Finally managed to get a decent brew day on the books. Irish red for St. Patricks day, turned out 10 points lower than expected but I really don't mind that. (1.032 OG, boil off was way low. Was supposed to be 1.042.)
What I do mind is my mash tun. I've been having issues with lower than expected mash temps, and upped the ante on how I measure temps for this brew...and I lost a whopping 16 degrees. Weather was upper 40's, no wind.
The cooler was about half full. I bought this size cooler with the intent of brewing 10 gallon batches for lower gravity beers, and 5 gallon batches for higher gravity beers. Currently the water supply for my counterflow chiller is not available, so I've been brewing 5 gallon batches so the brew kettle can be carried into the kitchen. There I can use my immersion chiller hooked up to the kitchen faucet.
So did I lose all my heat because the cooler wasn't full enough? I'm honestly not sure that's all it is...temps fell from 156 to 140 in about 50 minutes.