The differential in air pressure between the intake and output of a duct system is known as static pressure. If you look at it from a physics perspective, it’s the total force applied by the air against an object that won’t move.
In this case, we’re talking about a duct and the movement of air flowing through it. The more static pressure in your ductwork, the more resistance there is, leading to issues like back-drafting and poor airflow distribution.
A basic example would be if you have an open window in your home and want to keep it open during winter. You may use a smaller fan to blow out some cold air coming through that window. This will allow you to keep it open without feeling too chilly.
High vs. Low Static Pressure
High static pressure describes conditions when more forces are pressing on an object than what it can withstand; in this case, it refers to the air flowing through ductwork. Conversely, a low static pressure condition describes an area with less force pressing on an object than what it can withstand; in this case, it refers to air escaping from vents or grilles.
Low Static Pressure
Low static pressure is desirable because it allows more flow through your vents and grilles without as much resistance from your ductwork and other components in your HVAC system. This means you get better airflow throughout your home and fewer problems with ducts or registers blocking airflow out of the building envelope.
High Static Pressure
High static pressure is undesirable because it reduces airflow through your vents and grilles while increasing friction losses inside your ductwork and other HVAC system components. This often results in higher heating costs.
What Determines the Pressure
The amount of static pressure at a given point is determined by several factors like:
- Size of your ductwork
- Type of fan or blower is used
- The outside temperature and humidity
- The amount of insulation in the duct system (for example, fiberglass insulation)
How Will Static Pressure Affect My HVAC System?
The higher or lower the static pressure, the more force it takes to move air through your ductwork and air filters. It can cause several problems.
1. Noisier Operation
The harder it is for your HVAC unit to push air through your ducts and filters, the louder it will be. It’s especially true if you have an older unit with worn-out compressor bearings.
2. Parts May Wear Out Faster
If there’s not enough resistance to airflow, the fans that push air through the ducts may wear out more quickly than otherwise.
If there’s too much resistance to airflow through your ductwork, it could cause leaks or other damage over time.
4. Increased Energy Costs
Static Pressure causes the fan in your system to work harder to move air through your ductwork. This increases your energy costs and shortens the life of your HVAC equipment.
5. Airflow Inefficiencies
Inefficient airflow means that the air entering your home isn’t distributed evenly throughout all house areas. It causes hot and cold spots in different rooms, making it uncomfortable for you and your family and increasing your energy bills as you try to heat or cool those areas separately.
6. Air Quality Issues
If static pressure is too high in an individual room, it might cause an air leak that could lead to dirty air being drawn into the rest of your home’s ventilation system. This leads to poor indoor air quality (IAQ), which can be particularly problematic if allergies or people living with asthma live in the home.
How to Prevent Static Pressure Problems
There are several things to do to prevent static pressure from affecting your HVAC system.
1. Use Smooth Ductwork With No Bends or Curves
Ductwork with a lot of bends or curves can increase friction and cause increased pressure. Custom-made ductwork can help reduce the number of curves and bends in your setup.
2. Use Larger Diameter Pipes to Supply Air
This reduces friction and allows more airflow per unit of energy consumed by the furnace or AC unit.
3. Install Dampers on Interior Supply Vents
These allow you to adjust where the heat goes inside your home, which can help balance temperatures throughout the home better than having them all open at once.
4. Ensure All of Your Fans Are Properly Sized
If you have too much static pressure, you won’t be able to achieve optimal airflow through your HVAC system, and it will be more difficult for your unit(s) to remove moisture from inside your home or building.
5. Clean or Replace Your Filters More Often
The recommended interval for cleaning or replacing your filters is once every month or two, depending on the type of HVAC system you have and the conditions in your home. For instance, if you own pets, have allergies, or asthma, this should be done more frequently than recommended.
How to Fix Static Pressure Problems
Too much static pressure can cause the valve to stick open and allow air to escape through the supply ducts. On the other hand, too little static pressure may prevent the valve from closing completely, causing leaks.
The best way to fix a static pressure problem is to identify what has caused it and adjust your HVAC system accordingly.
1. Use a Booster Fan
A booster fan increases the amount of air being pushed through ductwork and reduces static pressure. A booster fan gets installed inside or outside your HVAC unit; however, it must be approved by AHRI for outdoor use if installed outside of your HVAC unit.
2. Add Dampers or Valves to Ductwork
These devices control airflow through ductwork and help reduce high static pressures in certain areas of your home where they’re needed most (for example, near windows).
3. Control Humidity Levels
Increasing the distance between bends reduces friction and allows more air to flow through the system for better comfort and energy efficiency.
4. Keep Air Filters Clean and Replace Regularly
This will keep your air flowing smoothly and help prevent dust from collecting in your ductwork. Clogged return grilles are located at the end of your supply duct, where fresh air enters your home or business. If this area becomes clogged with dust and debris, it can cause high static pressure problems by slowing down airflow into your home or business.
If you install a fan to run on your central air conditioning unit, and you have that fan turned on full blast, there will be a lot of air coming through those coils. As a result, there will be excess pressure that needs to get relieved from those coils.
You want to make sure that you have adequate static pressure in your system so that when it runs for an extended period, it won’t blow up any seals or gaskets or anything like that. You need a professional to work on the HVAC system.
Contact Protek Roofing, Heating, Air & Solar today for more insights or request professional help! We offer comprehensive heating and cooling services as well as roofing and indoor air quality solutions to the residents of Tampa, FL and surrounding communities.