Glossary

Btu/hr
British thermal unit per hour, also abbreviated Btu/h. One Btu equals the amount of heat needed to raise the temperature of one pound of water one degree Fahrenheit. Used for measuring heating and cooling equipment output.

Building Envelope
The Building Envelope is made up of the elements of a building that enclose conditioned spaces and through which thermal energy may be transferred to or from the exterior.

Climate Zone
The Energy Commission established 16 climate zones that represent a geographic area for which an energy budget is established. These energy budgets are the basis for the energy standards for Title 24.

Coefficient of Performance, Cooling (COP)
The coefficient of performance for cooling is "...the ratio of the rate of net heat removal to the rate of total energy input, calculated under designated operating conditions and expressed in consistent units, as determined using the applicable test method in the Appliance Efficiency Regulations or § 112."

Coefficient of Performance, Heating (COP)
The coefficient of performance for heating is "...the ratio of the rate of net heat output to the rate of total energy input, calculated under designated operating conditions and expressed in consistent units, as determined using the applicable test method in the Appliance Efficiency Regulations or §112." For residential buildings, the COP is used for large heat pumps, those with a capacity greater than 65,000 Btu/h.

Combined Hydronic Space/Water Heating
A combined hydronic space conditioning and water heating system is one in which both domestic hot water and space heating is supplied from the same water heating equipment. Combined hydronic space heating includes both radiant floor systems and convective or fan coil systems.

Conditioned Floor Area (CFA)
Conditioned floor area (CFA) is the [total] floor area (in square feet) of enclosed conditioned space on all floors of a building, as measured at the floor level of the exterior surfaces of exterior walls enclosing the conditioned space.

Conditioned Footprint Area
The conditioned footprint is the total area of the building footprint, in square feet, not including unconditioned space. The conditioned footprint area may be equal to the first floor area, or it may be greater. The footprint area is the total area of floor over unconditioned space (not over conditioned space), ambient air and slab-on-grade. One way to think of the conditioned footprint area is as the area of the largest conditioned floor in the building plus the conditioned floor area of any projections from other stories that extend beyond the outline of that largest floor.

Conditioned Space
In residential compliance, conditioned space is space in a building that is either directly conditioned or indirectly conditioned.

Controlled Ventilation Crawl Space (CVC)
The Energy Commission has approved an exceptional method for analyzing the energy impact of buildings with raised floors which use foundation wall insulation and have automatically controlled crawl space vents. The method is available as an option using an approved computer method with unique modeling criteria explained in Chapter 5, following installation guidelines found in Chapter 8.

Cooling Load
The rate at which heat must be extracted from a space to maintain a desired room condition.

Cool Roof
A cool roof is a roof surface with a high reflectivity and high emittance. To qualify as a cool roof with the standards, the initial reflectivity must be greater than 0.40 for concrete and clay tile roofs and 0.70 for all other roofs. The emittance must be greater than 0.75. A cool roof rejects solar heat before it enters the building by reflecting it back to the atmosphere.

Dominant Occupancy
In mixed occupancy buildings, the dominant occupancy is the occupancy type with the greatest percentage of total conditioned floor area.

Dual-Glazed Greenhouse Windows
"Dual-Glazed Greenhouse Windows are a type of dual-glazed fenestration product which adds conditioned volume but no conditioned floor area to a building."

EER (Energy Efficiency Ratio)
The energy efficiency ratio (EER) is "the ratio of net cooling capacity (in Btu/hr) to total rate of electrical energy (in watts), of a cooling system under designated operating conditions, as determined using the applicable test method in the Appliance Efficiency Regulation or § 112."

Electric Resistance Heating
As mentioned in the explanation of Energy Budget in this Glossary, electricity is inherently less efficient than gas as a heating energy source because it must account for losses associated with generation from depletable fossil fuels and transmission to the building site. A source energy multiplier of 3.0 (representing a net efficiency of 33 percent) is assigned to electricity by the standards.

Enclosed Space
"Enclosed space is space that is substantially surrounded by solid surfaces."

Energy Budget
"Energy budget is the maximum amount of source energy that a proposed building, or portion of a building, can be designed to consume, calculated with the approved procedures specified in Title 24, Part 6."

The low-rise residential standards are based upon the concept of an annual energy budget. This is the measure of source energy used per year in a building. The energy budget for low-rise residential buildings includes space heating, space cooling and domestic water heating. To comply with the standards, the energy use of the proposed building design must be less than the annual energy budget.

Energy Factor (EF)
Used to measure the efficiency of water heaters, the Energy Factor (EF) is "the ratio of energy output to energy consumption of a water heater, expressed in equivalent units, under designated operating conditions over a 24-hour use cycle, as determined using the applicable test method in the Appliance Efficiency Regulations."

Energy Obtained From Depletable Sources
"Energy obtained from depletable sources is electricity purchased from a public utility, or energy obtained from burning coal, oil, natural gas, or liquefied petroleum gases."

Energy Obtained From Nondepletable Sources
Also referred to as renewable energy, including solar and wind power, energy from nondepletable sources is defined as energy that is not obtained from depletable sources.

HSPF (Heating Seasonal Performance Factor)
The Heating Seasonal Performance Factor (HSPF ) is "the total heating output of a heat pump (in British thermal units) during its normal usage period for heating divided by the total electrical energy input (in watt-hours) during the same period, as determined using the applicable test method in the Appliance Efficiency Regulations."