HVAC For Beginners


A Guide to Understanding the System Behind Your Heating and Cooling

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 airflow 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. We will begin with a look at some of the pros and cons of each type of duct material. Cloth duct systems are mostly used in large commercial or industrial applications due to the fact that the ducts must be exposed. They are very inexpensive and are easy to install.

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You can watch our informative videos to learn about HVAC duct systems.

HVAC Duct Basics

Metal Duct System Installation

The insulated plastic ducts (commonly called flex ducts) consist of a reinforced plastic inner duct with a layer of insulation between it and the outer protective layer. The outer protective layer may be plastic or a very thin metal. These duct systems are the least expensive and the easiest to install but, if not done properly, it is easy to compromise the performance and efficiency of the system. You can use our installation guide to see how to install these systems properly.

The duct board system is a bit more difficult to install because of the special tools that are required to properly fabricate the ducts. The systems are more expensive than simple metal or flex ducts but offer better performance due to the fact that the systems are sealed and insulated at the same time that they are installed. The basic (uninsulated & unsealed) metal duct system is about the middle of the road as far as cost is concerned but is the hardest to install. These systems are typically more noisy and less efficient than the other types of duct systems.

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 hvac duct 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 hvac 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 the HVAC duct system

The installation of a hvac duct 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. If you are not going to do it yourself, then your selection of a hvac contractor is very important. Our partners will assist you in this process. With their free service, you can get up to four quotes from local hvac companies without even leaving your home. Simply provide some basic information and then local pre-screened contractors will be alerted and will contact you to give you a quote. It's that fast and easy!