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NCT Number: NCT07592117

Assessing the Effects of Cool Roofs on Indoor Environments and Health in Tavua, Fiji

Ambient air temperatures in Fiji are increasing due to climate change. Solutions are needed to build heat resilience in communities and adapt. 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 Fiji 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 Fiji. 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 Tavua, Fiji.

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Key information

Conditions

Resting Heart Rate Aberrant Motor Behavior in Dementia Aggression Behavior Behavioral Symptoms Blood Glucose Control Cognition Coping Ability Dehydration Depression Diabetes Mellitus Diastolic Blood Pressure Diet Quality Dyssomnias Endocrine System Diseases Food Insecurity Glucose Metabolism Disorders Health-Related Quality-of-Life Healthcare Provider Utilization Heat Stress Disorders Heat-related Symptoms Hospitalization Household Energy Expenditure Indoor Air Temperature Indoor Heat Index Indoor Relative Humidity Indoor Thermal Comfort Inner Ear Canal Temperature Life Satisfaction Mental Disorders Metabolic Diseases Nervous System Diseases Nutritional and Metabolic Diseases Pathologic Processes Pathological Conditions, Signs and Symptoms Personal Satisfaction Physician Diagnosed Heat-related Illnesses Productivity Psychological Well-Being Sleep Disorders, Intrinsic Sleep Initiation and Maintenance Disorders Sleep Quality Sleep Wake Disorders Social Behavior Systolic Blood Pressure Water-Electrolyte Imbalance Wounds and Injuries

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

About this study

Increasing heat exposure from climate change is causing and exacerbating heat-related illnesses in millions worldwide - particularly in low-resource settings. 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, is ideal for deploying interventions to reduce heat exposure and accelerate adaptation efforts. However, there is currently a lack of global, empirical evidence guiding the uptake of interventions to reduce heat stress in low-resource settings.

Cities and towns of LMIC 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 Fiji are exposed to year-round heat and low humidity. The combined burden of heat and NCDs places Fiji's population 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 Fiji.

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

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Permanent household resident.

Exclusion criteria

  • Roof damage, inaccessible or instability of roof adversely affecting cool roof coating application.
  • Participant unable to provide written/verbal informed consent.

Treatment and study plan

Cool roof

Other

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.

Primary outcomes

  1. Resting heart rate

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Resting heart rate in beats per minute measured as the average of three readings in the left arm over one hour using portable automated sphygmomanometers.

  2. Blood glucose control

    Time frame: Two measurements will be taken: one at baseline and one in the last month of three consecutive hottest months.

    Three month average of blood glucose in mmol/mol measured as glycosylated hemoglobin (HbA1c) using capillary blood and the HemoCue® HbA1c 501 System.

  3. Depression

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported presence and frequency of symptoms of depression assessed using aggregate score of the Patient Health Questionnaire 9 (PHQ-9). Minimum score of 0 and a maximum score of 27 with a higher score meaning a worse outcome.

Secondary outcomes

  1. Heat-related symptoms

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported heat-related symptoms in the past month, assessed using a recall questionnaire.

  2. Physician diagnosed heat-related illnesses

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported new diagnosis from a medical practitioner of a heat-related illness in the last month assessed using a recall questionnaire.

  3. Food insecurity

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported experience based measure of individual food security assessed using the Food Insecurity Experience Scale (FIES).

  4. Diet quality

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported individual food group consumption in the previous 24 hours assessed using the Diet Quality Questionnaire (DQQ).

  5. Hospitalization

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported overnight hospital stay in the past four weeks assessed using a recall questionnaire.

  6. Health-related quality of life

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Current self-reported health-related quality of life assessed using the EuroQol EQ-5D-5L quality assessment tool. The minimum and maximum scores for the EuroQol EQ-5D-5L quality assessment tool are -0.59 and 1, respectively. A score of 1 represents the best possible health state, while scores below 0 indicate health states that are considered worse than death.

  7. Indoor thermal comfort

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported household heat, humidity and comfort experience over the last four weeks assessed using a recall questionnaire.

  8. Coping ability

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported coping strategies for high indoor temperatures assessed using a recall questionnaire.

  9. Life satisfaction

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Current self-reported life satisfaction assessed using the World Values Survey. Values can range from 1 to 10 with a higher score representing greater life satisfaction.

  10. Healthcare provider utilization

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported healthcare provider utilization in the past four weeks assessed using a recall questionnaire.

  11. Systolic Blood Pressure

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.

    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.

  12. Diastolic Blood Pressure

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.

    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.

  13. Intimate partner violence

    Time frame: Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Recall questionnaire assessing the presence or abscence intimate partner violence in the past 4 weeks.

  14. Inner Ear Canal Temperature

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.

    Internal body temperature (℃) measured once using Braun digital ear thermometer.

  15. Dehydration

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Dehydration as indicated by urine specific gravity ≥1.020 measured as urine specific gravity using Siemens Multistix SG dipstick.

  16. Sleep quality

    Time frame: Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported sleep distrubance assessed using the Athens Insomnia Scale (AIS). Values range from 0 to 24 with a higher score indicating a worse outcome.

  17. Aggression

    Time frame: Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.

    Self-reported personal aggresion assessed using the Buss-Perry Aggression Questionnaire-Ultra Short Form (BPAQ-ML).

  18. Productivity

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.

    Self-reported job absenteeism and presenteeism assessed using the Health and Work Performance Questionnaire Short Form (HPQ-SF).

  19. Indoor air temperature

    Time frame: Measurements at 15 minute intervals for 12 months.

    Indoor air temperature (℃) measured using Hobo MX1101 heat and humidity measurement device.

  20. Indoor relative humidity

    Time frame: Measurements at 15 minute intervals for 12 months.

    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.

  21. Indoor heat index

    Time frame: Measurements at 15 minute intervals for 12 months.

    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.

  22. Household energy expenditure

    Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.

    Self-reported household energy expenditure assessed using a recall questionnaire from the head of the household.

Study contacts

Contact information is provided by the study sponsor or research team.

Aditi Bunker

CONTACT

[email protected]

+49 6221 565344

Sponsors and collaborators

Lead sponsor

Aditi Bunker

Other

Collaborators

  • Boston University
  • Fiji National University
  • Heidelberg University
  • Resene
  • Rutgers University

Registry information

Official study title

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

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
May 18, 2026
Registry last updated
May 18, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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