Protocol for maximizing energy savings and indoor environmental quality improvements when retrofitting apartments
Highlights
► Many building energy retrofits will impact indoor environmental quality. ► New retrofit selection method addresses energy, indoor environmental quality, costs. ► In 17 apartments, bathroom and kitchen fans had low flows or no exhaust to outdoors. ► Via $7700–12,700/apartment retrofits, we project 17–27% energy savings and better indoor environments.
Introduction
The U.S. is striving to improve the energy performance of housing in order to reduce carbon dioxide emissions, improve energy security, and reduce energy costs. Energy standards for new homes are being strengthened and various programs are underway to retrofit existing homes for energy savings. The largest retrofit program is the Federal Weatherization program targeting low-income populations that receive public assistance to pay energy bills. The Federal Weatherization program focuses on cost-effective retrofits, considering retrofit costs and energy savings; however, the legislation that initiated the program identified improved health as an additional goal [1]. Many energy retrofit programs are now underway, often implemented by energy utilities.
A variety of protocols, tools, and standards are available from energy utilities and state, federal and private energy organizations as well as from research projects to guide the selection and implementation of energy retrofits for homes [2], [3], [4], [5], [6], [7], [8], [9], [10]. Additionally, more sophisticated and time consuming algorithm-based approaches to identify retrofit strategies exist [11], [12]. The above-mentioned protocols, tools, and standards seek to maximize energy savings per unit expenditure, and often employ energy modeling, cost-benefit estimation, and engineering judgment. Ma et al. present an overview of methodologies widely used for selecting energy retrofits [13]. The existing protocols and tools, and much of the retrofit activity, emphasize single-family homes. If the U.S. is to meet energy policy goals, multi-unit housing, serving 20% of the U.S. population [14], must also be retrofit. Challenges faced include split incentives, with tenants paying energy bills and owners paying for retrofits. Additionally, many buildings have heating, ventilation, or water-heating equipment serving multiple apartments with associated costs split among residents – a disincentive to energy efficient behaviors. One approach has been to retrofit entire buildings; however, the required capital outlays can be prohibitive. Relatively few studies have focused on apartment-level retrofits.
Many energy retrofit measures will influence indoor environmental quality (IEQ), including thermal comfort conditions, acoustic conditions, and levels of indoor air pollutants that affect health [6], [7], [8], [15], [16], [17]. Changes in IEQ can be positive or negative, and some retrofits will not impact IEQ. Sealing leaks to outdoors without compensating measures, a widespread practice, reduces outdoor air ventilation and increases indoor air concentrations of indoor-generated air pollutants, while reducing indoor concentrations of some outdoor air pollutants. Sealing can also increase risks of pollutant backdrafting from natural draft vented combustion appliances when exhaust fans are operated. Caulking and insulation materials installed during retrofits can emit volatile organic pollutants. Replacing a gas stove with pilot light with a pilotless stove reduces natural gas consumption and eliminates the pilot light's emissions of nitrogen oxides and fine particles into indoor air. Adding insulation to exterior walls or replacing single pane windows with efficient windows reduces heating and cooling demands and improves thermal comfort by decreasing drafts and reducing thermal radiation to cold walls and windows. Table 1 lists the expected energy and IEQ impacts of several of the retrofits that are expected to significantly impact both energy and IEQ. The IEQ benefits are often not credited as benefits in the typical retrofit selection process.
Some of the existing protocols, tools, and guides for selecting or implementing energy retrofits [2], [3], [4], [5], [10] specify diagnostic measures and associated procedures to prevent retrofits from causing combustion pollutant backdrafting or spillage from furnaces and water heaters. Some protocols caution about disturbance of lead-based paint and asbestos-containing materials. Some protocols require adherence to elements of the ASHRAE Standard 62.2 [18] or suggest this standard as a guide. The U.S. EPA provides protocols for maintaining or improving IEQ during home energy retrofits [10]. The EPIQR and TOBUS methods also consider IEQ aspects based on occupant survey answers [6], [7], [8]. However, IEQ improvement has not been a primary goal of most retrofit programs; consequently, the U.S. is not capitalizing on a potentially large opportunity to improve IEQ.
The objective of this project was to develop methods for selecting packages of retrofits that simultaneously save energy and improve IEQ conditions in apartments with independent space conditioning (heating and air conditioning, if present) systems. The project also sought to evaluate and demonstrate the energy savings and IEQ improvements realized through application of the protocol and implementation of the retrofits. This paper describes the retrofit selection protocol, its application in 17 apartments serving low-income populations, the selected retrofits and their costs, the projected energy savings, and the results of diagnostic measurements made before and after retrofits. Future publications will present measured impacts of the retrofits on IEQ and energy.
Section snippets
Retrofit selection protocol
We developed a point-based protocol to account for retrofit costs and the expected impacts of retrofits on energy use, indoor air quality (IAQ), and comfort. Point assignments for specific retrofits, drawn from a list of candidate retrofits, were based on modeled energy savings, modeled changes in indoor air pollutant concentrations, and some professional judgments. Data obtained from apartment inspections and diagnostic measurements were used in the calculation of points. The sum of points
Buildings and apartments selected for retrofits
Major characteristics of the study properties and apartments are summarized in Table 2. The buildings were located in Sacramento (B1), Richmond (B2) and Fresno (B3). Climate conditions for these cities – specified in terms of heating and cooling degree-days are provided in Table 2. B1 apartments were retrofitted in summer; retrofit of B2 and B3 apartments occurred in winter.
In B1, we selected 3-bedroom (3BR) and 4-bedroom (4BR) apartments because they had gas heaters (a target characteristic)
Discussion
This paper presents a unique protocol for selecting energy and IEQ retrofits, and documents the use of this protocol. As illustrated in Table 1, many of the retrofit measures are expected to simultaneously save energy and improve some aspect of IEQ. The potential for retrofit packages to simultaneously improve both energy and IEQ appears high; however, the actual impacts have not yet been quantified for the apartments in this study.
The retrofit selection protocol has several strengths and some
Conclusions
There are opportunities to simultaneously save energy and improve IEQ when apartments are retrofit; however, IEQ is normally not considered at the time of retrofit selection. This paper provides a protocol for selecting retrofits based on predicted energy and IEQ benefits, retrofit cost, and initial apartment conditions. Examples of retrofits selected via this protocol include air sealing coupled with application of energy efficient ventilation equipment, replacement of gas ranges with pilot
Acknowledgments
Funding was provided by the California Energy Commission, Public Interest Energy Research Program, Energy Related Environmental Research Program, through contract 500-09-022 and by the Assistant Secretary for Energy Efficiency and Renewable Energy, Building Technologies Program of the U.S. Department of Energy under contract DE-AC02-05CH11231. The authors thank: Rick Diamond and Iain Walker for technical advice; Jim Fitzgerald and Terry Brennan for input on retrofit specifications and costs;
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