Ben’s Solar Garage
(NOTE: I’m writing this page WHILE building my garage. Some parts may change from future to present to past tense as I work on the project. Look for updates as this project progresses.)
For many years, I’ve wanted a new garage.
Our house is pretty nice. It’s not huge, but was remodeled before we purchased it, so it’s pretty modern in terms of good windows and insulation. However, the two-car detached garage had never been touched since it was originally built. And it wasn’t built well to start with.
When we moved in, the garage concrete had many cracks in it. I could see daylight right through the siding. There was no sheathing on the walls, just siding over studs. Of course, there was zero insulation and electrical was only a single 15 amp circuit. Besides that, the eves were rotting out, and occasionally pieces of wood would simply fall off.
My house has no basement, and is limited on storage space. One bedroom doesn’t even have a closet. So, since I needed to rebuild the garage anyways, I wanted to build it LARGER so that I would have some workshop and storage space.
1) Larger space, for storage and worksop
3) An Upstairs Level
4) Solar Power
The main thing is to have a larger space for working on projects, fixing cars, and general storage and workshop. Of course, in my area, it’s just plain COLD all winter. I want insulation and heat in my garage. Since the new garage will be built from scratch, that also meant that I could reorient the roofline. The old garage roof ridge ran north and south, which makes the faces of the roof east and west. That’s not ideal for solar access. The new garage will have a steeper roof, facing due south. Not only is that ideal for solar, but a steeper roof also means that I can have an upstairs that’s tall enough for me to walk in. Besides being used as storage space, it opens up the possibility of use as a home-office, clubhouse, secret headquarters, etc.
Of course, there’s also a number of limitations on the new garage, including but not limited to:
1) Total size
3) Tax keys
4) Foundation vs Water Table
My property is very narrow and on a corner. Part of the reason that it’s so narrow is that way back when, a local road was turned into a State Road, and right of way simply ate away at the property. Also, for whatever reason, my front yard and back yard were on separate tax keys. I just got two tax bills every year, but the one for the back yard was cheap, so that was fine. The County put a whole pile of requirements on me to get a zoning permit. I had to combine tax keys, get a new deed to my property, and jump through a number of legal hoops. This took about a year and a half and over $2,000, just to get the zoning permit. I was also restricted in building height and the upstairs was not allowed to have any form or permanent staircase.
In terms of physical restrictions, my property has a very strange water table and flow of water underground. That’s part of what caused the concrete of the original garage to break so badly. New concrete would have to be engineered to account for this. The new foundation would have to be much more like house foundations in my area, with a deep footing, several layers of concrete block, and reinforcing material in the concrete. That adds up to plenty of work and expense.
Speaking of expense, the total estimate of the garage cost, is significantly higher than just a plain garage. We changed our mortgage, getting a new one which paid off the remainder of the old mortgage, giving us both a lower interest rate as well as cash out to pay for the garage construction costs.
First of all, there are PLENTY of different ways to create a building – SIP, Strawbales, Advanced Framing, Steel, etc. etc. While there are advantages and disadvantages to each, it looked like “traditional” construction was the way to go on this project. My Dad and brother both have plenty of experience in typical residential remodeling construction. Wood framing is easy to do at a human scale. Wood and fiberglass are conveniently available at the local lumber yard and big box home improvement stores. For the actual construction of the garage, we chose typical wood framing with an engineered truss roof and metal roofing. Insulation will be typical household style of my area, which is fiberglass, with some exterior foam under the siding. Metal roofing has an extremely long life-time, is fireproof, and is 100% recyclable. Standing seam metal roofing also allows the use of special clamps to attach to the roof WITHOUT penetrating the roofing materials. That’s perfect for installing solar panels with no chance for leaks!
One of the biggest single goals of the garage is to provide solar electric power for the house. The south-facing roof is the right size for up to 5,000 watts of solar photovoltaic panels. The plan is to use grid-tie micro-inverters. Each solar panel gets it’s own inverter which then routes power to the garage, the house, and the local power grid. Unlike with a “series string inverter” if one solar panel is shaded, all other solar panels continue to produce power. Because it’s all AC power, this simplifies the system, eliminates a DC disconnect, and makes it easier to wire up myself. Our power bills right now average about 600 kWh per month, including all electricity for the house AND charging an electric car. According to my math and the average number of hours of good daylight in my area, 5,000 watts of solar should produce just about that much power per month. This should give us close to a NET ZERO AVERAGE ANNUAL electric use!
The heat for the garage will be ELECTRIC. I know, I know…. “Electric isn’t an efficient way to heat!” – What people really mean is that it’s not as CHEAP as natural gas and some other fossil fuels. By using electric for heat, I won’t have to install a natural gas pipe to run from my house to the garage (which would be somewhat expensive/complicated.) Besides that, I’m trying to get AWAY from fossil fuels.
The electric heat source will be a micro-boiler. This will connect to the Pex that was cast into the concrete floor. With the PV solar panels, I’ll be able to MAKE my own electricity. In addition, I can also get on a “Time of Day” program with my electric utility, in which I would pay HALF price for electricity at night. I can set the heat on a timer to run when rates are cheap. The thermal mass of the concrete should maintain a steady temperature regardless of when I’m heating it. (In some real world experience, a concrete slab at my parent’s property takes about 3 days to fully heat and then radiate heat continuously.)
For more information on this heating system, please read the installation manual for the heater.
Why not a Heat Pump? Of course, heat pumps are another option for electric heat. In fact, they are probably one of the BEST forms of electric heating currently available. However, after weighing the pros and cons, I decided against a heat pump. The main advantage is that a heat pump uses less electricity. In essence, a heat pump moves existing heat around and concentrates it, rather than creating heat from a resistive electrical element. The trouble with heat pumps is that they only work well down to a certain temperature. They’re great for moderate climates, but in Wisconsin we have true winters, with sustained below freezing temperatures all winter. The best heat pumps are geo-thermal. They circulate coolant through tubes in the ground to collect heat and move it to your heated space. The drilling of the wells takes a fair amount of yard space and considerable money. (Neither of which I have.)
“Mini-Split” air-to-air heat pumps are also great devices, but are less efficient than geothermal, and have issues with diminishing efficiency and icing as the temperature drops.
In my area, you NEED a backup heat source if you have a heat pump system. Because heat pumps are not common in my area, that also means there are few experienced and qualified installers.
Why not Solar Heat?
Another comment I’ve been getting a lot is that I should install flat-plate or vacuum solar collectors. These circulate antifreeze to collect heat from the sun, and then pump it to where you want it, usually for water heating, but it would also work great for a hydronic heated floor! That’s actually a GREAT idea, but it has two caveats. For one, you need the space for the solar collectors, and that space has to have good solar access – in the winter – when the sun is the lowest and the shadows are the longest. I would need quite a few of those solar panels to get enough heat for the garage. In the summer, those panels would do nothing for me, as I don’t need the heat! It would be a considerable investment in panels that would only work part of the year, and when I need the heat the most (winter, at night) that’s when the solar resource is least available. Secondly, those panels would only produce HEAT. The PV solar panels can produce heat, light, motion, whatever electricity can do for you. That’s useful power year-round!
The garage was laid out with the main section of roof pointed DUE SOUTH. This is ideal for solar collection. The overhead garage doors are also on the south side. Theoretically, on the rare sunny winter day, the low angle sunlight would shine right in through an open garage door. While the radiant heat would feel nice, I wouldn’t want all my warm air leaving through the open garage door. If that door was GLAZED-IN, I could get the benefit of solar gain AND keeping my warm air inside. There’s a great example of this over at Build it Solar. I would likely glaze in the one door, but not the other. That would let me park a car on one side using the automatic garage door opener and still have solar collection and work space on the other side. My Mitsubishi iMiev is so maneuverable that I could likely pull through one door, and yet park in the next space over.
Hybrid Heat – Wood?
Is there some other way that I could get heat into my garage which I could COMBINE with hydronic in-floor heat? Sure. How about wood-fired heat!? I already checked with my insurance company, and they will NOT insure a garage with a woodburning stove in it. (The logic is that there is gasoline, etc., stored in a garage.) They DO already insure my house with a wood-burning stove in my living room, and they also will cover outdoor wood boilers. I was excited when I stumbled on an old wood boiler on Craigslist. It’s pretty plain, but not too big, and can be used indoors or out. I could install this in my back yard and run the plumbing in to the garage. Whenever I’d be working in the garage, I could fire up, feed, and stoke the boiler. I DON’T like the idea of an outdoor boiler because imperfect insulation means that heat just gets lost to atmosphere. I’d also rather not be trudging through the back yard through the cold, wet snow, and/or mud. It would also be possible to replace my existing living room wood stove with the boiler. The down-sides to that are: the boiler is not as nice looking as my stove, it’s slightly larger, and I would have to run send and return insulated plumbing lines from the house to the garage.
So, that’s the garage in a nut-shell. Things will evolve a bit as the garage is built. What follows are links to my build blog as I build the garage.
Here’s a link to a video playlist of YouTube videos about the garage.
Demolishing the old garage: 2 Guys. 1 Day. No more garage.
Removing a tree to make way for the garage:
No internet, more chainsaws, and a concrete footer.
Garage update, Nov. 9 2016
Installing the PEX tubing. Tubing to go in the concrete to provide IN-FLOOR heat.
Beginning Building the Hydronic Heat System (1/25/2017)
Service Door, Solar Cable
Fiberglass Batt Insulation, March 14, 2017