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Indoor Air Quality Inspection

Unsure about air quality requirements for your construction project? Learn more about CA Building Codes!

Indoor Air Quality Inspection

Indoor Air Quality and Mechanical Ventilation

What is Indoor Air Quality? In regards to Building Inspections, Indoor Air Quality refers to the systems in buildings that dispose of stale air. Also known as IAQ, it can be measured by fan ventilation rate or by a whole building ventilation rate. In other words, how frequently does fresh air replace used air? In California, Air Quality is a privilege protected by Title 24 Building Codes. It is measured and verified by HERS Raters, just like any physical feature.  Nonetheless, there is a multitude of components that influence Indoor Air Quality. Let’s take a look at how this is done:

1) Exhaust Fans / Vents

Exhaust fans and mechanical vents expel indoor air. They must comply with standard airflow rates in order to meet a certain amount of air changes per hour (ACH). These rates can be verified by measuring the airflow in cubic feet per minute with a Balometer. Some examples include kitchen exhausts, bathroom fans, whole-house fans, and laundry exhausts.

Furthermore, there are different regulations for systems that operate continuously versus manually. Typically, manual systems require more airflow. In the 2019 code, for example, a bathroom vent would need to push 50 CFMs instead of 20 CFMs. Kitchen hood rates depend on the size of the kitchen’s volume. Usually, they need to make 5 air changes per hour or push 100 CFMs of air. Don’t forget to choose equipment that adheres to sound specifications. The maximum sound rating allowed is one Sone for continuous fans versus 3 Sones for manual fans.

As a reference, the Heating Ventilation Institute (HVI) has a directory of approved systems. Beneficially, the directory provides airflow and sound ratings on each piece of equipment.

2) Ductwork

The ductwork itself has a certain level of airflow resistance, which is measured by static pressure. Expressly, the less resistance there is the more efficiently air flows. Resistance varies on duct type (smooth or flex), as well as the length of the ductwork and the number of turns it makes. Ductwork must be a certain diameter based on those three factors. HERS Raters use an X, Y chart to determine the necessary values. So, make sure to discuss this requirement with your architect and engineers. 

3) Supply Air

Supply air is the air transferred from outdoors which compensates for exhaust air. Intake air should be at a balanced rate when compared to exhaust. Building Codes stipulate that air inlets should prevent particulate matter from entering with a combination of mesh screens and coverings. Also, they should be located within 10 ft of known sources of contamination (2019 Code).

4) Enclosed Garages

Garages must be completely sealed and separated from occupied living spaces. That means all exterior gaps are sealed with caulk or weatherstripping, etc. They must have their own exhaust air and supply air, as well. These regulations prevent harmful fumes from contaminating indoor air.

5) Filtration Systems

HVAC systems must have filtration, as they re-cycle indoor air. Air-cleaning filters are measured in removal efficiency by particulate size. When there is ductwork over 10ft in length, filters must meet 50% efficiency. In this case, they remove half of contaminants from the air with each cycle. Air filters must be accessible for maintenance


Other Factors

Multifamily buildings or single-family residences with more than one dwelling unit must adhere to unique regulations. Multi-branch exhaust is used in these cases to separate indoor air between dwelling units. Intake air can come through the same ductwork so long as a back-drat damper prevents unwanted airflow between units. Of course, air sealing measures should be in place between dwelling units. That means common walls should be free of any gaps and all doors in common areas should be weather-stripped. Once again, the goal is to minimize the spread of germs and particulate matter between occupied spaces.

Accordingly, non-dwelling units such as warehouses, or additional structures may have a unique set of codes. Frequently, the rules in these scenarios would be less strict.

Title 24 Compliance / Indoor Air Quality Inspection

In each case, you can see a wide set of variables are in place. Overall, it’s standard to employ a professional HERS Rater to fulfill your compliance verifications. The earlier you bring us on, the better your chances are at meeting Building Codes. Indoor Air Quality and Mechanical Ventilation features must be checked alongside the plans that have been approved. Give BarrierEnergy a call and get a free quote for assistance today.

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