BIAB Kettle Insulation Calculator

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worxman02

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Hey All,

I've been doing BIAB batches for a while and I was not satisfied with my temperature loss during the mash with my 1 layer of Reflectix "insulation". So being the architect/engineer/nerd that I am I decided to figure out how much insulation I actually need to only have a temperature loss of 1ºF/hr. The result is a BIAB Kettle Insulation calculator that takes into account the size of your pot, batch volume, mash temp, outdoor temp, and R-Value of your chosen insulation and spits out the required insulation thickness for a 1ºF/hr drop.

I also included a list of common insulation types with their respective R-Values to make it easy to find the R-value for your desired insulation.

I hope this helps you guys out. Link: https://docs.google.com/spreadsheet/ccc?key=0AmCFRdenGji4dFlHNlRXM19MUVlneE11aU1SR25LaEE&usp=sharing
 
Sounds awesome! But when I click the link, it says I need permission. So I requested it :)

Try it again. I forgot to change the sharing permissions before posting it. Let me know if it works now.
 
I too am a little concerned with the 3-4F I lose over a typical 60 minute mash. I've started firing up the burner again at about 30 mins, but it's a PITA. I'd love an easy way to maintain the temperature.

But, this does beg the question - Does a 3-4F loss over the mash really matter? In another thread, someone said their mash was done (negative start test) after 2 minutes! So does it matter that I'm losing a few degrees over the mash? (Serious question)
 
I was planning on getting some reflectix, but this seriously makes me reconsider. With your defaults and using 3.7 R value (minimum on HD's site), you would need 11 layers thick.

From this exercise, have you come up with anything that is cheap, easy to build and would work based on the <1F/hr loss?
 
I too am a little concerned with the 3-4F I lose over a typical 60 minute mash. I've started firing up the burner again at about 30 mins, but it's a PITA. I'd love an easy way to maintain the temperature.

But, this does beg the question - Does a 3-4F loss over the mash really matter? In another thread, someone said their mash was done (negative start test) after 2 minutes! So does it matter that I'm losing a few degrees over the mash? (Serious question)

That is a good question. I have heard that the mash can finish much sooner than the 60 mins that we typically use. This is a good thread on the subject: https://www.homebrewersassociation.org/forum/index.php?topic=4331.0 and Kaiser has a great article here: http://braukaiser.com/wiki/index.php/Starch_Conversion

It seems like the consensus is that while starch conversion occurs very quickly, attenuability of the mash increases with time with the sweet spot being around 40 mins.

I have also heard that a 3-4 degree loss isn't that big a deal, however some people can have a much greater loss if they are brewing in the dead of winter. I figured that I would rather err on the side of caution and slightly over-insulate my kettle so I don't have to worry about it and I know that I will only lose 1ºF/hr. Plus I figured that people can use the calculator as a starting point and change the amount of insulation they plan on using as desired based on their preferences.

I will be posting a thread with pictures soon of the 2" thick polyiso insulation wrap that I made over the weekend based on this calculator.
 
Working now. You were seriously thorough in your listing of insulations. Except I don't see the blanket that I use on there :)

I just copied the list from wikipedia or a similar site. I don't remember. If you calculate the blanket's R-value, let me know and I'll add it ;)
 
I was planning on getting some reflectix, but this seriously makes me reconsider. With your defaults and using 3.7 R value (minimum on HD's site), you would need 11 layers thick.

From this exercise, have you come up with anything that is cheap, easy to build and would work based on the <1F/hr loss?

The Reflectix is crap. The advertised R-value of 3.7 is basically a lie and doesn't apply to our situation. In order to get that R-Value you need to have a sealed airspace between the item you're insulating and the reflectix which requires it to be permanently mounted and it is not heat proof at all.

Yesterday I just made a 2" thick wrap out of rigid polyisocyanurate insulation. It wasn't difficult, just time consuming. I already had the polyiso from building my keezer. I used about a 1/4 of a sheet so maybe it cost $10-15 since I used a whole roll of aluminum tape on it.

I recommend getting some closed cell foam camping mats and gluing a couple layers together and wrapping that around your kettle. Or an old ski jacket or sleeping bag works really well since they are pretty well insulating (Thinsulate has an R-value of 5.75/inch) and you might be able to find one cheap if you dont have ones on hand. It all depends on how much time you want to spend vs. appearance vs. cost.
 
That is a good question. I have heard that the mash can finish much sooner than the 60 mins that we typically use. This is a good thread on the subject: https://www.homebrewersassociation.org/forum/index.php?topic=4331.0 and Kaiser has a great article here: http://braukaiser.com/wiki/index.php/Starch_Conversion

It seems like the consensus is that while starch conversion occurs very quickly, attenuability of the mash increases with time with the sweet spot being around 40 mins.

I have also heard that a 3-4 degree loss isn't that big a deal, however some people can have a much greater loss if they are brewing in the dead of winter. I figured that I would rather err on the side of caution and slightly over-insulate my kettle so I don't have to worry about it and I know that I will only lose 1ºF/hr. Plus I figured that people can use the calculator as a starting point and change the amount of insulation they plan on using as desired based on their preferences.

I will be posting a thread with pictures soon of the 2" thick polyiso insulation wrap that I made over the weekend based on this calculator.
Thanks for the info and yes, please post the pictures. I'm curious with what you came up with.
 
I have a 3 layer reflectix jacket on my kettle and I lose only 1 maybe 2 degrees by the end of the mash. It also has a reflectix cover for the lid that overlaps the sides of the jacket. It was easy to make and definitely works great.

Sent from my XT907 using Home Brew mobile app

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Looks good! Looks like you need a bigger lid though ;)

The more I think about it, the more I think I should use the cooler I already own and just get a new bag that will fit in there and mash in there and drain into my kettle. I'm sure that will maintain the mash temp more than any insulation system I can come up with for my pot. But, I almost feel like if I'm mashing in a cooler that I might as well switch to the typical AG setup. At least with BIAB you don't have to worry about stuck sparges. Hmmm... What to do, what to do?
 
Looks good! Looks like you need a bigger lid though ;)

The more I think about it, the more I think I should use the cooler I already own and just get a new bag that will fit in there and mash in there and drain into my kettle. I'm sure that will maintain the mash temp more than any insulation system I can come up with for my pot. But, I almost feel like if I'm mashing in a cooler that I might as well switch to the typical AG setup. At least with BIAB you don't have to worry about stuck sparges. Hmmm... What to do, what to do?

Before you use the cooler, be nice to me and try a shorter mash schedule. Try 30 minutes and see if you don't convert all the starch and get to your expected OG. :rockin:
 
Before you use the cooler, be nice to me and try a shorter mash schedule. Try 30 minutes and see if you don't convert all the starch and get to your expected OG. :rockin:
I'd believe you if you said it's all converted. Someone said theirs was converted in 2 minutes. I haven't checked mine except a couple times after the recipes mash time just to check.

But what about this:
It seems like the consensus is that while starch conversion occurs very quickly, attenuability of the mash increases with time with the sweet spot being around 40 mins.
And why do many recipes have 90 mins then?
 
Long mashes compensate for poor crushes. The thicker the piece of grain, the longer it takes to wet it to the center and until it's wet, there is no conversion. Then it takes time to leach the sugar back out of that fat piece of grain and that takes time too. If you give a poor crush long enough, your efficiency will be decent.

I'm the one that said I had conversion at 2 minutes and still insisted on mashing for 30 minutes. I haven't calculated the attenuation but my last brew that I just bottles started at 1.054 with a predicted FG of 1.011 and finally stopped at 1.004.
 
Thanks for the info on the long mash. Stupid newbie that I am, I just assumed I needed to follow the recipe and have done the long mashes as specified. Guess with my double crush with BIAB, I'm fine to shorten it.

Funny that you were the one talking about the 2 minute mash :)
 
Thanks for the info on the long mash. Stupid newbie that I am, I just assumed I needed to follow the recipe and have done the long mashes as specified. Guess with my double crush with BIAB, I'm fine to shorten it.

Funny that you were the one talking about the 2 minute mash :)

Not too funny, I do a lot of talking about doing shorter mashes on the BIAB board and recently in the thread on insulating the kettle I found corroborating evidence when Worxman02 listed a couple links to studies I had missed. https://www.homebrewtalk.com/f244/biab-kettle-insulation-calculator-451886/

Figure 8 in this article (http://braukaiser.com/wiki/index.php/Starch_Conversion) shows the conversion time at different mash thicknesses. There didn't seem to be any discussion about milling finer than average and the chart limited with 1:4 grain to water ratio but it shows the majority of the conversion in about 5 minutes.
 
I have a walmart blue camping pad - wrapped around pot once and cut to size, duct taped seam. I then took leftover piece and made a cover for the top. I then take a big contractor trash bag and cover the whole thing, pot, burner, insulation, etc. In my unheated garage, in 30* temps, I only lose about 1* an hour.
 
How does the camping pad compare with several thin cotton and wool blankets? I wrap up my kettle with several blankets, but I do lose more heat than I'd like. I can't really wrap underneath very well since it's sitting on the burner (obviously off).
 
I use a big moving blanket and wrap it around the kettle and over the lid and tuck it around the burner loosely at the bottom. This ensures the entire kettle and burner are surrounded by the blanket and I don't get cool air stealing heat from the bottom of the pot. I usually only lose maybe 1-2 degrees in an hour long mash.

As far as why I do the full hour... I just use that time to do other things. Get some lunch, set up for the boil, sanitize the fermenter, etc. Doesn't seem to hurt things and if it increases efficiency, that is just gravy!
 
My first brew I thought I could control mash temperature with the burner alone. That didn't work. I then moved to various combinations of sleeping bags and blankets held in place with bungee chords with limited success. I had a cooler around so I tried that, again with limited success. I finally settled on four layers of reflectix on the sides and top. My last brew I lost 1.5°F in a 27° garage.

My takeaway from my experience is that it is really important to seal the top of your mash tun. My cooler had cup holders in the top which allowed heat to escape because there is less insulation. This isn't a problem for its intended use of keeping things cold since cool air sinks. My first pot had a thin ill fitting lid which allowed a lot of heat to escape even when duct taped shut. If you can feel heat on the outside of the pot you are losing it too quickly.

My current solution is four layers of reflectix which fit tightly around the pot. I pull it down past the bottom. The reflectix extends about 6" above the top of the pot. I cut four circles of reflectix to fit over the lid as well. I fold the extra reflectix from the sides down over the lid insulation and hold it in place with some 5 and 10 lb weights I keep around for various uses.

I have a cheap laser thermometer I can use to test areas of the contraption for heat leaks. My setup is sealed pretty tight. The outside was about 35° (close to air temperature) on my last brew while it was a toast 152° inside the kettle.
 
One thing I've been wondering about is whether placing the kettle in a heated water bath would work well for maintaining temp. I'm planning to pick up a Sansaire soon, or one of the similar devices, and I figure I could set my kettle inside a larger vessel of water and set the sansaire to keep that water at my mash temp. Perhaps a degree or two higher to compensate for heat loss out the top. Sound plausible? It would probably be impractical for those using huge kettles, but for my current 5 gal kettle / stovetop setup I figure it should be ok.
 
If you're using a 5 gallon pot, can you put it in the oven?

I've considered that, and my concern is that my oven won't hold a temperature below 170. Perhaps turning the oven off beforehand and letting residual heat do the job would work?
 
Yes, that's how I've heard people do it. Seems ideal to me. But I brew outside in a 10 gallon pot, so I'd have to carry it up a flight of stairs and I'm actually not even sure my pot would fit in there.
 
The spreadsheet is marvelous for a first idea of how well it is insulated. Thank you.

I am glad that insulating the BIAB kettle is gaining - steam (pun intended). It saves much on energy cost along side stabilizing the mash temp. And several people have noted correctly that much of the heat is lost from the top and top seams.

My kettle has 4 wraps of Reflectix and the top has 2 layers. The rim was uninsulated and losing much heat. It improved immensely when I cut extra-large discs that overlapped the rim by 2 inches.
 
I've considered that, and my concern is that my oven won't hold a temperature below 170. Perhaps turning the oven off beforehand and letting residual heat do the job would work?

Yes, the residual heat will be plenty...even at 170, the temp is only slightly different the mash compared to the 90 degree differential from ambient and likely wouldn't raise the mash temp much.
 
I use an old sleeping bag. But, before I put it around kettle I put 4 towels folded in half on top. As someone said, this helps a lot.
 
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