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Indoor Air Quality Inspection

Unsure about air quality requirements for your construction project? Learn more about CA Title 24 Building Codes!

Indoor Air Quality Inspection

Indoor Air Quality and Mechanical Ventilation

What is Indoor Air Quality? In regards to building inspections, “air changes per hour” are the basis of Indoor Air Quality. A HERS Rater verifies how long it takes the exhaust and/or filtration systems to dispose of stale air. Also known as IAQ, it can be measured via fan ventilation rate (CFMs) or by a whole building ventilation (ACH) rate. In California, Indoor Air Quality is a privilege Title 24 Building Codes protect on behalf of property owners. Nonetheless, there are a multitude of factors that influence IAQ. 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 number of air changes per hour (ACH). Raters use a Balometer to verify airflow rates in cubic feet per minute (CFMs). Some examples include kitchen exhausts, bathroom fans, whole-house fans, and laundry exhausts.

You can determine the appropriate equipment to install by checking the requirements for various building types (ie single vs multi-family). Furthermore, there are different regulations for ventilation that operates continuously versus manually. Typically, manual systems, which can be turned off, require more airflow. In the 2019 code, for example, a bathroom fan would need to push 50 CFMs with intermittent use versus 20 CFMs with continuous. Kitchen hood rates depend on the size of the kitchen’s volume. The average manual downdraft would need to make 5 air changes per hour or push 300 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 ventilation 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 best to choose a professional HERS Rater to fulfill your compliance needs. The earlier you bring us onto a project, the better your chances are at meeting Building Codes without delays. We must compare Indoor Air Quality and Mechanical Ventilation features alongside the plans that your local Building Department has approved. Give BarrierEnergy a call and get a free quote for assistance with your Title 24 needs today.

(888) 383-HERS (4377)

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