Cool roofs study for 17 cities in Southwest Pacific with energy simulations (EnergyPlus)
EnergyPlus is the most accurate building energy simulation software, managed by the Department of Energy in the United States
Performed thousands of energy simulations with cool roofs using EnergyPlus to calculate heating and cooling loads to maintain the home and the office building between 20°C – 25°C during their occupation. Analyzed data to show cost-efficient solutions and the cost effectiveness of cool roofs
Reducing roof solar absorptance to compare savings in the cooling systems with penalties in the heating system using cool roofs
If ‘Total (kW·h/m2·year)‘ (penalties in the heating system minus savings in the cooling systems) is a negative number and ‘Cooling/Heating‘ (savings in the cooling system divided by the penalties in the heating system) is greater than 0, it indicates that savings in the cooling system are greater than penalties in the heating system, reducing solar absorptance and using cool roofs
Solar absorptance on the roof (0.2, 0.4, 0.6, 0.8). 0.2 would be a white cool roof and 0.8 a standard brown roof
Thermal transmittance (U) on the roof. (without insulation: 1.86 for home and 1.74 for office, and 0.67, 0.4, 0.33 W/m2·K). Technical building code (CTE) requirement in Barcelona is 0.4, most strict CTE requirement is 0.33
Scientific studies and experiments showed that the energy savings provided by by cool roofs are greater than the results in energy simulations because the software does not consider the lowest temperatures around the building, the energy savings due to ventilation and air infiltration with lower temperatures, and that the cooling systems work at higher performance. In addition, the climate files are not usually updated
In the United States, colder cities also regulate with cool roofs to mitigate the urban heat island and avoid peak consumption in summer
Simulations performed for a home and office building with a low level of air tightness, and considering an optimal level of air quality in offices, for homes and offices with a better level of air tightness and offices with heat recovery the benefits of using cool roofs are greater
Single family home
Cool roof analysis in a 100 m2 single family home
Office building
Cool roof analysis in an office building with 2 floors (800 m2 per floor)
Summary of cool roof results for 17 cities in Southwest Pacific
‘Total (kW·h/m2·year)’ (penalties in the heating system (positive number) minus savings in the cooling system (negative number)) difference and ‘Cooling/Heating’ (savings in the cooling system divided by penalties in the heating system) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7) for a single-family home (U1.86 and U0.40) and for an office building (U1.76 and U0.40). A cool roof should be used if ‘Total (kW·h/m2·year)’ is a negative number and ‘Cooling/Heating’ is greater than 0
Cool roofs in Adelaide
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in AliceSprings
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Auckland
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Brisbane
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Canberra
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Christchurch
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Darwin
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Hobart
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in KualaLumpur
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Manila
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Melbourne
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Nadi
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Perth
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Queenstown
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Singapore
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Sydney
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Cool roofs in Wellington
Single family home
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
Office building
Heating, cooling and total loads as a function of roof solar absorptance for four values of roof thermal transmittance (U). 0.2 would be a white cool roof and 0.8 a standard brown roof
“Heating (kW·h/m2·year)” penalties (positive number), “Cooling (kW·h/m2·year)” savings (negative number) and “Total (kW·h/m2·year)” (heating penalties minus cooling savings) difference and “Cooling/Heating” (cooling savings divided by heating penalties) reducing solar absorptance by 0.1 (e.g. from 0.8 to 0.7). A cool roof should be used if “Total (kW·h/m2·year)” is a negative number and “Cooling/Heating” is greater than 0
