Many organizations make building envelope improvements as part of a comprehensive energy efficiency program. In fact, building envelope improvements often rank at or near the top of the facility team’s to-do list, since they generally provide an attractive return on investment. A simulation study conducted by the National Institute of Standards and Technology for the U.S. Department of Energy found that building envelope improvements can reduce annual energy costs by as much as 36 % in heating dominated climates. Meanwhile, the National Research Council of Canada estimates that air leakage accounts for as much as half of a typical building’s heat loss in winter.
Improving Building Envelope
An energy audit is a proven strategy for determining where, when, why, and how energy is being used in a building and identifying ways to reduce energy consumption. A well-planned and well-executed audit can provide the information that a facility executive needs to identify, prioritize, and implement the right set of energy efficiency measures—including those impacting the building envelope. An effective audit can identify those measures that can reduce energy and operating costs in an existing building by as much as 40%.
If the facility team suspects that the building envelope is leaking, they should make sure that a building integrity assessment is included in the physical inspection that is a prelude to any energy audit. During the assessment, energy engineers look for air leaks that may be causing excessive energy use, building occupant discomfort, or infiltration of particulates. They also spray water on windows, doors, roofs, and wall assemblies to pinpoint spots where water may be able to infiltrate. They create a thermal image of the building and its components to identify areas where heat is entering or leaving the building.
An energy audit usually produces an extensive list of possible energy efficiency measures that need to be selected, prioritized, implemented, and tracked. Many of these measures include improvements to the building envelope such as repairing or replacing roofing materials, adding foam or blanket insulation, repairing cracks in walls or foundation, and sealing windows, doors, and skylights. In older buildings, window replacement is often a viable option. Advances in window technology include multiple glazing and insulated windows that include low-conductivity gases between panes and use low-emissivity coatings to reduce the flow of infrared energy into the building.
Indoor Air Quality
It is important to remember that changes to the building envelope can have a significant impact on the lighting, heating, cooling, and ventilation needs. For example, a tighter building will require less mechanical heating in the winter and cooling in the summer, causing facility teams to adjust building automation system (BAS) settings. In the case of new construction or an extensive energy retrofit, building owners and operators may even have the opportunity to downsize heating, ventilation and air conditioning (HVAC) systems.
As they implement energy efficiency measures to tighten the building envelope, facility leaders will want to monitor closely and address indoor air quality (IAQ) issues and ensure proper ventilation. Poor IAQ and inadequate ventilation are considered factors that can affect the health and well-being of building occupants.
As they evaluate their building’s IAQ, facility teams and their partners will want to follow the guidelines spelled out in ASHRAE Standard 62.1. The standard defines minimum requirements for mechanical and natural ventilation systems and the building envelope to provide acceptable IAQ.
Many organizations choose to work with a third-party expert to conduct air quality tests, assess their needs, and develop an IAQ management plan. In many cases, advanced HVAC technologies are applied to enable IAQ improvements. For example, advanced BAS technology can control temperature, humidity, building pressure, ventilation, and exhaust rates for the various areas within a building. BAS technologies enable the facility team to monitor critical areas, automatically identify anomalies, and address problems.
Air cleaning technologies help control dust, particulates, odors, volatile organic compounds, viruses, and bacteria. For example, catalytic air cleaning systems use three discrete technologies to deliver cleaner air and improve IAQ. They use minimum efficiency reporting value (MERV) 13 filters to capture particles. Photocatalytic oxidation technologies help eliminate volatile organic compounds, bacteria, and other small living organisms. Ultraviolet germicidal irradiation technologies help prevent microorganisms from reproducing.
Ventilation systems need to ensure proper amounts of fresh outdoor air, according to ASHRAE 62.1, which sets minimum requirements for various space types. For example, higher outdoor airflow rates are required for schools and retail facilities than other building types.
Controlling building pressure helps prevent infiltration of hot or cold air from outside, keeps moisture out of the building envelope, and limits the entry of airborne contaminants from outdoors. Maintaining temperature and humidity within the right parameters can restrict the growth and spread of bacteria, mold, and other pathogens.
Improving the efficiency of the building envelope needs to be a part of every well-developed and well-executed energy efficiency strategy. At the same time, facility teams need to recognize the impact of building tightening on ventilation and IAQ and take a whole building approach to creating an indoor environment that considers the health and comfort of building occupants.
Maldeis, PE, CEM, is an energy solutions engineering leader for Trane, a provider of indoor comfort solutions and services and a brand of Ingersoll Rand. He is responsible for the technical development, support, and review of performance based contracting solutions and activities on a national basis. He has more than 30 years of experience as a mechanical/project engineer in building construction and energy conservation.
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