Optimizing Energy Efficiency Across a Portfolio of Buildings
For many building owners, the challenge is not just to dial down energy use in a single building, but to improve efficiency across an array of buildings. The owner’s portfolio may include a variety of structures, each with a distinct history and context, each having taken its present form as a result of its original design team, assembled contractors, operations personnel, and past and present occupants. Buildings of different ages might present the owner with a mixture of equipment, infrastructure and control technologies that range from state-of-the-art to Art Deco era. Incorporating energy efficient building systems across this mix requires a property owner to understand the nature of each building and match unique characteristics to available options.
The optimal approach to increasing energy efficiency will vary from building to building. In some sites, a comprehensive retrofit project will produce the most energy efficient building system—reducing energy consumption by 25-50%. In other buildings, technical and financial constraints may prevent a retrofit project in the near term. In these cases, it is often desirable to implement low-cost and no-cost maintenance and behavioural changes.
How does an owner account for differences within a portfolio without having to start anew at each doorstep? The owner must account for features unique to each situation while maximizing the ability to apply solutions across the board, or at least across the street.
When it comes to assessing opportunities for efficiency across a portfolio, it is important to consider the unique characteristics of each building, but also to see how similarly situated buildings can be managed under similar strategies. A crucial early step is to find common denominators—to group buildings within the portfolio under solutions that fit that type of structure.
The chart below illustrates this type of portfolio planning for a sample organization. Like most collections of buildings, this portfolio is diverse – some buildings are old, some are new, some are large and complex, some are small and relatively “simple,” some have modern digital controls and others have none. The chart breaks up the total square footage of this portfolio into four “buckets” that are representative of different approaches to efficiency improvements.
Factors to Consider
Some of the most important factors to consider when sorting buildings within a portfolio include:
Renovation schedule: integrating a whole-building retrofit project into existing plans allows for major reductions with attractive financial terms. The Empire State Building recently announced a retrofit as part of its capital improvement program that will reduce energy consumption by 38% with a simple payback of only three years.
Expansion of cooling capacity: With tenants demanding higher levels of cooling because of higher occupant density, increased plug loads or the addition of data centers, many buildings are seeing a need to add cooling capacity. A retrofit of the building shell can eliminate the need to add equipment by improving the thermal efficiency of the building system.
Real estate plans: If a building is likely to be sold in the near future, ownership will likely avoid big investments in capital, such as infrastructure improvements or installation of high-efficiency mechanical equipment.
Size: The engineering effort required to design and execute a whole-building retrofit project should be directed to the largest impact projects for maximum savings
Vintage: Buildings older than twenty years old are prime targets for retrofits because of the large savings potential and advantage of integrating solutions. More recently constructed buildings are good candidates for either retro-commissioning (optimizing energy use for systems that were never commissioned) or re-commissioning (re-evaluating system performance and tuning to present conditions).
The US Environmental Protection Agency provides a tool to help organizations benchmark buildings across their portfolio. See the Energy Star Portfolio Manager for more information.