The intent of the project was to design and build an affordable, energy-efficient sustainable home for a single woman committed to these objectives. The site was selected for the orientation of the southern exposure. The site was an undeveloped lot in a fully developed urban neighborhood.

The home is slated for a Platinum USGBC LEED certification, and is a finalist for the Gold Energy Value Housing Award, International Builders Association in the affordable category.

Prevailing summer winds are typically from the southwest. However, on this site the north and northeast are heavily wooded. Prevailing winds are, for the most part, non-existent near ground level on this site. The site was an undeveloped suburban lot near Lake Worth. The lot had a treeless middle area that straddled a ridge with approximately 7’-0” of grade change. The trees around the perimeter and at the front of the lot were protected and used to augment the energy optimization strategies. Fill was brought into the site to create a level building pad to avoid disruption to the native landscape.

The plan is oriented to take maximum advantage of passive solar shading in the summer and heating in the winter. The floor plan was designed along an east to west axis to allow the greatest exposure to the south. All windows were placed strategically and sized to provide a high degree of thermal performance. The design features an open floor plan to maximize the absorption of natural light and solar heat gain in the winter. Overhangs were sized and applied where necessary. The greatroom was placed on the southwest end of the house to respond to evening lighting conditions. This position also allowed the west wall of the home to be virtually windowless as the entertainment aspects of the room as well as bookshelves were placed here. The kitchen and dining functions were placed in the middle of the plan and the east was reserved for the location of the master bedroom and bath and the second-floor bedrooms. All non-light dependant functions of the home were relegated to the north such as the master closets, 1/2 bath, laundry/mud room/office, pantry and general storage areas. The second-floor bedrooms face east and the closets were placed on the west.

In this manner, the home maximizes the introduction of natural light and solar heat gain. In the summer months the windows are shaded entirely by the fabric shading devices.

Additionally, the strategic placement of the storage areas and buffer spaces on the north and west contribute to minimizing solar heat gain. The carport is located on the north end of the home. Its design, coupled with the storage shed, creates a dogtrot-like breezeway on the northwest end of the home.

The house was conceived as a high performance thermal envelope. All walls were built using 4-inch SIP wall panels. All roof elements are 8-inch SIP panels. Windows are either casements or awning type. This design provides a better compression seal to close more tightly than a double-hung or slider window. The casement windows can be opened fully to act much like the smoke flaps on teepees to direct airflow into the home. The awning windows are located either at the lowest elevation of the home or the highest. This placement is used effectively to create a stack effect and induce the slow, natural movement of air through the home from floor level on the first floor to the high clerestory windows in the bedrooms upstairs.

The home is also equipped with a whole-house fan system. The fans are interlocked with motor operated window controls. As the fans are engaged, the windows open out of the mechanical space on the second floor. When the fans disengage, the windows automatically close. The placement of the awning windows creates a forced-air flow from the first and second floors, up through the mechanical space, and out of the home. The fans operate at two speeds, essentially allowing four fan settings to control personal comfort. The fans provide comfort a full 60 days past normal air conditioning demand days. Even in early summer, the fans were employed during the night to cool down the interior. In the morning, the windows were closed and the home stayed within a reasonable comfort range until sunset when the fan/window methodology was repeated.

Ceiling fans have been installed in all bedrooms and in the greatroom. The benefits of ceiling fans are well known, and are functioning extremely well in terms of providing comfort at higher temperatures.

The foundation is a post-tensioned slab on grade. The majority of the floors in the home are stained and sealed concrete. Only the bedrooms and stairs were finished in bamboo.

• The concrete floor stores the heat gain in the winter and retains cooling in the summer cycle.
• During the day, minimal heating is required in the home on sunny days in the winter. In the summer cycle, the floors remain cooler and allow the home to feel comfortable with just ceiling fans at an ambient temperature of 78 to 80 degrees Fahrenheit during the day.
  

Consistent with good passive solar design, windows and overhangs were sized to allow natural light to enter easily into the home and to shade direct solar gain from entering in the summer season while allowing it enter fully in the winter season. Windows were arranged to provide an even illumination of natural light, and to use the light in decorative and interesting ways. All walls and ceilings were painted in clean, flat white to enhance the reflectance, and to bounce the available light deeper into interior spaces. Windows placed high in the walls and in celestories were deliberately placed close to sloping ceiling planes to further distribute light into the spaces of the home.

A solar hot-water system was chosen to eliminate the inefficiency of constantly heating a tank of water and to provide an unlimited supply of water on demand. Solar hot water heating was desired as an opportunity to use this effective technology and renewable energy resource. This decision was also cost effective when coupled with the federal tax credits now available. The financial buy-back was 2 ½ years. The plumbing layout was thoughtfully planned to keep hot water pipe runs to a minimum to reduce lost hot water left standing in long pipe runs.

Placement of the water heater close to the points of significant usage also conserves water that would normally be lost while waiting on hot water to come from the tap, and reduces the amount of energy used to produce it.

The home was designed with all ductwork being located within the condition envelope. Minimal ductwork has been installed. The mechanical room is located at the very top of the home above the second-floor bathroom. Six-inch Aprilaire pleated HEPA spaceguard filters were employed.

The passive solar design, the high thermal mass and insulation coefficient of the shell, and the efficient movement of air allowed the home to be designed with a 2-ton mechanical cooling requirement. The system installed is 23 SEER variable speed Daiken compressor, which allows the unit to read the interior loads and dial down to the lowest demand. It also allows the system to ramp up in response to heavier loads driven by higher temperatures and increased occupancy.

The mechanical design also features a fresh air make-up and exchange ERV unit to provide fresh air at maximum efficiency. The driving design premise was to build the most efficient thermal envelope affordable in concert with ceiling fans, whole-house ventilating fans, natural ventilation, and the stack effect to reduce overall mechanical dependency to a minimum. The variable speed mechanical system employed uses very little energy to provide the small amount of cooling needed during high demand days.

The roof system is white EPDM on the flat roofs and highly reflective Galvalume standing seam metal. Decorative, integral white and light beige color stucco was chosen. These colors provide a high level of reflectivity to further reduce heat gain. The exterior wall cladding is masonry to shield the SIP surfaces from heat gain by utilizing thermal mass. The 1-inch cement stucco was chosen not only for thermal mass and highly reflective color, but also for a sustainable benefit in that they are virtually maintenance free.

The floor plan features a hallway-free design. There are no traditional hallways. The lack of unusable living area eliminates the need for artificial lighting and contributes to improved air movement and cross ventilation throughout the home.

Aprilaire, ENERGY STAR digital programmable thermostats control the first and second floors. These thermostats feature Solid-State microcomputer chips to program precise time and temperature control. The home features only two zones: an upper and a lower zone. The envelope is so efficient that more zones were proven to be unnecessary during energy analysis. A single HVAC fan coil provides what little supplemental cooling and heating is required. Thermostatically controlled dampers provide the effective zone control.

When the upper floors are not occupied, the temperature is adjusted depending on the season and the time of the day. Energy is conserved by this methodology. Depending on the season and the damper positions, the second-floor spaces benefit from the comfort level of the lower floors by either collecting warm air for redistribution or allowing cooled air to pass through to the lower floors thereby beneficially affecting the setting on the lower-level thermostat.

The home features a natural-gas fireplace. The sealed fireplace is equipped with sealed glass doors and a duct that provides outside combustion air. The design radiates the heat of the fire directly into the adjacent space. Most of the heat is delivered into the home rather than being pulled up the chimney. The fireplace is located in the middle of the home separating the greatroom from the dining room. Locating it here places heat immediately into the living areas of the kitchen, dining and greatroom. The fireplace radiates the heat back out into the space during burning.

The home was designed and built using effective construction systems. Conventional framing techniques were only used to frame the floors and the minimal interior walls. The open plan design reduced the overall interior wall construction by 35 percent. The exterior walls are 6-inch Structural Insulated Panels (SIPs). All roofs are 8-inch SIP panels. The completed envelope is one of the tightest possible in terms of infiltration and exfiltration. It is also one of the most efficient in terms of developed thermal mass and R-value. The perimeter joist ends and various soffit areas were insulated and sealed using Icynene insulating foam. The SIPs and Icynene represent significant environmental responsiveness and effective sustainable solutions.

The design represents a consciously integrated holistic approach to energy efficiency and sustainability. The intent was to create a home design that would be sensitive to the natural setting, optimize energy efficiency, provide a high level of comfort with natural daylighting, natural ventilation, and be virtually maintenance free. Materials chosen were selected based on the principles of sustainability, low toxic emissions, and environmental impacts.

The intent was not to increase initial construction costs excessively. The process determined the principal dollar amount that could be serviced on a 30-year mortgage by the energy savings calculated in the pre-construction energy analysis. The hypothetical mortgage principal amount served as a guideline for the maximum sum of money that could be allocated to increase construction cost in return for energy savings.

Not every material was evaluated based on energy savings payback. Many decisions were based on first cost versus replacement costs over the life of the mortgage. Galvalume roofing and fascias and integral color stucco was driven more by the desire to never have to paint or replace a roof than a seven year payback cycle. Over the course of a 30-year mortgage the cost of repainting or replacement of major exterior finishes far exceeded the first costs of these materials.

Other decisions were driven by a cost-benefit analysis that evaluated payback time to recover the increased first costs from energy savings. A seven-year payback period was deemed an acceptable investment. Decisions were also influenced by a conscious awareness to implement long-term elements that could never be implemented at a future date without major alterations to the physical shell of the building. Other components that could be easily retrofitted or upgraded later — mechanical systems were evaluated using a standard that was more economically driven. All energy-saving design features or products for the house that met the investment return objectives were only incorporated if they could be integrated into the overall design of the home and would not detract from the desired aesthetic appearance or functionality of the spaces inside. The completed home, while contemporary, doesn’t appear to be an energy-efficient, passive-solar home.

A great deal of hands-on experience was invested in the design of the home. A solid first-hand understanding of features and function that was cost-effective as well as thermal-effective drove the design process. The features employed in the design of this home have been time tested and proven to be effective. The baseline principles that most influenced the floor plan and appearance of this home were proven, regionally appropriate design techniques.

Products were selected to minimize volatile organic compounds (VOCs), which outgas and adversely affect indoor air quality. All products chosen were no VOC or low VOC, primarily natural materials or plant-based without biocide additives.

Natural ventilation strategies, the Aprilaire 6-inch pleated HEPA spaceguard filters and the whole-house ventilating fans contribute to a high level of indoor air quality. Low absorption materials were also chosen to reduce moisture retention in the home. The dishwasher and washing machine were selected due to their ability to reduce the introduction of additional moisture into the interior environment.

All interior paints were Sherwin Williams’ Harmony series, containing no VOC, paint. All interior wood floors and millwork was finished using Ardvos mineral oil without a stain coat. The resulting honey color of the native Texas Ash is a marvelous result. A termiticide was not used as alternative physical barriers were constructed to be effective over the long term. The home contains no fixed carpeting or draperies. Sound and perimeter insulation is Icynene.

The end result is that the home smelled fresh and did not exude the toxic brew “new home” smell.

An energy analysis was performed at several different stages of the design. The design was evaluated not against conventional home construction but established targets of performance that exceeded all energy codes and standards. The estimated energy performance and savings were reviewed to confirm the cost effectiveness of major building components in the manner described in paragraph 2.1 (a) and the established design intentions and goals. Detailed studies of component specifications were conducted to evaluate the cost benefit of various HVAC systems, including the solar hot-water heater.

It is well known that native tree and plant species, if mature, can reduce cooling and heating costs by 30 percent. The conditions present on this site were, and are, an extraordinary benefit both aesthetically and for climate control. The native trees, shrubbery and plants that are growing naturally help block cold winds in the winter and reduce air temperatures and provide evapotranspiration cooling during the warmer weather. The tree cover on the east and northeast screen the direct, low-angle, early-morning sunlight.

A protective barrier was set up to keep all construction activities to within 10 feet of the building pad. After construction was completed, 8-inches of shredded bark mulch purchased from a neighboring municipality’s curbside recycling program was spread on all exposed surfaces. The native ground cover, trees and plants have been augmented with additional native plants upon conclusion of construction activities. No permanent irrigation system has been installed.

The natural condition of the site has supported a re-population of abundant native bird and animal life. Squirrels, opossum, raccoon, fox and bobcats are seen regularly on or around this urban site. The variety of birds is indescribable.

The roof design was driven primarily by the formal qualities of the house and how best to incorporate shading devices on the home. Investing a little thought and planning on roof slope and orientation developed a solution where all rainwater falling on the roof could be collected and routed to one location for easy collection. The slope of the site off to the north was ideal for incorporating a 5,000-gallon water storage tank. Consequently only a minimal amount of guttering was necessary to route all the roof runoff to three downspouts. The downspouts are connected underground and buried under the drive to deliver the water directly to the top of the tank without additional pumping.

The water collected is designed to serve dual purposes. First, it will provide water to flush the toilets in the home. Second, it can be used as irrigation water for the landscape. Early on in the design of the system, an interconnection with the city water system was discussed to fill the tank when rain sequencing had not. These options were costly and required significant check valves and city oversight. The simplest and most cost-effective way was to provide manual valving and owner/user control. Heather will monitor the resource and when the dry season doesn’t replenish faster than demand, she can easily manipulate the manual valves to activate the potable city source for waste flushing. Very basic filtration and pressure tank/pumping equipment was installed to complete the functionality of the system. Since the water will not be used for potable purposes, further filtration and ultraviolet treatment isn’t necessary and was not installed.

The system was conceived primarily as a demonstration piece and an interactive way to monitor/evaluate the cost/benefit of such a system in the Weatherford, Texas climate region. Currently, the cost of municipal water is still relatively cheap. However, weather patterns are shifting. In recent years, this area of north Texas has been experiencing extended drought conditions. Storing water on-site will reduce down stream erosion from increased hard surface run-off into Lake Weatherford, benefit the natural landscape, and will reduce the potable water demand on the municipality by using the stored water for what are effectively non-potable needs. The cost of water is certainly going to increase over time as the area continues to add population in direct conflict with the limitations imposed by a fixed quantity resource and unpredictable weather patterns.

Ultimately, it will provide a cost benefit after the first cost of the system is recouped. Determining the payback of the system was another incentive to incorporate this feature as a methodology to substantiate its performance, promote and sell rainwater harvesting to future Ferrier Custom Home customers.

The initial benefits are primarily environmental as explained earlier. Pragmatically, the stored resource is also a safeguard and back-up supply of a limited and valuable commodity during times of restricted usage. Use restrictions now seem to be a normal aspect of the dry months of summer in every major municipality in this regional climate. Its represents a green benefit that just seems to make sound logical sense, and something that in short order may become a standard feature in homes across the region.