Here's a snapshot of a completed design model for a client in Oregon. The objective was to design a system to heat a 3000 sq ft straw bale home using exclusively wood heat, and to direct a portion of that energy into a hydronic heated slab at the first floor level. The completed design includes a masonry heater on the second floor with heated benches, wood storage box, and bake oven and also a wood fired masonry boiler on the first floor. The poured concrete foundation walls for the masonry heater are used as the housing for a masonry wood fired boiler. The boiler resides at basement level, which also happens to be where the bedrooms for the home are. On the right side of the boiler a 3" SS heat exchanger connects to pipe which will carry the heated water into a mechanical room where the energy will be transferred into the hydronic tubes and then circulated into the slab. The masonry heater will have an estimated output of 450,000 BTU daily. The wood fired masonry boiler will output 630,000 BTU daily. These output values are assuming two sixty pound burns daily through each system, or a total of about 240 lbs cordwood daily to heat the 3000 sq ft home at 15 degrees F. On normal heating days in Oregon the masonry heater and boiler will both be fired once.
The homeowner will build the stacked structure himself, and so the design project required detailed course by course layouts for both the boiler and masonry heater. Also included was a master materials list and suppliers for masonry, refractories, hardware, etc. The custom heat exchanger will be made locally at a fabrication shop. The model was completed in Sketch Up, which allows the homeowner to view the design in detail he has downloaded the program to his computer. Any details, sections, or plan views can be isolated from the model and printed for job site use. Or one can just put the laptop on the mortar board and take a look, which is what I typically do....so far so good...
