Mountain Solar: Page 3 of 4

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The home and its PV array.
The 2,148-square-foot floor plan includes three bedrooms and two bathrooms on the main level. The home’s semidetached garage can be accessed via a workshop space off the laundry and mudroom.
The Palmers relax on their deck.
In the coal-heavy state of West Virginia, solar shines at Rita Hennessy and Sean Palmer’s new custom-built home in Shepherdstown.
Windows in the dining area.
Large windows on the home’s south face provide ample daylighting to interior spaces. They also admit solar gain in the winter, reducing the home’s need for supplemental heating.
Clerestory windows let hot air escape.
Clerestory windows, which are opened and closed by remote control, aid in cooling the house by venting any accumulated hot air.
Thick, insulated walls and double-pane windows slow heat transfer, keeping the house cool in the summer and warm in the winter. The 4-inch-thick concrete floor acts as a thermal battery, storing and releasing passive solar heat gain.
Masonry heater has an oven.
Rita pulls a pizza from the Empire masonry heater, which serves as a backup source for space heating.
Minisplit heat pump, interior component.
Sean checks out the minisplit multizone heat pump, which provides auxiliary cooling during the hottest part of summer.
The outside heat pump component.
Sean and Rita’s dog guards the air-source heat pump’s outdoor unit.
Charging the electric car.
In addition to powering their home, Rita and Sean’s PV system also provides the power for an electric car-charging station. Here, Sean plugs in a friend’s EV.
Rita in her energy-efficient kitchen.
Rita stands in the kitchen, which features a Thermador steam oven and other Energy Star appliances.
The home and its PV array.
The Palmers relax on their deck.
Windows in the dining area.
Clerestory windows let hot air escape.
Masonry heater has an oven.
Minisplit heat pump, interior component.
The outside heat pump component.
Charging the electric car.
Rita in her energy-efficient kitchen.

Auxiliary Cooling & Heating

Given West Virginia’s hot and humid summers, keeping the house cool was a priority. While the operable windows provide some passive cooling, a 22-inch-diameter whole-house fan mounted in the attic boosts ventilation, helping move air throughout the house. Most effective whenever outdoor temperatures drop below indoor temperatures, the AirScape fan draws fresh, cooler air into the living space through open windows, the warmer air exiting through the roof vents. The fan can move 725 to 2,590 cfm, drawing 21 to 210 watts— far less power than a central air-conditioning system. At about $1,300, it is also significantly less expensive.

While the couple says that the fan works well for cooling, the window-opening strategy moves enough air so they rarely need it. However, in late July and August, when the humidity peaks and night temperatures remain in the 80s, they use a minisplit heat pump to keep the indoor temperatures cool and comfortable.

In the winter, they typically keep the house at about 69°F with one firing per day in their masonry heater. When outside temperatures drop below zero, they burn two or three fires. Popular in the wood-sparse tundra of Scandinavia and Russia, this massive heater works by directing the heated gases from a small, hot fire through baffled chambers, where nearly all the heat is absorbed by the masonry. Usually, one or two fires will provide enough heating for a 24-hour period. Because the fires burn at very high temperatures, very little ash or smoke is produced. The couple purchased a kit from Empire Masonry Heaters, and hired a mason to assemble the core. A subcontractor hired by the builder finished the exterior with river stones collected from the property. The Phoenix kit, roughly $4,800, included the core, doors, cleanouts, damper, and a pizza/bread oven.

For backup cooling and heating, they consulted with building systems engineer David Butler of Arizona-based Optimal Building Systems. This service is part of Coleman’s design package. Based on information provided on the plans and specifications, as well as phone calls and correspondence with the couple, Butler developed the home’s heating, ventilation, and air-conditioning (HVAC) system specifications. “More often than not, passive solar and other high-performance homes end up with grossly oversized HVAC equipment. This not only undercuts potential energy savings, but can lead to comfort and moisture-related problems,” Butler says.

Butler used Manual J protocol (often called “heat load calculation” or “cooling load calculation”) to estimate how much heating and cooling the home might require. However, based on his experience, the Manual J “significantly overstates” heating loads, even for conventional homes, and ignores internal and solar gains. Knowing that, he says, the numbers are merely a starting point. Given the low electricity rates in the area (about 9.5 cents per kWh), Butler calculated that a ground-source heat pump would be less expensive to operate than most other HVAC options. However, with the home’s small heating and cooling loads, it would have taken the couple many years to recover the system’s high installation costs. Instead, he recommended an electric Mitsubishi Mr. Slim multizone minisplit heat pump, with two ductless wall-mounted units (for loft and living areas) and a small ceiling-mounted ducted air handler for the bedrooms—all supplied by a variable-capacity outdoor unit. The system has a SEER rating of 17.5.

Minisplit systems work like a standard air-source heat pump, with an outdoor condenser/compressor, but without the expense or space required for ducts. The systems are more efficient, with fewer conditioning losses than with a conventional furnace. However, without ducts, there was the problem of getting conditioned air to the bedrooms. With each distribution unit costing about $3,500 installed, it would have been too expensive to put individual wall units in each bedroom. Even the smallest minisplit unit, he says, would have had several times more capacity than a bedroom’s peak load need—thus leading to large temperature swings as the unit cycles.

Instead Butler recommended ducted air distribution. The 8-inch-tall Mitsubishi ducted air handler, concealed in the hallway’s dropped ceiling, preserves the thermal integrity of the primary ceiling. The duct runs down the hall, feeding the bedrooms, where ducts are routed in the attic above the primary ceilings and buried under 16 inches of blown-in fiberglass insulation.

Comments (16)

DaisyAdk's picture

Thank you Michael Welch. This price is closer to what I've found. Where did you come up with this info? I'd like to track it down further even if it does cost more.

Michael Welch's picture

It was sent to us as a correction by the manufacturer, after they saw the misprint in the article.

DaisyAdk's picture

Thanks again. Can you provide the link or contact information you have...I'm getting a website but I wonder if you have anything more direct.

Michael Welch's picture

I web searched Empire Masonry and found their web site, which has this content:
EMPIRE MASONRY CORP.
231 Norfolk Street Walpole, MA 02081
508-660-1011

DaisyAdk's picture

The Phoenix kit from Empire Masonry sounds exactly right for my place in the Adirondacks. I wonder where you were able to purchase this kit at "roughly $1300" ? This is not the price currently listed anywhere I can find it. I do have a mason to assemble the core.

Michael Welch's picture

We do not know the source of this error, but this kit costs $3,900 and an additional $900 for the bake oven, according to the manufacturer. We have corrected the online version here.

Rise2012's picture

There was a mix up in the interpretation of the state tax laws. Originally we were expecting to take full advantage of the tie in of the car charging station and the large solar array that would have credited us with $10,000, but as the laws were not finalized at that time, we only qualified for $4,000. That is where the other $6K went to. The charging station installed and inspected probably added $2K to the cost. You can find cheaper ones at your local stores then add in the electrician and permit if necessary.

DM Lewis's picture

Thanks for the quick, and thorough response. I am sure you are heart broken over the lost $6k. I was hoping the charging station credit was $6k but only cost $2k -- then everyone would add one to their project. :-)
You still ended up with a very nice place. Enjoy.

DM Lewis's picture

At the end of the article, the PV system was listed as costing $34,860, with $10,458 federal credit and $4,000 state incentive. Where was the other $6,000 credit/incentive to come up with a net of $10,458? Was this the car charging station? Unfortunately, I cannot find any incentive in Virginia. How much do you think the charging station added to the cost? Thanks.

Debra Coleman's picture

Marc and Micheal, both of your comments on the slight easterly orientation of the plan/south wall are valid in that often it can be good practice in any location that has hot summers, but it does depend upon the particulars of the micro-climate, views, topography, etc. In even warmer climates I often recommend even further orientation that 10 degrees since the south wall can be in shade much sooner on summer afternoons. With one of my favorite design tools, the effect of plan orientation can be visualized and you can enter data on the other factors that affect overhang length: http://susdesign.com/overhang_annua...
Debbie Coleman, Sun Plans (Architect of the RISE house)

Marc Fontana's picture

The architect recommended that the house be oriented 10 degrees east of south to minimize afternoon heat gain in this West Virginia climate. That sounds like good advice to me. Wouldn't this practice be a good idea anywhere in the northern hemisphere?
What kind of water heater was selected ? With surplus PV energy, an electric heat pump heater would make sense.

Rise2012's picture

Hi Marc, Yes, an electric hybrid, heat pump, GE Geospring hot water heater.

Rise2012's picture

Hi Marc,

With my limited expertise in solar home construction, I could comment about the 10 degree east of south orientation. It would depend on the amount of southern glazing %, how much thermal mass the home may have, and how tight the envelope. A passive solar home with much less glazing may want to take full advantage of direct 180 degree orientation and summer heat gain would not be so much of an issue.

In regards to the hot water heater, we have two. The primary is a GE Geospring hybrid (heat pump/conventional) and a point of use Rheem under the kitchen sink. The POU eliminates the long run from the main heater and waste of water just to get warm at the faucet or dish washer. With the excess energy that we're producing I have found that it makes sense to run the primary unit in heat pump mode during the summer and gain some dehumidification and cooling of the air then switch to conventional during the winter months. It is harder to extract heat energy from cooler air and who needs to make the air cooler inside the house in the winter.

Regards,
Sean Palmer, the "SE" of RISE.

Michael Welch's picture

The benefit of offsetting from south a few degrees would also depend upon geography (are there mountains or buildings nearby), landscape (a forest to block sunlight on one side), and microclimate (is the area foggy for part of the day).

Rise2012's picture

RISE Builder - Thomas Sandretzky, TS Construction, Shenandoah Junction, WV

Debra Coleman's picture

It's unfortunate that the article didn't talk a bit more about Tommy's role in construction, but I know space is limited. Tommy did a very good job of paying attention to detail and listening to the client. Clients often tell me that they cannot find a builder with passive solar experience in their area, and my response is that since the passive solar components are typically nothing unusual, then look for a builder willing to listen and follow good building and energy principals in general.
Debbie Coleman, Sun Plans

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