California Title 24 Part 6 has mandatory requirements for residential occupancy to provide mechanical ventilation to the ASHRAE 62.2 requirements and they apply to ADU’s, Single Family New Construction, Single Family Additions, and Single Family alterations. There are three major areas to be aware of:
- 1) Whole home ventilation requirement: It is mandatory to provide a whole building ventilation system to exchange old indoor for fresh outdoor air. This ventilation rate is required to be specified before the permit can be issued. The method of compliance is up to the owner. The three approved methods are supply, exhaust, and balanced.
- Supply: A fan provides fresh outdoor air to the conditioned space and the surplus air exits the building through the exhaust fan ducts or building leakage. Good because you know where the air is coming from, bad because the positive pressure can have impacts on combustion appliances and the HVAC system
- Exhaust: Exhaust is the most common because it is the easiest. You choose one, (or a couple if needed to meet the air flow requirement,) of your bathroom exhaust fans and you leave them running continuously. The home is depressurized and the make up air comes in around the doors, windows, or other areas typically not sought after for fresh air like crawlspaces, plumbing drain chases, water heater exhaust vents, or the dryer exhaust.
- Balanced Ventilation: Integrated system or a system of two separate fans which supply’s as much air as the system exhausts so the home is neither pressurized or depressurized. Integrated systems have the ability to transfer some of the energy from the air being exhausted to the air being supplied, reducing the energy penalty for exhausting air you have expended energy to heat or cool. These systems are known as heat recovery ventilators or enthalpy recovery ventilators and use a heat ex-changer to transfer heat and humidity between the supply and exhaust air. Balanced systems are the preferred IAQ system for whole home ventilation.
- 2) Kitchen Range Hood: Kitchens have minimum ventilation requirements based on the cooking fuel. The stove and cook top have to be ventilated and the ventilation system must be ducted outside. The ventilation system has to be verified through a listing with HVI or AHAM to move at least 100 cfm while not making more than 3 sones of noise. The installed hood must be listed with HVI or AHAM and a HERS rater would have to verify the listing. An alternative would be to provide a ventilation system that can provide at least 5 ACH for the kitchen when ever the cook top is in use.
- 3) Bathroom: Bathroom exhaust fans are required to provide 50 cfm if on demand or 20 cfm if continuous. There are also Title 24 Part 11 CalGREEN requirements and if the bathroom fan is providing the whole home ventilation requirement then it must meet that flow rate and be rated for continuous operation.
We will be providing other content on air filtration covering MERV 13 filters, whole house fans and the best strategy for controlling indoor pollutants. Contact Anchors Aweigh Energy LLC with your IAQ questions.
