The Heart of HVAC Design

the heart of hvac design image

Many in the building industry believe that the heart of a home is the HVAC system, but what is the heart of the HVAC system?

Just as a heart has four chambers that work together to pump blood around the body, the HVAC system has four components that, when integrated, create a system that works in unison to create comfort in the home.

  1. Manual J evaluates and describes the tight well-defined and constructed thermal envelope.
  2. Manual S provides guidance for how to properly size the heating and cooling equipment.
  3. Manual D directs the design of the duct system that will deliver conditioned air around the home.
  4. The ASHRAE 62.2 standard ensures that we have the proper balance between air tightness, efficiency, durability and comfort with ventilation needed for the occupants and background moisture control.

In the heart of the HVAC System: Manual J

Manual J is used to determine the heating and cooling load for the house and directs us toward the heart of the HVAC design. The objective of the heating and cooling load is to tell the designer how much energy is needed to achieve the design goals with a specific thermal envelope and piece of mechanical equipment. Heat moves from warm to cold and the thermal envelope retards or slows that flow. The International Energy Conservation Code (IECC) and the International Building code (IRC) both lay the ground work for the HVAC design.  These codes give us design temperatures.  In other words, they tell us the temperature difference (or Delta T) between inside and outside in the winter and summer seasons.

R-Values & U-Values, the Thermal Envelope

The R-values and U-values of the thermal envelope resist or slow the movement of energy from the inside to the outside in the winter and from the outside to the inside in the summer through the building envelope. The thermal envelope happens to be one of the most important components in the HVAC heart because its execution determines the success of most of the other interactions that take place to allow the home to be efficient, durable, safe, and comfortable. The IECC lays out climate zone-specific minimum R-values and U-values and construction installation techniques that have been deemed to create comfort in each area of the country.

When a designer inputs the specification for the insulation, windows, air barriers, and assemblies into the software to create the heating and cooling load for the house at the summer and winter design temperatures, the assumption is that the installation of the specification is perfect. The installed R-value is achieved, the house is airtight, and there is complete alignment between the thermal barrier and the air barrier of the home, as required by the IECC to ensure that the energy generated by the furnace and AC system will heat or cool the house during worst case conditions. A well-designed and constructed thermal envelope better resists the flow of energy through its assemblies. If the insulation, airtightness, and alignment of the air barrier and thermal barriers of the home are not executed well, modern HVAC systems that are not correctly sized could have difficulty maintaining comfort in the home. The ultimate objective is for the systems to run continuously to maintain the indoor design temperature when the worst case outdoor temperature has been reached or exceeded for those few hours of a day.  It turns out that the HVAC design process already has a built in safety net. If you thought that oversizing the system is a technique to ensure comfort, you would be wrong.  In our modern homes oversizing leads to equipment that will not perform properly – freezing coils, short cycles, etc.

Our homes are integrated systems that rely on each component of the system to work in unison with the other components. This is why EnergyLogic begins our HVAC design process with an understanding that we will evaluate the construction of the thermal envelope and its compliance with the requirements of codes and programs that aim to ensure that high-performance homes perform. To learn more about EnergyLogic’s HVAC design process, visit our New Residential HVAC Design page.


Robby Schwarz (faked)

Who to Contact:

Robby Schwarz
Principal, Director of Builder Relations

Email Robby

EnergyLogic, Thrive Home Builders and USGBC Strengthen Their Synergy by Completing the First Two LEED v4 Certified Single-Family Model Homes in Westminster, Colorado

Through the new Department of Energy Zero Energy Ready Home Alternative Compliance Pathway (DOE ZERH ACP), two of Thrive Home Builders Hyland Village model homes achieved LEED Silver certification, raising the bar and bringing something new to a compact, mixed-use development community.

Many builders have completed LEED certifications, but this newest alternative pathway enables production builders to use the Environmental Protection Agency’s ENERGY STAR® and Indoor airPLUS programs, as well as the DOE ZERH program as tools to achieve LEED certification.

As the largest Zero Energy Ready home builder in Colorado, Thrive Home Builders has achieved well-deserved recognition for focusing on areas beyond traditional energy efficiency such as materials and resources, location and transportation, and occupant health and comfort. LEED v4 is a tool that allows Thrive Home Builders to bring its various programs together into one holistic certification that will easily be recognized by consumers, as well as easily identified homes in the Hyland Village community recognized for building above and beyond standard code requirements.

“LEED has made significant inroads in the commercial sector, but has yet to catch up in the single-family home world,” said EnergyLogic’s Principal and Director of Builder Relations, Robby Schwarz. “LEED’s commitment to create a program that is not only meaningful but also is workable in the production home building environment should be applauded. EnergyLogic is pleased to contribute to the development of this new avenue for homes to be certified under the LEED for Homes program.”

“Thrive has been the perfect partner to work with, as their commitment to sustainable construction for their buyers aligns perfectly with what EnergyLogic and the LEED for Homes program are trying to achieve,” said EnergyLogic’s Schwarz.

Thrive Home Builders CEO Gene Meyers relates that Thrive has been excited about the possibility of building LEED-certified homes for a long time. “With this new certification path, the U.S. Green Building Council (USGBC) has paved the way for large-scale adoption of the LEED program in residential home construction, and we intend to lead the way in that adoption.”

USGBC is committed to transforming the way buildings are designed, constructed and operated through LEED — the top third-party verification system for sustainable structures around the world. Every day USGBC is helping to advance spaces that are better for the environment and healthier for us to live, work and play. Through its community network, continuous collaboration with industry experts, market research publications, and LEED professional credentials, USGBC remains a key driving force in the green building sector.

“The USGBC has achieved a remarkably high level of public awareness for the LEED program due to the inroads they’ve made in large-scale commercial construction projects. With this new certification path, there’s now a practical way for production homebuilders like ourselves to certify significant numbers of homes in the program,” said Thrive’s Myers.

“The residential sector is responsible for 21 percent of U.S. carbon dioxide emissions, making it a real contributor to climate change,” said Mahesh Ramanujam, president and CEO of USGBC. “LEED-certified homes like Thrive’s Hyland Village model homes are a measurable and impactful way individuals can make a difference for the environment, and this project serves as an example to the community of the benefits of doing good by living well.”

About EnergyLogic

Berthoud, Colorado-based EnergyLogic is a software and building consulting company that provides expert resources, education, and support to new home builders and energy raters involved in the construction of high‐performance homes. EnergyLogic serves as a resource to other organizations that are influential in creating energy-efficient housing across America and also built the system that analyzes and detects fraud in all of the country’s residential energy ratings. For more information, visit, and connect on Twitter, Facebook, and LinkedIn.

About Thrive Home Builders

Thrive Home Builders has been a leader in the design and construction of energy-efficient homes since 1993. Founder Gene Myers is recognized as a pioneer in zero energy building, and the company is repeatedly recognized by industry associations for its sustainable construction of single family homes and rowhomes. The company continues to lead the homebuilding industry into the next frontier by building well-crafted homes that promote both energy-efficiency and homeowners’ wellness. Its award-winning, DOE Certified Zero Energy Ready and Zero Energy homes are available throughout Denver and its suburbs. For more information, visit

About the U.S. Green Building Council

The U.S. Green Building Council (USGBC) is committed to a prosperous and sustainable future through cost-efficient and energy-saving green buildings. USGBC works toward its mission of market transformation through its LEED green building program, robust educational offerings, an international network of local community leaders, the annual Greenbuild International Conference & Expo, the Center for Green Schools and advocacy in support of public policy that encourages and enables green buildings and communities. For more information, visit, and connect on Twitter, Facebook and LinkedIn.

For the original version on PRWeb, visit:

EnergyLogic Makes Its Own Luck

EnergyLogic has been featured in the BizWest article, “EnergyLogic makes its own luck” by Tommy Wood.

With EnergyLogic’s positive growth, projecting to grow by $1 million this year, they’re redefining Steve Byer’s (CEO) definition of what it means to be a “big” company.

Read more about EnergyLogic’s roots, core values, and their projected future.

EnergyLogic’s 2017 ENERGY STAR® Award!

EnergyLogic has won the 2017 ENERGY STAR® Partner of the Year award for Sustained Excellence! This is EnergyLogic’s 8th consecutive year being named an ENERGY STAR Award winner.

At the heart of this award lies a passion for a healthy future, a commitment to energy efficiency, and a continuous drive to protect our environment. EnergyLogic embodies each aspect of this award by ensuring the work we do is creating a brighter tomorrow.

EnergyLogic has proudly received ENERGY STAR partner of the year awards since 2009. EnergyLogic’s partnership with ENERGY STAR began in 2001. In those 15 years, EnergyLogic has helped certify 22,000 ENERGY STAR homes across the state of Colorado!

Not only does EnergyLogic’s partnership with ENERGY STAR help protect the environment, it also reinforces our vision of a future in which all homes have the least possible impact on the Earth.

For more information, check out the EPA’s news release.

Why all HERS®/ERI Index Scores are Increasing Nationwide

It is important to understand the Home Energy Rating System (HERS®) and Energy Rating Index (ERI) are describing the same thing. HERS is a proprietary acronym created by the Residential Energy Services Network (RESNET), so the term ERI has been used for the code language. RESNET is the governing and standard setting body of the home energy rating world. RESNET recently created the ANSI/RESNET/ICC 301-2014 standard that describes how the Index score is developed. Within the 2015 IECC language that used to describe how to develop an ERI score has been replaced in the 2018 IECC with the ANSI 301 standard. In addition, the standard has now been incorporated into every software used to develop a HERS® or ERI Index score.

The ANSI standard change has, and will, cause all HERS/or ERI index scores to increase across the country. Due to this score increase and other fixed mandatory requirements in the ERI pathway, it is unlikely that jurisdictions will see builders using the ERI path for quite some time.

For more information on why this is happening, please refer to the following article: HERS® Energy Rating Index Scores are Going Up!

Software developers have incorporated the new ANSI/RESNET/ICC 301-2014 standard into their systems. As stated before, they are all consistently seeing the HERS/ERI index scores increase. Currently, there are three software systems available:




EnergyLogic is in the process of transitioning to the Ekotrope compliance software which will change the look of the reports but will not affect the content of the reports. Click here to see a sample Ekotrope report. All three software versions have incorporated reference homes to developed code compliance documents for the UA Tradeoff, Simulated Performance, and Energy Rating Index pathways through the energy codes.

What is a reference home?

Imagine your two hands are two homes that are geometric twins of each other. Your left hand, the reference home, is a house built with the energy and aesthetic features defined by the code which uses a quantifiable amount of energy that the code has deemed to be the minimum amount allowed by the jurisdiction.  Your right hand is the home you want to build, the proposed design, with the energy and aesthetic features you believe, are best to achieve whatever goal you have for the home: cost- effectiveness, safety, aesthetic beauty, comfort, durability, efficiency or livability. Your home, the proposed design, on the right, is compared to the code reference home on the left and if your home’s performance is equal to or better than the reference home it complies with the code and can be permitted to be built. The jurisdiction, an approved third-party, or both will inspect, verify, and report that the home was built as proposed in order for the certificate of occupancy to be released. 

For more detailed information, please refer to the following article: Simple Explanation of the IECC

In summary, changes and upgrades to software systems are inevitable. The creation of the ANSI/RESNET/ICC 301-2014 standard was the most impactful, but every version upgrade affects something. As a result, RESNET has developed a standard that governs when Energy Raters must transition to the most recent version of a software.

For more information on this subject, please refer to the following article: Important RESNET® Amendment on Rating Software Changes (Persistence)


Robby Schwarz (faked)

Who to Contact:

Robby Schwarz
Principal, Director of Builder Relations

Email Robby