In recent years, the number of extremely hot summer days has increased, and the number of people suffering from heatstroke indoors is increasing. Concrete, the building material, stores heat, so the temperature inside the building does not drop much even at night. It is important to take measures such as using the air conditioner appropriately indoors.

　What should we do about buildings? 　 How effective is it?

　We have created a greening calculation program that easily calculates the rooftop surface temperature and the amount of carbon dioxide associated with air conditioning when a roof is greened or a highly reflective paint is applied.

 

　Regarding the heat balance of buildings, some of the heat radiation from the atmosphere and the ground is absorbed by the walls and transmitted to the inside of the walls. Some of it goes into the atmosphere through convection, and the rest goes toward the atmosphere and ground through radiation.
 
　The greening calculation program assumes that this heat balance is only on the rooftop, and calculates for one year when the indoor temperature is maintained at a comfortable temperature. We use environmental data from a standard year at 146 locations across Japan.

　Below is an example of calculation without greening. An example graph with greening is included for comparison.

１．When you start the rooftop greening calculation, the following screen will appear.

start English

 ２．Select “Analysis Period” and set the analysis period and time step.

time Emglish

３．Select “Environment” and set the environment.

environment English

４．Select “Rooftop Settings” and set the roof material.

property English

５．Select “Set boundary conditions” and “All”.  If you have a rooftop garden, also set ”Transpiration”.

Boundary Condition English

６．Save it with “File” on the menu bar and click “Analysis” to perform the calculation.

When the calculation is completed and you click “Result processing” on the menu bar, the following screen will appear.

result English

７．Select “Annual Flux Amount” to display the annual flux amount and annual carbon dioxide amount.

result year English

８．Select  “Monthly Flux Amount” to display the monthly flux amount and monthly carbon dioxide amount.

result monthly English

９．Select “Rooftop surface temperature”, the daily maximum and minimum temperatures of the rooftop surface and the maximum and minimum temperatures of the outside air temperature will be displayed.

result temperature English

Click on a date, a time history graph of the rooftop surface temperature and outside temperature for that day will be displayed. The graph (no greening) on July 24th is displayed in the figure on the left below. Furthermore, we have calculated the case where rooftop greening was applied under the same conditions, and the graph (greening) on July 24th is also shown on the right below.

no green green
temperature English temperature English

１０．Select “Flux Time History” under “Graphs”, excel will start and display a time history diagram of absolute flux flowing from the rooftop surface.

flux_English

１１．Select “Temperature Inside Rooftop” under “Graphs”, excel will start and display a time history chart of the temperature inside the rooftop. Here we are displaying the time history chart for July 29th.

temperature inside rooftop English