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Every New Home Should be Zero-Energy Ready

A longtime advocate for green building design makes a case for the Zero Energy Ready Home label

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Armando Cobo designed this Zero-Energy Ready Home in Texas. The 4,800-square-foot, three-bedroom house was built by Davis Signature Homes of Dallas. The house has a HERS score of 43, without the 9.8 kW photovoltaic system, and a HERS score of 8 with the PV.
Image Credit: All photos: Armando Cobo
Armando Cobo designed this Zero-Energy Ready Home in Texas. The 4,800-square-foot, three-bedroom house was built by Davis Signature Homes of Dallas. The house has a HERS score of 43, without the 9.8 kW photovoltaic system, and a HERS score of 8 with the PV.
Image Credit: All photos: Armando Cobo
This 6,470-square-foot house has five bedrooms and 5 1/2 bathrooms. The ZEHR certified house tested at 1 ach50 and has a HERS score of 43 without photovoltaics. Cobo says most of his clients do not install PV because their electricity bills are too low to make the investment worthwhile. The house was built by Thornhill Custom Homes, Dallas. This Spanish Colonial style house was built to zero-energy ready standards but was not certified. The 8,500-square-foot home has five bedrooms and 5 1/2 bathrooms. On the performance side, airtightness was measured at 1 ach50, and the house scored 45 on the HERS Index without PV. The house was built by BCG General Contracting, Albuquerque, New Mexico. This infill project in a Dallas Conservation District, built by Davis Signature Homes, is 3,935 square feet with five bedrooms and 5 1/2 bathrooms. Airtightness was measured at 1 ach50; and the house got a HERS score of 42 without PV. It was built to zero-energy ready standards but not certified.


Reprinted with permission from Dallas/Fort Worth Building Savvy Magazine.

A desire to design and build better homes led Armando Cobo, designer, to help develop the LEED for Homes and NAHB Green Building programs and advocate for local, state, and national green building codes. Then, when the Department of Energy developed the Zero Energy Ready Home (ZERH) program in 2008, Armando became a DOE-approved instructor and started educating builders and clients on the advantages and processes to design and build the homes of the future.

With more than 30 years of experience in designing homes and the past 20 years spent establishing a specialty in designing high-performing homes, Armando is a staunch believer in the ZERH program. “It’s a timely solution for differentiating a builder’s product from existing homes and setting apart their homes from others that merely meet minimum code requirements,” he says. “The DOE’s Zero Energy Ready Home label symbolizes homes that are so energy-efficient that most or all of the extra cost for building the home with renewable energy systems is offset by savings in annual energy consumption,” he explains.

The DOE program builds upon the comprehensive building science requirements of Energy Star for Homes Version 3.1, along with proven Building America innovations and best practices. Other special attribute programs are incorporated to help builders reach unparalleled levels of performance and homes designed to last hundreds of years. Armando adds that less than 1% of U.S. builders qualify to build homes to this level of quality and high performance.

Substantially better than code

A DOE Zero Energy Ready Home is a home that meets all of the ZERH criteria and is verified by a qualified third-party entity. All homes are at least 45% more energy-efficient than a typical home built to standard new home code. “This generally corresponds to a Home Energy Rating System (HERS) Index Score in the low 50s, depending on the size of the home and region in which it is built,” Armando explained.

After working for years with LEED for Homes and NAHB Green, Armando prefers the ZERH program because it allows builders to be more independent in their way of building homes. “They simply achieve the requirements for the ZERH home program. There are no points to count and no army of consultants required other than the HERS rater and verifier,” he said.

In order to qualify and build a ZERH, Armando provides his clients with a full set of detailed drawings and specifications to build homes designed with very low utility and maintenance costs in mind. But his involvement in the building process doesn’t stop there. He coordinates the truss layout and design with manufacturers and often puts his native Spanish language to task in training framers on the job site. He works closely with the HVAC contractor and energy rater assigned to each project, both during the design and construction process. The amazing results speak for themselves.

In the past 15 years, all the homes that Armando has designed have received HERS ratings of less than 45. His design goals also strive to achieve one air change per hour when tested at 50 pascals of pressure (1ach50). Compare that to the local jurisdictions’ adaption of the state energy code in Climate 3, which includes North Texas; they allow up to 5 ach50, which Armando argues is ridiculously lax.

Further, Armando’s successful design formula calls for just one ton of HVAC system per 1200 to 1500 square feet. “It is still not uncommon to find central air conditioners in residences that are far larger than needed to meet the load requirements,” he said. “When you’re significantly improving the house envelope and efficiency of the distribution system, you reduce the necessary heating and cooling loads. Proper sizing of the AC can be a cost-saver and most importantly allows more efficient operation and provides a more comfortable environment.”

And what about solar, we ask? Armando says the combination of a good conservation approach, with envelope efficiency, Energy Star lighting, appliances, and hot water distribution, produce such a low energy demand that, if the client wishes, they could install a much smaller and more reasonable photovoltaic system with a great return on investment.

Last October at the Energy and Environmental Building Alliance (EEBA) Conference in Atlanta, Armando’s client, Thornhill Custom Homes, earned honors for a project at 5717 Preston Haven in Dallas. Thornhill was selected as a 2017 Housing Innovation Award winner in the custom spec category. Armando says he expects two other builders to compete for the award in 2018 and more in 2019, based on projects currently under construction.

No cost to join program

Armando stresses that it is free for builders to become a ZERH program partner. All a builder needs to do is to register online by completing their contact information, uploading a company logo, and making some additional commitments. Once the builder has provided an electronic signature and submitted the registration, the DOE sends them a confirmation by email with their password to access their account. The next logical step might be to contact Armando, but he stresses that everyone should truly care about building a structure to the very best standards, and anyone who does can easily understand and meet the requirements of the program — with or without his direct supervision.

The ZERH program mandatory requirements stipulate:

  • Homes must be certified under Energy Star version 3.1.
  • Envelopes shall meet or exceed Energy Star requirements for 2015 IECC.
  • Grade 1 insulation installation and airtightness of 2.5 ach50 or less.
  • Window U-factors less than 0.3 with a solar heat gain coefficient of less than .25.
  • Duct systems must be located inside the conditioned space or optimized to comparable performance in a ventilated space (encapsulated or double-wrapped).
  • Minimum efficiencies in HVAC systems and ASHRAE 62.2 whole-house mechanical ventilation system.
  • Hot water delivery shall meet efficient requirements.
  • Indoor air quality certified under EPA Indoor AirPLUS.
  • Renewable-ready checklist must be completed.

Builders and homeowners can learn more about the DOE Zero Energy Ready Home by joining Armando at a teaching event or jobsite tour, taking part in online training and webinars, and browsing the ZERH program’s other resources. The program includes free ready-to-use marketing materials to promote consumer awareness of homes that feature high-performance products in their most effective applications. “I urge you to take advantage of the opportunity to be among the one percent of builders in the country by starting to build the homes of the future today,” Armando concludes.

Armando Cobo is a home designer in Albuquerque, New Mexico, and Frisco, Texas, with more than 30 years of experience and 450 sustainable custom home designs to his credit. You can learn more about Armando and his work at his website.

This post has been updated to correct the name of a builder in a photo caption.


  1. jackofalltrades777 | | #1

    Awesome homes but...
    Why are all these homes in the 4,000 - 8,000+ square foot rage?
    Beautiful homes but extremely large and pushing into the million dollar+ ranges. It would be nice to see some 1,500 - 3,000 sqft homes.

  2. JC72 | | #2

    IMO, unless you are thinking gut-rehab, generally speaking sub 3k sqft puts you squarely in tract housing.

  3. Expert Member
    Peter Engle | | #3

    Tract housing
    Perhaps for a larger builder, they might need to build that large to feel like a custom builder. But there is still demand for custom-built, and well-built homes in the sub-3000 sf range. Not everybody wants a McMansion - even an energy efficient one. We need to move into an environment where all houses are built with something like net zero energy in mind, from rehab to new construction and at all ends of the size and features scale.

  4. GBA Editor
    Martin Holladay | | #4

    Average size of a new single-family home
    In 2017, the average (mean) size of a new single-family home was 2,571 square feet.

    The median size was 2,371 square feet. That means that half of all new homes built in the U.S. measure less than 2,371 square feet.

    Source: New Home Size Continues to Fall.

  5. jackofalltrades777 | | #5

    2,371 square feet
    Only people I know that are building >3,500 sqft are millionaires who don't care if they pay a $400 per month utility bill. They have $$ to burn.

    I would rather build < 2,000 sqft and build it right and energy efficient. Unless you have a family of 6 kids, I don't see the reason to build larger than the 3,000 sqft range.

  6. Expert Member
    ARMANDO COBO | | #6

    Big vs small houses
    Against my own judgment I'll comment on designing big houses. I've said this before... most houses I've designed are large custom homes that cost $1-5M to build in TX, and 3 times more in CA. But I've also designed hundreds of homes in the 500-1k-2k sq ft as well. I've designed affordable housing projects in different states, plus several Pro-Bono homes through out the years, and I make no apologies. You can see plenty of small houses on my website.

    There are people that spent "wasteful" money in BMWs, Mercedes Benz, boats, guns, golf clubs and other expensive DEPRECIATING assets, or folks that would rather travel or eat at fancy restaurants and drink $100 bottles of wine, or buy $1000+ purses and shoes, or even more "stupid" money in smokes, alcohol or drugs, yet nobody judges them.

    Why can't a family that has worked hard all their lives have the pleasure of having a house with all the pleasure rooms, like wine cellars, theaters, game rooms, swimming pools, etc.? At least every 5k sq ft house I designed uses the energy of a typical 1500 sq ft house. We've been monitoring a 6500 sq ft house in Dallas for the last 7 years, and the highest energy bill they have is $172, and they have no PV system. Most 5k sq ft houses have less than $150/mo energy bills w/o PV, and typically "normal" houses here in the summer have 3 or 4 times the energy bills.

    If I were to tell one of my clients that instead of designing their 5k sq ft house I'll design them a 2k sq ft house because "the house size police" doesn't like it, they'll go somewhere else, and their house will not be designed high-performance. It's just that plain and simple!

  7. user-349933 | | #7

    Median house size
    I recently read that about half of all housing permits are issued for apartments and multifamily units. Are these units counted towards the average house size or is new living space actually much smaller then reported when theses multifamily units are included.

  8. Expert Member

    Client base
    Sure there are all sorts of questions around house size and it's implications on efficiency, resource use, etc etc. But if Armando's client base wants houses of a certain size, and the choice is between him and someone unconcerned with the things he addresses, then surely it's better that he ends up designing them?

  9. Jon_R | | #9

    energy use
    As we see more renewable energy and more time of use energy pricing, energy use (ie, kwh/year) will become an increasingly inaccurate measure of anything people care about (eg, $ and environmental impact).

  10. Mitch_Costa | | #10

    Comfort and resiliency
    Super insulation may well become less of a desirable factor with increasingly affordable renewable energy sources available. However, the good air and water sealing techniques that contribute towards resiliency and comfort in a home, as well as a certain minimum R value of a structure needed for even temperatures for comfort, should remain important to informed buyers. From the many interactions I've had with this generation of high school and college grads, sustainable, green, and healthy building practices should become bigger selling features for new builds and refurbs. Resiliency, sustainability and comfort tips are already the key reasons I'm a GBA member. The efficiencies required by the ZERH standard appear to be flexible and reasonable while encouraging better building practices - just need to find a way to incentivize better building standards like these in cheap tract housing and multifamily dwellings.

  11. JC72 | | #12

    Perhaps, but in my neck of the woods (Metro Atlanta) very few custom-built homes go up that have a GLA of less than 3k. Those that do go up are basically limited to infill urban lots. The financing just won't work otherwise because of the high cost of land.

    I personally went down this road a couple of years ago when looking to build.

  12. itserich | | #13

    response to Armando Cobb
    "Why can't a family that has worked hard all their lives have the pleasure of having a house with all the pleasure rooms, like wine cellars, theaters, game rooms, swimming pools, etc.? At least every 5k sq ft house I designed uses the energy of a typical 1500 sq ft house."

    Why is it important to build 5,000 square foot homes which are energy efficient?

    If there is an answer to this question, the answer also applies to why smaller homes are better than big homes.

    It is certainly true that a less wasteful big home is better than a more wasteful big home, but pretending it is not a waste is dishonest.

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