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Strategies for net zero energy vary by household, climate, region and housing type.

Passive House Institute

The passive house standards in Germany and Austria have demonstrated that performance and cost savings can result when peak heating loads are reduced significantly.

Building Sciences Corporation completed a comprehensive renovation of a 100 year old home that resulted in a 60% energy savings while increasing the living space by 80%. (Pettit 2008)

Energy Efficiency Strategies That Work

A deep reduction approach with comprehensive insulation and air sealing can make a conventional furnace and air circulation system unnecessary, thus using simpler technical solutions to combustion safety distribution systems, durability and indoor air quality.

A deep energy retrofit could eliminate a conventional chimney, furnace and attic ductwork and replace these building elements with a mechanical ventilation system that manages indoor air quality and moisture control.

The Canadian Mortgage Housing Corporation (CMHC) recently published a study, "Approaching Net Zero Energy in Existing Housing" and concluded that climate, housing stock, energy loads, solar gain and occupant behavior all contribute to the feasibility of reaching net zero energy use in existing homes.   With no incentive available, it is not cost effective to achieve net zero energy in most Canadian housing.

Energy Efficiency Justification

Solving problems with wet basements, radon, outdated mechanical equiment and inadequate indoor air quality can help justify energy efficiency choices.

Reducing heating loads is relatively easy.  It is more challenging to achieve deep reductions in baseloads and cooling loads which are more dependent on occupant behavior and lifestyle.  Motivated occupants are essential.

The California energy crisis of 2000-2001 resulted in a 15% reduction in electrical energy use that was primarily the result of occupant behavior, not technology.  The actions of a small number of supersavers and modest efforts by many residents were deemed responsible for the reduction.

Utility programs can substantially reduce energy use with energy efficient features such as low-e windows and building enclosure improvements that focus on reducing air infiltration and upgrading insulation performance.  Also helpful are replacement of heating nd cooling systems, duct leakage reduction, and use of other controls for electrical and cooling loads.

Community Solutions

Homeowner choices sometimes affect lifestyle choices significantly.  Possible strategies can include use of renewable energy supply or a change in the use of space or the number of people in a home.  Highly effective choices can include co-housing with efficient shared cooking, water heating, clothes washing and entertainment facilities.

Reduce the Load First

Marc Rosenbaum suggests a simple maxim, "Invest as much as you can afford to reduce the load, even if it means completing a project in phases."  These load-reducing options that can help achive optimum results are major systems such as siding and roofing. 

Choices for Thermal Comfort

Thermal comfort accounts for 25 - 80% of residential energy use.   Some of the options available include:

Community Solutions

• Comfort centers
• Cogeneration or micro-cogen
• Community thermal storage
• Community-based renewable energy supply
• Use of waste heat from industrial processes
• GHG reduction campaigns
• Feedback, benchmarking, aggregation
• Competitions and challenges
• Technical, financial and regulatory support

Behavioral Choices

• 24/7 set point adjustment or setback
• Apply comfort zone
• Change use of space with new thermal boundaries
• Adaptive comfort (clothing, surface temperature, air movement)
• Increase occupancy
• Reduce internal gains with behavioral cooling loads
• Decrease occupancy size with relocation or demolishing space

Technical Solutions with Higher Cost

• Superinsulation (walls, ceiling, floor, foundation - climate specific for R25-R80)
• Efficient windows  (U 0.1 to 0.3)
• Super air tightening  (0.2 CFM/ftx2 floor space)
• High efficiency mechanical ventilation
• Ultra high efficiency HVAC system
• Automatic movable window insulation
• Highly insulated doors

Technical Solutions with Lower Cost

• Fill cavities with insulation
• Air sealing
• Do-it-yourself superinsulation
• Seal / insulate attic ducts or eliminate ducts
• Point heat or cooling source
• High performance storm windows
• Manually controlled movable window insulation
• Reduce internal gains with technical fix of cooling loads
• Control systems to optimize comfort, indoor air quality and humidity

On-Site Renewable Energy

• Increase solar gain through windows
• Sunspace or solar buffer to reduce heat loss
• Active solar thermal
• Solar PV
• Wood heat
• Trees vegetation or other shading to reduce cooling loads

EPA notes that it is easier for a 5,500-square-foot house to get the Energy Star seal than a 1,500-square-foot house -- even though the bigger house likely consumes much more energy.

The EPA is preparing to roll out tougher rules to ensure the logo represents robust environmental standards. But it has to walk a fine line, particularly during the recession. If it pushes too hard, builders are likely to bow out of the voluntary program due to the added expense.

EPA's concerns come as the Obama administration is pushing for what amounts to a mandatory nationwide building-efficiency rule.   Builders worry it will raise the sticker price of new houses.

Talk of energy efficiency typically focuses on fuel economy on the road. But buildings burn more than automobiles.

Together, residential and commercial buildings account for about 40% of U.S. energy use, compared with about 17% for cars and light trucks.

A recent Department of Energy study concluded that a typical house's energy use could be cut by at least 30%.

And it found the monthly mortgage payment needed to cover the higher construction costs would be more than offset by lower monthly energy bills.

The Energy Star standard is compared to a "model" building-efficiency guideline used by state and local governments. To earn the Energy Star label, a new house must score at least 15% better than what that "model" guideline stipulates. The rating takes into account such things as insulation, windows, heating-and-cooling ducts and appliances.

Energy Star has succeeded in popularizing efficient products. It has become the most consistent guide for consumers who want to know the energy efficiency they're getting for their money -- boosting demand and driving down costs. The modern residential thermal window, which curbs energy waste, used to be expensive but is now common in entry-level houses.

But the program's shortcomings show how difficult it can be to achieve widespread energy savings.

Big houses would lose their advantage under the tougher rule the EPA is preparing. It includes what would amount to a gas-guzzler penalty for houses.

Learn more at EfficiencyFirst

David Rodgers, Deputy Assistant Secretary for Energy Efficiency , appeared before Congress to discuss the potential for increased energy efficiency in new and existing buildings to reduce greenhouse gas (GHG) emissions.

In order to provide a solid basis for efficiency improvement in the buildings sector we are working to evaluate and strengthen building energy codes.

Residential: To ensure that all new homes become more energy efficient, DOE has long participated in the development of the International Code Council's (ICC) International Energy Conservation Code (IECC). The ICC, a voluntary, consensus-based industry standards development organization, updates the IECC every three years.

The Department's current goal is a residential energy code that is 30% more efficient than the 2006 IECC.

The ICC is currently considering code proposals that have the potential to improve the residential code by 18 to 22% when the next IECC update is published in 2009.

Commercial Energy Efficiency Sector

In the commercial sector, DOE is also partnering with the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to develop model building codes that are 30% more efficient by 2010 for all new commercial buildings compared with 2004 standards.

ASHRAE and DOE have signed a Memorandum of Understanding (MOU) to demonstrate their mutual commitment to work together toward this goal. Additionally, the MOU includes commitment by ASHRAE and DOE to improving the efficient use of energy, promoting viable and widespread use of renewable energy sources, and minimizing the impact of energy use on the environment. 

Design Guides for Energy Efficiency

As it is much more cost-effective to realize profound improvements in building performance at the time of construction than to retrofit homes or buildings, we encourage and are helping states to adopt and implement these code changes.

We are also expanding assistance available to states and local governments and working with the private sector to develop 30% and 50% "beyond code" design guides to encourage maximum efficiency in buildings nationwide.

DOE projects that its building energy code-related activities save the nation's home owners $200 million and commercial building owners $1.9 billion in 2010 (2000 dollars). Cumulatively, since the inclusion of the 1992 Model Energy Code as part of the 1992 Energy Policy Act, DOE estimates savings from codes (in 2008) at $6.4 billion for commercial buildings and $600 million for homes.

By 2030, DOE estimates that full adoption and implementation of 30% model codes in America's homes and buildings has the potential to save approximately 2.7 Quads of energy per year and to avoid nearly 160 million metric tons of C02 equivalents per year, which could potentially save consumers up to $20 billion in annual energy expenditures.

Net-Zero Energy Buildings -- The Goal

We are working ultimately to enable builders and the construction industry to increase production of net-zero energy buildings--grid-connected buildings that, over the course of a year, produce as much energy as they use--and make it more profitable for them to do so.

The Builders Challenge

In February, Secretary Bodman launched the Builders Challenge:

The Builders Challenge is a voluntary national energy savings program calling on the U.S. homebuilding industry to build 220,000 high-performance, energy efficient homes by 2012.

A high-performance home would use at least 30% less energy than a typical new home built to meet criteria of the 2006 International Energy Conservation Code.

Homes qualifying will meet a 70 or better on a new EnergySmart Home Scale, or E-Scale, that will be affixed to the homes allowing buyers to understand at a glance the energy performance of that home.

To date, 185 builders and 99 other partners have already pledged to build an estimated total of 10,000 high-performance homes. Ultimately, DOE aims to see 1.3 million homes of this high standard constructed by 2030. Significantly increasing the energy efficiency of homes is essential to achieving the DOE goal that, by 2020, a consumer will have the opportunity to buy an affordable net-zero energy home. The Builders Challenge establishes a framework for continuous improvement that will help propel the market toward zero-energy performance.

SOURCE: 
Testimony of David Rodgers, Deputy Assistant Secretary for Energy Efficiency before the Committee on Energy and Commerce Subcommittee on Energy and Air Quality, United States House of Representatives. Topic: Buildings Energy Efficiency and Greenhouse Gases, July 17, 2008, http://www1.eere.energy.gov/office_eere/rodgers_testimony_071708.html