FAQ

One of the most common reasons for duct testing is to tell whether a new HVAC system has been installed correctly. A reputable contractor will usually offer to perform the test after installation to demonstrate to a customer that everything is as it should be as far as airtightness is concerned.

If you have an older system and have noticed that airflow is low even after changing filters or replacing the HVAC unit, it could be worth checking whether the solution is related to leakages in the ductwork.

The standard pressure used for duct leakage testing is 25 Pa, which is similar to the regular operating pressure of a typical duct system. 

As a result, leakage test results are usually given in the airtightness measurement CFM25. CMF25 stands for ‘cubic flow per minute’ at 25 Pa.

In basic terms, this translates to a reading in which 100 cubic feet per minute of duct leakage at 25 Pa equals 100 CFM25. 

This measurement adds up to a relatively precise reading for the quantity of air escaping through leaks in the ductwork.

A leakage test will usually take around 40 minutes. It takes around 30 minutes to prepare the supply and return vents and 5-10 minutes to run the test.

Depending on the area covered by the ductwork, it will take more time to locate leakage points if the test indicates they are present.

Ductwork usually passes through sections of ceiling or flooring that often contain large amounts of dust.

If you have a leak in the ductwork, your system could be sucking up this dust and then dispersing it in your living space. 

If this happens, the very system that is supposed to keep your air clean and crisp could be causing a drop in overall air quality.

Leaks can lead to the build-up of moisture inside the ductwork. The presence of moisture makes ductwork the ideal breeding ground for mold and mildew. 

When the spores from these microorganisms are spread through the air in a building, they can harm its inhabitants' health.

Ductwork usually passes through sections of ceiling or flooring that often contain large amounts of dust.

If you have a leak in the ductwork, your system could be sucking up this dust and then dispersing it in your living space. 

If this happens, the very system that is supposed to keep your air clean and crisp could be causing a drop in overall air quality.

Leaks can lead to the build-up of moisture inside the ductwork. The presence of moisture makes ductwork the ideal breeding ground for mold and mildew. 

When the spores from these microorganisms are spread through the air in a building, they can harm its inhabitants' health.

Providing the contractor who is performing the test has the requisite skills and experience. No harm should come to your ducts.

On the other hand, not getting leaky ducts repaired promptly can increase the cost of future repairs.

Duct leakage testing is a complex operation that should be done by a trained HVAC professional. When choosing a contractor, look for BPI Infiltration and Duct Leakage (IDL) certified contractors like Air and Energy of NWFL!

This certification ensures that the contractor has the knowledge, skills, and field experience to conduct an effective duct pressurization test to calculate total system leakage, the degree of leakage to the outside, and general analysis.

Leaks in ductwork cause a loss of air pressure inside an HVAC system. 

This forces an air conditioning unit to work much harder to produce the same amount of hot or cool air. The extra work the unit must do to maintain indoor temperature means more energy is consumed, lowering the system's overall energy efficiency.

In a perfect world, your ducts should be one hundred percent airtight. However, this is rarely, if ever, possible in reality.

While every system will have one or two natural air escape points, ENERGY STAR®, the joint program run by the U.S. Environmental Protection Agency and the U.S. Department of Energy, states that an energy-efficient system should only have a maximum of 6% air leakage.

While you are not required to test your ducts for leakages as the owner of an existing building, new buildings containing Florida HVAC systems are now subject to mandatory duct testing.

According to the 2017 Florida Building Code Energy Conservation, 6th Edition Section R403.3.2 Sealing (Mandatory):

“Duct tightness shall be verified by testing in accordance with ANSI/RESNET/ICC 380 by either individuals as defined in Section 553.993(5) or (7), Florida Statutes, or individuals licensed as set forth in Section 489.105(3)(f), (g) or (i), Florida Statutes, to be “substantially leak free” in accordance with Section R403.3.3.”

A blower door is a diagnostic device that comprises a variable-speed fan that is mounted in a flexible airtight covering. This covering is designed to fit snugly in a doorway of a building.

A blower door device is designed to provide a measurement of airflow in a building using hoses and a manometer. The device includes associated software, control mechanisms, and a pressure gauge to measure the difference in air pressure inside and outside a building through a process of pressurization and depressurization.

Blower door testing is a process carried out to determine the air infiltration rate of a building. A blower door device to come up with an airtightness reading which involves the use of a pressure gauge to calculate the amount of air that is coming in through any unsealed cracks and openings. The results of the test will indicate whether it is necessary to spend time and money on sealing these leaks.

Blower door tests are usually used as part of the code of compliance testing in the construction of new homes. These tests are also a central part of building energy audits.

A blower test on its own will not make your home more energy-efficient. However, the results of the test will give you a good indication as to the action you can take to improve energy efficiency.

A structure with a low degree of airtightness will need more energy to both heat and cool. During the hot summer months in Florida, your air conditioning system will have to work overtime to compensate for the cool air that is constantly escaping through exfiltration and the warm air that is entering via infiltration. The same process applies to the energy consumed by your heating system in the winter, except this time, it is the warm air escaping and the cool entering.

Blower door tests are performed in Florida and across the country by contractors who have certification from one of the two different blower door test certifying authorities.

Before you call in a contractor to inspect your home and carry out these diagnostics, it is important to make sure they are certified as HERS rated by RESNET or by the Building Performance Institute (BPI).

If a blower door test reveals that your building has a high rate of air leakage, the next course of action is to locate some of the places that you suspect airtightness is being lost. During the test, you can walk around checking the gaps around windows, doors, and other openings with your finger for any noticeable leakages.

Generally speaking, if you invest time and money in attacking airflow leakage points with sealant or filler, you can usually achieve a 20% to 30% reduction in the readings given by a blower door test. This percentage will come down markedly if your house already has a low level (25-30 CMF50) of air leakage.

Remember that airtightness is only desirable if you have adequate means of ventilating a building.

One of the key benefits of improving a building’s airtightness relates to air quality. Reducing airflow into a structure can mean a significant reduction in the numbers of air-borne pollutants, allergens, and microbes.

A greater degree of infiltration can also result in the accumulation of moisture inside the building envelope as airflow allows the entry of water molecules from rain, snow, and water vapor.

As of 1 July 2017, Florida law (Section 402.4.1.2, Florida Building Code, 5th Edition 2014 Energy Conservation) stipulates that all new residential constructions must pass a blower door test to ensure compliance with energy code.

Specific requirements are that each new home must have 7 ACH50 or less to pass a blower door test. Existing buildings are not subject to this law but reducing a building’s ACH50 reading is recommended to increase energy efficiency and cut down on energy costs.

Infiltration is the uncontrolled inward leakage of outdoor air that enters a building through cracks, gaps, and other unintentional breaks in the structure.

Exfiltration is the opposite—it describes the uncontrolled outward leakage of indoor air from a building through these cracks and openings.

The most common time to perform a blower door test is at the final stages of building construction when all wall finishes, fixtures, doors/windows, and appliances have been installed.

Blower door tests are also commonly carried out to test the airtightness of older buildings. Over time, seals can wear out, and cracks can open up in the structure envelope, which allows an increase in infiltration and exfiltration. If you begin to feel drafts or notice any unexplained increases in your energy bill, you should consider the option of investing in a professional blower door test.

The results of a blower door test will be delivered in the form of two readings: CFM50 (leakage rate measured in cubic feet per minute at a 50 Pa) and ACH50 (air changes per hour at 50 Pa).

The CFM50 reading is taken from the manometer on the conclusion of the test. The ACH50 is then calculated by multiplying the CMF50 reading by 60 (minutes per hour) by the volume of the building (including the basement) in cubic feet and then dividing the number by the building’s volume.