Assessing the Effects of Cool Roofs on Indoor Environments and Health in Niue (REFLECT)

A Cluster Randomised Controlled Trial (cRCT) Evaluating the Effects of Cool Roofs on Health, Environmental and Economic Outcomes in Niue

Ambient air temperatures in the Pacific have broken record highs in 2024. Solutions are needed to build heat resilience in communities and adapt to increasing heat from climate change. Sunlight-reflecting cool roof coatings may passively reduce indoor temperatures and energy use to protect home occupants from extreme heat. Occupants living in poor housing conditions in the Pacific are susceptible to increased heat exposure.

Heat exposure can instigate and worsen numerous physical, mental and social health conditions. The worst adverse health effects are experienced in communities that are least able to adapt to heat exposure. By reducing indoor temperatures, cool roof use can promote physical, mental and social wellbeing in household occupants.

The long-term research goal of the investigators is to identify viable passive housing adaptation technologies with proven health benefits to reduce the burden of heat stress in communities affected by heat in Niue. To meet this goal, the investigators will conduct a cluster-randomized controlled trial to establish the effects of cool roof use on health, indoor environment and economic outcomes in Niue.

Study Overview

• Status: Completed
• Conditions: Aggression; Depression; Food Insecurity; Dehydration; Sleep Quality; Hospitalization; Cognition; Diet Quality; Health-related Quality of Life; Life Satisfaction; Systolic Blood Pressure; Diastolic Blood Pressure; Resting Heart Rate; Productivity; Blood Glucose Control; Heat-related Symptoms; Physician Diagnosed Heat-related Illnesses; Indoor Thermal Comfort; Coping Ability; Healthcare Provider Utilization; Inner Ear Canal Temperature; Indoor Air Temperature; Indoor Relative Humidity; Indoor Heat Index; Household Energy Expenditure
• Intervention / Treatment: Other: Cool roof

Detailed Description

Increasing heat exposure from climate change is causing and exacerbating heat-related illnesses in millions worldwide - particularly in low resource settings. June 2024 was the 13th consecutive hottest month on record globally - shattering previous records. Heat exposure can instigate and worsen health conditions including cardiovascular, metabolic, endocrine and respiratory disease, heat-related illnesses, pregnancy complications, and mental health conditions. Adaptation is essential for protecting people from increasing heat exposure. The built environment, especially homes, are ideal for deploying interventions to reduce heat exposure and accelerate adaptation efforts. However, there currently is a lack of evidence on a global scale - generated through empirical studies - guiding the uptake of interventions to reduce heat stress in low resource settings.

Pacific Islands and other small island developing states are among the most vulnerable to the adverse impacts of climate change and are likely to experience increases in ambient air temperature over the coming decades. People in Niue are exposed to heat and humidity year-round. The Pacific Islands have a large burden of non-communicable diseases (NCDs), with nearly three-quarters of deaths due to NCDs. The combined burden of heat and NCDs places Pacific Island populations at greater risk of adverse health effects from heat extremes.

Sunlight-reflecting cool roof coatings passively reduce indoor temperatures and lower energy use, offering protection to home occupants from extreme heat. The investigators therefore aim to conduct a cluster-randomized controlled trial investigating the effects of cool-roof use on health, environmental and economic outcomes in Niue.

The trial will quantify whether cool roofs are an effective passive home cooling intervention with beneficial health effects for vulnerable populations in Niue. Findings will inform regional policy responses on scaling cool roof implementation to protect people from increasing heat exposure driven by climate change.

• Study Type: Interventional
• Enrollment (Actual): 288
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Niue
  • Auckland, Niue
    • University of Auckland

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

Participant criteria:

• Consenting adults aged 18 years and over.
• Expected to be available to participate in the study for at least nine months in the next 12 months.

Household criteria:

• House has a metal roof.
• House is single-story.

Exclusion Criteria:

Household criteria:

• Unstable house structure that does not permit the application of cool roof materials.
• Inaccessible by the research team.
• Significant roof damage defined as any penetrative roof defect that results in a hole in the roof OR over 25% of the roof rusted.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Intervention; Households will receive sunlight reflecting 'cool roof' coating on their roofs.	Other: Cool roof; Cool roofs are a heat-reflecting material that can be applied to existing household roofing in the form of a liquid-applied membrane. Cool roofs work by increasing solar reflectance (the ability to reflect the visible wavelengths of sunlight, reducing heat transfer to the surface) and thermal emittance (the ability to radiate absorbed solar energy) thereby reducing the amount of heat transferred into the home.
No Intervention: Control; No cool roof application. Households will keep their original roofing for the duration of the trial.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Resting heart rate	Resting heart rate in beats per minute measured as the average of three readings in the left arm over one hour using Blip portable automated sphygmomanometers.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Blood glucose control	Three month average of blood glucose in mmol/mol measured as glycosylated hemoglobin (HbA1c) using capillary blood and the HemoCue® HbA1c 501 System.	Two measurements will be taken: one at baseline and one in the last month of three consecutive hottest months.
Depression	Self-reported presence and frequency of symptoms of depression assessed using aggregate score of the Patient Health Questionnaire 9 (PHQ-9).	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Heat-related symptoms	Self-reported heat-related symptoms in the past month, assessed using a recall questionnaire.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Physician diagnosed heat-related illnesses	Self-reported new diagnosis from a medical practitioner of a heat-related illness in the last month assessed using a recall questionnaire.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Food insecurity	Self-reported experience based measure of individual food security assessed using the Food Insecurity Experience Scale (FIES).	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Diet quality	Self-reported individual food group consumption in the previous 24 hours assessed using the Diet Quality Questionnaire (DQQ).	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Health-related quality of life	Current self-reported health-related quality of life assessed using the EuroQol EQ-5D-5L quality assessment tool.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Indoor thermal comfort	Self-reported household heat, humidity and comfort experience over the last four weeks assessed using a recall questionnaire.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Coping ability	Self-reported coping strategies for high indoor temperatures assessed using a recall questionnaire.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Life satisfaction	Current self-reported life satisfaction assessed using the World Values Survey.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Healthcare provider utilization	Self-reported healthcare provider utilization in the past four weeks assessed using a recall questionnaire.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Hospitalization	Self-reported overnight hospital stay in the past four weeks assessed using a recall questionnaire.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Systolic Blood Pressure	Maximum blood pressure (mmHg) during systole measured as the average of three readings in the left arm over one hour using Blip portable automated sphygmomanometers.	Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
Diastolic Blood Pressure	Minimum blood pressure (mmHg) during diastole measured as the average of three readings in the left arm over one hour using Blip portable automated sphygmomanometers.	Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
Cognition	Accuracy and response time to the four-choice Deary-Liewald Test measured using the CogniFit app-based assessment tool.	Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Inner Ear Canal Temperature	Internal body temperature (℃) measured once using Braun digital ear thermometer.	Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
Dehydration	Dehydration as indicated by urine specific gravity ≥1.020 measured as urine specific gravity using Siemens Multistix SG dipstick.	Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Sleep quality	Self-reported sleep distrubance assessed using the Athens Insomnia Scale (AIS).	Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Aggression	Self-reported personal aggresion assessed using the Buss-Perry Aggression Questionnaire-Ultra Short Form (BPAQ-ML).	Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Productivity	Self-reported job absenteeism and presenteeism assessed using the Health and Work Performance Questionnaire Short Form (HPQ-SF).	Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
Indoor air temperature	Indoor air temperature (℃) measured using Hobo MX1101 heat and humidity measurement device.	Measurements at 15 minute intervals for 12 months.
Indoor relative humidity	Ratio of the amount of water vapor present in the air to the greatest amount possible at the same temperature (%) measured using Hobo MX1101 heat and humidity measurement device.	Measurements at 15 minute intervals for 12 months.
Indoor heat index	Index that combines air temperature and relative humidity (℃) based on temperature and humidity measurements from the Hobo MX1101 heat and humidity measurement device calculated using the formulae endorsed by the US National Oceanic and Atmospheric Administration.	Measurements at 15 minute intervals for 12 months.
Household energy expenditure	Self-reported household energy expenditure assessed using a recall questionnaire from the head of the household.	Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.

Collaborators and Investigators

• Sponsor: Aditi Bunker
• Collaborators: London School of Hygiene and Tropical Medicine; Boston University; Heidelberg University; Rutgers University; University of Ouagadougou, Burkina Faso; Pacific Community; Indian Institute of Public Health, India; Secretaría de Educación Pública, México; CogniFit Limited; Labfront; Resene; Habitat for Humanity; The Tindall Foundation
• Investigators: Principal Investigator: Collin Tukuitonga, Sir. Dr., University of Auckland, New Zealand

Publications and helpful links

Helpful Links

• Related Info

Study record dates

Study Major Dates

• Study Start (Actual): September 4, 2024
• Primary Completion (Actual): January 31, 2026
• Study Completion (Actual): January 31, 2026

Study Registration Dates

• First Submitted: August 22, 2024
• First Submitted That Met QC Criteria: August 22, 2024
• First Posted (Actual): August 26, 2024

Study Record Updates

• Last Update Posted (Actual): February 27, 2026
• Last Update Submitted That Met QC Criteria: February 25, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Depression; Diabetes; Cardiovascular; Mental health; Heart rate; Blood glucose; Housing; Humidity; Hot Temperature; Heat Stress; Cool roof
• Additional Relevant MeSH Terms: Aberrant Motor Behavior in Dementia; Endocrine System Diseases; Nervous System Diseases; Mental Disorders; Wounds and Injuries; Pathologic Processes; Metabolic Diseases; Behavioral Symptoms; Glucose Metabolism Disorders; Sleep Wake Disorders; Water-Electrolyte Imbalance; Sleep Disorders, Intrinsic; Dyssomnias; Pathological Conditions, Signs and Symptoms; Behavior; Nutritional and Metabolic Diseases; Social Behavior; Depression; Dehydration; Diabetes Mellitus; Sleep Initiation and Maintenance Disorders; Aggression; Heat Stress Disorders; Psychological Well-Being; Personal Satisfaction
• Other Study ID Numbers: 3728160; 226745/Z/22/Z (Other Grant/Funding Number: Wellcome Trust UK)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

IPD Plan Description

Data that can be shared unconditionally underpinning the published research articles will be made available to other researchers at the time of publication, and data will be linked via the article DOI. Data that cannot be unconditionally shared upon publication owing to confidentiality or data protection requirements will be identified as such and a contact email will be provided in relevant publications for data access enquiries by other researchers.

It is expected that demographic data of people at the study sites (family size and composition, basic socioeconomic indicators) may contain personally identifiable information and location data. All such data will be removed prior to storage on online data repositories and therefore will be available to be publicly shared at the time of publication of manuscripts.

• IPD Sharing Time Frame: At the time of publication.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No