Grantee Research Project Results
Final Report: Green Retrofitting Residential Buildings
EPA Grant Number: SU833558Title: Green Retrofitting Residential Buildings
Investigators: Peters, Catherine A. , Oliver, Ben , Parushev, Doba , Chua, Dora , Weissinger, Emily , Johns, Katrina , Yang, Regina , Borchard, Sam , Anderson, Stuart , Liang, Yin
Institution: Princeton University
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 30, 2007 through August 29, 2008
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2007) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Awards , Sustainable and Healthy Communities
Objective:
Our world faces an impending energy crisis due to overreliance on fossil fuels. As our stores of fossil fuels run low, China, India, and other countries around the world are modernizing and increasing their energy use, and the threat of human-induced global climate change is increasing. Half of the United States’ 23% consumption of the world’s energy is from buildings. Organizations like LEED and the SBIC are working to make new building designs as efficient as possible, but very little work is being done to improve existing buildings, which is the focus of our work. Our specific focus is on the diametric relationship between air exchange and energy efficiency in buildings. The relationship is conceptually simple, but often goes unacknowledged in the industry – homeowners are advised to conserve energy and decrease their heating bills by sealing up the leaks and cracks in their home; rarely is it mentioned that this can adversely affect indoor air quality. According to Dr. Richard Corsi (UT 2006), “… exposure of Americans to toxic substances is dominated by what we breathe and touch while we are indoors,” and “If you put indoor radon and indoor air pollution together, they are by far the number one environmental threat to the American public.” Information regarding this threat to human health needs to be well publicized for homeowners. Additionally, quantitative tools need to be made available to homeowners trying to navigate complex retrofitting decisions.
To address these concerns, we began work on objectives in three areas of increasingly broad scope. The first area of focus was collaboration with the team’s original partner, the Stony Brook-Millstone Watershed Association, hereafter referred to as “The Watershed Association.” The team’s objective in this area was to provide the Watershed Association with the information necessary for them to transform an existing residential structure, the Buttinger Nature Center, into a model of efficient and renewable energy. The team performed a wide range of assessments on the building. In spring of 2007 we conducted an air exchange test as a measure of indoor air quality in the building. Using this data and other measurements, team members constructed a mathematical model of the thermal flows in and out of the building to analyze heat loss. From spring to fall of 2007, the team collated and analyzed several years of historical data related to the building’s photovoltaic array and “grid” electric consumption to increase the understanding of electricity usage patterns and suggest areas for improvement.
Our second objective for Phase I was to quantify air exchange rates – a key factor in air quality – in typical American homes and relate these rates to specific house features. To collect data for this analysis, the team began a study of air exchange rates in homes in the Princeton area. The team used a blower door test at each house to measure the air exchange rate. To supplement the data collected from the blower door tests, the team gathered data on a number of factors that could potentially affect home air exchange rates and energy efficiency using a questionnaire, which also increased awareness about the interrelated nature of energy efficiency and air quality. This study provided the foundation for our third area of study, and offered the local community a valuable service.
Our third objective was the creation of a quantitative online tool to share the results of our study with the public. We named the tool Greentrofit™ – a combination of the words “green” and “retrofit.” Greentrofit™’s goal is to assist homeowners in estimating and understanding their home’s air exchange rate and energy consumption by providing them with quantitative information based on the statistical correlations determined during our study. Greentrofit™ was written in the Java programming language using modular design.
Summary/Accomplishments (Outputs/Outcomes):
Watershed Association:
Analysis of the data from the air exchange test at the Nature Center showed an approximate air exchange rate of 0.56 air changes per hour (ACH), meaning that the air within the building exchanges completely with outside air every 2 hours. A second test, using the blower door method calculated the rate to be 0.53 ACH, confirming the results of the initial test. The mathematical model provided insight into the energy use of the Watershed Association’s facilities, showing that the majority of heat loss occurs through the radiative transfer of the windows and air leakage. Analysis of the data from the solar panel inverters and monthly meter readings showed that the 15kW array has met approximately 89.2% of the Watershed Association’s power needs since the completion of its installation. All results from these studies were reported to the Watershed Association.
Air Exchange Rate Study
The raw data from the blower door were analyzed, revealing a large range of air exchange rates, as shown in Figure 1. The homes we tested have rates varying from 0.2 to 2.1 ACH. The mean air exchange rate is 0.9 ACH, the median rate is 0.7 ACH, and three of the homes have air exchange rates near or below 0.35, the minimum for healthy air for humans as suggested by ASHRAE.
Figure 1 - Histogram of Air Exchange Rates from Study
One home surveyed during the study adopted a series of low-cost retrofits (less than $50), consisting mainly of weatherstripping, after our test. We performed a second test on the house after these retrofits were put in place and found a large decrease in the air exchange rate from its initial value of 1.35 ACH to a final value of 0.69 ACH.
Greentrofit™
The team completed a prototype design of the Greentrofit™ online tool. Greentrofit™ is implemented via five main modules that collect user input, process the data using the regression equation in Figure 2, and output the results to the homeowner. Each module of the program is designed so that it can be independently modified or exchanged as our model expands and improves.
ACH = -.0001A + .0001Aa-u + .0001Ab-c + .0032N + .0018W + .2444D
A = Total Area Ab-u = Unconditioned Basement Area W= # of Windows
N = House Age |Aa-u = Unconditioned Attic Area D=#of Doors
Figure 2 - The statistical relationship used in Greentrofit™ was determined by performing multivariate linear regression analysis of the data from the air exchange rate study.
Greentrofit outputs the results of the analysis to the user in a comprehensible form, shown in Figure 3. The estimated air exchange rate for the home is compared to national averages and indoor air quality standards. In addition, the dynamic output allows the user to see the effects of selectable retrofits appropriate for his or her home.
Figure 3 - Screenshot of Greentrofit™ output display
Conclusions:
Since its creation, our team has made significant progress in addressing the conflicting information available regarding energy conservation and air quality in residential environments. The team has and will continue to increase awareness of the effectiveness, costs, and risks associated with green retrofitting in homes. We have created and will continue to refine quantitative, predictive tools to help homeowners navigate the complex decisions that surround energy efficiency and human health in the context of green residential retrofitting.
Our findings demonstrate the risks created by the lack of information and quantitative tools available to homeowners regarding the interaction of air quality and energy efficiency. Three homes in the study were at the threshold of the recommended minimum air exchange rate according to the ASHRAE standard, yet the homeowner of at least one of these homes was considering implementing retrofits to seal his home for energy savings. This is particularly concerning given the results from the home tested before and after retrofits, the data from which show that after the retrofits were applied the air exchange rate dropped 48.9%. Applying this finding to the homes in our study reveals that 45% of the houses we tested would fall below health standards for air exchange rates if they implemented similar retrofits.
In light of these findings, we recommend an increase in public awareness regarding the possible dangers of over-sealing one’s house to conserve energy. We urge the government to increase awareness of these issues through educational programs and endorsements of organizations that recognize the Greentrofit™ concept. The government should also increase funding for the development of quantitative tools to help homeowners make informed decisions regarding their homes and their health. These initiatives will help the general population use energy more efficiently, and do so in a safe way.
The creation of a prototype of Greentrofit™ marks the beginning of a movement to acknowledge the connection between air quality and energy conservation in the residential sector. The potential influence of such a tool extends to the entire building industry, and the universal accessibility of Greentrofit™ broadens the impact of the tool beyond the borders of the US to the entire planet. Given customized quantitative information, homeowners can make smarter, more sustainable decisions about energy efficient retrofitting and the maintenance of personal health. Full development of this tool is a major part of the plan for the Phase II project.
Phase II
While Phase I focused on laying the groundwork for Greentrofit™, the goal of Phase II will be to increase the tool’s functionality, accuracy, and exposure. During Phase II we will expand the scope of Greentrofit™ in three ways:
First, using a building provided by Princeton University, the team will conduct a detailed analysis of various retrofitting strategies, quantifying effectiveness in reducing energy consumption as well as potential detrimental impacts on indoor air quality. We will focus on the positive effects of heat recovery ventilation systems that can be used in concert with efforts to seal the building envelope. We will begin by conducting baseline tests on the house to measure an initial air exchange rate, air quality, and energy efficiency. We will then implement and test retrofits, the effects of which will be evaluated through comparison with the base values.
Second, using data from our retrofit tests, we will develop Greentrofit™ further to include more quantitative information about retrofitting strategies, expanding our current work with five common retrofits: the installation of weatherstripping, CFLs, solar panels, heat exchangers, and double-paned windows.
Third, we will begin working with a new project partner, Isles, on retrofitting solutions for low-income housing. While investments in energy efficient technology may save homeowners money in the long run, many low-income households can’t afford upfront costs with payback times of many years. As a result, little is done to improve these residencies. The team will work with Isles to analyze their low-income housing modules within the context of energy conservation and air quality. From our analysis we will recommend low-cost, realistic retrofitting strategies that improve energy efficiency without endangering air quality. This service will be directly beneficial to tenants and ultimately benefit the greater society through preservation of natural resources. Our recommendations will also aim to be applicable to low-income housing in other areas of the nation and world.
Supplemental Keywords:
energy, renewable energy, indoor air, climate change, health effects, innovative technology, Northeast, community-based,, RFA, Air, climate change, Air Pollution Effects, AtmosphereRelevant Websites:
http://www.princeton.edu/~greenfit Exit
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.