California’s Title 24 adds new HVAC requirements aimed at reducing a new home’s energy use by 25 percent.
This is the third in a series on how new Title 24 building code requirements are affecting homebuilders in California—and beyond.
Heating, air conditioning and ventilation (HVAC) uses about half a home’s energy, so when California touts that its new Title 24 requirements are aimed at reducing a new home’s energy use by 25 percent, you can bet a big portion of that means HVAC. But don’t just think heating and air conditioning. Proper ventilation, especially in tighter built homes, is being stressed.
The new HVAC regulations are also interesting in that they can integrate some of the latest technologies such as smartphone-controlled thermostats.
The California Energy Commission’s standards for HVAC alone are 128 pages long.
Temperature Sensors and Thermostats
Homes with central air and heating must have setback programmable thermostats with a minimum of four programmable time periods during a 24-hour cycle. A single thermostat can control two separate sources (heating and air-conditioning) or there can be individual thermostats. Additionally, each sleeping zone and living zone (kitchen, living room, office, etc.) must have an individual temperature sensor. The thermostat does not have to be able to communicate with the utility provider for demand response program purposes, but it must have the capability for such a feature to be installed at a later date.
Tighter Homes Need Better Ventilation
Under California’s new Title 24 regulations that went into effect last month, the infiltration default, meaning the amount of air leaking in and out of a building, has been reduced from 3.8 Specific Leakage Area or seven air changes per hour, to 3.8 SLA (five ACH). This means two things: that ventilation through controlled means is also increasing, and that air infiltration testing for a tighter home is unlikely to result in credits that can offset other features required under Title 24, according to an impact study conducted by the California Homebuilding Foundation.
That being said, “It is good building science to ventilate the tight buildings the energy code demands,” the study reads.
Double the Venting?
Whole house ventilation has been a requirement for the last couple rounds of code updates, but the newest regulations put whole house fans on the list of recommendations for California’s climate zones 8 through 14. The fans, while noisy in some cases, can reduce the need for air-conditioning. According to the CEC’s compliance manual, whole house fans are relatively inexpensive; both in installation and operating costs, and are “highly effective if used properly in the right climate.”
While whole house fans are recommended for most of California’s climate zones, fan watt-draw tests are mandatory, though there is a workaround.
The test measures how much electricity the fan uses at full power. Reducing the wattage drain of the fan can significantly reduce an HVAC system’s energy consumption. The test must be done by an expert certified by the CEC to conduct the testing after the system is installed.
Therein lies a problem, according to the CHB’s study, but the code has a way out of that as well.
“If you don’t want to do that testing … you need twice as much returned air as before,” says Mike Hodgson of ConSol energy consultants, who authored the CHF’s study. He says builders will most likely choose to double the duct size rather than take the chance of failing the fan watt-draw test.
Since many builders may not want to rely on a compliance test that happens “post-construction,” the regulations allow the builder to opt instead to increase the size of the return duct intake grill to specifications defined in the code. The CEC table requires return duct sizes that are double the size of typical current construction practices.
Air Conditioners, Furnaces, and Federal Standards
If one thinks California is way ahead of the rest of the country in every aspect of energy efficiency, think again.
The latest revision of the National Appliance Energy Conservation Act Standards for air conditioner efficiency (14.0 SEER, 12.2 EER) takes effect on Jan. 1, 2015, six months after the CEC’s 2013 Standards took effect. While the CEC did not incorporate the new federal standards into its regulations, the CHF study recommends that builders over the next six months use the upcoming national standards for air-conditioning, and the CEC has assured builders and that its compliance software will include the more stringent federal requirements before Jan. 1.
As Robert E. Raymer, senior engineer/technical director for the California Building Industry Association, told TecHome Builder, building to 14 SEER AC in California is now assumed, but if a builder wants to build to 13 SEER it could until the federal requirements go into effect early next year.
As for furnaces, the CEC was able to incorporate the Annual Fuel Utilization Efficiency (AFUE), which changed to 80 percent last May.
The new Title 24 requirements also mandate duct sealing and raise duct insulation from R-4.2 to R-6.
Everything in the new requirements ensures that air goes where it’s needed, when it’s needed and doesn’t escape outside until it’s finished its job.