With the increase in types of heating and cooling systems, the decision on what type of system is a best fit for you and your home has become more complex. The best type for you is dependant on the amount it is used and when, and your local climate. I hope to make this decision a little easier for you by providing you with a better understanding of the basic principles that affect us when the temperature outside falls outside of our range of comfort.Our sense of comfort depends on a combination of the actual temperature and the relative humidity of the air. In warm seasons, relative humidity plays an even more important role than it does during cooler periods. As a result, cooling is much more complex than heating because of the importance of evaporation.
Cooling is also dependent on the movement of the air. The rate of heat loss by evaporation is determined by the amount of water on the skin “sweat” and the capacity of the air to accept it. The amount of moisture available to keep us cool does not decrease much as the air temperature drops below 75°F. When the air temperatures reach about 80°F, heat loss from conduction/convection and radiation are not enough to keep us cool and evaporation becomes an important means to shuck the excess heat. The amount of moisture on the skin, the movement of the air and the humidity of the air are all key elements.
We become more uncomfortable if our sweat does not evaporate. Decreasing humidity during summer thus enhances comfort. When the temperature of the surrounding air and surfaces exceeds the body temperature, the only way the body can lose the heat it generates is by evaporation. Humidity control and air motion are not only important to summer comfort, but are essential to sustaining life in an extremely hot environment.
Generally, when conditions are cool the most important determining factor for comfort is the radiant temperature of the surroundings. As little as a five-degree increase in the radiant temperature can offset a seven-degree reduction in air temperature. Materials in your home that have a high thermal mass that are warmed by the sun will reduce your heating bill.
