

(Original post on E-Kettle and Toolbox Control Panel for the curious)

I would think this would help when using an immersion chiller in summer. Last batch I made, I was running my water through an ice bath and still having a hard time getting the wort down to 70°. When the air temp is 90° you're fighting against the air heating up the outside of the kettle.

I will say that the insulation is warm, but I can rest my hand on it.

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Is that because the insulation is doing its job, or because it has a lower specific temperature than metal?

I'd love to see the same graph done in 30F ambient temps.

Sweet sight glass by the way ;-)

And I would like to see the same test done with a lid.

I agree that most of the heat must be lost through the top. Looking at the slope of that last, highest temperature, line segment, it appears that you are heating at about 100ºF per hour. Assuming 5.8 gallons of water which weighs about 48.3 pounds at room temp., your net power into the water is 48.3 * 100 = 4830 BTU/hour which is 4830/3412 = 1.42 kW, or a net loss of 3 kW - 1.42 kW = 1.58 kW. If you can keep your hand on the outside of the pot with the reflectrix, I can't imagine that you have more than a fairly small fraction of that 1.58 kW coming through the sides.

Also, FWIW, the beginning segment looks like about 180ºF/hour, or 2.55 kW net power into the water, and the average power into the water from start to finish (temp. rate of about 164ºF per hour) is 2.32 kW.

You have no air between the insulation and the kettle, that's important in insulating. Unless you have an air pocket or insulation that's "poofy" (like the pink stuff in a house), it's not going to work very well.

My method is wrap aluminum foil around the kettle, it works pretty well and leaves some airspace between the foil and kettle. It does help some that I use an electric stove and wrap the foil underneath the heating element as well.

bovineblitz said:

You have no air between the insulation and the kettle, that's important in insulating. Unless you have an air pocket or insulation that's "poofy" (like the pink stuff in a house), it's not going to work very well.

My method is wrap aluminum foil around the kettle, it works pretty well and leaves some airspace between the foil and kettle. It does help some that I use an electric stove and wrap the foil underneath the heating element as well.

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Reflectix is basically bubble wrap with aluminum foil glued to both sides, so there is an air pocket.

As others have said, you probably wouldnt see much of a difference in time to boil since you are boiling uncovered, where most heat is lost out the top. Where insulation has made a difference is when boiling cant be achieved due to not enough wattage, and by adding reflectix some can get to boiling temps.

Reflectix may not be the best solution, but it does work. Three layers (including top and bottom) on my keggle mash tun and i loose less than 1F/hr. I have a 5000W element in my BK, so I don't insulate it.

I actually use 4 layers on a polarware BK (mash tun) and normally loose less than 1 degree/hr (with temps in the 60s). Last April I had 25lbs of grain for 90 minutes (Barleywine) and the temperature actually went up 2 degrees.

When I do the mash out at 170 I take the relectix off (I use velcro) and stir the hell out of the mash as the temp comes up. I never had a scorching problem...just have to stir constantly.

I like this stuff so much, I just bought a Blichmann 10 gal and am in the process of fitting it with reflectix. I plan on using a HERMS now to do my mash out.

The reflectix does help add additional insulation to coolers. I've made rectangular cooler covers from reflectix for years to conserve ice in coolers when camping. I'm planning on making a 'coozie' for my mash cooler to help maintain temps, so if you don't want to use it on your kettle, consider using it for the mash cooler.

Bear with me on this, I am drunk and haven't taken heat transfer yet. Doesn't the heat transfer rate to air completely suck? Like I use my thermapen in a solid or liquid and it'll read temp in two seconds, in air it takes a while to adjust.

If your kettle is losing heat slowly to air, might it make sense not to wrap the kettle with a real material since via actual contact it may actually lose heat faster to it?

I'm sure it can be done with diff eq and maybe some function maximizing, but I have a hunch on some instances insulation may even be detrimental.

petep1980 said:

Bear with me on this, I am drunk and haven't taken heat transfer yet. Doesn't the heat transfer rate to air completely suck? Like I use my thermapen in a solid or liquid and it'll read temp in two seconds, in air it takes a while to adjust.

If your kettle is losing heat slowly to air, might it make sense not to wrap the kettle with a real material since via actual contact it may actually lose heat faster to it?

I'm sure it can be done with diff eq and maybe some function maximizing, but I have a hunch on some instances insulation may even be detrimental.

Click to expand...

Air is a very poor conductor of heat (it's a gas, with very little mass per unit volume). It convects very well (because it is fluid).

When air is captured so it can't move (convect), it becomes a great insulator. Insulation like Reflectix uses a material that is not thermally conductive (i.e., plastic) to capture that air.

I get your point, and if the reflectix was made of copper, you'd be right. But it's not made of copper, it's made of plastic, a poor conductor.

The Reflectix facts say that the temperature range is -60 to 180F. Has anyone had any trouble with it melting on your brew kettle?

Nobody has mentioned this yet, but if you just wrap the Reflectix around the kettle it's rated R1. To get the max available R4.5 for Reflectix you have to make bands around the kettle and then wrap the Reflectix around that, leaving an air pocket in between.

http://www.reflectixinc.com/images/...struction pdf files/diy water heater 0512.pdf

Of course everyone is right that its kinda pointless on a boil kettle, but on a mash tun it works quite well.

No melting noticed on mine. I have since had it coated in a truck bed liner.

I don't have the exact numbers with me, but I remember something said about covering a pot of water prior to boiling. After the water temperature exceeds 180* F, whether it is covered or not doesn't really affect the time to boil, but from cold to 180* F really needs to be covered to boil quickly.

Your greatest thermal loss will be from the lack of the lid. The loss from the walls pale in comparison if you could try this test with the difference being the lid I think it would show more representative data. Also the insulation would show more use on aluminum due to the thermal conductivity of the materials (http://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html). Another thing to consider is the aspect ratio of the kettle which will translate to a surface area/volume ratio, the higher that ratio goes the greater your thermal loss through the walls will be.