By Meghan Prisuta • May 6, 2020

How does an existing building reach net-zero energy?

Net-zero energy buildings, or zero energy buildings, are buildings where energy consumption and emissions are fully offset by renewable energy generation. As sustainability efforts become more aggressive, the interest in net-zero energy buildings has intensified. Innovative technology, process and design improvements are breaking down barriers associated with the time, complexity, and costs involved in retrofitting buildings to reach this pinnacle achievement in energy performance.

Existing commercial buildings have unique challenges when it comes to extensive energy retrofits, as most have stricter constraints around schedule, budget and space than new construction projects. So how does an existing building even begin to tackle such a daunting task? Planning is key, and when it comes to the details, each unique building has special considerations. Setting goals and a strategy for execution with a team of professionals is crucial, but there are three overarching technical steps that we believe are universally important to most net-zero energy retrofits for large commercial buildings.


1. Maximize Energy Efficiency with Energy Conservation Measures

The first overarching step towards reaching net-zero energy is to reduce energy usage. A baseline energy assessment will determine the building’s existing energy profile, energy use intensity, and maximum technical potential – or the lowest possible energy use that can be achieved for the building. This analysis helps to identify large energy users and processes that present the opportunity for energy conservation measures.

An energy conservation measure (ECM) is a project or technology initiative that, once implemented, will reduce the consumption of energy within a building. ECMs come in a variety of forms and can be anything from equipment replacements or upgrades to process or design improvements. For example, a popular ECM for large commercial buildings is the replacement of fluorescent bulbs with light emitting diode (LED) bulbs. This type of ECM often offers the opportunity for a large reduction in lighting energy use and a significant payback for building owners. Other more aggressive ECMs might include the elimination of inefficient steam plants or the use of air cleaners to reduce the the amount of energy used for ventilation.

Innovative energy conservation measures are the backbone of any net-zero energy retrofit. Since NZE buildings need enough renewable energy generation to offset energy consumption, reducing energy usage will reduce the amount of renewable energy needed. To put it simply, the more energy consumption, the bigger the photovoltaic arrays and geothermal well-fields, and the more money, space and time needed. Optimizing energy efficiency FIRST helps to alleviate these constraints.


 2. Right-Size and Properly Design the Geothermal Heat Pump System

Eliminating fossil fuel consumption is one of the biggest challenges for large facilities looking to reach NZE status. HVAC systems are often the biggest culprits when it comes to energy consumption and CO2 emissions. Electrification of these systems, particularly in an efficient and cost-effective way, can prove to be a major challenge – geothermal heat pump systems are often the answer.

Geothermal, or ground source, heat pump systems (GHP) are the most efficient and cost-effective HVAC systems available. This technology requires zero fossil fuel burning and utilizes the ground beneath the surface of the earth to transfer heat for space heating, space cooling and water heating. Properly designed GHPs can have a coefficient of performance (COP) of 4 or more. Thanks to ultra-efficient equipment and relatively low maintenance, building owners who invest in GHP systems can expect a great return on investment in the form of better energy savings and lower operating costs. For all of these reasons, geothermal heat pumps are often the most viable option for heating and cooling when looking to achieve net-zero energy.  

The most important (and expensive) aspect of a geothermal heat pump system is the ground loop, or the critical link that allows geothermal heat pumps to use the Earth as a heat source in the winter and a heat sink in the summer. The ground loop is a series of piping which sits within a geothermal well field, the most important design element for GHPs. Properly designing and sizing the well field will ensure the system works efficiently and effectively and doesn’t cost building owners more than it should.  


3. Decide On a Renewable Energy Generation Plan

Up until this point, the focus should be on reducing energy consumption with innovative ECMs and a properly designed geothermal heat pump system. Both of these steps will help position the project for success when selecting and sizing renewable energy alternatives. Due to declining costs and increasing knowledge around the subject, solar power by way of photovoltaic arrays (PV) is the most popular form of renewable energy generation for reaching net-zero, but it doesn’t come in a one-size-fits-all option.

On-site PV generation can offer a very good payback to owners. One might be attracted to this option due to government tax incentives, the possibility for new income streams from excess power, or if energy independence is an important goal.  While on-site PV is a viable option for many, it might not be possible for every retrofit project due to the space, planning, and first-cost it requires.

Two alternatives to on-site PV generation are Physical or Virtual Power Purchase Agreements. These types of contracts are increasingly popular because they allow building owners to achieve their renewable energy goals with little risk, investment or space. Neither physical power purchase agreements (PPAs) or virtual power purchase agreements (VPPAs) typically require the space or the large up-front investment that on-site PV requires.

A PPA is a contract between two parties whereby one party sells both electricity and renewable energy certficates to another party. In this agreement, the buyer takes ownership of the electrons produced by the renewable energy project. A VPPA differs in that the transaction is purely financial and involves the exchange of cash flow and renewable energy certifates. VPPAs are attractive to buyers looking for the path of least resistance.

Most Importantly: Build the Right Team

With any deep energy retrofit, planning is the most important part of the process. This starts with building the right team of experienced partners to guide owners on the path to Net-Zero. Planning ahead, analyzing the current situation and setting goals with a team of experts in the design, engineering, and financing of energy efficiency and renewable energy projects will provide owners with comprehensive guidance and peace of mind as the project moves forward.

EffectivEnergy Solutions is an energy efficiency consulting firm specialized in developing Master Energy Plans, including Net-Zero Master Energy Plans, that help large facilities reduce their carbon footprint and save money. Where certain conditions exist, we have developed a Master Energy Plan that can reduce the carbon footprint of a building or campus, even where gas fired steam boilers are concerned.

For assistance in determining the feasibility of net-zero energy at your facility, please contact us at 610-235-9066,, or click the link below.