12. Job done. But did it work?

After finishing our rooftop garden we needed to start collecting data once again to see if the project would eventually help lower temperatures inside our classrooms.  We started right away to collect temperatures.  We could do that because grass is already a full plant and we didn't need to wait for it to grow. For two months we collected data, calculated the daily average temperature. Finally we calculated the average temperature of the classrooms for both the Control and Experimental classrooms.  Average values were:

Average Temperatures Classroom #1 (Control)  vs   Classroom #2 (Experimental)

Difference in temperatures between classrooms

                                   Classroom #2 with the Rooftop Garden

You might think that a two or three degrees change is no big deal, but that actually a rise on body temperature of that magnitude can be life treatening. According to the document "Heat Stress",  created by the Ohio State University (OSU) Agricultural Safety Program (N.D), an increase in body temperature of two degrees Fahrenheit can affect mental functioning and five degree Fahrenheit increase can result in serious illness or death by  "heat stress".

Heat stress (OSU, N.D.) is a buildup of body heat generated either internally by muscle use or externally by the environment. As the heat increases, body temperature and the heart rate rise painlessly.  During hot weather, heat illness may be an underlying cause of other types of injuries, such as heart attacks and falls.

The most serious heat related illness is heat stroke. The symptoms are confusion, irrational behavior, convulsions, coma, and death. While over 20% of heat stroke victims die regardless of health or age, children seem to be more susceptible to heat strain than adults. In some cases, the side effects of heat stroke are heat sensitivity and varying degrees of brain and kidney damage (OSU, ND).

Any heat stress can impair functioning. People work slower and less efficiently when they are suffering from heat stress. Heat stress is serious and should be handled as such.  As strain from heat increases, body temperature and heart rate can rise rapidly. Exposure to heat can be serious to children and adults, concludes the document.

According to the American Society of Heating, Refrigeration and Air- Conditioning Engineers (ANSI / ASHRAE) (2004) thermal comfort is defined as the state of mind in humans that expresses satisfaction with the surrounding environment. It’s also known as the “Perfect Temperature”, because is on that range of temperature where people can perform comfortably.  

If you think about it, thermal comfort is definitely different to every people and to every area of the world, but according to Sonia Cosme (2012), biologist of the environmental company EDS, here in Puerto Rico and in most tropical areas thermal comfort temperatures range from 73 – 79 °F (23 - 26°C) . Below or above these temperatures people feels uncomfortable enough so they are distracted to perform tasks.

All of this is very important to know, because:

• By building a green roof we achieved to lower the inside temperature to an average 79.7 °F, almost reaching the threshold of what is thermal comfort. 
• If we can reach that range for the “perfect temperature” we might be improving the thermal conditions inside the classroom,
• mproving students comfort temperature zone which eventually could create a more pleasant environment for both teachers and students

ANSI/ASHRAE  (N.D) also states that thermal comfort is closely related to Thermal Stress , which lowers peoples performance about 11% compared to their performance at normal thermal conditions . Also, human performance in relation to thermal stress varies greatly by the type of task you are completing. Some of the physiological effects of thermal heat stress include increased blood flow to the skin, sweating, and increased ventilation.

With roof gardens we lower our ecological footprint on the WORLD:  HOW?  Figure this. Comfort temperature is often used in stores to create a pleasant space for the buyer and worker so they stay longer. So if, we can reach that thermal comfort temperature through building Roof Gardens, there would be no need for air conditioning systems and we would end saving LOTS of money because, according to the web page hubpages.com (2012) for every 1°C cooler could  increase your power costs by about 10 to 15%. Call tha an ECO saving!!