Overview


 


I began building my solar heated barn (workshop/garage) in 2012. Much of what I knew at the time was based on a book entitled "Solar Water Heating" by Bob Ramlow. I also used “Modern Hydronic Heating” by John Siegenthaler and a number of other reference books and papers. I calculated that it would be practical to heat my shop with solar energy using an array of eight flat-panel collectors that would heat a liquid solar solution. The solution is circulated through a sand mass under the floor of the shop. This is covered in Ramlow’s book and is referred to as a High Mass System. I heat the sand mass every day that the sun shines and it simply radiates up through the floor to heat the shop. The system has been working for several years now and I think I should share some of the things I learned as I was building it.

I began by designing the workshop/garage in 2011. I didn’t know at the time that it would be a barn, that is, it would have a gambrel roof. That was dictated by the required pitch of the roof. Per Ramlow, for solar heating you will want a “winter” angle on the roof. That is, the panels need to be perpendicular to the angle of the sun during the winter months. At our latitude in Colorado the ideal angle is 55 degrees. The best match for that angle is the lower part of a gambrel roof. It turns out that the roof design I came up with has a 60-degree angle but that works very well to catch the winter sun and reduces the panel’s efficiency during the summer. The workshop/garage is now referred to as “The Barn”.

I did several calculations on the heat loss of the barn and determined that for the size of the structure I wasn’t going to be able to put enough panels on the roof to heat the whole building. The desired size was 44’ by 32’ but only 18’ by 32’ was going to be a workshop. The rest of the main floor was garage and that didn’t need to be as warm as the workshop needed to be. This made the calculations work. The 18’ by 32’ workshop could be kept to a 60 degree or higher temperature most of the time. I would need eight 4’ by 10’ panels to heat 200 tons of sand mass under the floor to heat the building. Most of the heat would be under the area of the workshop.  The garage would have fewer radiant heat loops. The upstairs was a bonus area created by the gambrel roof. I didn’t plan on heating it at all thinking that the heat from the main floor would rise and it would be reasonably warm. Because I needed to insulate the workshop area quite well, I didn’t have that much heat rising to the attic as anticipated, but it still stays well above freezing most of the time.

Barn Design

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