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Super Insulated Home

Homes that are designed to minimize heating need run into a particular "sustainable" heating problem: 

Once you've taken pains to eliminate thermal bridges and mazimize insulation, paid top dollar for thiple-paned windows and designed the home to maximize solar gain, you're left with such a small heat need that many will tell you that an electric heat pump is about your only option to keep warm, because it can run well on "low".   Many people who love the idea of superinsulating their homes also love the idea of sustainable, natural heating fuel and the security of locally sourced cord wood.

     We solve both problems and provide an opportunity for an architectural grade element to be integrated into the home.

    Heaters in Superinsulated Homes

         

          Because we can build small and light (relative to Russian or Finnish masonry heaters) we can avoid the "too much heat" problem that happens with woodstoves and brick heaters that take too much to heat up.  Because we are large and heavy (compared to that super-tiny wood stove that will maybe overheat the space) we buffer the heat produced by the fire.  In essence we take less wood than would overheat your space if burned in a woodstove and spread the effect of the super-clean fire over 18 hours or so.  We'll take you through the night and into tomorrow's solar gain.

         MASONRY HEATERS and RADIANT FLOORS.

        Let's think of a 1,000 square foot room.  If you want to maintain around 72 degrees in that room, the radiating surface needs to be warmer than the room or heat won't flow into the room.  Outupt of any radiant surface depends on surface area and temperature.  Most radiant floors operate at a minimum of 80 degrees.  80 degrees x 1,000 square feet = what I'll call 80,000 Magic Heat Outputs (MHOs)

         In a super insulated 1,000 square foot home, even 80,000 MHOs will raise the temperature too high, and because it's thermal mass based and 4" of concrete is a typical thickness for a radiant floor, you're stuck with this output for a long time, so the system will shut down and the house will cool off until the floor is well-below active temperature, at which point the boiler will go "click" and the floor will becgin to charge again, and the house will slowly transition from too cold for the last six hours to too warm for the next six hours.

         Let's compare that equation with a Masonry Heater for that same space.  Our theoretical heater is a 24"diameter cylinder about 6' high, which gives it a surface area of around 36 square feet.  Let's put a fire in that stove and get the surface up to 130 degrees.

           At 130 degreees our 36 square feet puts out, say, 8,000 Magic Heat Outputs, and let's say the wall thickness is balanced to give that output for 12 hours.  Assuming 80% combustion efficiency that means we're burning 10,000 MHOs of wood in our firebox all at once.  That happens to be about 9"x 12" worth of sticks laid upright.  Stack it, light it, and when it's done, shut the damper.  It's easy, and you get convenience and that sense of security that wood burning brings, without the Freight-Train effect of the thick radiant floor and the enjoyment of a real wood fire! 

    MASONRY HEATERS beat WOOD STOVES

       Where the Radiant Floor fails be being too massive, the woodstove fails by being to... un-massive.   Light a fire and you boil yourself out in a short time, because wood burns cleanly only at high temps, and a woodstove built for an 8,000 MHO need doesn't actually exist.  If you made one it would have a very small firebox that would hard to lay, light, and tend.  

    CONCLUSION:

          Masonry Heaters with appropriate wall thicknesses, fireboxes, and surface areas solve both these problems at once.   The first by shrinking surface area, and the second by buffering the heat from a reasonable size fire (that is, a fire that is convenient to lay and light). 

         Rather than an impossibly small fire impossibly well tended for a 8 hours you have an easy, right-sized fire that burns for 30-45 minutes and charges the right-sized mass for 8-12 hours of output.  The space is kept warm without overheating whether power's on or not, and most importantly, the experience of burning real wood is provided.   

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