malindo's portfolios
Using Cool Roofs
Background
During the final year of undergraduate study, I worked on a project to simulate cool roofs' efficacy in reducing air-conditioners' energy consumption in a building under a tropical climate. The simulations were performed using EnergyPlus. A cool roof is a roof having a high reflectivity value. Reflectivity is the ability of a material to reflect solar radiation. You can access the full report of my final-year project here.
Pros of Cool Roofs
-
It is not expensive and fast to implement.
-
It is very effective in Indonesia's climate.
Cons of Cool Roofs
-
Not suitable in cold climate countries since the roofs will prevent heat gain during wintertime, thus making you consume more energy for heating.
Implementation
The cool coating available in market:
-
Sika® CoolCoat
-
Rainguard Professional Cool Coat ™ Acrylic Thermal Defense Sealer
-
Aquaproof HeatGard
-
Avian Brands Sunguard All in One
Analyses
A model is constructed in Google SketchUp and EnergyPlus to represent a room with the details below. Actual temperature data obtained from the sensors installed in the room is used to calibrate the model.
A model is calibrated until it satisfies the 2 criteria below. The graphs show the relative difference between measured data and simulated result.
Once we are confident that the model can give a relatively close result with the measured data, it is run monthly for 1 year to produce the graphs below (result for October is shown here).
Discusion of the Results
The benefits of using a cool roof (reflectivity = 0.9, emissivity = 0.9) from my simulations using EnergyPlus:
-
There is a reduction in the peak temperature from 33 degrees C to 30 degrees C.
-
There is a reduction by 2 degrees C on average in the mean air temperature inside a room without an air conditioning system.
-
There is a reduction in the air conditioner energy consumption by 39% yearly for a room with an AC system turned on throughout the year. The energy-saving will be more since we do not usually turn on an AC non-stop for one year. Plus, with the reduction in the peak temperature and mean air temperature, probably you do not need to use an AC anymore.
-
Electricity consumption for one year (the year 2011 is taken as an example) and one month (October is taken as an example) between different energy-saving methods (cooling the roof and insulating the roof). Using a cool roof gives more energy savings (around a 39% decrease in electricity consumption yearly) than increasing the roof insulation method (18.5% decrease) although a high-resistivity insulation material used.
