Tag Archives: net-zero energy building

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

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

How California’s New Solar Mandate Will Affect Homeowners

In 2018, the California Building Standards Commission approved a mandate requiring all new homes under three stories in the state of California to install solar panels. This solar roof mandate, which is the first of its kind in the United States, will go into effect on January 1, 2020. Continue reading

Affordable Net-Zero Energy Home Construction in 12 Steps

net-zero energy

Net-zero energy home

Building and designing affordable zero energy homes involves 12 integrated steps that utilize commonly available building materials and equipment along with easy-to-learn building strategies. By following these steps, you can build a new home that is cost comparable to a conventional home. 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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Sun Control and Shading Devices

fh150jad_cropped_house copyThere are many reasons to control the amount of sunlight admitted into a building. In warm, sunny climates excess solar gain will result in overheating, in cold and temperate climates winter sun entering south-facing windows can contribute to passive solar heating, and in any event controlling and diffusing natural illumination will improve daylighting. Continue reading

The Role of Buildings and the Case for Whole Building Design


The ‘Whole Buildings’ process draws from the knowledge pool of all the stakeholders across the life cycle of the project, from defining the need for a building through planning, design, construction, building occupancy, and operations.

Buildings are deceptively complex. At their best, they connect us with the past and represent the greatest legacy for the future. They provide shelter, encourage productivity, embody our culture, and certainly play an important part in life on the planet. In fact, the role of buildings is constantly changing. Buildings today are life support systems, communication and data terminals, centers of education, justice, and community, and so much more. They are incredibly expensive to build and maintain and must constantly be adjusted to function effectively over their life cycle. The economics of building has become as complex as its design.

Data from the U.S. Energy Information Administration illustrates that buildings are responsible for almost half (48%) of all greenhouse gas emissions annually. Seventy-six percent of all electricity generated by U.S. power plants goes to supply the building sector and buildings often contribute to health problems such as asthma and allergies due to poor indoor environmental quality. Safety is also paramount in buildings with security-related expenditures one of the fastest rising expenses.

The federal government has responded to these challenges by putting into place Executive Orders and Mandates. High performance buildings were defined in the Energy Policy Act of 2005 (Public Law 109-058) as: “buildings that integrate and optimize all major high-performance building attributes, including energy efficiency, durability, life-cycle performance, and occupant productivity”.

The Energy Independence and Security Act (EISA) of 2007 further established a new and aggressive plan for achieving energy independence in our nation’s building stock by the year 2030. The Act requires that federal buildings (new and renovations) achieve fossil fuel-generated energy consumption reductions on the order of 55 percent in the year 2010 to 100 percent in 2030. The Act also requires that sustainable design principles be applied to siting, design, and construction. It is of note that the Act defines High-Performance Buildings as the integration and optimization on a life cycle basis all major high-performance attributes, including energy conservation, environment, safety, security, durability, accessibility, cost-benefit, productivity, sustainability, functionality, and operational considerations. These issues are synonymous with whole building design.

Several programs, both public and private sector, define standards and measures for sustainable buildings. Of the government programs, the most well known and influential is Energy Star, providing an energy performance rating system applied to buildings. Of the private sector programs, the best known and most influential is the USGBC’s LEED® rating system. Others include Green Globes®, the NAHBGreen® certification system administered by the National Association of Home Builders, Greenguard®, and the Living Building Challenge® administered by thhe International Living Future Institute.

Whole Building Design encompasses all of these issues and programs and is an essential way of approaching building projects. Understanding Whole Building Design concepts will enable you to think and practice in an integrated fashion to meet the demands of today’s as well as tomorrow’s high-performance building projects.

Article based on that found at the Whole Building Design Guide website, a program of the National Institute of Building Sciences.

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.


The Dew Point in Insulating Wall Assemblies


Diagram depicting dew point in relationship to elements of wall assembly. This assembly utilizes cork board as the exterior insulation (courtesy Siegel+Strain Architects, Emeryville)

A reader recently queried in response to our recent posting The Brave New World of Insulating Wall Assemblies, “will adding exterior insulation act to decrease the probability of a condensation issue”?

The short answer is, adding exterior insulation will always decrease the risk of condensation within the wall assembly.

That said, in the design of the entire wall assembly including insulation in the stud bay + outboard insulation, we want to design the whole assembly with the dew point outboard of the wall sheathing. That way condensation, in the rare event it does occur, does not take place within the stud bay.


Ratio of exterior-interior insulation to control air leakage condensation. Courtesy Building Science Digests: Controlling Cold-Weather Condensation Using Insulation, John Straube,  03/10/11

The chart at right provides recommendation for balancing the insulation. In a commercial application we can assume indoor RH of 35%. In Santa Cruz, the average for the coldest three winter months (Dec, Jan, Feb) is 49.7 degrees. Cross-indexing these (35% x 50 deg F) results in 0.00. In other words, in our climate zone since temperatures are mild, insulation balancing is not likely to be a consideration.

The most conservative estimate might assume an indoor RH at the highest end of the spectrum i.e. 60%. In the same temperature range (50 deg F) this results in a 24% ratio for the exterior insulation. If we seeking to attain an R-20 wall this means it’s recommended to design R-4.8 into the exterior insulation, and the remainder (20.0 – 4.8 = 15.2) in the cavity. Using conventional insulation, options might include: A. R14 batt + R6 rigid = R20 target B. R19 batt + R1 rigid = R20 target. Since the ratio is less than 24%, Option A is the better of the two, since it is the least likely of the two option to result in condensation within the cavity.

There is a detailed and comprehensive article at Building Science.com: http://www.buildingscience.com/documents/digests/bsd-controlling-cold-weather-condensation-using-insulation. It’s author, Dr. John Straube of the University of Waterloo, is widely considered to be an authority on the subject of moisture transport within building materials and systems.