Net Zero?

Lily Pond House Solar Plant

It has been exactly a year since we moved to our Lily Pond House. So how did our passive and active solar design perform? How close did we get to our net zero goal where annual energy consumption is roughly equal to renewable energy generation?

Starting with the passive solar design with South facing wall of glass, every sunny day was a joy during winter. On those sunny days with freezing temperatures, we often had to open windows as the temperature reached about 78 degrees after the living room cement slab could no longer absorb the sun’s heat. If the cement slab was not covered with furniture and rugs, we could have stored more solar energy but life trumps energy efficiency. Radiant heating did not have to kick in about 3+ hours after sunset while the cement slab warmed the house releasing the stored heat.

One of the best decisions our HVAC contractor Jim Godbout Plumbing & Heating made at the suggestion of our solar contractor Revision Energy was to go with an all electric energy for the house. Daikin Altherma, air to water heat pump that provides low temperature hot water for radiant heating and radiators, proved to be an efficient workhouse. We didn’t have a single day laboring to heat the house thanks to Theodore and Theodore Architects high performance shell design with minimal thermal bridging. Having radiant heating in the living room and basement cement slab, and bathroom tiles also  helped the cause with heat retention.

For active solar, Revision Energy designed a ballasted system that does not require the installation to penetrate the roof, which is a plus. However, solar panels are then limited to 15 degree pitch because beyond that the wind load gets too high and the required ballast gets too heavy for roof support. Although the optimal angle for solar panels is about 40 degrees for our location, the total annual production is fairly insensitive to installation angle since we can bank excess production for 12 months by feeding the excess solar electricity  into the grid. This is because the lower installation angle is optimized for the summer months when the sun’s radiant energy is at its highest. The penalty for 15 degrees tilt is less than 8%. Low pitch installations also hold snow longer than steeper ones;however, the penalty for snow cover is about less than a 10% effect in southern Maine.

Revision Energy estimated our expected electricity consumption at 11 MWh per year:

Plug Loads: Design estimate was 450 kWh a month, or 5,400 kWh per year. Although it was on the low side for a 2,500 sq. ft. house, it was justified by all LED lighting and  energy efficient appliances.

Heat: Design estimate was 15,000 BTU/sq. ft. for the expected annual heat load. That translates into 38 MBTU/year for space heating, given the 2.5 Coefficient of Performance (COP) for Daikin Altherma heat pump  yields an expected electricity consumption of an additional 4,450 kWh per year.

Domestic Hot Water: Design estimate was 40 Gallons per Day (GPD) load with two occupants at 20 GPD each. That translates to an annual load of 10 MBTU/year. Given the 3.25 Energy Factor  performance of our Voltex Hybrid Electric Heat Pump  water heater, that translates to an additional electric load of 1,200 kWh per year.

11 MWh solar plant design called for 36 255 -Watt Canadian Solar photovoltaic panels. Unfortunately, our two roofs could only accommodate 27 panels. So we had to go with the more efficient 300 Watt LG NeON panels resulting in a 10 MWh per year power generation.

Best Month – May

Worst Month – January

Since roughly half of our total electric load is space heating, our electric consumption in winter is effectively supplied by our solar production in summer. Our best month was May with 50 kWh electricity production on sunny days while our worst month was January with 20 kWh electricity production on sunny days except when the panels were covered with snow, which was about 10 days. Since photovoltaic panels can capture scattered sunlight to create electricity, they generated electricity even on cloudy days.

Solar Electricity Production by Month

Revision Energy’s initial design employed Solectria PVI inverters, which convert the DC output of a photovoltaic (PV) solar panel into AC that can be fed into the electrical grid or used by house electrical network.  As the solar  crew was laying out the roof and moving panels around to accommodate the parapet, and roof obstacles (e.g. vent pipes), they felt there might be enough partial shading on this system so it would really benefit from a slightly more advanced inverter solution. At their suggestion, we went with a Solaredge system that combines a central string inverter in the basement with individual panel optimizers on the back of each individual panel to improve system performance, especially when part of the array is shaded. In contrast to a traditional inverter system where the partial shading of a panel typically results in the total loss of power from that panel in order to optimize the power of all panels in the same string, Solaredge recovers the partial power from the shaded panel. In addition, Solaredge provides module level monitoring and performance information, which is a pretty neat bonus.

Upper Roof Panels Performance

Solar system was designed to be a net generator in summer and net consumer in winter.  As the data shows, Lily Pond House Power Plant is a net generator roughly 5 months (May, June, July, August, September), a net consumer 5 months (November, December, January, February, March), and roughly balanced  in the transition months (April, October).

Generated vs. Consumed Electricity

So what is the bottom line? We consumed 11.5 MWh while the consumption estimate was 11MWh. So if we could generate 11 MWh per our original design, we would have a net zero home. We took a 10% hit due to roof constraints, and another 10% hit because 10 MWh solar design produced only 9 MWh, mostly due to parapet shading. At the end, we generated 9 MWh of solar electricity while we consumed 11.5MWh. For the 2.5 MWh shortfall, we paid $300, which we really can’t complain about given the environmental wellness, which encourages us to live in harmony with the Earth by taking action to protect it:

 

 

Let there be lights

Thanks to Energy Star, Unites States is making its slow migration from the incandescent light bulb to LED lighting with an intermediate stop at CFL. Incandescent light bulb produces light with a wire filament heated with an electric current. In 1,880, the filament in Thomas Edison’s  incandescent light bulb lasted 1,200 hours while 95% of the energy went to producing heat instead of visible light. After 135 years, it still does the same wasteful thing. In contrast,  Compact Fluorescent Lighting (CFL) lasts 8,000 hours and produces the same amount of visible light with 25% of the energy expended by an incandescent light albeit with the necessity of mercury recycling. Light Emitting Diodes (LED) lighting lasts a whopping 50,000 hours and produces the same amount of visible light with only 10% of the energy expended by an incandescent light. As with every energy saving choice, the up front cost of an LED light is higher although the operating cost of an LED light is 10% of an incandescent light. The savings is not trivial as according U.S. Energy Information Administration lighting consumes 14% of the electricity in a typical American home.

Residential Electricity Usage

The Energy Independence and Security Act of 2007 (EISA) set energy efficiency standards for light bulbs. Under the new law, household light bulbs will use at least 27% less energy by 2014 for a similar lumen output. The standards are technology neutral, which means any type of bulb can be sold as long as it meets the efficiency requirements. In fact, a number of manufacturers met the law by replacing the filament in the Edison light bulb with a halogen element. Given the performance we are going after in the Lily Pond House, we set out to eliminate not only the incandescent and CFL light fixtures but also the Thomas Edison era screw sockets by ensuring only LED lights can be used throughout the house.

Lily Pond House lighting was designed by Wiebke Theodore with a valuable assist on lighting fixtures by Greg Day Lighting. In selecting fixtures, especially for recessed lights, Insulation Contact (IC) rated new construction housings are attached to the ceiling supports before the ceiling surface is installed. IC housings must be installed wherever insulation will be in direct contact with the housing. The housing needs to be Air Tight (AT), which means it will not allow air to escape into the ceiling, thus reducing both heating and cooling costs. Unless you take care, some of these IC units are huge, taking valuable insulation space. For the recessed lights, we considered WAC and twicebright, and chose twicebright because the WAC option with its 0.9 cu ft volume took more than 10 times the volume of the twicebright option that took only 0.08 cu ft:

WAC 0.9 cu. ft.

twicebright 0.08 cu. ft.

As with most green products, the origin of the space saving twicebright offering is from outside of USA. This company brings Scandinavian lighting innovations to the North American market. When you get rid of the Edison era screw base, you get the bi-pin base invented by Reginald Fessenden for the 1893 World’s Fair in Chicago.  The International Electrotechnical Commission (IEC) periodically updates the bi-pin standards. GU10 10 mm twist-lock bi-pin for the MR16 light bulb in twicebright fixture has been around since mid-2000s. As a historical note Westinghouse won the contract to wire the first electrified fair with Tesla’s Alternating Current (AC) against Thomas Edison’s Direct Current (DC), and invented the bi-pin base because Edison’s General Electric company refused to allow his patented screw-base bulbs to be used.

120 volts of AC line voltage needs to be transformed into 12V or 24V DC for LED lighting. There are two kinds of transformers for this purpose: Large and heavy Magnetic Low Voltage (MLV) transformers, and small and light Electronic Low Voltage (ELV) transformers that are typically enclosed in the lighting fixture rather than hidden somewhere by the electrician. Magnetic transformers generate a low frequency hum while electronic transformers are virtually silent. It is ironic that more and more of the electronic equipment and lighting in our homes (e.g. laptops, phones, LED lights, etc.) run on DC power while the electricity is distributed by AC, necessitating the distribution of dozens of AC/DC transformers around the house. As a case in point, our design called for dado StepLine LED lighting that fits into the thickness of drywall. However, its installation requires running wires to a remote transformer, a hassle after the plaster is done. So we ended up going with WAC LED200 that is an integrated design that fits into a standard junction box.

WAC LEDme Step Light

dado StepLine LED

For Lilly Pond House, we have about 3 dozen twicebright recessed lights (used mostly on interior ceilings so as not to interfere with the house envelope) each with its dedicated electronic transformer. What is the carbon footprint of that? Wouldn’t be better if we had a DC distribution system? It is coming. The data centers with banks of computers have been using this solution for some time. EMerge Alliance – open industry association is developing a 24V standard for DC power distribution in commercial buildings. There is a big push in boating industry for distributed DC electric distribution system that will also save weight by replacing the mechanical fuse boxes with solid state ones. So the future of residential wiring will most likely be two independent wiring systems – a low voltage (24V DC) system for electronic equipment, lighting, and DC powered small appliances and a high voltage (120V AC) system for major appliances but until then we have to deal with the transition headaches.

 

Mechanical Wizardry

Based on the nicest looking mechanical rooms in the portfolio of homes we visited, our Design Development conversation, and  our architect’s and builder’s recommendations, we went with Jim Godbout for our mechanical subcontractor. As a preference, we wanted radiant heating in order to avoid forced hot air with its space wasting duct work, noisy operation, dry air generation, and dust ball production that we grew to hate over the years. Current green builder consensus is to use ductless mini-splits to reduce the cost of radiant heating installation. Mini-splits eliminate the noise of conventional forced hot air systems by locating the noisy compressor and condenser outside the house, and do away with the  bulky ductwork by pumping refrigerant directly to wall mounted blowers – albeit ugly – inside the house. However, they still produce an uneven heat distribution as you don’t have to be a heat transfer specialist to see that radiant heating which makes the whole floor the heat source will produce a more even heat distribution than a mini-split with a point heat source. At the end of the day, we just couldn’t accept a forced hot air solution with mini splits after observing that every house with radiant heating we visited seemed more comfortable. Plus subfloor heating has been around for centuries from the hypocausts in Turkish baths to hot water pipes under floors in Frank Lloyd Wright’s buildings in 1930’s.

For Lily Pond House, Jim Godbout designed a radiant floor heating system everywhere except panel radiators in the bedrooms. In contrast to forced hot air, which is a convective system that uses air to distribute the heat, radiant heating system uses mostly energy waves to distribute heat from warmer (i.e. floor) to cooler (i.e. people) objects, is more efficient, and provides a more uniform temperature distribution with less dry air issues. For the living room, entrance, and basement, Crete-Heat foam insulation panels (3″ R-15) were installed in the cement slab to secure the Viega PEX radiant tubing in place. For first and second floor common areas and baths, radiant tubing were applied below sub floor with Low-E Tab insulation under radiant system. For the bedrooms, we went with high efficiency low temperature Biasi steel panel radiators.

Viega PEX radiant tubing over Crete-Heat insulation

Radiant heating needs low temperature water (85º-95º for radiant tubing, 105º-120º for radiator panels), and saves energy by having to heat to the lower temperature. Design Development called for propane fired Viessmann Vitodens condensing boiler (one of the highest efficiency (98%) boilers with excellent reliability) for delivering the low temperature water to the radiant PEX tubing and Viessmann Vitocell for domestic hot water. Before the Construction Documents got finalized, we decided to install solar panels on the second roof in order to complement the passive solar design towards a net-zero home. Our solar energy subcontractor Revision Energy came up 8.1 kilowatt-hours (kWh) photovoltaic array with 27 LG Mono X NeON  300 watt solar panels. Maine has a progressive solar energy policy with “net energy,” which is the difference between the energy used and the energy generated over a month. If Lily Pond House panels generate electricity in excess of our monthly usage, the unused kWh credits go into a “bank”. Our utility CMP invoices based on net energy for the month, taking into account any accumulated kilowatt-hour credits from the previous 12 months, which is better than the net billing in Massachusetts where the utility purchases the excess electricity at the wholesale price. Our solar panels are expected to generate roughly 10,000 kWh of clean electricity annually, and offset roughly 9,000 lbs. of CO2 emissions annually. Currently, our electric utility charges $0.15/kWh. Assuming that electricity costs stay constant over the next 25 years as we are also ignoring the cost of capital, we will recover our solar energy capital investment in the first half of the life span. In other words, we will have free electricity for the second half and beyond after the first half. Another way to think about this is that we are locking the price of electricity at $0.08 for the next 25 years, which translates to $18K of savings if we had purchased the same electricity from our utility at the current price. Currently, Maine does not provide the State incentives that, for instance, Massachusetts provides, which substantially reduces the period for recovery of capital.

Radiant heat transfer aluminum plates for PEX sub floor installation

In The Third Wave, futurologist Alvin Toffler coined the term “prosumer” when he predicted in 1980 that the role of producers and consumers would merge in the future.  Given our decision to become a prosumer of electrical energy that we’ll be able to generate abundantly in the summer and bank it for winter use, our mechanical subcontractor changed the heating design to Daikin Altherma – an air to water heat pump with backup electric coil. Altherma air-to-water heat pump uses a sustainable energy source – heat from the outside air. The heat extracted by the Altherma outdoor unit is transferred via refrigerated lines to the indoor Altherma heat exchanger, which uses the intake to heat and distribute the water to the radiant heating tubes in the floors, and low temperature radiators. Altherma delivers about 4 kWh of usable heat for every 1 kWh of electricity it uses, giving it a high coefficient of performance (COP) of 4. For the domestic hot water, the design changed to Voltex Hybrid Electric Heat Pump from A. O. Smith. Voltex reduces water heating cost by 2/3 by extracting the heat from the ambient air. In our application, the water heater is placed in the unconditioned basement so as not to rob off the heat from the conditioned space. In addition to the heat pump, this model also has heating elements that help the water heater recover quickly during periods of high demand.

In older New England homes, it is not uncommon that Air Changes per Hour (ACH) can record between 12 to 30. Maine Uniform Building and Energy Code is currently based on the 2009 International Residential Code (IRC), which calls for 7 ACH. The Department of 2012 Energy Air Leakage Guide  ratchets up the target to 3 ACH for our climate zone, which is yet to be adopted in Maine. Our architect specified 0.6 ACH – the Passive House standard as the target, which dictates fresh air ventilation. The ventilation design called for Venmar Energy Recovery Ventilator (ERV).  Using the energy consumed by a compact fluorescent bulb, ERV provides cost effective fresh air ventilation while recovering the heat exhausted out of the house. In the winter, the heat and humidity of the outdoor fresh air is transferred to the intake air stream, thus not drying out the inside air during the heating system. In the summer, the heat and humidity of the outdoor fresh air is transferred to the exhaust air stream, to keep the inside air humidity low. We shall see.

Topping out

Topping out Lily Pond House

Topping out is a builders’ rite traditionally held when the last joist is placed on the roof during construction. On our team, Wiebke Theodore makes sure that we celebrate these time honored traditions, and made sure that our framing crew Mike & Co. nailed a live tree branch to celebrate the occasion. In high performance home construction, it is distressing to see that US lags Europe, Australia, New Zealand, Japan, and Korea from high efficiency heat pumps to solar panels, and from Energy Recovery Ventilation (ERV) systems to radiant heating. So it was refreshing to witness US green building progress beyond the traditional dimensional lumber based framing. In our Lily Pond House, the engineered subfloor panel AdvanTech manufactured by the Maine company Huber proved its resistance to wet soaking during a Northeaster that lasted for about a week. AdvanTech subfloors consist of highly compressed wood chips with resins that prevent swelling during long-term exposure to the elements. It does work but I do think there has to be a better practical way to be invented to prevent new construction from such exposure. Based on Steven Theodore’s specifications, Spang Builders used Boise-Cascade VERSA-LAM laminated veneer beams and headers that eliminate twisting, shrinking and splitting, and deliver flatter, quieter floors along with BCI Joists that are wooden I-beams with flanges made from laminated veneer lumber sandwiching engineered sheathing. I-joists enable simpler floor/roof layouts while saving half of the wood fiber used in dimensional lumber. I can’t argue with Boise-Cascade’s I-joist marketing collateral: “Clean appearance pleases the structure’s owner which makes the builder look good:-)”

I-Joist

I-Joist close-up

I-Joist floor

AdvanTech flooring by Huber

Laminated engineered wood posts

Engineered laminated wood beam

In a high performance home, the house envelope’s insulation, its resistance to air leakage, and moisture control within the envelope are of paramount importance. If you want to want to get up to speed with high performance envelopes, Building Science Corporation’s list of high R-value wall assemblies is a good place to start. For Lily Pond House, our architect specified R-25 3.75″ closed cell foam to all exterior wood-framed walls with an interior 3/4″ R-5 foil faced polyiso rigid foam board that gave an effective R-30 insulation for the walls. For the roofs, we ended up with R-42 6.25″ thick closed cell foam to all rooflines above finished living space with 5.5″ R-23 Roxul stone wool batts that gave an effective R-65 roof insulation. For the underside of living space at unconditioned area, the we went with R-42 6.25″ thick closed cell foam. Finally, our insulation subcontractor applied sealant to vertical and horizontal seams between dimensional lumber of double top plate, bottom plate, multiple studs, around window headers, and wall corners to get ready for the blower test. Spang Builders foreman Chad Richardson made sure that all of the areas missed got sealed right by the insulation subcontractor, which shows the builder’s value in enforcing quality assurance. We also used Roxul mineral wool sound attenuation batts in all partitions and ceiling assemblies within the living space. It was interesting to see the impact of the insulation during installation. Closed cell spray foam improved the rigidity of the frame and attenuated outside noise while Roxul quieted inside the house quite a bit. Besides its strength, and high R-6 per inch insulation value, closed-cell foam provides a barrier against air or water vapor. In contrast to building materials that slap on the green label on marketing collateral, closed cell polyurethane foam is the choice of green building construction as full life-cycle analyses show that this insulation provides a substantial reduction in carbon footprint. We selected Roxul made from stone and recycled slag from steel manufacturing over fiberglass for the interior because of its fire retardant, water repellant, and sound proofing properties. The fascinating Discovery Channel video explains how Roxul is made.

Closed cell spray foam insulation

Roxul insulation for interior

Polyiso insulation board

While the insulation keeps the house warm or cool, in windy weather the envelope needs a breathable membrane to keep the wind and moisture out. In our house, the membrane is SIGA Majvest that forms a part of the vented rainscreen system along with the exterior tongue and groove siding with a strapping in between to provide the spacing to form the drainage plane. We enthuistically support our architects’ preference for local sourcing of construction materials so the original specs for the siding was Eastern white cedar. Unfortunately, we found out that the the Eastern white cedar in our original estimate was  knotty making it not desirable as we were not going for a rustic look. The clear grade Eastern white cedar proved to be too expensive. So we ended up going with Port Orford cedar from Oregon, which ended up costing 3 times as much as the original siding estimate. Oh well such is the fun of building a custom home. Port Orford cedar is used in building boats, and docks because of its resistance to the elements. We were happy to find out that Port Orford cedar plays a spiritual role in the lives of the Hupa indigenous people of Northwestern California as ornaments used in spiritual ceremonies and dances are made of the cedar wood. Finally, the windows and doors are one of the most important components of a high performance envelope, which we will cover in our next post.

 

Marvin vs. Duratherm vs. Loewen vs. Intus

In their predictions for US high performance buildings in 2014, Hammer & Hand, recipient of the 2014 Green Home of the Year Award from Green Builder magazine, states that US window manufacturers have pushed performance as far as they can with existing “American” profiles, so more will move to a European sash and frame design, with better glass, better hardware, thicker frames to accommodate thicker insulated glazing units and better thermal breaks. So were we able to source a high performance window from North America, or did we have to source it from Europe? For our bake-off, Steven Theodore selected high four performance custom window manufacturers – Marvin and Duratherm from US, Loewen from Canada, and Intus from Europe. We included Duratherm as it is a Maine company that makes contemporary windows with the sleekest contemporary lines using a wide variety of woods from mahogany to teak. We couldn’t consider other European windows like Optiwin  because they didn’t have a dealer in Maine. The table below compares the performance metrics from the four vendors for the Lily Pond House. All of the windows have triple pane glazing, and the performance metrics are shown only for the South elevation sliding doors that will be used passive solar heating of our thermal mass cement slab. The actual comparison is pretty complicated as each elevation (South, West, East, North) and configuration (e.g. door vs. window) have different specs from the same vendor.

South facing sliding doors performance comparison

The National Fenestration Rating Council (NFRC) is a nonprofit organization that sets the standards for measuring the performance of windows and doors in US. The metrics include U-Factor, Solar Heat Gain Coefficient (SHGC), Visible Transmittance (VT), Air Leakage (AL), and Condensation Resistance (CR). For reporting, AL and CR are optional for manufacturers. Comparing the vendor quotes is instructive for assessing each vendor’s approach to performance. Both Loewen and Intus provided the whole window ( including glazing, frame and spacers) U, SHGC and VT values for each  window and door. Duratherm provided two sets of numbers – the center of glass U value and SHGC for the South facing and other windows while Marvin did not include any performance specs in their quote although Marvin does provide an interactive calculator on their Web site. The U-factor indicates the heat loss through the window assembly. The lower the U-factor, the greater a window’s resistance to heat flow and the better its insulating properties. The reciprocal of the U-factor gives the R value of the window assembly. Referring to the table, in thermal performance, Loewen has an R-4 value whereas the Intus provides an impressive R-10. SHGC  is the fraction of solar energy transmitted through a window, which was about 60% for Duratherm, 50% for Marvin and Intus, and 40% for Loewen. VT is an optical property that indicates the fraction of visible light transmitted through the window. For this metric, the range was a low of 45% for Loewen to a high of 70% for Intus. The higher the VT, the more the window maximizes daylight. AL measures the infiltration through cracks in the window assembly, and is defined as the cubic feet of air passing through a square foot of window area. The lower the AL, the tighter the window assembly. CR measures the window’s resistance  to condensation on the inside glazing under humid conditions. The higher the CR, the better the window resists condensation.

The price in the table is normalized by the lowest cost Intus windows and shows the increase was 23% for Loewen, 55% for Marvin, and 300% for Duratherm, with some of the difference attributable to the exterior/interior clad used in the frame. Intus does offer wood and aluminum cladding as well at higher price points. Unlike PVC, unplasticized polyvinyl chloride (U-PVC) is rigid and recyclable. U-PVC windows are the most popular windows in Europe. It  was clear  that the Intus windows had the best performance specifications, which we ended up going with.

From Lithuania to Maine

Shrink wrap on a crate

South facing sliding doors

South facing windows

Our builder ordered the windows and doors through the Portland based Intus dealer – Performance Building Supply. We visited the store twice to look at the in store installations. The dealer could not arrange a site visit to see the windows/doors in the field. In ordering Intus windows, we thought we were making an early adopter decision, and our experience validated that. Intus order says that the delivery time for windows  is approximately 12-14 weeks but ours arrived a month later than expected. To top it off, the windows got delivered in a shrink wrap on a crate. Unfortunately, one of the panes in our largest window was cracked during transit. On the up side, our builder’s assessment after installation is that the quality of the windows and doors is top notch. We think they look great with their sleek contemporary frames. Plus they remind us of our time in Europe where every window opened inside. We’ll report on the performance and level of service by our dealer after the blower test.

Passive solar

Passive solar house design is not new. During 9th through 13th century, American Indians built their homes in south facing Pueblo canyon hills that provided them heat from the low winter sun, and cool from high summer sun with natural overhangs. It is a shame that these centuries old best practices are ignored today in new residential construction. Passive solar is different than Passive House – a standard developed in Germany for European climate and adapted to American climate by Passive House Institute US (PHIUS). In our house tours, we got to see one Passive House design, and a number of passive solar designs. Passive House design with super thick walls and small windows looked like a bunker to us – not our cup of tea. In contrast to a Passive House that needs to limit the intake of winter sun because of over heating due to super insulation, passive solar welcomes the winter sun’s warmth, stores it for night time use, treats our winter blues with sunlight, and lets us enjoy the scenery outside.

If you are interested in passive solar home design, “The Solar House: Passive Heating and Cooling” by Daniel Chiras is a must read. After researching passive solar design in Building Science, Green Building Advisor, Mother Nature Network, Zero Energy House, I dived into The Solar House by Chiras. Passive solar has a pretty straightforward set of high level rules. You need large south facing windows (north facing in the southern hemisphere)  with high Solar Heat Gain Coefficient (SHGC), a thermal mass to store the sun’s heat, and overhangs to block summer sun on the south facing glazing while letting winter sun in. Of course, you still need a professional to design the system as there are several intricate nuances (e.g. different SHGC ratings of south, east, west and north facing windows, backup heat system sizing, air quality in a super tight house shell, etc.) in passive solar design but that shouldn’t prevent you learning more about it to become a more knowledgeable homeowner, and better yet an evangelist.

The US Federal government in its infinite wisdom gives tax credit to energy efficient windows with U-factor 0.30 or lower, which is fine, and SHGC 0.30 or lower, which is not fine. U-factor is the reciprocal of the area weighted sum of R-values for the various window components (e.g. glazing, frame, etc.). So the smaller the U-factor, the better the window keeps the inside hot, or cold air in. SHGC represents the fraction of the solar energy that the window passes through to heat the house. So a window with an SHGC of 0.30 based on Federal guidelines block 70% of the sun’s energy that can be used to heat the house. That may be a great design objective for hot climates like Florida but for cold climates like Maine, windows with SHGC 0.55 or higher is the desired target. Given the one size fits all standard in US, you need to shop for Canadian, or European windows if you want passive solar. More on that at a later post.

Perimeter slab insulation

Stego wrap vapor barrier

XPS slab insulation, Crete-Heat insulated floor panel, Uponor radiant heat tubing

In passive solar design, if the south-facing glass is less than 7% of the floor area, then thermal mass is not needed as building mass in framing, drywall, etc. is sufficient to absorb the solar gain but you won’t be getting passive solar heating after sunset. South facing wall of glass in our Schematic Design dictates thermal mass. In our home, cement slab in the front living area, and secondarily the basement slab serves as thermal mass. As a rule of thumb, for every sq ft of south facing glass area over that 7 percent of total sq ft of the house, you need about 5½ sq ft of 4-inch-thick slab.  Overhangs are designed to block out the solar noon on summer solstice (June 21 when the sun is the highest in the sky), and let the solar noon completely in on winter solstice (Dec. 21 when the sun is the lowest in the sky). Our architect specified 4 ft. south facing sunscreens in Design Development. There are on line calculators like the Overhang Design tool by Sustainable Design to design the overhangs with the final size often dictated by compromise. Here is the expected shading performance of our sunscreen design. We’ll get full use of sun’s warmth October through March, and transition in to full shade in April, and out of shade in October.

Expected south facing sunscreen shading performance

Spang Builders filled the interior of the foundation below the slab level with gravel, and mechanically compacted. Before pouring the cement for the slab to be used as thermal mass, a vapor barrier is placed at the bottom. Our slab subcontractor used Stego Wrap vapor barrier, and foundation rebar and wire mesh to give strength to the cement. The slab bottom and perimeter is insulated with XPS insulation. Our mechanical design also called for radiant heating so that had be in place before the concrete. Our mechanical designer used Crete-Heat floor panel system with its own insulation and vapor barrier, and Uponor radiant heating. For additional reading, I recommend Designing a Passive Solar Slab that explains the diminishing returns of a slab depth more than 4 inches. More on our mechanical system in a later post.

You don’t have to have an ugly cement slab to go with passive solar. Flatwork craftsman can make a concrete slab look like marble. These folks use a power trowel (sort of like a floating orbital sander with multiple steel trowels rotating at the bottom) to apply a smooth finish to concrete slabs. This process is called burnishing, which produces a shiny, smooth and abrasive resistant hard surface. Burnishing brings a marbleized non-uniform metallic-look to the floor. Our architect/builder team chose S. Richer of Sanford to perform this feat. The results speak for themselves. Our team used a poly backed fabric blanket cover to ensure wet curing over a 28 day period. The blanket ensures that the slab remains wet for the entire curing period.

Slab before burnishing

Power trowel

Slab after burnishing

greenGoat Deconstruction

There are two schools of thought for when to bring the builder into an architect designed residential construction project. The traditional way is to invite several selected builders to bid after the completion of Construction Documents. This approach ensures cost certainty for the project. At the recommendation of our architects, we went with an alternative approach and  invited selected builders to bid on the Schematic Design. This approach only generates a cost range but promotes an architect/builder team to develop a better quality product with greater efficiency by soliciting the builder’s experiential knowledge into the design process. Steven selected four highly recommended Southern Maine builders to bid on our project. After reviewing the bids, we visited builder portfolio homes to get a feel for fit and finish, and spoke with their references. It was hard to discern based on the build quality of the builder portfolio, or on their references as they were all excellent. Based on the enthusiasm for the project, cost range and proximity to our home, we decided to go with Spang Builders, who as it turns out, built our dock on Lily Pond over 25 years ago.

Once we decided to let our cottage go, we wanted to make sure that maximal amount of the materials got recycled for another useful life. In particular, we wanted the pine paneling, and maple floors to be recycled in addition to finding good homes for the old appliances. We first invited Habitat ReStore, which is a retail outlet that sells donated used building materials, appliances and furniture at reduced prices using the profits to support Habitat for Humanity home building projects. Since Habitat depends on volunteers, it was clear they could only recycle the appliances and paneling. We then invited Amy Bauman of greenGoat, which saves residential building materials typically destined for land fills and finds new projects that need those materials. I have been on the Board of greenGoat for the last 10 years, and consider Amy to be the most environmentally conscious person among my friends. Even her annual Board reports are printed on the back of architectural blueprints meticulously cut to letter paper size!

Ted removing floor

Master bedroom floor

Recycled flooring

Balsam Wool insulation

Living room

Open floor concept

Amy didn’t disappoint. She made an arrangement with Ted Whitesmith, who teaches English in Boston during the winter, to deconstruct our Maine cottage taking advantage of his summer vacation. As it turns out, Ted was building a cottage in Northern Maine. So he was able to repurpose any material not sold for his own cottage. We gave the keys to Ted after July 4h, and greenGoat was able to deconstruct by the end of July not only the maple floor boards and tongue and groove paneling but also interior floor joists, doors, windows, walls, ceilings, insulation, exterior walls, deck, shingles, slate patio and steps, and other items too many to list. Ted worked tirelessly to deconstruct as much of the cottage as possible while losing over 20 pounds during the process. Who knew we could have had an open floor plan with Cathedral ceilings in our old cottage:-) We only kept the granite fireplace mantle from the cottage thanks to an assist by Spang Builders. One of the most satisfying moment came when Amy shared the photo below showing our deck reborn in Northern Maine. The next step was the actual demolishing, which was a lot harder to take than we anticipated.

Cottage deck reborn

Schematic Design

South Elevation features large glass area for passive solar design

Architects use a four stage process consisting of Schematic Design, Design Development, Construction Documents and Project Management. Schematic Design involves the development of visual conceptual design. Design Development refines the Schematic Design by specifying mechanical, electrical, plumbing, structural, and architectural details and materials. Construction Documents stage involves with the input of a structural engineer the generation of written and graphic instructions for the builder to build the house. Project Administration pages ensures that the architect’s design is interpreted by the builder as intended.

Theodores initially presented us two different schematic designs – one that involved moving our original square footprint towards East for a rectangular footprint with living room, dining room, kitchen, master bedroom in a row on the first floor, and the second one that shrunk the original footprint with living and, dining room in the front, and kitchen, and master bedroom in the back. While both designs had appealing features, we went with the second design because of its stronger connection to our old cottage footprint.

West Elevation – South and West elevation window overhangs let winter sun in and keep summer sun out

 

We loved several aspects of the design. The split-level design with two floors in the front, and three floors in the back with a basement fits perfectly into the topography of the ledge the house is built upon. In addition, the new design gives up the South West corner of the original footprint, connecting the outside living areas in front of the South and West elevations. While we had a barely usable basement before, Steven managed to include a study room, bathroom, and a utility room in the new basement by slightly raising the master bedroom. Three boxes with clean exteriors and flat roofs contribute to a stunning contemporary look. Expansive use of large sliding doors, corner windows and transoms  connects the inside and outdoor living areas. While the corner windows makes the corners disappear, transom windows act as natural landscape paintings that change with seasons. The interior open floor plan with suspended stairs visually connects the living areas. The design’s multi-level approach makes it a more livable place. For instance, the entry is a couple of steps lower than the main living area while the master bedroom, bathroom, and first floor hallway is a couple of steps are higher than the main living area, thus dividing the stairs into more easily climbable chunks.

East Elevation entrance integration with garage

One of our requirements for our Lily Pond House design was passive solar. Using passive solar design, the energy of the sun can provide a significant portion of a home’s heating needs even in Maine as Bill and Debbi Lord’s pioneering Maine Solar House has shown for the last 15 years.  One of the fortunate aspects of our location is that the southern exposure coincides with our ocean view as passive solar needs southern exposure for access to the sun between 9am to 3pm during the heating season. The new design’s South Elevation features large glass area for passive solar design. The floor of the living and dining area in the front is a concrete slab for thermal storage. South and West elevation window overhangs let winter sun in and keep summer sun out. North and East facing glass is minimized. During Design Development, some features of the schematic design got simplified but overall the design stayed intact. Onto Design Development.

 

 

Steven in situ with model

North Elevation has minimal glass for passive solar design

Selecting an Architect

Our cottage on Lily Pond has been our summer home for over 25 years. Margaret and I always wanted to build a contemporary house on this location blessed with spectacular views in a private setting. We also wanted our new home to be green – respecting its environment sort of off the grid without going overboard towards a German passive house.

Initially, we researched prebuilt contemporary high performance homes. Santa Monica based LivingHomes sets the state of the art on the West coast while Blu Homes does the same on the East coast. While these companies offer several customizable plans, it became clear to us that our home on a ledge from the ice age within the constraints of the shore land zoning made the prebuilt option not feasible.

LivingHomes RK2 Model

So we really needed an architect that can take advantage of the site’s southern exposure for passive solar but also can fit into the ledge dictated constraints while expanding allowed by the zoning laws. We knew that we would have no trouble finding green architects and builders after all Maine attracts environmentally conscious people. However, we were a bit apprehensive our unorthodox contemporary taste did not fit into the traditional Maine architecture.

We were pleasantly surprised that Maine is blessed with some outstanding  contemporary architects with green design portfolios that include Elliott + Elliott Architecture of Blue Hill, Theodore + Theodore Architects of Bath, Carol Wilson Architect of Falmouth, Van Dam Architecture and Design of Portland, Kaplan Thompson Architects of Portland, Briburn Studio of Portland, and Caleb Johnson Architects and Builders of Biddeford.

If you want to get a feel for the green contemporary architecture in Maine, check out the book Houses of Maine by Elliott + Elliott Architecture, Maine Modern: 50 Years of Contemporary Architecture in Maine exhibition, Green Architects’ Lounge edutainment podcast by Chris Briley of Briburn and Phil Kaplan of Kaplan Thompson.

Lily Pond House

Lily Pond

We started our architect selection process in the summer of 2013. We interviewed a number of the contemporary architects to understand their contemporary design philosophy, exterior and interior level of design services, experience with high performance building design, and coastal zoning, and their approach to collaboration with the builder. After visiting portfolio samples, and having them visit our home to get their initial impressions, we decided to go with Steven and Wiebke Theodore as Steven’s and  Wiebke’s taste, and their philosophy of design meshed with ours, and we felt at ease with their personality and collaborative style. It is just that once you see a home in an architect’s portfolio (Ledge House, Island House ) that you can imagine living in, you are less worried what the new design will look like. So the journey starts.

 

Going for Contemporary

This blog chronicles our journey in building a contemporary energy efficient home in Maine. We have been spending our summers in our cottage for the last 27 years. In 2014, my wife Margaret and I decided to take the plunge by selling our Massachusetts home, and settling in Maine to experience life as it should be for the whole year.

Over the years, while our tastes varied with the styles of the times, our preference for the modern minimalist design stayed constant. We still adore our Scandinavian furniture that we bought right after getting married, and fondly remember our stays in Copenhagen, Rome, Prague shopping for contemporary home furnishings, and living with the modern design in Istanbul.

Scandinavian Design dining room furniture – circa 1979

Deck View of our Conantum Home

We lived 20 years in this Carl Koch and Donald Gillespie designed contemporary in Conantum – a neighborhood of Concord, MA with about 100 contemporary homes nestled next to Sudbury River and Walden Pond. Conantum was the idea of MIT economics professor, Rupert McLaurin, who envisioned affordable cost housing for young couples. Carl Koch, an architect and also a MIT professor, planned the houses. Joseph Kelley, a local contractor, was the builder. Carl Koch spent some time after graduation in Sweden where  blended  clean Scandinavian design into his work . Our Conantum home is an example of Koch’s mid-century architecture design with multi levels and walls of glass that invite the outdoors in. For an excellent overview of Conantum homes, see Bill Janovitz’ tour of Conantum.

Conantum houses were designed when energy was too cheap to matter. Our house tripled its original size with architect Donald Gillespie before we bought it. We spent our 20 years upgrading the heating system into a distributed one, insulating just about the whole house, installing energy efficient doors and windows house while remodeling without destroying the character of the house. No matter what we did, it never could reach the ACH (Air Changes per Hour) specification of a Pretty Good House. So we wanted a high performance contemporary design for our next house. So in the summer of 2013, our journey started with looking for an architect who could turn our needs and wants into a buildable vision.