Mary in PA
From research I did, and informal input from other people who know a lot more than me, I wanted to try to operate the shop with a low reliance on mechanical heating during the winter. I ran this by John, who will after all be the main user of the building, and he was game to try it. Brave fellow. I have to admit, this is a keen area of interest for me so I appreciate John’s willingness to give it a try… and to accept a target indoor winter temp of 55 degrees F. Certainly most would find that too chilly for a house, but for a shop we think it will be just fine. And if 55 to 60 degrees is achievable with no ongoing energy bills and no astronomical upfront investments (which is pretty much a given with our budget)… then all the better.
Here’s the basic idea: Use the Earth’s deep soil temp (about 55-58 degrees in our area) to temper the building interior during winter. Use available solar energy to add heat during the day. Limit heat loss during the night.
Here are some of the things we did (or are doing, or planning to do) to try to make this work. Keep in mind, this is likely a multi-year project to get everything done.
-Orient building with long side to solar south. Plan south-side wall space for installation of thermosyphons we’ll design and build. To gain some working knowledge in this area, this past winter I designed a rough prototype thermosyphon and John helped me build it. We installed it in our current house in a door to the south-side deck. It was temporary for the winter, but a great learning experience and quite the conversation piece. ;-) The BuildItSolar website is a great resource for this stuff.
-Place windows on the south wall so that winter sun can fall on ‘always open’ slab just inside the overhead door (on the east wall).
-Insulate the foundation wall and slab perimeter with 2” rigid foam, also known as XPS. This will (hopefully) isolate the slab and the soil under it from cold outside temps seeping through the foundation wall and under the slab.
-Insulate the typically exposed slab edges at the man doors and especially at the 12x12 overhead door. This is very important, and I’m still working out the details on this, but feel pretty confident we’ll be able to do it. Apparently a LOT of heat flow occurs through the edges of the slab.
-Insulate the walls and ceiling of the shop – better than is typically done in these types of buildings, but still keeping our budget in mind. Install heavy-duty thermal covers for the windows and possibly for the 12x12 overhead door. I’m thinking these are items we get raw materials for, design and possibly use a local tarp company to sew up for us. This should reduce nighttime heat losses.
So, that’s the general (albeit some might call squirrelly) idea – in a nutshell.
|Building prototype thermosyphon. Yes... in kitchen of current house. Too much snow to work outside. Now that's flex-space, eh?||
|Thermosiphon installed in doorway on south deck. Open (existing) door only during times of good sunshine.||
|Interior view: Room air drawn into collector at bottom, heated by sun, rises & passively vents into room at top. Not pretty, but simple. :-)|
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|Posted by Joe in Hermiston, OR on 8/18/2010|
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John & Mary,
I don't know what kind of headroom you plan to have in the shop, but I would plan on having some kind of ceiling fan to bring the heat back down to people level. I saw an ad for Bigassfans.com in Fine Homebuilding. If you had the room, it might be worth the investment. Just a thought.
|Posted by Mary in PA on 8/21/2010|
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Joe, thanks for the input! A fan is a great idea and you would think with 14' we would have plenty of room. ;-) But John's eventual plan for the shop is to have a bridge crane which will only allow a few inches of clearance between the ceiling and the top of the crane. He is therefore planning everything (overhead doors, lights, etc.) with the crane in mind.