Compelling Case to Provide Livable Indoor Conditions
High heat and air pollution harm individual health and increase public health costs. Low-income renters in the Bay Area typically suffer these impacts more acutely than other residents as they are less likely to have air conditioning and are more likely to be located in areas with high ambient levels of particulate matter pollution (PM) from transportation and industrial activities.
The changing climate increases both the number of high-heat days, and instances of significant exposure to dangerous wildfire smoke. In addition to the environmental justice aspect, there is a strong racial justice component as well: low-income neighborhoods in the region tend to over-represent BIPOC communities.
We can immediately improve living conditions – indoor air quality and temperatures – by providing portable electric HVAC units (known as heat pumps) and air purifiers to low-income residents in impacted communities. The Fast Path to Clean Indoor Air pilot project explored the conditions for success for this approach, to determine whether the equipment makes a real difference in indoor air quality and livable temperatures, and whether this approach is cost effective.
Summary of Findings
1. Supplying equipment is not enough – people need education and support
Portable electric HVAC units
The brilliance of the portable electric HVAC units is that they provide both efficient cooling and heating. The AC aspect was immediately understood, but only 77% of surveyed participants reported using the equipment for heating. Several reminders were needed to prompt their use for heating. Furthermore, education is required for most effective use, and, even during the short duration of this project, a couple of the units needed repair.
Air Purifiers
Indoor air quality results are overall inconclusive. Participants’ survey responses reported they were using the air purifiers, but the data showed alarming spikes in fine particulate matter pollution (PM2.5) throughout the day, typically during times of meal preparation. We know that air purifiers are effective, but only when they are turned on with the windows closed. Education and ongoing reminders may increase use during cooking times, but the reluctance to increase electricity bills is likely to play a role here (see below for more).
1. The portable electric HVAC units require skilled labor to install
Skilled installation is required not just for the window interface, but also for safety. Direct experience and survey results show that the window interface assemblies are clumsy to install, and insufficient; 3-inch-plus intake and exhaust tubes must be threaded through the window and are held in place by rigid but flimsy plastic. Manufacturers need to focus their attention on improving the interface. Participants were overall skeptical that they could install the equipment themselves, which increases the likelihood that they will leave the equipment behind if they move.
2. Electric energy costs impact use of equipment
When it was stiflingly hot, people used the AC for immediate relief. Survey results indicate that electric costs are a factor for consistent use; it is unclear if it is due to a general reluctance to turn on electrical devices.
3. Ongoing support is critical for low-income communities
For very low income communities, support from local community groups will be critical to success. In addition to ongoing education about using the air purifiers, repair of the portable electric HVAC units might be required. Air purifier filter replacements are also necessary, and are typically expensive.
4. Despite the challenges, this equipment will improve health and reduce costs to the community
High heat events have severe consequences to individual health and public health costs, and according to the National Weather Service, are the leading cause of weather-related deaths in the US. UCLA researchers report both excess deaths and ER visits during high heat events. Access to air conditioning is a public health necessity. This project showed that the units helped people keep their homes below the Discomfort Index. We know that exposure to PM2.5 has severe health consequences damaging lung, heart, cardiovascular, and fetal health; there are no safe levels of exposure, and the damage is cumulative. The economic impact includes direct public health costs, loss of productivity, and premature death. Even small reductions in exposure yield significant savings. Air quality measurements do not show overall improvement in indoor AQI, but do show indoor improvements during smoke events. All survey respondents said they felt purifiers had improved their indoor air quality.
1. Implications for Policy Development
Low-income communities need intensive support, not just equipment-
- Skilled installation to manage the window interface and safety issues around potential outlet overload
- Extensive and ongoing education about when and how to use the equipment
- Ongoing support for repair, maintenance, and supplies
- Successful programs will include on the ground participation by trusted community organizations, and with capacity for multilingual outreach
Extensive education is required about the severe health impacts of air pollution
- The general population is not aware of how harmful air pollution is, and how important it is to reduce exposure
- Air purifiers don’t take that much energy and protect households’ health
People need to be educated about heat pumps
- The terminology is inaccessible, and a better description would better convey that they offer both heating and cooling. In this report, we sometimes use “portable electric HVAC units” to convey that they both heat and cool
- As temperatures rise, portable heat pumps serve an important interim role in the transition to all electric appliances. People are buying room air conditioners now, and need to understand the benefits of the heat pump technology
Incentives need to be simplified and provided at the point of sale
- People will choose heat pumps if they’re cheaper
- The incentive discount and efficient heating function need to be highlighted
Scaling the program
The project has opened up opportunities at the state level faster than anticipated, which is a great outcome. The Fast Path team submitted a proposal to the California Public Utilities Commission’s CalMTA program to continue exploring how to most effectively get portable electric HVAC units into low-income homes and they are conducting a similar, bigger study based on our initial results. Included in the scope of their project is working with heat pump manufacturers for product improvements. The 350 Bay Area team will use the results of this project to develop policy frameworks and to reach out to local governments to educate them about this approach, and the benefits of providing this equipment to low-income communities.
The Project
350 Bay Area provided 30 low-income tenant households with electric portable HVAC units (efficient heat pumps that both cool and heat), providing livable indoor temperatures and offering the opportunity for efficient heating that can reduce the use of methane. We also supplied participants with air purifiers, so that tenants can stay in their homes during high heat/high smoke events while consistently reducing their exposure to harmful particulate matter pollution. Each household was supplied with one air purifier for the larger living and kitchen area, and one smaller air purifier for each bedroom. Each household also received an air quality monitor that tracked and stored air quality and temperature data, which we could periodically remotely collect. We also provided energy monitors for the equipment.
Low-income renters do not typically have access to air conditioning in their units. Expensive renovations lead to increased rents, and portable HVAC equipment is expensive enough to be out of reach to most low-income households. Consumers are generally not aware that heat pump AC units come with heating capacity and are more efficient than gas-powered alternatives.
The main goal of the project was to test the approach of providing free portable electric HVAC units and air purifiers to improve indoor air conditions, improving indoor temperatures and indoor air quality quickly, instead of relying on landlord renovation projects to install AC and/or electrify HVAC systems.
Project Background: Participants and Equipment
350 Bay Area served as the project lead, sourcing and managing the installation of the equipment, data gathering, and reporting. 350 Bay Area is a San Francisco Bay Area regional nonprofit working to pass policies reduce emissions that harm health and cause a warming climate.
El Concilio of San Mateo County is a community organization that supports very low income community members, connecting them to government and nonprofit services. El Concilio identified 30 low-income households from the population they serve that could most benefit from this equipment.
The Redwood Energy team conducted the analysis and provided language support. Redwood Energy is an engineering design firm focusing on all-electric affordable multi-unit housing, and they also engage in policy advocacy and research.
Lonny Grafman, Instructor of Sustainable Design at Cal Poly Humboldt, assisted with the study design and reporting.
350 Bay Area is grateful for the contributions of this team. Redwood Energy and El Concilio of San Mateo County were professional, capable, and reliable partners, and a true joy to work with. We are also grateful for the TECH Clean California program for providing a generous grant and other program support, and for the Redwood Family Trust for providing financial support and advice (the Redwood Family Trust is not associated in any way with Redwood Energy.)
Did this equipment improve indoor temperatures for the participants?
The portable electric HVAC units are effective. Using indoor temperature and air quality data from the Qing Ping air quality monitors (QPs) and comparing it to outdoor weather data, we show that the heat pumps shaved off temperature peaks. Throughout the study, on aggregate the daily max median home temperatures were between 65° F and 85° F (Figure 2). On the warmest days, max indoor temperatures were about 10 degrees lower than outdoors, and during the coldest days the homes stayed about ten degrees warmer.
77% of respondents reported using the heat pumps for heating. Survey respondents reported that before they had access to the portable heat pump:
- 53% heated their homes with small electric room heaters;
- 35% used a gas wall furnace;
- 12% said they do not use any heaters.
Considering some participants said they did not use the heat pump for heating, and that 12% said they do not use any type of heating prior to the study, the findings suggest that for some homes the indoor temperatures may already be comfortable enough in the winter without the heat pump, or residents compromised on comfort. In contrast, 92% of respondents to our first survey, collected during the summer, said they use the heat pump for cooling.
Comments from surveys support the effectiveness of the heat pumps during the summer (transcribed from interviews and translated from Spanish):
“I’m grateful to be able to participate. The heat has been so manageable with the heat pump.”
“The AC is so helpful, especially living on the second floor. Before I couldn’t sleep in the heat.”
During a heat wave in October of 2023, temperatures reached over 90 degrees outside from 10/4 to 10/8. To assess indoor comfort during this heatwave, we calculated the Discomfort Index (DI), which includes both temperature and humidity and gives a better measure of comfort. Heat pumps also dehumidify, so peak humidity levels were also reduced within the homes in this study, compared to the outdoors.
Figure 3 shows that the median hourly DI across all the participants during the heat wave never crossed the threshold for even mild discomfort. The Mild designation is 50% of the population feeling discomfort. Moderate levels mean most feel discomfort, and Severe is all of the population feels discomfort. The portable heat pumps reduced peak indoor temperatures and humidity within homes: indoor temperatures stayed within safe levels.
For individual homes (Figure 4), 15 homes experienced some mild discomfort. However, the other 10 homes did not experience any hours even in the Mild Discomfort range (and are not shown on the figure below): no homes experienced moderate or severe discomfort hours. Outdoor weather stations in Palo Alto, San Carlos and the San Francisco Airport show 15% of hours during the heat wave days experienced moderate and severe discomfort. Though some homes experienced mild discomfort, the intensity of discomfort was greatly reduced.
Did this equipment improve indoor air quality for the participants?
Overall, the data do not reflect a consistent, general improvement to indoor air quality from providing air purifiers. It appears that cooking contributed the most to poor indoor air quality, with spikes in PM2.5 observed for all homes during typical cooking times, though participants reported using the air purifiers: 42% said they used them all day, and 42% reported once a day, and all respondents said that they feel the air purifiers improved air quality in their homes. Comments from surveys support the effectiveness of the air filter (translated from Spanish):
“I really like the help with the installation and the heat pump and air purifiers help so much, and I have asthma.”
“I can feel the difference and my allergies have lessened due to the changes.”
Looking at Figure 5 below, 95% of the time PM2.5 (x axis) was at or below 50 PM2.5 ug/m3 indoors. Indoor values ranged up to ~1000 PM2.5, though spikes in the 60-200 range were more common. The max outdoor values were 95-270 PM2.5, but indoors was 362 to ~999.
Although high spikes in PM2.5 were observed in the participant’s homes, 60% of the time the PM2.5 levels were under 9 ug/m3, which is the EPA’s standard for PM2.5. For the outdoor locations, the time under this level was 74% of the time.
In September of 2023, fire smoke made its way to the Bay Area, degrading both outdoor and indoor air quality. During this event, measurements show that the participant median PM2.5 was lower than outdoors by about 10 ug/m3. This suggests that participants may have been using their air filters at this time to reduce the PM2.5 in their homes (Figure 6, below).
The data clearly shows that indoor activities, likely cooking, are driving PM2.5 values to dangerous levels in homes. This points to a broader issue of the need for education and general public awareness about how to manage indoor air quality. Simply supplying air purifiers alone is not sufficient and reminders about how and when to use the air purifiers are required.
Is this approach affordable for low-income recipients?
Generally, very low-income households have no room for additional expenses. Free equipment is welcomed and appreciated, but ongoing support is required for filter replacements, and filter replacements will likely need to be supplied directly. Financial support for filters may understandably be redirected to other pressing needs. During the study, repairs were necessary for two of the heat pumps, one due to manufacturer problems and one due to improper care in the home. Filter replacements are expensive as well. For the Medify units we provided, filter replacements range from $36 to $43 each, for a small family, that can add up to more than $100 a year. Without ongoing support, the air purifiers are likely to become inoperable.
Some participants reported that the cost of operating the equipment was too high, so they stopped using it. PG&E utility bills have been going up because of rate increases, even for those on PG&E’s subsidized plans. From our survey, 53% of respondents noted that their energy bill had gone up, 18% said it went down, 18% said it had not changed, and 12% were not sure if their bill changed.
Some respondents noted that they were worried about operating the equipment due to cost, 47% said they were worried about the energy cost of the heat pump, and 30% said they were worried about the energy costs of the air purifiers. The costs – filter replacements and anticipated operating costs – are a barrier to appropriate adoption and use. This is a broader social issue as well: many in our community struggle with even minor incremental costs. We analyzed six participants’ energy use and bill data (See Appendix 2). The research team reached out to all participants multiple times to get more data, but it was challenging to get a larger sample size of utility data. As a caveat, the data presented is not normalized by weather data, and in general it is hard to tease out the reasons why energy use increases or decreases in a home (for example, perhaps a new person moved into the house). Also, the individual energy monitors on the heat pump and air purifiers were abandoned earlier in the project due to likely improper use and inconclusive results, so the utility data is our sole resource on providing a snapshot of energy use in the participant’s homes.
Looking at the average monthly reporting for the homes for which we have data (Table 1 in Appendix 2), the electricity use from July to September increased by 90 kWh, and subsequent utility costs increased by $29, compared to the same time frame from the year prior. Electricity energy use was expected to increase because the homes did not already have cooling or air filters at the beginning of the study. The range of utility bill impacts were from -$3 to $103 per month on average for summer from the utility data.
QP02, QP18, and QP30 (we keep the household identifiers anonymous by referring them to the QingPing air quality monitor numbering system) clearly had an electricity use peak in August, likely at least partially due to using the heat pump for cooling. These three homes had a range of $30-$100 increase in their bill compared to last year July-September, and an increase of 68-320 KWh on average per month or 2 to 10 KWh on average per day. This energy use is comparable to other studies conducted by Redwood Energy where they found that portable heat pump energy use varies from 5 to 30 kwh/day. This cost range also tracks with the survey responses we received asking respondents to report how much their bill has changed. The respondents reported a bill increase in the range of $30 to $250 monthly.
One of our goals was to also assess if gas use went down. All six homes reporting data decreased their gas usage looking at the time period from December to January in 2023 and 2024. On average, gas energy use decreased by 17 Therms, and the subsequent utility cost decrease was $13. Although it is not known exactly why gas usage decreased, both QP17 and QP20 both had spikes of electricity energy use in January, suggesting these homes may be using the heat pumps for heating (see Appendix 2).