HVAC Duct Design: The Importance of Duct Efficiency and Air Flow
What is Air Flow?
Air flow is the most important factor to the efficiency of your HVAC system. Common problems with air flow can lead to hot and cold spots, unbalanced temperatures in certain areas or rooms, and high electricity bills for overworking your system. The comfort of your home rests greatly on the efficiency of your duct design and its compatibility with your HVAC units.
How Does a Ducted System Work?
In a central HVAC system, the properly-sized air handler/furnace unit pulls air through the return air vent, where it is pushed through the filter to the blower motor and then redistributed throughout the rooms through the ducts. It is important that your duct design is efficient and up to code to adhere to energy efficiency standards, health standards, and your comfort needs.
What Affects Duct Efficiency?
It is important for your duct design to be efficient and properly fitted to your home and comfort needs. Your expensive new HVAC system will not work properly if your ducted system is inefficient or in poor condition. Here are few factors that affect the efficiency of your duct design:
Depending on the type of home/building, the ducts can be located in the attic, basement, or a crawlspace. If the location of the ducts is not big enough to fit the size of ducts needed, this can cause air flow problems. Also, if the location of your ducts does not properly protect them from outside weather, sunlight, or animals, this can lead to extra deterioration of your ducts.
Duct insulation (R-Value)
The quality of ducts you install is important to prevent air leakage. The R-Value of the duct determines how well-insulated the ducts are and how much air leakage was reported in factory tests and lab settings. The minimum required R-Value for new installations of ducted systems is R-6.
Duct surface area/ size
The bigger the area, the longer it takes to change the temperature. This is why it is important that your ducts and units are properly-sized for each other. If your home requires a bigger unit for your comfort needs, your ducts should be larger in size to match the amount of air that needs to be pushed through your units. Likewise, if you have a smaller unit for a smaller home, if your ducts are too big then you will run into airflow problems as your unit works harder to try to push air through ducts that are too big.
Air leakage of duct system
If there are holes or gaps in your ducts, air will leak through and your system will have to work harder to balance air flow. Gaps can occur with lazy installation if cheap ducts or improper sealing materials are used, or poor design if ducts have to be stretched to reach air vents. Over time, stretched ducts pop-off or become detached and allow air to escape. Holes can be caused by exposure to weather, sun deterioration over time, or from rodents chewing holes and nesting in the insulation. Make sure that your ducts are properly protected from outside elements, and that any rodent issues are dealt with immediately to prevent further damages to your ducts.
When you upgrade your HVAC units, make sure that they are properly-sized to your comfort needs and duct design. It’s a common mistake to oversize your unit thinking that it will increase the efficiency of your system. In actuality, an oversized unit will increase air flow problems if it is not correctly sized with your duct design and comfort needs.
“HVACR systems function at 60-70% of their lab-tested efficiency if they are not installed properly” – The Air Conditioning Contractors of America
It is important that you have a knowledgeable and trustworthy company design and install your duct system to ensure that it is properly sized, sealed, that proper materials are used to connect and close all gaps, and to ensure no ducts are kinked or stretched. They should also provide the proper duct testing and commissioning to make sure your system is up to standard for city and state energy efficiency codes. For a FREE ESTIMATE on upgrading or installing a new duct design contact us here.
Stamped Face registers/grilles
These are older style vents that are characterized by their one-way facing blades. Blades are set in place and are not adjustable. There may be blades that face different ways on the vent, but the direction of air flow is set in place.
Bar Type registers/grilles
Bar type registers have adjustable blades that can open up vents for more or less air flow according to your needs. Bar type registers are rated for higher and better air flow than stamped face registers.
Often times, traditional single-zone systems can leave hot or cold spots. For example, the upstairs may run hotter since hot air rises, or the East side of the house may be warmer in the morning because of the sun rising and directly hitting that side of the house. Also, rooms that are furthest away from the thermostat may vary in temperature, sometimes getting up to ten degrees warmer or colder than the area near the thermostat.
How Does Zoning Work?
With zoning, dampers are added in the duct design and multiple thermostats can be installed depending on the number of zones. Zones can be divided to individual comfort needs so that rooms that are used more often are conditioned as needed. This can potentially save energy as only rooms or areas that are being used are conditioned as needed and no extra energy is being wasted trying to cool the whole house when only one area is being used.
At Castillo Heating & Air Conditioning, Inc. we can talk to you about your current duct design or a new design for your new system to give you the best comfort for your individual needs. Call us today for a FREE ESTIMATE on a new system or a new duct design.
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