Heat pumps: Coming to a home near you?

Washington building code proposal prompts debate as Inflation Reduction Act could spur Heat Pump use.


Karl Johnson was just looking for a way to keep his Corbin Park home, built in the early 20th century, comfortable.

The gas-fed furnace was on its way out, and his central air conditioner had already failed. To cool the home, Johnson had several portable units running throughout the day in the summer, belching hot air back into the rooms and driving up his energy bill each month.

“At some point, it’s just insanity to keep up with trying to address the issue,” Johnson said.

So he started researching central air systems online and settled on a heat pump for his home – a combination heating and cooling, electrified system that policymakers and the White House have been pushing as a method to reduce greenhouse gas emissions.

Democrats’ Inflation Reduction Act, which passed the Senate by a razor-thin 51-50 vote on Sunday, includes a major boost for climate-friendly energy systems, including heat pumps. 

The bill includes rebates and incentives for the purchase of heat pumps for both air and water conditioning in residential structures. The legislation would provide rebates of up to $8,000 to install heat pumps in homes for the next decade, according to Bloomberg. Those who wouldn’t qualify for the rebate could still get tax credits of up to $2,000.

The inflation act also piggybacks on a decision made by President Joe Biden in June to use the Defense Production Act to spur domestic production of appliances that help curb carbon emissions, including heat pumps, by providing $500 million in that effort, according to The Hill.

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Do DIY air filters work against California wildfire smoke? What to know about cost and safety

Do-it-yourself air filters are safe, effective and can be used to protect your lungs from California wildfire smoke.

Wildfire smoke is harmful and can stretch hundreds of miles. The smoke from the 2021 Dixie Fire in California was felt as far as Denver, The New York Times reported. Here are two safe options, according to the University of California, Davis, the U.S. Environmental Protection Agency and the California Air Resources Board.

Good air filters can remove dangerous smoke particles from your home. According to the California Air Resources Board, indoor air cleaners help filter out small particulate matter that can cause health concerns.

Wildfire smoke produces harmful air pollutants that can aggravate existing health problems and increase the risk of heart attack or stroke.

The resource board recommends using a certified air cleaner whenever the air quality index is at an unhealthy level, which you can check at AirNow.gov. The agency also says if a board-certified commercial system is not an option for your home, a DIY is an OK alternative.

“These temporary air cleaners should be used with extreme caution, and only if other air cleaning options are unavailable,” the board writes on its website. It says never leave the device unattended and only use box fans manufactured in the last 10 years (after 2012), as those fans “will have a fused plug, which will prevent electrical fires if the device is knocked over.”

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cover of Journal of Building Engineering

Modeling Impacts of Ventilation and Filtration Methods on Energy Use and Airborne Disease Transmission in Classrooms

Lowering the potential of airborne disease transmission in school buildings is especially important in the wake of the COVID-19 pandemic. The benefits of increased ventilation and filtration for reducing disease transmission compared to drawbacks of reduced thermal comfort and increased energy consumption and electricity demand are not well described.

A comprehensive simulation of outdoor air ventilation rates and filtration methods was performed with a modified Wells-Riley equation and EnergyPlus building simulation to understand the trade-offs between infection probability and energy consumption for a simulated classroom in 13 cities across the US. A packaged heating, ventilation, and air conditioning unit was configured, sized, and simulated for each city to understand the impact of five ventilation flow rates and three filtration systems. Higher ventilation rates increased energy consumption and resulted in a high number of unmet heating and cooling hours in most cities (excluding Los Angeles and San Francisco).

On average, across the 13 cities simulated, annual energy consumed by an improved filtration system was 31% lower than the energy consumed by 100% outdoor air ventilation. In addition, the infection probability was 29% lower with improved filtration.

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Seeley Climate Wizard Hybrid: Packaged Roof Top Unit with Integrated Heat Pump and Indirect/Direct Evaporative Cooling

A packaged heating, ventilation, and air conditioning (HVAC) system is an integrated piece of mechanical equipment that provides all three mechanical functions for a space. Packaged roof top units (RTUs), which are the baseline technology assessed in this study, are the predominant method of building conditioning in California. It is estimated that 75% of commercial building floor area in California is conditioned with packaged systems [1]. The emerging technology assessed in this study is the Seeley Climate Wizard (CW) Hybrid, which is a packaged RTU that integrates a heat pump with an indirect-direct evaporative cooling (IDEC) system that is designed as a direct replacement for a traditional RTU. This project evaluates the Climate Wizard (CW) Hybrid, manufactured by Seeley International, in a field study and compares its performance to a baseline packaged RTU.

The CW Hybrid combines an indirect-direct evaporative cooling (IDEC) system with a heat pump, which results in the energy saving benefits of evaporative cooling with the capabilities of a heat pump. The IDEC system portion of the CW Hybrid operates with 100% outdoor air filtered by MERV 13 filters on the inlet. The system operates using both indirect and direct cooling in series by passing the air through an indirect evaporative heat exchanger followed by direct evaporative media. The resulting supply air is below the wet bulb temperature of the ambient air, meaning that comfort can be maintained in buildings in dry climates like California using significantly less electricity than compressor-based air conditioners. The single-speed heat pump side of the system can provide either heating or cooling based on the position of the reversing valve. The supply air on the heat pump is recirculated from the room and filtered with a MERV 13 filter.

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small wireless ventilation sensor outside an office

Addressing Need for Low-Cost Ventilation Screening Tool in a Pandemic World

COVID-19 has permanently or temporarily altered numerous aspects of our lives. As a testing, adjusting and balancing provider, NorthWest Engineering Service, Inc. was one of many entities to immediately recognize the importance of ventilation and ASHRAE recommended air changes per hour in mitigating the effects of coronavirus. In fact, ventilation is arguably one of the more important recommendations being discussed in the first months of the crisis.

Unfortunately, the answer was not as simple as maximizing outside air and walking away – that is a temporary solution at best. It is important to recognize the energy and equipment lifetime impacts that can happen when HVAC systems are called upon to operate beyond design intent.

The ideal solution, technically, would be to undertake a full room-by-room TAB project to make sure all building occupants are breathing properly diluted air in every part of every room.

But this is certainly not the ideal solution from the standpoint of budget. In particular, clients with many, multi-story buildings, like hospitals, colleges and large school districts, don’t typically plan for a campus-wide TAB project in a single year. And even if money can be found, more time cannot.

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Research Team Selected for $4.6 M Department of Energy Award to Advance Concentrating Solar-Thermal Power

Concentrating solar-thermal power technologies can help eliminate carbon dioxide emissions from the energy sector. UC Davis and eight partnering institutions were selected to receive $4.6 M from the Department of Energy to advance high temperature receiver development for industrial process heat and solar thermal power generation. The team, led by Vinod Narayanan and Erfan Rasouli at UC Davis, will design, develop, and de-risk a 150-kilowatt solar-thermal receiver able to heat supercritcal carbon dioxide or air to temperatures from 600-900°C.

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A District Energy System Design Could Cut More Emissions for Proposed Davis Innovation Sustainability Campus

Report analyzes greenhouse gas emissions of two heating and cooling systems

Homes and businesses use over 25 percent of California’s energy. With a number of different space heating and cooling technologies available to developers, it is important to understand and quantify potential greenhouse gas (GHG) impacts.

A study, completed by the UC Davis Western Cooling Efficiency Center (WCEC), analyzed the GHG emissions for two different heating and cooling options for a proposed development in Davis – the Davis Innovation Sustainability Campus (DiSC). Researchers analyzed GHG emissions for: 1) the proposed all-electric, high-efficiency design, which would use packaged heat pump equipment for heating and cooling the buildings and 2) a potential upgrade to an all-electric, very high efficiency design, which would use a district energy system. A district energy system uses a central plant heat pump and chiller to heat and cool water that is piped to buildings for heating and cooling. 

“Based on predicted energy consumption data provided be Trane, we found that a district energy system could further improve energy efficiency by 26%, reduce total energy consumption by 14%, and reduce GHG emissions by 16% over the already highly efficient proposed design,” said lead researcher David Vernon, Co-Director of Engineering for the UC Davis Western Cooling Efficiency Center.

DiSC energy system options
DiSC is a proposed development that would build new residential, office, laboratory, and manufacturing buildings on the eastern edge of Davis. The developer team is required by the Davis City Council to build an all-electric design with an energy efficiency level 30% more efficient than required by Title 24 building codes.

“The developer funded us to look at a district energy system design with large thermal energy storage because it has the potential to greatly reduce GHG emissions,” Vernon said. “It can help stabilize the grid by using energy when renewable generation is high and reducing energy consumption when renewable generation is low.”

To meet California’s climate goals requires large increases in renewable energy generation, energy storage, and load shifting technologies. District energy systems with large thermal energy storage have the potential to be an effective energy storage and load shifting strategy. The WCEC mission is to advance design, monitoring, and objective reporting of the performance of these types of technologies to inform policy and economic decisionmakers.

Energy modeling and analysis
The heating, ventilation, and air conditioning (HVAC) manufacturer Trane completed energy models of the proposed baseline and district energy system designs and provided the hourly energy consumption results. The WCEC researchers then used these hourly energy consumption results to calculate Time Dependent Valuation—a metric that incorporates the social and environmental impacts of energy used to evaluate energy efficiency, total energy consumption, and GHG emissions of the designs.   

“Our analysis shows that district energy systems offer significant opportunities to reduce energy consumption and GHG emissions compared to more common HVAC designs,” said Vernon. “It is important to note that our results are on the conservative side, and implementation of this design could result in even larger GHG savings.”

This study was funded by Ramco Enterprises, Inc. and the Buzz Oates Group of Companies.

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WCEC Alumni

Our students and staff go to work for a variety of industry, academic, public, and non-profit organizations. You will find our alumni in the following places.

Associate Engineer, Gas Transmission Systems, Inc

Banks Integration Group

Bio-Rad Labs

California Energy Commission

CBS Interactive




Consultant, Navigant


E la Carte Inc.

EcoAgriculture Partners

Electrify My Home

Embryo Engineering

Financial Analyst, Vision One Credit Union


GE Transportation

Integral Group

Lawrence Berkeley National Lab

LightRiver Technologies

Load and Dynamics Engineer for Northrop Grumman

Lockheed Martin


McMillen Jacobs Associates

MCR Performance Solutions

MHC Engineers, Inc.



National University of Science & Technology, Karachi.

New Relic, Inc.

Northrop Grumman

Northrup Grumman

Pacific Gas and Electric Company

PARADIGM Structural Engineers, Inc.


Project Waves

Residential Design Services

Sacramento County



State Water Resources Control Board


UC Berkeley

UC Davis

UTC Aerospace Systems

ZAP Engineering & Construction

Market Transformation Research Group Publishes Study on Human Factors and Indoor Air Quality in Schools

Classrooms are often under-ventilated, posing risks for airborne disease transmission as schools have reopened amidst the COVID-19 pandemic. 

While technical solutions to ensure adequate air exchange are crucial, this research focuses on teachers’ perceptions and practices that may also have important implications for achieving a safe classroom environment. 

We report on a (pre- pandemic) survey of 84 teachers across 11 California schools, exploring their perceptions of environmental quality in relation to monitored indoor environmental quality (IEQ) data from their classrooms. Teachers were not educated regarding mechanical ventilation. Errors in HVAC system installation and programming contributed to misunderstandings (because mechanical ventilation was often not performing as it should) and even occasionally made it possible for teachers to turn off the HVAC fan (to reduce noise).

Teachers did not accurately perceive (in)sufficient ventilation; in fact, those in classrooms with poorer ventilation were more satisfied with IEQ, likely due to more temperature fluctuations when ventilation rates were higher combined with occupants’ tendency to conflate perceptions of air quality and temperature. We conclude that classroom CO2 monitoring and teacher education are vital to ensure that teachers feel safe in the classroom and empowered to protect the health of themselves and their students.

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WCEC Newly Published Journal Article on Greenhouse Gas Emission Forecasts for Residential Heat Pumps

This study aims to inform policymakers about the greenhouse gas emission impacts of heat pump deployment in residential homes.

Electric heat pumps eliminate direct burning of fossil fuels in homes but result in indirect emissions due to fossil fuels burned for electricity production.

This paper presents the first detailed emission forecasts for operating either a heat pump or gas furnace for residential heating over a 15-year period, starting in year 2022 through 2036, in six regions across the US. The study accounted for long-run marginal emissions from electricity generation, emissions from natural gas combustion in homes, and fugitive methane and refrigerant emissions from leaks.

The population weighted US average results show emission reductions for a heat pump over furnace to be 38–53% for carbon dioxide, 53–67% for 20-Year global warming potential (GWP), and 44–60% for 100-Year GWP, with reductions increasing over time. The impact of fugitive emissions from the furnace is significantly higher than that of the heat pump. While more energy efficient construction reduces overall emissions for both heating types, the forecasted percent emission reduction for replacement of a gas furnace with heat pump was not impacted by changes in home construction parameters.

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