insulating your mash-tun for BIAB??

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Hello what is the best way to insulate your mash-tun for doing BIAB Brewing ?
I've heard of people using sleeping bags and blankets. I also saw a video where the guy popped his vessel in a big electric smoker to keep it at temp. I throw a couple beach towels in the clothes dryer for 5 minutes and then wrap the vessel with the towels. On a colder day (50s, I'm in CA) it holds temp for 60 minutes; sometimes it will drop off a degree or two in the last 15 minutes. I suppose it depends on whether you are brewing indoors or out, and what region you live in. My method probably wouldn't work well for garage brewing in North Dakota.
It's generally not necessary. You have a fairly large volume of water, plus the mass of the grain and the kettle itself. The temperature should be pretty stable. After a half hour, I don't think it much matters if the temperature drops out-of-range because most of the conversion was done in the first 20 minutes. The only reason you mash for a full hour (or close to it) is to extract more flavor from the grain; the sugar was done a long time ago.

My method probably wouldn't work well for garage brewing in North Dakota.

:) Yes, in that case you might want to wrap a blanket around the kettle.
A $14 youth sleeping bag works perfectly for me. It fits just right over my 15gal kettle/burner. It holds temps within a few degrees for 60min (always within 1deg for the critical 1st 15-20min).

It can be easily zipped open if I need to access the kettle lid. My temp probe wire exits cleanly out the end of the zipper opening. I line up the zipper with the propane hose, so the zipper can be adjusted to seal around the hose area.

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Here's me using a blanket; it looks like a quilt, but that's just a print. The kettle is sitting on the burner.

Whatever works to keep the heat in is appropriate. Blanket, sleeping bag...

I have a 20 gallon pot. I have a roll of duct insulation that I cut to length and I wrap it around the pot and hold snug with a bungee cord. I also brew in West Central Florida so not many of my brew days are cold.
pretty much did exactly what the above did, except I taped both side up to stop the fiberglass from going everywhere, also put it in my oven.


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I use foil bubble wrap insulation, currently 3 layers thick. I work part-time so I mash in the morning and then go to work. Return 4.5 hours later and get the boil on, temp only drops by 2-3°C.
Most of us have been informed that the mash takes 60 minutes and you need to keep the pot at the mash temperature for that long. Actually, conversion can happen very quickly if the grains are milled fine and from then on you aren't doing a lot except extracting the sugars and flavors which can happen at a much cooler temp.

Yes, if you are mashing where it is cold you should insulate the kettle but in warmer areas it isn't really necessary.
I also do the Reflectix method. Took a few hours to put it all together, but it's lasted quite well. Here's some info on putting it all together:

I lose less heat with bigger mash volumes, but for sake of the thread, in the dead of Winter I lose about 3-4 F (in the garage) with 8 gallon mashes (5 gallon batches) and about 2-3 F for 11-12 gallon mashes (11 gallon batches). I lose less than half of that heat during the Summer.
What @RM-MN says.
I BIAB in New England, in the garage (door closed), even in sub zero. Not the same as balmy North Dakota, but you get the idea.

I bought the 25 ft roll of reflextrix (sp?).
I don't leave kettle on propane burner (couple reasons --heat continued to warm after strike reached and wasn't predictable and I am all about predictable repeatability; secondly, I can insulate the bottom)
I set a milk crate on garage floor, laying a couple layers folded towels thereon, then kettle on towels, insulating bottom. Do *NOT* set kettle on concrete floor.
I wrap two layers reflectrix around sides, I only have handles, no spigots or ports or sight glasses. Then two layers on the lid.

I used to wrap with moving blanket then wrap that with a sleeping bag.
You don't need to. Temp drop over an hour is same, for me, and as @RM-MN has said, with my Corona fine grind, things are done way before then anyway.
I use a padded moving blanket secured with bungee cords then a sleeping bag wrapped around the blanket also secured with bungee cords.

The biggest difference was made when I started insulating the top with a few layers of blankets, heavy towels, whatever. After I started doing that my mash temps never dropped over the course of an hour mash.

I also insulate with the BK while it's still on the burner (clearly with the burner off). That helps to hold heat also.
Another option is to use a sous vide immersion cooker to maintain the mash temp more precisely. It also makes step mashes really easy.
I just put a beach towel over my kettle. I'm in VA and the garage stays fairly warm in the winter. Since I'm using an induction burner, I just cover the kettle as soon as I turn off the burner and dough in. It'll drop over the course of an hour by 4-6 degrees, but it seems to work fine.