Mash Tun Insulation

As many of you know, its is very important to keep the mash at a steady temperature. Insulating the mash tun and keeping a lid on it is the easiest way to do this. Since the lid was complete, it was time to look into getting some sort of insulation around the vessel.

Construction material

My old mash tun used to be covered by a piece of fiberglass insulation used to cover water heaters. While this idea was cheap and effective, it does have certain drawbacks. One problem was the few times I direct fired my old mash tun (it used to be an insulated modified keg), the insulation would sometimes catch on fire. The other point is that I find it esthetically unpleasing to put fiberglass around a stainless mash that I build from scratch.


The material I choose to use as insulation was redwood. Wood has a fairly high insulation factor, though not as high as fiberglass insulation. It also resist heat to some degree and redwood in particular also resist water damage. Redwood slats can be replace if a portion gets damaged and it also looks very nice once you put on a coat of varnish.

I decided to use 1x4" kiln dried heart redwood. This particular wood is already dry from all moisture, making it a long lasting and light weight wood. All the pieces easily match because they are made from the "heart" of the wood.



I cut all the slats and varnished them with Man of War Marine Spar varnish. This stuff is a great wood preservative and gives the it a deep red hue.

In order to fasten the redwood slats, I built a lip at the top of my mash tun which added rigidity to the structure and allow the slats to be place underneath it. To hold the pieces on the bottom, I made another lip that I fastened with screws. This lip is 1 1/8" by 7/8" L shaped and not only keeps the pieces in place but will hopefully protect the wood to some small degree from heat rising from the propane element. If any of the pieces becomes damaged, replacing the slat can be done easily by unscrewing the bottom lip and replacing the slat.


The Mash Tun vessel Sparge Manifold Recirculation Manifold Mash Lid Insulation HOME