When designing or sizing a central cooling system we follow the guidelines set forth by the American Society of Heating and Air Conditioning Engineers or (ASHRE). ASHRE has set forth design temperatures for hundreds of areas across the United States based on temperature and humidity records over a period of decades. KEIL uses the design temperatures for the Paterson, New Jersey area, the area closest to us.
In northern New Jersey we have a design temperature of +10 degrees for heating and for +90 degrees for cooling. These temperatures reflect the typical highs and the typical lows of our area. We size heating and cooling system to perform their best within these temperatures as we only exceed these temperatures on rare occasions or for only hours at a time during the course of a typical year.
When the temperature reaches 90 degrees outside (Our design temperature) we can expect under best conditions to have the inside of our homes reach 70 degrees inside with a much lower humidity level than outside. Remember this is under best conditions!
All residential air conditioning systems are mechanically engineered to provide a 20 degree temperature drop. 90 degrees outside = 70 degrees inside. This assumes that the outside unit and the inside unit are properly matched and designed to work together to achieve the 20 degree drop.
Why can’t I achieve the 20 degree drop in temperature?
There are other factors that come into play, such as:
Air infiltration, also known as leaky house syndrome: In this instance the home allows warm moist air in the summer to infiltrate the walls of the home, typically where the masonry foundation meets the studded walls. The warm humid air enters the home and travels through the home warming your air conditioned air and adding humidity, eventually exiting through ceiling mounted lights, attic hatches or other openings on the top floor. This is a continuous process that prevents the home from properly cooling and it only gets worse when the temperature rises.
A Leaky air duct system: Air leaks in the supply or return sides of the air duct system will greatly reduce the efficiency of the system. As air is escaping the home into the attic or basement on the supply side or on the return side warm moist air is brought into the system which will overwhelm the system’s capacity.
Insulation: An air duct system located in an attic or open crawlspace needs to have the proper amount of insulation and it must be properly attached. The same goes for the attic of the home. Areas without insulation or where insulation is improperly installed will create hot spots and allow heat to infiltrate into the home. Today it is recommended to have at least 18” of insulation in an attic and this is almost never the case.
Additional items like leaving a window open a few inches, leaky doors and windows, improperly sized air duct system, too little return air or too little supply air, blocked registers, etc. All of these things will cause your home’s cooling system to underperform.
The problems only get worse as the temperature rises!
Once we reach 100 degrees the best you can expect a properly sized system to perform, assuming there are none of the other issues mentioned above is about a 15 – 17 degree drop in temperature. So 85 degrees inside with a relatively low humidity level is really good.
These type of heat waves don’t usually last very long so consider the following additional steps to help your cooling system work its best!
- Turn on your system now and give it a chance to do its job before it gets over 90 degrees.
- Make sure the outside unit can breathe and is not covered with bushes or other debris.
- Make sure it is clean – If not hose it down with a soft flow of water from a hose and clean off as much of the dirt as possible.
- Close the drapes on the sunny side of the house preventing the sun from adding additional radiant heat into the home.
- Close all windows and doors tightly to eliminate air leaks.
- Block off the attic hatch or drop down stairs to prevent air leaks and heat infiltration.
- Set your thermostat to an achievable setting NO more than 18 – 20 degrees below the outdoor high temperature. Setting the thermostat to 60 degrees will not help, but it could cause your system to freeze and will turn it into a block of ice at which point it will not work!
- Make sure all of the registers are free of any type of restriction like furniture, clothing or other items that will block the flow of air.
- Make sure your air filter is clean and will not restrict the flow of air in any way.