Heat Shield: Retain that wasted energy

As an engineer by trade, I find that I have a natural tendency to improve upon things to make them more efficient, cheaper, and faster. If you’ve seen Dilbert’s “the Knack” clip, you get the idea. Brewing, with its numerous processes and large number of variables, will likely provide me with years and years of tinkering.

I’m currently in a phase of my brewing hobby where I want to upgrade to a single, standalone unit for my all-grain brewing. In my online research of single-tier brewing systems, I started reading about burner height in reference to the bottom of the kettle. Recent studies have suggested that controlling the burner exhaust to vent out the back of the setup results in preventing your valves and sight glass from overheating and promotes better combustion. even sells single-tier stands and heat shields based around this principle determined from their own experimentations.
Before spending too much money on building an entire single-tier setup, I decided to make my own single-burner stand that allowed directed venting of the exhaust gases from the burner. Needless to say, it worked! My sight glass and valve stayed cooler and all the exhaust gases vented out the back. However, after feeling the large amount of heat I was venting, it bothered me. I paid for that heat, and it’s just blowing away, not providing me any value. As any good engineer, I thought to myself, “I can fix this!”, which resulted in the heat shield described here.

Typical homebrewing setups involve putting all the heat in the bottom of the kettle only. The rest of the kettle dissipates heat. As an example, I brew in keggles that are 15.5 in. diameter x ~23.5 in. tall (40 cm x 60 cm). For easy figuring, let’s just assume those dimensions are in contact with the wort. Normal homebrewing, with heat only applied to the bottom, results in ~189 in.2 (0.12 m2) of the keggle absorbing heat. The total surface area of the keggle (not including the top) is ~1,333 in.2 (0.86 m2) meaning, as homebrewers, we’re heating 189/1333 or ~14% of the kettle. The rest of the kettle is dissipating heat, which is working against us when trying to put heat into the kettle for boiling. Pro brewers typically use jacketed kettles so they’re heating on all sides, or at least more than just the bottom. This improves overall efficiency. Adding a heat shield to a homebrew setup that captures the hot exhaust gases and channels them up along the side of the kettle results in those exhaust gases continuing to heat the kettle. Or at a minimum, reduce my heat loss from the sides of the kettle.

I typically brew batches of 10+ gallons (76+ L) utilizing 90-minute or more boils. Between heating my sparge water and boiling, I usually use close to an entire 20-lb. propane tank. The addition of the heat shield appears to have reduced that to approximately around 1⁄3 of a tank!

I designed the heat shield shown to maintain a gap of about ¾ in. (1.9 cm) all around the kettle sides, go 3 in. (7.6 cm) below the kettle bottom to ensure collection of exhaust gases, and only cover an arc around the kettle that doesn’t include my valve and sight glass (to keep those components cool). So let’s get into it.

Tools and Materials

  • 18-gauge sheet metal (Thinner is fine)
  • Homemade sheet metal brake
  • Tin snips or angle grinder with cutting wheel
  • ¾-in. sheet metal screws
  • Drill