Integrated Systems Retrofits: A Strategy for Optimizing Building Energy Use

Approximately 40 percent of all carbon emissions in the U.S. are produced by buildings, with most coming from commercial and residential buildings. These buildings are significant contributors to total electricity consumption and greenhouse gas emissions in the U.S. Retrofit projects provide opportunities for existing buildings to correct their negative environmental impact and provide new benefits for tenants, such as improved indoor air quality and thermal comfort. Traditional building retrofits generate energy savings by upgrading equipment incrementally, typically as individual components reach the end of their functionality. In contrast, the Integrated Systems (IS) approach targets improvements for multiple building systems simultaneously to maximize energy and cost savings.

In order to quantify the additional savings potential for IS retrofit projects, researchers at the Lawrence Berkeley National Laboratory conducted a case study of a commercial building located in Hawaii. As part of this study, researchers compared the energy and Life Cycle Cost (LCC) savings of the IS approach to two traditional retrofit approaches: the standard practice of replacing old equipment to meet minimum code requirements and the improved practice of upgrading equipment voluntarily to meet higher efficiency standards. The researchers studied energy conservation measures, including modifications to the building envelope (the building’s exterior covering), lighting, heating and ventilation and air conditioning (HVAC) systems. Overall, the results of the simulation provided confirmation that, while the savings can vary depending on the building and climate, an integrated approach to building retrofits can lead to energy use reductions of 50 percent or greater, which is not the case with the other retrofit methods. Based on this finding, the researchers recommended that the IS approach be adopted nationwide as the industry standard for building retrofits.

Using EnergyPlus Version 6.0, the primary simulation tool supported by the U.S. Department of Energy, the authors developed three distinct models to represent each retrofit approach and determine energy savings. The IS strategy included upgrades to the window glazing and exterior shading systems, a complete redesign of the lighting system and planned replacement of existing plug loads (devices and equipment plugged into the electrical system).  Taken together, these retrofits significantly reduced cooling needs and enabled the replacement of the existing HVAC system with a more efficient natural ventilation system. The standard practice strategy included code-required modifications to the existing HVAC system in the first year and upgrades to the lighting system in the tenth year. Not regulated by energy code, the existing plug load remained unchanged in this scenario. The improved practice strategy included renovations to the HVAC system in the first year and both lighting and plug load system upgrades in the tenth year. Unlike the standard approach, the improved practice approach involved upgrades to much higher efficiency systems. Consistent with current industry practice for traditional retrofits, building envelope upgrades were not considered for the standard or improved retrofit strategies. While the IS retrofit approach required greater initial capital investment, it resulted in significantly higher energy savings of 84 percent. When compared to energy savings gained from the standard and improved approaches—12 percent and 33 percent, respectively—the IS strategy represented a clear advantage over the two more traditional retrofit strategies.

Similarly, the IS retrofit approach represented the highest LCC savings in the long term. As part of the LCC analysis, the authors compared the initial equipment and installation costs to the energy cost savings attained over the lifetime of the equipment. While the standard practice retrofit approach cost the least, savings were also considerably lower. In comparison, the IS retrofit approach cost the most, but also resulted in the biggest savings. When capital investments were adjusted to enable a fair comparison, the 20-year LCC savings for the IS retrofit were more than twice those of the improved practice results, and 30-year LCC savings were even higher.

As illustrated by the results of this case study, IS is a critical strategy for increasing energy savings and reducing greenhouse gas emissions. While the IS approach has gained more traction in recent years, barriers to IS retrofit design and application prohibit this strategy from being more widely implemented. To address these barriers to adoption, policymakers should support research that enables further cost reductions in energy efficient technologies and the development of analytical tools and best practice guidelines. In addition, policymakers should consider improving or adopting new standards for existing building retrofit programs modeled on the IS approach. Investments in these efforts will be critical for enabling continued progress toward electricity consumption and emissions goals.

Article source: Regnier, Cynthia, Kaiyu Sun, Tianzhen Hong, and Mary Ann Piette, “Quantifying the Benefits of a Building Retrofit Using an Integrated System Approach: A Case Study,” Energy and Buildings 159 (2018): 332-345.

Featured photo: cc/(Iurii Garmash, photo ID: 861291290, from iStock by Getty Images)