Electrical

Tiny Tuesday: The Nomad

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My dear friend MK lives in a house she built on a 24-foot-by-8-foot trailer. The Nomad (as she named it) is parked in her hosts’ sloping backyard in the Finger Lakes region of New York; legally, it’s an accessory dwelling. It’s not a house on wheels at the moment, because she jacked and leveled the house and removed the wheels.

MK previously served as an intern at Yestermorrow Design-Build School, and the courses she took there gave her the expertise to design the house herself. She drew plans with Sketchup. She cut material costs and overall weight using advance framing: rafters align with studs and floor joists to eliminate plates, and strategic placement of windows and doors allows for light header beams. She hired local talent to build a custom trailer (with floor joists in the right places), and she leveraged a building class to contribute labor.

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MK’s Sketchup plans for the Nomad.

I love the house’s wedge shape, using a shed roof with a shallow 1.5-on-12 pitch to create headroom without complicated roof lines. As you enter through double doors near the low end, an eat-in kitchen stretches out to your left, with open cabinets, a 3-burner stove, and a huge chest freezer (which MK intends to convert to a fridge). To your right is the bathroom and the mechanical area, including an array of batteries for a future PV installation. The far end contains a steep stairway to a landing that serves as a dressing room, then turns to a loft, which is entirely filled by a queen-size mattress. The stairs and the loft floor frame a living room with built-in shelving and a loveseat tucked into the far wall.

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Eat-in kitchen, stairs/dressing area, and living room with loft above.

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Handsome finishes on the living room’s built-in shelving.

Right now the house is pretty much off the grid. There is no running water or electricity, although the hookups are all there. (MK uses a composting toilet and showers at the gym.) Insulation is tight with no thermal bridges, and MK expects her marine wood-burning stove and her heat recovery ventilator will be more than sufficient to keep the place comfortable as she prepares to spend her first winter there. In the meantime, the Nomad helps her save money for her dream of one day running a farm and rustic B&B.

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MK says it was a challenge to level the house on a wooded, sloping site.

Tiny Tuesday: What’s Your Solar Potential?

/ Scott / 1 Comment

If you wish to reduce your carbon footprint through solar power, you’ll want to know just how much solar energy you can get. These maps from the National Renewable Energy Laboratory (NREL) provide a great starting point.

You’ll notice two types of maps: photovoltaic (PV) and concentrating solar power (CSP). These are two different ways of generating electricity from the sun. PV panels use semiconductor materials to convert solar energy directly into electricity, and can be installed on a roof or in any open space. CSP uses an array of reflectors to focus a large area of sunlight onto a small central receiver, which then powers a heat engine (usually a steam turbine) to generate electricity. Because a CSP installation requires many acres of clear land, nearly all home and private installations are PV.

Photovoltaic (PV) installation on a roof.
Concentrating Solar Power (CSP) array.

The PV map is color-coded, showing average kilowatt-hours per square meter of panel per day. Two major factors dictate a location’s solar potential: latitude and weather. The desert southwest (southern and sunny) has the nation’s greatest solar potential, peaking above 6.5 kWh/m2/day. This region is followed by the southeast (southern and cloudy), and then a band between the midwest and the interior northwest (northern and sunny). Next comes the northeast (northern and cloudy), and finally the Pacific northwest and Alaska (northern-er and cloudier), where a PV installation averages less than 4 kWh/m2/day.

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For larger maps, link to NREL at the top of this article.

NREL compiled these maps with data assuming a stationary PV panel oriented due south at an angle equal to the location’s latitude. Such an installation would point directly toward the sun twice a year, on the equinoxes at solar noon. Sun-tracking panels, which move to face the sun for all daylight hours, can increase the solar potential. (But sun-tracking panels are more expensive and take up more space.) More importantly, PV technology has improved since the maps were created in 2008-2012, so the values are conservative for a new installation today.

This Saturday, June 18, is Celebrate Solar Day in Vermont, with events statewide. Click here to find an event near you!

Can Do

/ Scott / 1 Comment

My parents asked me to replace three recessed lights, aka cans. Typically, a hole in the ceiling is a puncture in the home’s thermal shell, allowing air and heat to escape. With older recessed light fixtures there’s no way to close this hole. The new cans are shielded on top, enabling a homeowner to air-seal and insulate over them without creating a fire hazard.

I started by removing the bulbs and the trim kits – the parts you see from below. I also switched off the electrical circuits, of course. Then it was up to the attic where I would pull out the fixtures using a headlamp for light. To avoid crashing through the drywall ceiling I had to stand on adjacent joists and kneel over the existing fiberglass insulation. I cat’s-pawed out the four electrical staples holding the fixtures in place, then ripped the metal spikes from the joists.

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The old can, surrounded (but not covered) by attic insulation. Access is tricky.

Limited access made it tricky to install the new cans. They came with a metal spike and a nail at each of the four corners. I positioned a can, jammed each spike between the joist and the ceiling drywall, and pounded in each nail, all the while kneeling atop the joists and keeping the headlamp trained on my work. Two of the three existing ceiling holes were tight against a joist, which forced me to take apart the sliding mechanism in order to mount the cans directly above the holes.

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Old can removed; new can awaiting installation.

Electricals were pretty straightforward. The old cans used wire nuts and the new cans used clip-in connections, so I didn’t even need a wire tool. It was simply a matter of re-threading the feed cable and matching like wires – black to black, white to white, ground to ground.

On the other hand, installing the new trim kits was a real bear. They’re poorly designed with an awkward spring-loaded connection to the fixtures and the vaguest instructions I’ve ever read. It took me half an hour to realize I could adjust the depth of the socket inside the fixture by removing one screw completely (no instruction mentioned this) and tightening another to make room for the trim kit. As the most visible part of the installation, the trim needs to look right, and I wish it screwed into the fixture or otherwise attached in a more foolproof way.

Oh well. The lights work. And now the house is better insulated. De nada, Mom and Dad.

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New can installed with a new trim kit.