HVAC Duct, a Homeowner’s Guide

Your hvac duct system is the heart of your home’s heating and cooling system. Without a healthy system you could be wasting a lot of money. Like the human body, if the heart isn’t healthy you are in trouble.

A duct system provides a controlled path for air flow throughout the home. The system can be made out of sheet metal, fiberglass ductboard, insulated plastic, or cloth. Many times, a combination of these materials is used in the same home.

There are three main parts to the system. A problem in any part results in a sick system.


How A Duct System Works…

The first section is called return air. This part provides a path for air from the individual rooms to the inlet of the furnace or air handler. The air is usually cleaned in this section of the system. In a healthy system, fresh air is introduced here. In some cases moisture is required and added here as well.

Next, the air passes into the furnace or air handler. This is where heat is added or removed to make the home comfortable. In most older systems, the filtering was performed here. This was not very convenient for the owner and caused service problems. Finally, this conditioned air enters the supply section of the system. The
purpose of this part of the system is to deliver conditioned air to the individual rooms.

The two main types of supply systems are extended plenum and central plenum. A central plenum system is a system where all of the branch ducts start at the same location called a plenum.

The extended plenum system consists of a supply air plenum which is connected to the outlet of the hvac equipment. The main supply ducts are attached to this and typically run to the end of the home. The size of them is reduced as necessary to maintain adequate air flow. The branch ducts attach to the main ducts and carry the conditioned air to the individual registers. That is the basics of how a system works. Now we will look at some common problems and how they can be fixed.


My System Is Noisy…

So, how will you know that your hvac duct system is sick? One of the first symptoms will be a whistling, wheezing, or popping noise. This is a sign that the system is working harder than normal to maintain your comfort. It is like the beginning of chest pains for a heart patient.

As the condition gets worse, the next symptom will usually be an abnormally high utility bill. Many times this will go unnoticed until the unit is unable to keep you comfortable. This is where the situation gets really critical. Intervention is required to save your heating and air conditioning equipment.

If this is a new system (less than a month old), it is likely that the ducts are not properly sized or the system is not properly balanced. For an improperly sized system, there are a few things that can be done to minimize the effects. The first thing is to retrofit a zone system but this can be expensive. If too much air is being delivered to a room, a damper can be partially closed to lower the amount of air. Many registers have a built in damper to allow you to do this. If there is not enough air being delivered to a room, then a duct booster fan may be installed to increase the amount of air delivered to the room. If it has been operating for a month or longer, the system filter may need cleaning or replacement.


Upgrading Your System…

If you have an uninsulated metal duct system, you can do some easy upgrades to enhance your comfort as well as saving you money on your utility bill. You can begin by sealing the system which is applying a special mastic to the cracks and connectors to make them airtight. This ensures that the conditioned air does not leak out into areas where it is not needed. After sealing the system, you should insulate the ducts if they are located in an unconditioned basement, crawlspace, or attic. This is an easy project that can provide a quick return on the investment.


Installing Air Ducts…

The installation of a system is not overly complicated and the work does not require a huge amount of technical knowledge. The process starts with a proper design and then it is simply a matter of following the duct plan.

With our air duct installation guide you can install your own metal duct system and save. You can also use our flexible duct installation guide for situations that require insulated ducts such as an attic or crawlspace. If you are not going to do it yourself, then your selection of a hvac contractor is very important.

Contact Above All Air Heating & Cooling today for a free inspection and estimate.