Iain S. Walker

Iain S. Walker
University of California, Berkeley | UCB · Lawrence Berkeley Laboratory

Doctor of Engineering

About

142
Publications
34,140
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,625
Citations

Publications

Publications (142)
Article
Full-text available
Most of the residential building stock in the US and EU was built according to the building and construction code prevailing at time of construction and have poor energy performance that contributes to higher carbon emissions. Energy and carbon reduction upgrade projects of existing residential buildings are still a niche market compared to convent...
Article
Full-text available
This work aims to characterize how home energy upgrade projects and programs in the US have evolved over the past decade. It also identifies what changes are needed to drive expansion of the US energy retrofit market in such a way that addresses carbon emissions from buildings, improves resilience and upgrades the housing stock. This review focuses...
Conference Paper
Full-text available
The upgrading of existing homes through electrification will play a critical role in the decarbonization of the residential building stock in the US. Currently, upgrade project cost is the key barrier that the buildings industry and homeowners are facing. These costs must be reduced in order for home decarbonization to scale. The buildings industry...
Conference Paper
Full-text available
Decarbonization of energy use in homes will be necessary for the US to meet its climate goals. Currently, very few homes are undergoing decarbonization upgrades and pathways are needed to scale up these efforts. This study combined a literature review, an industry survey and a project cost database in order to identify the key barriers and potentia...
Article
Full-text available
Recent studies have succeeded in relating emissions of various volatile organic compounds to material mass diffusion transfer using detailed empirical characteristics of each of the individual emitting materials. While significant, the resulting models are often scenario specific and/or require a host of individual component parameters to estimate...
Conference Paper
Unintended Infiltration in buildings is responsible for a significant portion of the global housing stock energy demand. Today, the fan pressurization method, also known as blower-door test, is the most frequently used measurement method to evaluate the airtightness of buildings and determining the total air change rate of a building or a building...
Conference Paper
The fan pressurization method is a common practice in many countries for measuring the air leakage of houses. The test results are sensitive to uncertainties in the measured pressures and airflows. In particular, changing wind conditions during a test result in some pressure stations having more or less uncertainty than others. Usually, it is neces...
Article
Full-text available
In order to meet climate goals, it will be necessary to significantly reduce the greenhouse gases emitted by homes. A key factor in the US is to reduce the on-site combustion of fossil fuels for heating end-uses and to replace this with use of electric heat pump technologies connected to a low-carbon grid. The replacement of natural gas furnaces wi...
Technical Report
Full-text available
Cost is a major barrier when upgrading homes to reduce carbon emissions required to meet DOE’s climate-related goals. This report summarizes a nationwide effort to gather home energy upgrade project cost data along with household energy performance data. The goal was to develop cost benchmarks and to guide future R&D efforts aimed at cost compressi...
Article
Full-text available
Today, the fan pressurization method is the most frequently used method to evaluate a building's airtightness. However, the localization and quantification of leaks remain difficult. In this paper, an acoustic method is introduced to estimate the leakage size of single leaks. Acoustic and airflow measurements were conducted and compared in laborato...
Article
Full-text available
This study examined the use of zoned ventilation systems using a coupled CONTAM/EnergyPlus model for new California dwellings. Several smart control strategies were developed with a target of halving ventilation-related energy use, largely through reducing dwelling ventilation rates based on zone occupancy. The controls were evaluated based on the...
Article
Full-text available
Venting range hoods can control indoor air pollutants emitted during residential cooktop and oven cooking. To quantify their potential benefits, it is important to know how frequently and under what conditions range hoods are operated during cooking. We analyzed data from 54 single family houses and 17 low-income apartments in California in which c...
Article
This paper presents pollutant concentrations and performance data for code‐required mechanical ventilation equipment in 23 low‐income apartments at 4 properties constructed or renovated 2013‐2017. All apartments had natural gas cooking burners. Occupants pledged to not use windows for ventilation during the study but several did. Measured airflows...
Article
In many countries, the fan pressurization method is the most frequently chosen approach for measuring the air leakage of houses. The measurements are usually performed at pressures that far exceed pressures to which buildings are exposed to under normal conditions. A fit of these tests to the power-law formulation allows an extrapolation to data po...
Technical Report
Full-text available
This project investigated smart ventilation approaches to minimize energy use for providing indoor air quality (IAQ) in high performance new California homes. Evaluation criteria included annual ventilation-related energy, peak energy and time-of-use savings, and the indoor air quality relative to a minimally code-compliant ventilation system. The...
Article
Full-text available
Data were collected in 70 detached houses built in 2011‐2017 in compliance with the mechanical ventilation requirements of California's building energy efficiency standards. Each home was monitored for a one‐week period with windows closed and the central mechanical ventilation system operating. Pollutant measurements included time‐resolved fine pa...
Article
Full-text available
Peak power demand strains electrical grids and increases cost of electricity generation, transmission and distribution infrastructure. Many studies have examined ways of reducing peak power demand, including modification of room air temperature setpoints or reduction of lighting levels. However, very few or no studies have examined the peak power r...
Article
Full-text available
We simulated the energy performance of smart ventilation controls based on outdoor temperature in homes located in California climate regions, designed to comply with the 2016 Title 24, Part 6 California Energy Code prescriptive requirements. The smart controls shift ventilation rates in time, but ensure an annual occupant pollutant exposure equal...
Article
Full-text available
Proper ventilation of residences is essential for occupant health and comfort, and is responsible for a significant portion of energy consumption in homes. This study examines a method for providing adequate ventilation in homes while reducing energy consumption and peak demand: “smart” control of ventilation through sensing of occupancy and modula...
Technical Report
Full-text available
This study is intended to demonstrate the potential for energy savings while providing acceptable Indoor Air Quality (IAQ) for ZNE homes. It uses the concept of Smart Ventilation where ventilation systems are designed and controlled to produce the same, or better, IAQ compared to simple, continuously operated ventilation systems. The key energy sav...
Article
Full-text available
As ventilation systems become more sophisticated (or ‘smart’) standards and regulations are changing to accommodate their use. A key smart ventilation concept is to use controls to ventilate more at times it provides either an energy or IAQ advantage (or both) and less when it provides a disadvantage. This paper discusses the favorable contexts tha...
Article
Cooking activities are a major source of indoor air pollutants. To control pollutants generated from cooking activities, a range hood is commonly used in residential kitchens. Several building codes require that a range hood be installed in new homes to control pollutants from cooking, and the required airflow rates for range hoods are specified by...
Article
Full-text available
To better address energy and indoor air quality issues, ventilation needs to become smarter. A key smart ventilation concept is to use controls to ventilate more at times it provides either an energy or indoor air quality (IAQ) advantage (or both) and less when it provides a disadvantage. A favorable context exists in many countries to include some...
Article
Full-text available
This study evaluated nine ventilation and filtration systems in an unoccupied 2006 house located 250m downwind of the I-80 freeway in Sacramento, California. Systems were evaluated for reducing indoor concentrations of outdoor particles in summer and fall/winter, ozone in summer, and particles from stir-fry cooking. Air exchange rate was measured c...
Article
In determining ventilation rates, it is often necessary to combine naturally-driven infiltration, with air flows from mechanical systems. When there are balanced mechanical systems, the solution is simple additivity, because a balanced system does not impact the internal pressure of the space or the air flows through the building envelope. Unbalanc...
Article
Full-text available
As part of a study of energy retrofits in nine California buildings indoor measurements of temperature and relative humidity were made between 2010 and 2012. The aim of this paper was to compare the temperature and relative humidity measurements in relation to recommendations for a healthy, comfortable and low energy consuming indoor environment. E...
Technical Report
Full-text available
Duct leakage often needs to be measured to demonstrate compliance with requirements or to determine energy or Indoor Air Quality (IAQ) impacts. Testing is often done using standards such as ASTM E1554 (ASTM 2013) or California Title 24 (California Energy Commission 2013 & 2013b), but there are several choices of methods available within the accepte...
Article
Full-text available
Durability of the building envelope is important to new homes that are increasingly built with improved levels of airtightness. It is also important to weatherized homes such that energy savings from retrofit measures, such as air sealing, are persistent. This paper presents a comparison of air leakage measurements collected in November 2013 throug...
Article
Full-text available
This study uses an advanced airflow, energy and humidity modelling tool to evaluate the potential for residential mechanical pre-cooling of building thermal mass to shift electricity loads away from the peak electricity demand period. The focus of this study is residential buildings with low thermal mass, such as timber-frame houses typical to the...
Article
Full-text available
Changing the air exchange rate of a home affects the annual thermal conditioning energy. Large-scale changes to air exchange rates of the housing stock can significantly alter the residential sector's energy consumption. However, the complexity of existing residential energy models is a barrier to the accurate quantification of the impact of policy...
Article
Full-text available
Today's high-performance homes are reaching previously unheard of levels of airtightness and are using new materials, technologies, and strategies for which impacts on indoor air quality cannot be fully anticipated from prior studies. This research study used pollutant measurements, home inspections, diagnostic testing, and occupant surveys to asse...
Conference Paper
Full-text available
Durability of the building envelope is important to new homes that are increasingly built with improved levels of airtightness. It is also important to weatherized homes such that energy savings from retrofit measures, such as air sealing, are persistent. This paper presents a comparison of air leakage measurements collected in November 2013 throug...
Technical Report
Full-text available
This study evaluates the energy, humidity and indoor air quality (IAQ) implications of residential ventilation cooling in all US IECC climate zones. A computer modeling approach was adopted, using an advanced residential building simulation tool with airflow, energy and humidity models. An economizer (large supply fan) was simulated to provide vent...
Conference Paper
Full-text available
As we move to high performance housing and especially toward zero-energy homes, ventilation represents a larger and larger fraction of the space conditioning energy requirements. Ventilation standards, such as ASHRAE Standard 62.2 (or codes that use it, such as California Title 24), are typically met by continuous ventilation for their whole-house...
Article
Full-text available
The PerFluorocarbon Tracer (PFT) method is a low-cost approach commonly used for measuring air exchange in buildings using tracer gases. It is a specific application of the more general Continuous-Injection, Long-Term Sampling (CILTS) method. The technique is widely used but there has been little work on understanding the uncertainties (both precis...
Article
Effective residential envelope air sealing reduces infiltration and associated energy costs for thermal conditioning, yet often creates a need for mechanical ventilation to protect indoor air quality. This study estimated the potential energy savings of implementing airtightness improvements or absolute standards along with mechanical ventilation t...
Conference Paper
Full-text available
Occupant concern about indoor air quality (IAQ) issues has led to the increased use of more effective air filters in residential heating and cooling systems. A drawback of improved filtration is that better filters tend to have more flow resistance. This can lead to lower system airflows that reduce heat exchanger efficiency, increase duct pressure...
Article
Full-text available
Air tightness is an important property of building envelopes. It is a key factor in determining infiltration and related wall-performance properties such as indoor air quality, maintainability and moisture balance. Air leakage in U.S. houses consumes roughly 1/3 of the HVAC energy but provides most of the ventilation used to control IAQ. There are...
Article
Elevated outdoor ozone levels are associated with adverse health effects. Because people spend the vast majority of their time indoors, reduction in indoor levels of ozone of outdoor origin would lower population exposures and might also lead to a reduction in ozone-associated adverse health effects. In most buildings, indoor ozone levels are dimin...
Article
Full-text available
Furnace energy use and filter pressure drop was measured for forced-air heating/cooling systems in ten California homes. Each home was monitored for at least one year. Measurements were made of the blower energy, filter pressure drop, supply and return plenum pressures, and temperatures, as well as the indoor temperature. At least two filter types...
Article
Full-text available
The purpose of outdoor air ventilation is to dilute or remove indoor contaminants to which occupants are exposed. It can be provided by mechanical or natural means. In most homes, especially older homes, weather-driven infiltration provides the dominant fraction of the total ventilation. As we seek to provide good indoor air quality at minimum ener...
Technical Report
Full-text available
Whole-house ventilation systems are becoming commonplace in new construction, remodeling/renovation, and weatherization projects, driven by combinations of specific requirements for indoor air quality (IAQ), health, and compliance with standards, such as ASHRAE 62.2. At the same time we wish to reduce the energy use in homes and therefore minimize...
Technical Report
Full-text available
Building codes increasingly require tighter homes and mechanical ventilation per ASHRAE Standard 62.2. These ventilation flows must be measured so that energy is not wasted with over ventilation and occupants’ health is not compromised by under ventilation. Flow hoods are used to measure these ventilation flows, but there is currently no standard s...
Article
Full-text available
We ventilate buildings to provide acceptable indoor air quality (IAQ). Ventilation standards (such as American Society of Heating, Refrigerating, and Air-Conditioning Engineers [ASHRAE] Standard 62) specify minimum ventilation rates without taking into account the impact of those rates on IAQ. Innovative ventilation management is often a desirable...
Technical Report
Full-text available
Changing the rate of airflow through a home affects the annual thermal conditioning energy. Large-scale changes to airflow rates of the housing stock can significantly alter the energy consumption of the residential energy sector. However, the complexity of existing residential energy models hampers the ability to estimate the impact of policy chan...
Article
Full-text available
To assess whether houses can meet performance expectations, the new practice of residential commissioning will likely use flow hoods to measure supply and return grille airflows in HVAC systems. Depending on hood accuracy, these measurements can be used to determine if individual rooms receive adequate airflow for heating and cooling, to determine...
Article
Existing ventilation standards, including American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) Standard 62.2, specify continuous operation of a defined mechanical ventilation system to provide minimum ventilation, with time-based intermittent operation as an option. This requirement ignores several factors and concern...
Article
Full-text available
Although it has been used for many years in commercial buildings, the application of demand controlled ventilation in residences is limited. In this study we used occupant exposure to pollutants integrated over time (referred to as 'dose') as the metric to evaluate the effectiveness and air quality implications of demand controlled ventilation in r...
Article
Full-text available
Experts state that designers and engineers can face significant challenges in sizing HVAC equipment in a building. The process needs to involve some sort of a loads calculation to determine the amount of heating and cooling necessary over each hour of the year. A key part of a loads calculation is specifying activities that will take place in the b...
Article
Full-text available
This article uses an analytical approach to determine the dilution of an unsteadily-generated solute in an unsteady solvent stream, under cyclic temporal boundary conditions. The goal is to find a simplified way of showing equivalence of such a process to a reference case where equivalent dilution is defined as a weighted average concentration. Thi...
Article
Full-text available
Ventilation reduces occupant exposure to indoor contaminants by diluting or removing them. In a multizone environment, such as a house, every zone will have different dilution rates and contaminant source strengths. The total ventilation rate is the most important factor in determining occupant exposure to given contaminant sources, but the zone-sp...
Article
Full-text available
Ozone is an air pollutant with that can have significant health effects and a significant source of ozone in some regions of California is outdoor air. Because people spend the vast majority of their time indoors, reduction in indoor levels of ozone could lead to improved health for many California residents. Ozone is removed from indoor air by sur...
Article
Full-text available
The purpose of ventilation is to dilute or remove indoor contaminants that an occupant is exposed to. In a multizone environment, such as a house, there will be different dilution rates and different source strengths in every zone. Most homes in the United States have central HVAC systems, which tend to mix the air, and thus, the indoor conditions...
Article
Full-text available
The performance of air-handling systems in buildings needs to be improved. Many of the deficiencies result from myths and lore and a lack of understanding about the non-linear physical principles embedded in the associated technologies. By incorporating these principles, a few important efforts related to diagnostics and controls have already begun...
Article
Full-text available
The purpose of ventilation is to dilute indoor contaminants that an occupant is exposed to. In a multi-zone environment such as a house, there will be different dilution rates and different source strengths in every zone. Most US homes have central HVAC systems, which tend to mix conditions between zones. Different types of ventilation systems will...