Sustainable Engineering – Delivering Better Buildings

Process for energy-efficiency retrofitting

Most commercial buildings can be made more energy-efficient by following a logical process that delivers measurable results and return on investment at every stage.  By minimizing your initial investment, this process defers higher capital input until initial energy cost savings begin.


This approach is staged in an order that causes positive impacts of each phase to improve the results of the next (EPA Energy Star).



The Preliminary Energy Assessment is a simple, quick and inexpensive way to determine how your building compares to the average building like yours.  This will tell you how your building’s doing in terms of overall energy efficiency.  Often this helps owners and managers establish energy efficiency goals.  This can be done in as little as a day’s time using the US EPA’s Energy Star database for commercial buildings.

The Building Energy Audit naturally follows the Preliminary Energy Assessment (PEA).  The reason is that the PEA helps you establish energy efficiency improvement goals, and the Building Energy Audit defines the selection of measures that can meet those goals.  In nearly all cases, quick, low cost measures can be revealed by the simplest of energy audits: the Level 1 audit.  If your energy efficiency goals are more ambitious, the Level 2 audit could follow the Level 1 audit.  The Level 2 audit provides more in-depth development of the measures to more closely predict capital cost and potential energy cost savings.  Often this helps owners and managers make larger capital decisions.  The level 3 audit is the most developed version of energy audits, often used for analyzing the very largest capital measures, and incorporates instrumented analysis.  ASHRAE Standard 100, 105 and the ASHRAE Procedures for Commercial Building Energy Audits form the framework of energy audits performed in all non-residential buildings.

Re-tuning” is an on-site, collaborative, process that studies your building’s operation and returns the building to optimal function per the original design intent, while providing training to operating staff so they are better able to self-perform the steps for on-going success.  Re-tuning provides improved performance through energy savings, better comfort, and more reliable operation.  For most buildings, the overall process should take one year.  Implementing any system operating changes should be done slowly, incrementally, while checking results to confirm desired results.

Retro-Commissioning is a relatively structured on-site process involving inspections and operation testing to identify, correct, and improve existing systems operation to improve energy-efficiency, overall performance and reliability.  It is often performed by outside technicians managed by a commissioning authority, but can be a team comprised of in-house staff and outside technicians.  According to ASHRAE the average existing commercial building in the US can save from $.12 to as much as $.45 per square foot in operating costs through implementing retro-commissioning. BACK


Most commercial buildings have energy savings potential associated with interior lighting.  Often this has to do with how the lighting is controlled, but can also come from factors impacting the indoor lighting conditions, such as level of controls available, making use of more natural light, and basic maintenance.  Interior lighting that provides proper visibility by IESNA (Illuminating Engineering Society of North America) standards is possible with less connected watt-per square foot than what was originally installed in most commercial buildings.  Reducing interior lighting overall wattage saves energy, but will also reduce air conditioning load for interior spaces (further reducing energy usage by eliminating some of the load on the cooling system). BACK


“Plug” load is a term used in the buildings industry to represent the collective electrical energy delivered to office equipment, personal computers, kitchenette appliances and other amenities and novelties that are plugged in to electrical receptacles.  While it may seem like a small portion of the overall energy usage of a commercial building it is actually a considerable energy user, due mostly to the fact that many plug loads operate around the clock in the average commercial building.  Much like interior lighting, opportunities for reducing this load can come from usage patterns and how those loads are controlled.  More and more of the business equipment and appliances that comprise interior plug loads in commercial buildings are available on the market with greatly improved energy efficiency when compared to their predecessors.  As was true of interior lighting, reductions in plug load will also reduce air conditioning load for interior spaces (further reducing energy usage by eliminating some of the load on the cooling system). BACK


This phase of the retrofitting process will begin to incorporate more capital intensive measures, so it is important that it is preceded by analysis, reducing interior lighting load and reduction in plug loads.  Successful completion of the previous three phases may well reduce needed capacity of heating and cooling distributed to particular spaces or areas of your building, which needs to be accounted for before any modifications to flow rates, control setting or equipment replacements are determined for distribution systems.  Not all measures undertaken in this phase are necessarily high-capital.  The analysis phase could reveal anomalies with how your distribution behaves, or is controlled; which waste energy.  These are not unusual to find in the average commercial building, and can normally be corrected through adjustments or updates to control components or logic sequences. BACK 


The final phase of the retrofitting process.  The previous phases will all shape the requirement for the central equipment in terms of peak capacity, part load capabilities and control logic.   These will likely be the most capital-intensive measures of a commercial building’s retrofit plan, but can also be the most impactful in terms of long-term energy savings.  As was true with the optimization of the distribution systems, it is possible previous phases could uncover  opportunities to improve upon existing central equipment operation through balancing, adjustments, updates to control components or revising control sequences. BACK