What the Heck Is Manual J, and Why Is It Important?

You may have heard of Manual J if you’ve done any sort of research into air conditioning systems. Whether you’re actively looking to purchase a new unit or you’re just now starting to think about one, you should familiarize yourself with this term as soon as possible. The reason is that while it may be industry jargon, it is also a very important factor that will have a substantial impact on your indoor comfort for several years.

Why it’s Important

Manual J is critically vital if you’re having a new air conditioner installed. The term is simply an industry standard that helps you and your installer figure out the correct size that your new system should be. The main factors that determine Manual J are the size and kind of house in which you live.

Most building codes around the country require that a Manual J is performed, because this will help ensure that your new system lasts as long as possible, operates as efficiently as possible, and makes you as comfortable as possible. It is a fundamental step toward making sure you get a quality installation. In fact, if your contractor says that you don’t need a Manual J, you should seriously consider choosing someone else.


Some contractors may tell you that because your home is a certain square footage you need a certain size of unit. However, this is often an extremely inaccurate method of determining the correct size – many times it will lead to the installation of a unit that is too large for your needs. Not only will this result in you paying too much for your system and too much for your monthly bill, it will also make you uncomfortable. The reason is that an air conditioner that is too large will not do a good enough job of removing humidity from your indoor air.

Don’t run the risk of a so-called “professional” putting your comfort at risk by not performing a Manual J when installing your new air conditioner. Go with the experts with One Hour Heating & Air Conditioning® of Elk Groveand make sure your installation is performed correctly. Call us at (847) 744-9447 or contact us online to learn more or set an appointment.

American Comfort One Hour Heating and Air Conditioning provide HVAC services for the cities of Elk Grove Village, Roselle, Park Ridge, Schaumburg, Chicago, and the following cities in Illinois.