A Net-Zero-Energy House for $125 a Square Foot
General Specs and Team
Location: Seattle, WA
Living Space : 1915 sqf
Cost (USD/sq. ft.): $124/sqf
(Note: Reported cost of $124/square foot excludes the cost of the land and the value of the PV incentives. The cost per square foot after the PV rebates is $114.)
Designer: Zero Energy Home Plans (Ted L. Clifton)
Builder: TC Legend Homes (Ted W. Clifton)
SIP(SIP) Building panel usually made of oriented strand board (OSB) skins surrounding a core of expanded polystyrene (EPS) foam insulation. SIPs can be erected very quickly with a crane to create an energy-efficient, sturdy home. Manufacturer: Premier SIPs, Fife, Washington
Foundation: Slab on grade, R-20 horizontal rigid foam insulation beneath, R-10 vertical rigid foam to footing at perimeter
Walls: 6 1/2" SIPs, R-26 including siding and drywall
Roof: 10 1/4" SIPs, R-42 including roofing and drywall
Windows: Vinyltek vinyl windows glazed with Cardinal 180/i81 triple glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. with low-e coatings and argonInert (chemically stable) gas, which, because of its low thermal conductivity, is often used as gas fill between the panes of energy-efficient windows. gas fill. Glazing specs (center-of-glass, not whole window): 0.50 SHGCSolar heat gain coefficient. The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. and U-factors from 0.15 to 0.20, depending on size, configuration, and opening means
Siding: James Hardie HardiePlank fiber-cement siding
Roofing: Pabco Premier asphalt shingles
Space heating: Unico UniChiller air-to-water heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump., 3-ton, 35,400 BTUBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. /h capacity, 9.2 HSPF. Space heat distribution: hydronic PEXCross-linked polyethylene. Specialized type of polyethylene plastic that is strengthened by chemical bonds formed in addition to the usual bonds in the polymerization process. PEX is used primarily as tubing for hot- and cold-water distribution and radiant-floor heating. tubing in first-floor slab. Hydronic heating system is supplemented by electric-resistance in-floor heating mats in upstairs bathroom.
Ventilation: Balanced ventilationMechanical ventilation system in which separate, balanced fans exhaust stale indoor air and bring in fresh outdoor air in equal amounts; often includes heat recovery or heat and moisture recovery (see heat-recovery ventilator and energy-recovery ventilator). system using a Fantech 240-cfm supply fan with HEPA filter, a Fantech kitchen exhaust fan, and Panasonic WhisperGreen exhaust fans. Supply air is delivered to the bedrooms and great room; exhaust air is pulled from the bathrooms, kitchen, and laundry room.
Domestic hot water: Preheated by the air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. and brought up to temperature by electric resistance water heater
Appliances: Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. rated appliances (where applicable), LG front-loading clothes washer and dryer set, Bosch dishwasher, Frigidaire refrigerator, Viking electric range
Lighting: Solatube daylightingUse of sunlight for daytime lighting needs. Daylighting strategies include solar orientation of windows as well as the use of skylights, clerestory windows, solar tubes, reflective surfaces, and interior glazing to allow light to move through a structure., combination of LED can lights and LED and CFLCompact fluorescent lamp. Fluorescent lightbulb in which the tube is folded or twisted into a spiral to concentrate the light output. CFLs are typically three to four times as efficient as incandescent lightbulbs, and last eight to ten times as long. CFLs combine the efficiency of fluorescent light with the convenience of an Edison or screw-in base, and new types have been developed that better mimic the light quality of incandescents. Not all CFLs can be dimmed, and frequent on-off cycling can shorten their life. Concerns have been raised over the mercury content of CFLs, and though they have been deemed safe, proper recycling and disposal is encouraged. Edison-base lights
Blower-door testTest used to determine a home’s airtightness: a powerful fan is mounted in an exterior door opening and used to pressurize or depressurize the house. By measuring the force needed to maintain a certain pressure difference, a measure of the home’s airtightness can be determined. Operating the blower door also exaggerates air leakage and permits a weatherization contractor to find and seal those leakage areas. results: 0.56 achACH stands for Air Changes per Hour. This is a metric of house air tightness. ACH is often expressed as ACH50, which is the air changes per hour when the house is depressurized to -50 pascals during a blower door test. The term ACHn or NACH refers to "natural" air changes per hour, meaning the rate of air leakage without blower door pressurization or depressurization. While many in the building science community detest this term and its use (because there is no such thing as "normal" or "natural" air leakage; that changes all the time with weather and other conditions), ACHn or NACH is used by many in the residential HVAC industry for their system sizing calculations.@50 Pa
PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. system: 6.4-kW rooftop PV array (28 Solar World PV modules, each rated at 230 watts), Power One PVI-6000 Aurora String 6-kW inverterDevice for converting direct-current (DC) electricity into the alternating-current (AC) form required for most home uses; necessary if home-generated electricity is to be fed into the electric grid through net-metering arrangements.
Space heat demand: 3.3 MMBtu/yr (1723 BTU/ft2/yr)
Energy used on site (12 months): 6,064 kWh
Energy produced on site (12 months): 7,903 kWh
Net energy balance (12 months): 1,429 kWh surplus
• Low-flow plumbing fixtures
• Caroma combination sink and toilet, recycles hand-washing water
• PEX and copper piping
• All storm water handled on site via rain garden and recycled oak wine barrel cisterns
Indoor Air Quality
• No-VOC paints and finishes, hard wax coating on interior wood beams
• Stained concrete slab flooring (first floor), reclaimed wide-plank fir flooring and stair treads with water-based finish (second floor), and tile (upstairs bathroom)
• Balanced ventilation system provides fresh air to living spaces and bedrooms
• Motion-sensor exhaust fan in upstairs bathroom
Green Materials and Resource Efficiency
Regionally sourced reclaimed wide-plank fir flooring (upstairs), fir bar top made from a downed tree, SIPS manufactured 30 miles from site, recycled cast-iron tubs and kitchen sink, low-waste engineering resulted in no dumpster on site during or after construction.
The housing bubble had burst, the banks weren't lending, and we were newlyweds who had no business even thinking about building a custom home, let alone Seattle’s first net-zero house.
By Eric Thomas
We were attracted to an empty south-facing lot, one of the last undeveloped parcels in our neighborhood. Were we naïve to think we could make our dream of an affordable green home a reality?
“Mom and Dad must have paid for that one,” one of our elderly neighbors told me when I met him for the first time.
He was commenting on the new net-zero-energy home we had just moved into, apparently assuming that it had cost a small fortune to build. I told him that our house was actually much less expensive than most new houses in the city, but I could see by the way that he was skeptically eyeing the array of sleek new photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) panels on the roof that he didn’t believe me.
Perhaps my neighbor can be forgiven for doubting me. What I’ve come to discover over the last year — during which time my wife Alex and I moved into our new home and opened it up for several public tours — is that green building has an identity problem. Many people I talk to think it costs exponentially more than standard construction.
And who can blame them? The most publicized “green” homes are usually custom jobs — big, beautiful, modern, and totally inaccessible to the average homebuyer. Think affluent retirees or newly minted dot com millionaires.
When Alex and I decided to build a home, we went a different route because we had to. We knew we couldn’t afford a modernist masterpiece coming in at two or three times the average cost per square foot to build. In fact, we couldn’t even afford the average.
At the same time, we were committed to making the smartest choices our budget would allow. We knew this would be an opportunity to create a home that saved us money on energy bills for many years to come.
Net-zero versus Passivhaus
For most people, planning a house involves compromise. Lots of it. In our case, we chose to put our money into making the shell of our house tight and the R-values high. For everything else, we tried to choose efficiency and practicality over glam, with an emphasis on enduring style and simplicity. We could always upgrade the cosmetics later, but it would be extremely expensive to replace all our windows or undo a poor choice in insulation.
After some searching, I found Ted L. Clifton, whose company, Zero Energy Plans, was based on nearby Whidbey Island. My wife was out of town, but I immediately drove up to meet with him and to see some houses he had designed and built.
Driving between building sites, I asked him about the Passivhaus standard I had once read about and if his houses were different. He explained that Passivhaus seeks to minimize mechanical heating requirements. His designs, while also taking advantage of passive solar gain and high levels of insulation, seek the most cost-effective route to reach (or surpass) net-zero, even if it requires a mechanical system larger than what one would find in a certified Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates..
While I appreciate the minimalist approach the Passivhaus standard takes to mechanical systems, I found myself gravitating toward Ted’s no-holds-barred, pragmatic approach to reaching net-zero, the “standard” that was most important to me.
We decided to go with one of his designs for an open-floor plan, three-bedroom, two-story home, 1,915 square feet in size. It was to be constructed of structural insulated panels (SIPs), which were manufactured by Premier SIPs just south of Seattle out of EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest. foam and OSB plywood. We bought a set of plans for $1,275 and had Ted modify them slightly to save on construction costs and let in more light.
A process of elimination
To make our house affordable, we eliminated a few things we didn’t need. We didn’t build a garage, for instance. On our small urban lot, the only available spot for it would have been underneath the house. At the time, we didn’t own a car, and we didn’t see the need for such an expensive addition. Also, we didn’t like the idea of exhaust fumes inside our house or the look of a street-facing garage door.
Here in the damp Pacific Northwest, basements tend to be breeding grounds for mildew, which can aggravate my wife’s asthma. We chose a slab foundation instead, which allowed us to eliminate something else: flooring on the ground level. The builders simply applied an acid stain to the concrete, which resulted in a beautiful, durable floor.
Our design also omitted a heat-recovery ventilator (HRV(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. ). Although many people in the building industry have questioned us on this, we found that it was more cost-effective to add a few more watts of PV power than to install one of these ventilation units. Instead, we have a balanced ventilationMechanical ventilation system in which separate, balanced fans exhaust stale indoor air and bring in fresh outdoor air in equal amounts; often includes heat recovery or heat and moisture recovery (see heat-recovery ventilator and energy-recovery ventilator). system without any heat recovery.
The house has several exhaust fans: one in each bathroom, the laundry room, and the kitchen. The exhaust fan in the upstairs bathroom is motion-activated; it runs steadily at a low rate and ramps up when someone enters the room. When the powerful exhaust fan in the kitchen is switched on, it also activates a Fantech supply fan that sends fresh air to all three bedrooms and the living room. The supply fan includes a HEPA filter.
We keep the house at 69 degrees in the winter, and the air stays at a comfortable 55% relative humidity.
We eliminated almost all heat delivery to the upstairs rooms; the only exception is an electric resistance radiant heat system under the bathroom tile floor, which we rarely need to use. With the living room open to the upstairs, warm air that is heated by the hydronic loops embedded in the concrete slab circulates freely, keeping the loft area warm. The two enclosed upstairs bedrooms stay one or two degrees cooler than the rest of the house — a small price to pay for not having to install an upstairs radiant floor system.
Unique energy-saving features
In addition to the somewhat unusual ventilation system, the house also uses off-the-shelf equipment to achieve energy savings. Our UniChiller air-to-water heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump. was originally designed by Unico as a remote cooling unit for industrial refrigeration and cost a fraction of the cost of a comparable home HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. system by a manufacturer like Daikin.
Our hot water system has three tanks: The first tank (a standard 50-gallon water heater with its element removed) is kept at a constant 105 degrees by the heat pump; it serves as a reservoir for the radiant floor and the rest of the system. When needed, a small circulating pump sends hot water from the first tank to the second tank. The second tank acts as a heat exchangerDevice that transfers heat from one material or medium to another. An air-to-air heat exchanger, or heat-recovery ventilator, transfers heat from one airstream to another. A copper-pipe heat exchanger in a solar water-heater tank transfers heat from the heat-transfer fluid circulating through a solar collector to the potable water in the storage tank. that preheats domestic water before it enters the third tank, a standard resistance-electric hot water heater.
So, how much does this cost?
Out of necessity, we went into this project with the goal of keeping the cost of our new house about the same as the price of a townhouse in the neighborhood. The cost of the land was $180,000, and construction, PV system, taxes, and permits added another $237,000. (The 6.4-kW PV system cost $32,696 before rebates.)
After a $9,000 federal tax credit for the PV system, and an approximately $9,000 Washington solar production credit (paid out over 9 years), the grand total came to about $399,000. We were pleased because the cost to build was only $124 per square foot (or $114 if you count the rebates and incentives), whereas the average cost for new residential construction in Seattle is $200 per square foot. Plus, we won’t be paying for energy, which comes to about $150 per month, or $1,800 per year, for the average Seattle household.
Now that we’ve lived in the house for a year, we’ve found it to be warm in the winter, cool in the summer (even without air conditioning), and comfortable overall. We were anxious to see if it would live up to its energy calculations, and we were thrilled when our net meter hit zero almost three months ahead of schedule. Twelve months after moving in, we had produced a surplus of about 1,400 kWh.
Even though we sailed past net-zero with our current PV array, we could be producing even more power. We currently have twenty-eight 230-watt Solar World panels covering about two-thirds of the roof. We still have room for about sixteen more. This would allow us to produce more than enough power to charge an electric car.
During construction, we noticed how footsteps carried from the second floor to the first-floor master bedroom. We asked for fiberglass insulation to be added between the two floors, which helped greatly. However, we didn’t anticipate how vibration from the heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump., carried through the pipes, would make the back wall of the house resonate. We are planning to add flexible rubber hosing from the unit to the exterior wall, but we wished we had paid more attention to sound deadening earlier.
Have your financing in order
Closing on our construction loan was the most stressful and difficult part of the whole process. Most banks were avoiding construction loans at the time. Even after we found a bank that would approve our project, we quickly discovered that the financing process was going to take much longer than we’d expected. The bank asked for more and more documentation and a larger down payment. It came to a head when we received a letter from the seller’s lawyer stating that we would lose the lot if we didn't close within the next week. After countless phone calls and emails, we managed to close just hours before the deadline. Looking back, we wished we had talked to the escrow people we were working with and asked them which banks were lending and, equally importantly, which were quick to close.
Find a trustworthy builder who shares your vision
Despite our best efforts to put every detail of construction in the building contract, the fact is that some things are still subject to the builder’s interpretation. And, for people like us who could never afford an expensive lawsuit, a lot comes down to trust. Luckily, we chose Ted Clifton Jr., our designer’s son, to be our general contractor. When we went to see his work, we fell in love with a pared-down yet refined home he had built for a budget-minded young couple in his Bellingham, WA, neighborhood. We liked how he had used trees from the building site to make massive exposed beams and had made creative use of inexpensive materials that cut costs while giving the house a solid feel and a pleasing look. Knowing that his design sense matched ours gave us peace of mind going into the project, and we were extremely pleased with the results.
Be realistic about DIY savings
In an effort to borrow less money from the bank, we asked our builder if we could lend some sweat equity to the project and even leave some of the upstairs rooms partially unfinished. He was very obliging, but, in the end, the bank was not. After initially approving our DIY plans, the underwriter changed his mind and required that the house be 100% complete. We were still able to do some things ourselves, like paint the trim and install the reclaimed wide-plank fir floors upstairs, but we overestimated the amount of work we would be able to take on and vastly underestimated the time it would take us to complete it, especially since our builder finished a month ahead of schedule. One area where we did save a considerable amount of money was to handle all the permitting and paperwork ourselves.
A marketing copywriter by trade, Eric Thomas founded the Ballard Green Building Talks, is a communications advisor to local environmental and green building groups, and was recently appointed to the Seattle City Light Review Panel. Click here to read Eric's blog.
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- Eric Thomas
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