Tag Archives: net zero energy

What is a Passive House?

‘Passive House’ is a design standard that achieves thermal comfort with minimal heating and cooling by using insulation, airtightness, appropriate window and door design, ventilation systems with heat recovery, and elimination of thermal bridges. Originally developed in Germany in the 1990s, Passive House principles are now being used throughout the world. Passive House standards are performance-based: they set performance targets to be met but do not dictate specific materials or products. The Passive House Institute administers a certification scheme that allows a building to be called a Certified Passive House once it has met certain performance standards. Continue reading

Glass Blocks Could Soon See Buildings Generating Their Own Power

Buildings could soon be able to convert the sun’s energy into electricity without relying solely upon solar panels, thanks to innovative new technology. University of Exeter, England, researchers have been developing a pioneering new technology that could accelerate the widespread introduction of net-zero energy buildings through the latest innovation in Building Integrated Photovoltaics (BIPV). Their innovative glass block, which can be incorporated into the fabric of a building, is designed to collect solar energy and convert it to electricity. Continue reading

What Is Sustainable Architecture?

Sustainable architecture is a general term that refers to buildings that are designed to limit humanity’s impact on the environment. An eco-friendly approach to modern day building encompasses every aspect of the planning and construction process. This includes the choice of building materials; the design and implementation of heating, cooling, plumbing, waste, and ventilation systems; and the integration of the built environment into the natural landscape. Continue reading

Sorting Out Solar Requirements on New CA Homes

In May 2018, the California Energy Commission (CEC) unanimously approved the 2019 Building Energy Efficiency Standards. The Standards now require solar PV on new homes constructed after January 2020. The CEC also created a solar plus storage option to give credit toward the new Standards. Continue reading

Solar Incentives in California

Solar panels on  house

Solar Rebates and Tax Credits
California is far and away the most mature residential solar market in the country, which can be both a blessing and a curse in some ways. Overall, it is definitely a net positive for homeowners who live here because they are usually more informed about the intricacies of solar and the state’s solar lobby is powerful enough to fight for important savings tool such as net metering.

But the downside of the mature market is that, unlike other states like Massachusetts and South Carolina, where rebates and energy credits are used to incentivize homeowners to consider solar, California has discontinued almost all of its state-specific solar incentives because the industry is strong enough to sustain itself. Continue reading

New California Energy Standards Effective January 1, 2017

code-changesEvery three years, the California Energy Commission (CEC) revisits its energy efficiency standards, augmenting the building code to align with recent technological advancements and the state’s new efficiency goals. The commission underwent this process again this year, identifying areas for improvement in both new construction and retrofits for residential and nonresidential properties.

With this most recent set of revisions, the commission is striving toward a pair of new state efficiency targets: achieving net zero energy for new residential construction by 2020 and for new commercial construction by 2030. Referred to as the 2016 version, these standards will go into effect January 1, 2017. Continue reading

Green Architecture: What Makes a Structure a “Living Building”?

EarthTalkLivingBuildingsA Pacific Northwest organization has defined an environmentally sound structure as one that generates its own energy, captures and treats all of its water, operates efficiently, and is aesthetically pleasing. Many readers will recognize the movement as the Living Building Challenge, launched in 2006.

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Selecting the Size of Your Solar PV System

Solar panels on newly build house

Whether your goal is to generate your own clean energy, increase your home’s appraisal value, save money on your electric bill, or all of the above—investing in a small-scale solar electric system is a wise decision. A small solar electric system—or distributed generation (DG)—can produce reliable, emission-free energy for your home or business. However, it is important to make sure that your solar photovoltaic (PV) system is correctly sized, sited, installed and maintained, in order to maximize your energy performance. Continue reading

10 Steps Towards the Affordable Net-Zero Home

What is a Net-Zero Energy Home?

Detail of Vega House, an NZE home located in the Santa Cruz Mountains.

Detail of Vega House, an NZE home located in the Santa Cruz Mountains.

Net-zero simply means that a building produces as much energy as it consumes. Net-zero energy buildings (NZEBs) minimize energy use through efficiency and by meeting remaining needs through renewable energy sources. Because NZE is a relative newcomer to the construction industry, it behooves all involved to be well-educated as to the steps necessary to successful design of the NZEB.

The acid test of whether a NZE home is performing as intended generally comes an entire year after it’s constructed, when the first year of energy bills are evaluated. By then it can be far too late to correct any deficiencies in the design. Moreover implementing NZE strategies, if not done cost-effectively, can completely erase potential energy savings (operating costs) due to excessive construction costs (initial costs), thus resulting in a failed building from a costs-benefits standpoint.

To help avoid these pitfalls we’ve outlined the following ten steps towards the affordable Net-Zero Energy Home.

Santa Cruz Style concept house. South facing glass is optimized, while excessive solar gain is controlled by exterior shading devices such as eaves and trellises.

Santa Cruz Style concept house. South facing glass is optimized, while excessive solar gain is controlled by exterior shading devices such as eaves and trellises.

1. It begins with the Design Process: The first step towards the affordable NZE home begins with an integrated design process, a team approach ideally including the owner, builder, architect and an energy consultant. Obtaining a cost-effective NZE home requires that a vast array of design decisions, many normally deferred until relatively late in the design process, be effectively identified and decided right from initiation of the design. To do this effectively requires hands-on involvement from all parties, including the owner whose job it is to make the decisions, the contractor advising on cost-effective options, the analyst verifying major decisions with energy modeling, and the architect facilitating orchestrated design decisions towards the optimal result.

An ideal site will have a broad east-west exposure free of obstruction to the sun (courtesy: Real Goods: The Passive Solar House Book)

An ideal site will have a broad east-west exposure free of major obstructions to the sun’s energy (courtesy Real Goods: The Passive Solar House Book)

2. The Site: For the most cost-effective NZEB, site selection must consider climate, weather patterns, wind, sun exposure, shade, heating/cooling degree-days, and topography. Ideally one should choose a site with a long east-west lot line to allow design imperatives such adequate south-facing roof for solar collectors and south facing windows for solar gain. The site should be free of obstructions such as trees, neighboring homes, and land-forms interfering with solar access.
A solar analysis is an important tool for evaluating passive solar, solar photovoltaic (PV) and solar thermal (hot water) potential by objectively measuring a site’s limitations for solar gain potential. Taking full advantage of the solar potential for each site is one of the most cost-effective strategies for achieving the successful NZE Home.

3. The Basis of Design: After the site analysis has been concluded, the next step is for the project team to collaborate with the architect in preparing the NZE’s program brief. The “Brief” is simply a detailed, itemized list of the strategies to be implemented for this particular home on this particular site to achieve the intended goals. It thus serves as a checklist or “road map” for the project.
The Brief encapsulates key components and measures such as the building’s area, projected construction budget, size and characteristics of various rooms, appropriate construction type for foundation, walls and roof assemblies, targets for appropriate ratio of floor area to percentage of window glazing, and targeted sources for renewable energy.

Santa Cruz Style concept house: a Net-Zero Energy home can be both contextual and high performance.

Santa Cruz Style concept house: a Net-Zero Energy home can be both contextual and high performance.

4. Size and Shape Matter: When contemplating the design and construction of an affordable NZE home, size and shape matter. Smaller homes use less energy for space heating and cooling, thus reducing operating costs. The savings from building, say, a 10% smaller home that achieves the same level of comfort and livability as a standard home represents a significant lowering of the cost construction, thus improving the bottom line right from inception. The well-known strategies of the Not So Big House movement can be used to result in a smaller home designed to look and feel larger,more spacious and comfortable without wasted space, resulting in a smaller home which functions as well as a larger home without unnecessary expense. Shape is also important. For example, an axially arranged organization of rooms will increase the surface area available for south-facing windows, optimizing opportunities for passive solar gain as well as daylighting. Similarly a thin organization of rooms will increase opportunities to cross-ventilate the home, thus facilitating passive cooling.

An east-west oriented, axial arrangement of rooms. Design sketch, Sun & Sky House, Santa Cruz Mountains.

An east-west oriented, axial arrangement of rooms. Design sketch: Sun & Sky House, 2011, built in the Santa Cruz Mountains.

5. Design to use the sun: To be successful, NZE homes must be designed to take advantage of the sun’s energy to the greatest extent possible, using it for example as the energy source for passive solar gain, generating electricity, and collecting solar hot water. After site analysis the conceptual model of the home can be appropriately located and massed appropriate to climate and site conditions, allowing mapping of potential energy performance and energy savings from the start.
Using this data the total area of southern-facing glazing will be determined – generally speaking it’s better to have too much rather than too little south-facing glass since excess solar gain can always be mitigated, but there is no remedy for inadequate amounts of glass.
Once the appropriate amount of glazing is determined, control features such as eaves, light shelves, trellises, horizontal louvers, brises soleil, external shades and shutters, and glass selection are used to fine tune performance to avoid excessive heat gain in the summer and optimize solar heat gain in the winter.
The design effort can then focus on the non-solar energy sources contributing to the overall energy picture by quantifying photovoltaic, solar hot water and other on-site renewable energy sources necessary to balancing the NZE home’s energy equation.

With responsible design approach, the NZE home need not be type-cast into a traditional architectural style.

With a responsible design approach, the NZE home need not be type-cast into a traditional architectural style.

6. Design for added insulation: Think of the home as a six-sided box in which all six sides need to have the most cost-effective insulation specific to the project need. R-value is the unit of measure for insulation, and R-values on each side of the box, as determined by energy modeling, must meet but not exceed the net-zero energy goals. Once NZE goals are meet, surplus insulation in excess of project needs is not a cost-effective use of resources.
Features such as thicker walls, deeper floor framing assembly or slab-on-grade, and raised roof-truss heels may be incorporated in the design to accommodate the appropriate insulation. Here in coastal California, the design issues are relatively less challenging. Nonetheless, as with any other aspect of the design, it is important that these strategies be weighed, decided upon, mapped, and incorporated into the design documentation to ensure that the subcontractors on the jobsite understand unambiguously the design intent and how it is to be built in order to ensure success.
More challenging climate zones such as inland California, the Mountain States and Midwest may require measures such as 8-inch to 12-inch thick, off-set stud walls to provide for adequate insulation. Moisture related issues must also be considered in the design of the highly insulated and airtight building assemblies of the NZEB. Designing assemblies that are both breathable and airtight prevents moisture-related issues in the realized building.

Detail for attachment of outboard rigid insulation to limit thermal bridging. Courtesy Segal & Strain Architects, Emeryville

Detail for attachment of outboard rigid insulation to limit thermal bridging. Courtesy Segal & Strain Architects, Emeryville.

7. Minimize thermal bridging: During the course of the design thermal bridging must be eliminated as much as possible from all six sides of the six-sided box. A slab-on-grade foundation system for instance is always placed atop an insulative barrier separating it from grade. In conventionally framed walls, every nail, every screw, and every stud in the wall assembly is a potential thermal bridge. For this reason advanced framing using offset studs are coming into favor. An alternative is the use of outboard rigid insulation, which must be carefully detailed if thermal bridging is to be avoided.

8. Windows and doors: If the NZE home is a well-insulated, highly airtight, “six-sided box,” windows and doors are relatively poorly insulated “holes” in that box. Moreover they are far and away the most expensive element in the wall assemblies that make up that “box”. For these reasons optimizing the location and size of openings is among the most important design strategies for achieving the affordable Net-Zero Energy Home.
Generally, most glazing will be south-facing, with lesser amounts allocated to east and west facades. North-facing glazing will be minimized. The exact ratios will be evaluated, determined by the energy modeling, and captured into the design documents. In terms of detailed requirements and by way of example, casement and fixed windows are less susceptible to infiltration than sliding, single- or double-hung windows. Fewer, larger windows are more energy efficient and more cost effective than more, smaller windows because there is a higher glass-to-frame ratio in larger units.


Kumin Residence, an off-the-grid, passive solar home utilizing strawbale construction. Designed in 2003.

9. Alternative Construction Technologies: Although conventional wood framing and it’s derivative, advanced framing (a.k.a. optimum value engineering) are most commonly in use, many other construction technologies lend themselves to NZE. Systems which might lend themselves to a satisfactory result and which might be considered include timber framing, Structural Integrated Panels (SIPs), Insulating Concrete Forms (ICFs), Wood Waste Masonry, strawbale, rammed earth, PISE, and traditional wattle and daub techniques.
In each case the technology of choice will be a function of the owner’s preferences, the builder’s familiarity and comfort level with the technology, and the costs-benefits accruing to its implementation specific to the project.

10. Design for builders: Given that the NZEB is a relatively newcomer to the construction scene, a great many of the kit-of-parts contributing to the successful NZEB will benefit from reality-checking for constructability and cost-effectiveness to build from an experienced contractor. For this reason, as mentioned previously, we generally encourage bringing the builder on board early in the design process, when ground-floor decisions informing subsequent stages of the design process are being made. Although not an absolute essential, having a contractor either as an integral member of the design team or in a consulting capacity will facilitate cost-effective decision-making right from project inception.

While building an affordable Net-Zero Energy homes is within reach of anyone who is in a position to commission a new or remodeled home, the too-be-desired results – namely affordable initial (construction) costs plus high return on investment in the form of low recurring (energy) costs – requires a host of sound decisions, systematic design and documentation, and a concerted, diligent construction effort to realize. We hope the foregoing 10 points have provided you guidance towards that end.

NZEB is one of many aspects of sustainable practice with which we have experience. To see more examples of our work in green building design click HERE.


Integrated Design Process (I.D.P.)

LEED NC 2.2-registered SLVWD Facilities Consolidation Project exemplifies results arising from the IDP process.

LEED NC 2.2-registered SLVWD Facilities Consolidation Project exemplifies results arising from the IDP process.

Integrated building design or Integrated Design Process (I.D.P.) is the name given to the high levels of collaboration and teamwork necessary to the delivery of a high performance green building project.

Charles Kibert in Sustainable Construction: Green Building Design and Delivery describes I.D.P. as design which, “considers site, energy, materials, indoor air quality, acoustics, and natural resources as well as their interrelationship with one another. In this process, a collaborative team (architects, engineers, building occupants, owners, specialists in indoor quality, materials, and energy and water efficiency) uses systems thinking to consider the building structure and systems holistically, examining how they best work together to save energy and reduce environmental impact”

IDP shown diagrammatically, depicting the ongoing feedback loops in which the original intent is considered holistically, the goals that original design intent are re-examined, tested, reconfirmed, and then integrated towards the intended result.

IDP shown diagrammatically, depicting the ongoing feedback loops in which the original design intent is considered holistically, the goals that original intent are re-examined, tested, reconfirmed, and then integrated towards the intended sustainability goals for the project.

The Integrative Design Guide to Green Building defines a truly integrative design process as one which “optimizes the interrelationships between all the elements and entities associated with building projects in the service of efficient and effective use of resources.”

Traditional design process, in which results deemed irrelevant to the design outcome are gradually eradicated from the design result over the course of the design process.

I.D.P. is characterized by early, intensive collaboration between key members of the design team. Those design decisions fundamental to the intended goal of obtaining a high performance green building are identified and substantively mapped. They are then conscientiously revisited and strengthened through mapping against other competing priorities throughout the entire duration of the design process, thus resulting in the highest, best result within the scope defined for that performance.

The San Lorenzo Valley Water District Facilities Consolidation Project located in Boulder Creek, CA is a LEED NC2.2-registered design exemplifying the benefits of implementing Integrated Design Process. Green building design goals were identified, qualified, and then sorted along with all other priorities,  early on. These initial goals were then shared collectively through the LEED charrette and other collaborative communications with all key members of the project team, resorted, and re-prioritized among all the values brought to the table by the project team, most especially those having to do with projected construction costs. This regimen of evaluation and re-evaluation was adhered to from schematic design, through design development, and culminating in having those goals manifested in the 100% construction contract documents, thus assuring the responsible implementation of those goals once the built project is realized.

More detailed discussion and updates to the status of S.L.V.W.D. Facilities Consolidation Project can be found here. For more information about Integrated Design Process, the American Institute of Architects has identified I.D.P. to be an essential to sustainable design practice. The resources they have compiled are available here.