I started my build of my MLT that has been in my head for 2 weeks. My project will utilize a 15 gallon poly food grade water container obtained from a local container supplier for $30. The insulation materials are all on hand as I am an insulation guy. My design goals were 1) to have a higher capacity than a 10 gallon bev cooler, 2) incorporate some building science knowledge to maximize thermal performance and 3) Have a container that I could batch sparge or fly sparge with with good grain bed depth even with smaller gravities. After cutting off the top, I was left with a capacity around 58 quarts. Anything bigger than that, goes in my old MLT as a 5 gallon batch.
I created 1 inch furring strips of rigid XPS blueboard as a depth guide for a 1 inch layer of 2 part spray foam from a 200 board foot kit. The bottom is lined with 1 inch rigid XPS also.
This will be my first layer to stop conduction through the sides of the MLT. My second layer (to be updated later) will be a radiant barrier(reflectix) enclosing a completely air sealed 1/2 air gap.(which is essential for a radiant barrier to work). This will reflect radiant heat transmitted from the heated foam layer back to the MLT and provide an additional 1-2 r-value to the overall conductive thermal barrier.
The final layer will be a to-be-designed sheet metal shell and cover. It will protect the insulation on the bottom and have side handles to assist in lifting.
PICS - (click on any for full size slideshow)
15 Gallon Poly water container
Cut off the top. Started with rotozip and quickly switched to sawzall with a fine wood blade. Found that the container went out of round after being cut, so I will have to consider that when designing a top - can't just drop the cut top back on.
Using a piece of 1 inch XPS to cut a bottom out 1 inch wider than container
Here is my bottom cut out and attached to bottom along with the 1 inch furring strips I will use as spray foam depth guide.
Almost ready for foam - furring strips installed
Foam is on, with excess cut off with hack saw.
Here is my first furring strip that will be for the radiant barrier. I will have to fill in these gaps. I plan to use duct sealant (mastic or "pookie") for the final air sealing and to seal the reflectix to the MLT. It is much more workable than caulk. I used 1/2in blue board for the reflectix air barrier furring strips, backed it with duct tape and cut it every 1 inch in order to make a round furring strip. This will be more conducive to maintaining the radiant barrier air gap than vertical furring strips.