Your HVAC system does more than remove or add heat to your home. This system also needs to distribute that treated air throughout the home via a network of ducts and registers. In order to work efficiently, the ductwork needs to be correctly fitted and installed based upon the requirements of the specific HVAC system. Both the HVAC system and the ductwork must be carefully matched, or the entire system may be less effective. But, how is ductwork sized to fit a specific space? In this article, we will explore this topic in more detail and explain the importance of a professional installation.
The importance of Ductwork Sizing
We invest a great deal of money in our HVAC systems, and great strides have been made by manufacturers in recent years to produce more efficient systems. This has been done to meet stringent environmental standards, but it does make HVAC systems cheaper to run. But, much of this efficiency can be lost if the ductwork and the HVAC system are not carefully matched and installed correctly.
What Does HVAC Efficiency Mean?
We hear the term efficiency a great deal when it comes to cooling and heating, but most of us don’t understand what that really means. Essentially, an HVAC system is deemed to be efficient if it can heat or cool a home without consuming more energy than is required. In order to determine how much air conditioning or heating is needed for a specific home, an HVAC professional will need to carry out load calculations.
What is a Load Calculation?
A load calculation is a complex formula that determines home much air conditioning or heating a specific room requires. The result is expressed in cubic feet or airflow per minute or CFM. There are free online tools to carry out a load calculation, but they are inaccurate because they are only based on the square footage of the space. There are many more factors to consider when making load calculations, such as the orientation of the home, the number of windows, nearby sources of shade (trees and buildings), insulation levels, and others. Obviously, these factors cannot be included in load calculations made with an online tool. An accurate load calculation must be performed by an HVAC service technician on a room by room basis. They will visit even room in the home and input their gathered data into a Manual J protocol. This will interpret the data and calculate the load for the entire home.
What is the Relationship Between a Load Calculation and the Duct Size?
Remember that the load calculation represents the heating and cooling requirements of the space. This, in turn, must be factored against the output capacity of the air conditioner or furnace. The result provides the HVAC technician with an “output vs. requirement” calculation. This is a chart that can be used to determine the required duct size to match the heating or cooling equipment for that home.
What Happens if the Ductwork Size is Wrong?
If you’ve hired a local HVAC specialist to carry out your load calculator for you, the calculations should be correct. But, what if you’ve purchased a home with an HVAC system already installed or you had a system installed recently by someone with no formal HVAC knowledge? If the ductwork is the wrong size, there are three major problems that could occur, they are:
- Static Pressure
If the ducts are undersized for the HVAC system, there may be an increase in the amount of static pressure in the entire system. This typically translates into an excessive amount of noise when air is moving through the ductwork. This noise isn’t background noise, it can get really loud, and most people cannot ignore it for long. Another problem with static pressure issues is that it can cause the heating unit to become overworked. When heating and cooling equipment is placed under additional stress components, start to fail. This often happens when the equipment is working hard already, which would be on a cold or hot day. So, if you notice a load noise as treated air is passing through your ductwork, contact a local HVAC specialist and get them to take a look. Changing the duct size will get rid of the annoying noise, and it may help you to avoid an unexpected series of repair bills.
- A Lack of Performance
If the duct is too large, it may prevent the treated air from reaching its destination. The airflow is simply inadequate to direct the air to where it needs to go, and this results in rooms that are under conditioned. The temperature on the thermostat will be hard to achieve, and again, this places the equipment under a great deal of stress. Essentially, you will be paying energy bills and receiving a lack of performance and damage to your HVAC system for your trouble.
- Inadequate Returns
If the duct layout or size is not correct, this can lead to inadequate returns throughout the entire system. This means that the system cannot pull enough air from the rooms in your home back into the HVAC system. This, in turn, leads to an imbalance in the internal air pressure throughout the entire home. This will make the affected space feel stuffy because they are poorly ventilated.
As you can see, there are significant disadvantages to ductwork that is too small or too large. It’s vitally important to get the ductwork size correct if you want to get the best performance and optimal efficiency from your HVAC system. The layout of the ductwork is also a key factor, and a poor installation can wreck the efficiency gains that you would have received from your new HVAC system. The result is a poor level of performance and energy bills that can get out of hand quickly.
If you’re concerned about the performance or efficiency of your HVAC system, contact a local heating and cooling specialist. They can carry out a professional load calculator or energy audit for you and suggest ways to make your heating and cooling more efficient.