ASHRAE Journal- September 2008 - 83

Photo 3 (left): Barrel Location Sweet Spot. In every warehouse there is a location where the bourbon tastes better than bourbon from anywhere else. To find sweet-spot barrels, each barrel is tasted by an expert bourbon taster. I wonder if they are hiring? Photo 4 (right): The high mass warehouse consists of a metal roof over timber deck, stone walls, a dirt crawlspace, cross ventilation and stack ventilation. The temperature of the ground and the thermal resistance and thermal mass of the walls moderate the building’s temperature swings. The metal roof is cooler than asphalt shingles or a built-up roof. Size, that surface area to volume thing, is something else. After 200 years, there is absolutely no size consensus according to bourbon folks. Some bourbon is made in larger than standardsized barrels, some in smaller than standard-sized barrels, but most in standard-sized barrels.II Oak barrels used in the manufacture of bourbon are charred to varying degrees in processes that are closely held secrets (Photo 2). The particular type of oak, where it is grown, how old, and what part of the tree the oak comes from are even more closely held secrets. A clear liquid spirit is obtained from the distillation of a secret mixture of grains in a process called sour mash fermentation. Bourbon results when the spirit is stored for varying periods of time under varying conditions in the charred barrels. The varying periods of time under varying conditions is where building science comes in. Bourbon makers are logical folk. They make stuff, keep track of how they make it, taste it, and if they like it, they make more. Then, they make changes one at a time and compare the effect of the change to the taste of the stuff they like. They don’t share information with other folk who make bourbon. But, you can tell a lot from how they store their barrels and by asking questions such as “what’s with the thermometer in the barrel?” during distillery tours (Photo 3). The temperature-time regimen of barrel aging apparently is a big deal. In every warehouse there is a location where the resulting bourbon tastes better than bourbon from anywhere else. Clever bourbon makers want to understand why. Measuring the temperature profile of the liquid over daily, weekly, monthly §This is not true for bulging middle-aged engineers. Photo 5: A Beautiful Sight. The barrels are stored in a manner that allows air circulation. Warehouses don’t have floors in the typical sense. They have catwalks between stacks of barrels that are both cross ventilated and stack (airflow from low to high) ventilated. and yearly cycles of the sweet-spot barrel helps manufacturers create more sweet spots and build warehouses with bigger sweet spots. How do you know if it is the sweet-spot barrel? Each barrel is tasted and an expert bourbon taster says what is what. The goal is to have an entire warehouse of sweet spots. It should come as no surprise that the construction of the warehouse in which barrels are stored has a huge impact on II This sounds like a consensus to me because most of it is made this way. Apparently I do not understand the concept of consensus. I think I have been going to ASHRAE meetings for too long. I have been intrigued by small craft bourbon makers who are experimenting with barrel size and aging time. I think size matters. Smaller seems better to me, but most folks aren’t impressed. Maybe I am starting the conversation incorrectly. September 2008 ASHRAE Journal 83

ASHRAE Journal- September 2008

Table of Contents for the Digital Edition of ASHRAE Journal- September 2008