A Preliminary Proposal for Replacing Black Roofs at IIM Calcutta with White

Roofs

Ramaswamy SankarMBA Student, Indian Institute of Management, CalcuttaPh.D., Chemical Engg, University of Massachusetts, AmherstBTech, Chemical Engg, Indian Institute of Technology, Madras

Why Black Roof is Bad in Hot Weather?

• Dark Colors absorb more heat from the sun! o if you wear a black shirt on a summer day in

Joka, you will feel much hotter compared to wearing a white shirt.

• Black color heats up the most!!

http://heatisland.lbl.gov/CoolRoofs/

Reflection of Sunlight (%)

Increase in Roof Temperature (F)

Black Roofs on Some Buildings at IIMC

• The black roofs absorb sunlight and heat up the buildings

• Due to high thermal mass of the roof, the building interior remains hot even after sunset.

• This leads to high A/C costs.

Admin Block – L1 & L2 NF2 PGPEX Family Hostel

Staff Cafeteria

What is the Payback Period for a White Roof?• Cost/benefit analysis for cool roof at Satyam Learning

Center has been carried out which suggests that the cool or white roof coatings have a 2.37 year financial payback period in the composite climatic conditions of India.

Determination of energy saving with cool roof concept using calibrated simulation: Case of a learning centre in composite Indian climateAviruch Bhatia*, Vishal Garg**, Jyotirmay Mathur**Mechanical Engineering Department, Malaviya National Institute of Technology, Jaipur (India), **Centre for IT in Building Science, International Institute of Information Technology, Hyderabad (India)

White Roof Reduces Energy Consumption

Lower AC Costs with Cool Roof

2006: Experiment at IIIT, Hyderabad

http://www.iiit.net/research/cbs/Projects/cool%20roof.htmlSavings ::• The average daily maximum roof-surface

temperature of the initial concrete roof was about 52 C, for the black roof was 60 C, � �and for the white roof was 32 C. �

• The average daily a/c savings (applying cool coatings on concrete roof) were 30 kilowatt-hours (5% of total a/c use, annual saving of 9000 kWh). At Rs 5 per kWh, the total discounted savings over the expected life of the roof are estimated to be Rs. 430,000.

• Is there a subsidy from Govt of India through the National Mission on Energy Efficiency?

Grey roof

White roof

Work Done By Dr. Akbari, Lawrence Berkeley National

Lab

White Roof or

Dr. Akbari, Lawrence Berkeley National Lab

Obama's green guru calls for white roofs

http://www.telegraph.co.uk/earth/earthnews/5389278/Obamas-green-guru-calls-for-white-roofs.html

• Professor Steven Chu, the US Energy Secretary, said the unusual proposal would mean homes in hot countries would save energy and money on air conditioning by deflecting the sun's rays.HOW ABOUT TAKING

THIS FURTHER AT IIMC?