Thousands of U.S. homes are certified zero energy ready, with California and Massachusetts leading the way with mandates that all new homes must be zero net-energy (ZNE). While ZNE and zero energy ready are not exactly the same, the overall concept is simple and many professional construction companies and homeowners are embracing it.
But, why would you want to build a zero energy ready or ZNE home, and what steps will you have to take to get your home certified?
I described my motivation in tackling my first net-zero home renovation in an earlier article. It makes 100% sense to live in a sustainable, energy-efficient home that reduces monthly bills and is more comfortable to live in than one that isn’t net-zero.
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ZNE homes are built to optimize energy efficiency, and they produce as much energy as they consume. Net zero-ready homes are built so that owners can upgrade to ZNE when they are ready.
More specifically, zero energy ready homes are constructed in compliance with rigorous requirements set by the Department of Energy (DOE) to ensure outstanding levels of comfort, health, energy savings, and durability. Unlike zero net-energy homes, the renewable energy system or some of its elements, solar panels, for example, can be added later, when finances allow. But everything is in place for them to become ZNE homes.
Solar energy is the most accessible (and usually the cheapest) green energy solution. Typically, ZNE homes include solar rooftop panels that potentially produce all the power needed for a home. This reduces the carbon footprint of ZNE buildings and makes them energy self-sufficient.
It’s important to recognize that having solar panels on the roof of your house is not enough to achieve net-zero energy. While they are an integral factor in both zero energy ready and ZNE homes, there is a lot more to consider, from window design to insulation.
My home is a zero net-energy design, and I love it! No upgrading needed unless superior technology provides new opportunities in the future.
The Department of Energy’s Zero Energy Ready Program
The U.S. DOE created the Zero Energy Ready Home Program in 2008 to encourage healthier, energy-efficient home construction. The aim is to encourage the construction of homes that achieve exceptional performance.
An ENERGY STAR-certified home is a start, but a DOE zero energy ready home offers a much higher level of cost-effective performance.
In essence, the program is designed to make our lives better, ensure our homes work better and guarantee that they will last better.
Ultimately, a DOE zero energy ready home will be at least 40-50% more energy efficient than typical new American homes.
Your first step in building a zero energy-ready home is to find a builder that is registered with the DOE. If you are a builder, you will need to register as a partner.
For your home to be certified, the building process must follow a specified path, and there are two to choose from:
- A prescriptive path that has a single set of measures the builder will need to follow. The path doesn’t require modeling and no trade-offs of any kind are allowed.
- A performance path that allows a degree of customization and flexibility. Builders must meet the performance levels of the DOE Energy Ready Home HERS Target Home. Additionally, modeling is required, but measures can be optimized for individual projects and they are flexible.
The DOE’s prescriptive path has seven mandatory requirements. They supply links to technical guides on the energy.gov website that include installation instructions needed to meet the requirements. There are also training tools and a detailed explanation of the DOE’s standard requirements for national program certification on the website.
All the required elements are checked and verified by qualified third-party inspectors who are the people who will certify your home.
There are seven mandatory requirements for all homes to be labeled zero energy ready:
These certification requirements are updated frequently and some states adopt region-specific versions of ENERGY STAR Certified Homes. This information is based on the most recent version specified.
The process is extensive and inspectors verify homes in terms of five checklists:
- HVAC design report
- Rater design review checklist that verifies the home design meets the HERS target
- Water management system builder requirements
- Rater field checklist completed during two site visits, one before the drywalls are installed and the other when construction is complete
- HVAC commissioning checklist which is provided by the installer
Additionally, homes must achieve a Home Energy Rating System (HERS) score that is better than the score required for homes that comply with the requirement for an ENERGY STAR Reference Design Home used for different climate zones.
Fenestration, which covers all openings in buildings including doors and windows, must meet ENERGY STAR requirements.
Also, slab, floor, wall, and ceiling insulation must be at least at the 2015 International Energy Conservation Code (IECC) levels.
Water efficiency is essential for zero energy homes. To get certification, your water heaters and fixtures must meet efficiency criteria whether they are electric, gas, or utilize heat pumps. Hot water delivery systems must meet the requirements of efficient design.
It also makes 100% sense to use high-efficiency lighting that saves energy (and money) in your home. At least 80% of light fixtures must be ENERGY STAR qualified or you must have ENERGY STAR bulbs in at least 80% of the light sockets in your home.
The air quality of your home must be certified in accordance with the Environmental Protection Agency (EPA) Indoor airPLUS checklist. This, in itself, is a relatively extensive list that includes combustion pollutants, HVAC systems, moisture control, and pests.
Again, the DOE provides links to technical guides as well as a link to the EPA’s Indoor AirPLUS Construction Specifications, which is a 16-page document.
The DOE specifies two checklists, one to make homes ready for solar photovoltaic (PV) installations and the other for solar water heating.
Only the PV-ready checklist is mandatory, but the DOE encourages builders to meet the solar-hot water requirements too. Both cover an assessment of the site, structural and safety considerations, and infrastructure.
The person verifying the DOE Zero Energy Ready Home requirements uses software accredited by the Residential Energy Services Network (RESNET) to qualify homes. The results are in keeping with those achieved using the prescriptive route, but the software that verifiers use creates a DOE certificate that is specific to a particular home.
The DOE Energy Ready Home HERS Target Home determines performance levels:
All HVAC equipment must meet specified efficiency requirements. Additionally, if a whole-house mechanical ventilation system is used, it must meet the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Ventilation and Acceptable Indoor Air Quality in Residential Buildings standard.
Insulation must meet the 2015 IECC, Grade 1 installation (RESNET) standards.
Infiltration, or air leakage, must meet ACH50 requirements. It indicates the differential for air changes per hour at 50 pascals (Pa) pressure and is an important metric for determining energy efficiency. Tests in different zones will determine if the building envelope is leaking air.
Unless fenestration is part of a passive solar design, window specifications must meet SHGC and U values for cold climate zones.
ENERGY STAR minimum efficiencies must be used for all styles of water heating.
To maximize performance levels, a programmable thermostat may be installed to control heating and cooling equipment.
Builders may select custom combinations of measures that are equivalent in performance to those achieved by the mandatory requirements described in the prescriptive path. ENERGY STAR provides the models.
Many people are committed, in principle, to building or renovating homes that are zero net-energy, producing as much energy as they consume. But they can’t all afford a renewable energy system right now.
A zero energy-ready home provides the opportunity to build according to net-zero energy standards with a future commitment to link up solar power.
The process is intense, but there are loads of resources to help zero energy builders achieve the results. I know, from experience, that it’s worth it.