Annual Fuel Utilization Efficiency (AFUE): an efficiency descriptor of the ratio of annual output energy to annual input energy as developed in accordance with the requirements of U.S. Department of Energy (DOE) 10 CFR Part 430.
Baseline Building Performance: the annual energy cost for a building design intended for use as a baseline for rating above-standard design.
Boiler: an appliance intended to supply hot fluid or steam for space heating, processing, or power purposes.
Closed System: a piping system that is sealed at all points from the atmosphere and contains non-potable solution.
Conditioned Space: a cooled space, heated space, or indirectly conditioned space defined as follows:
1. cooled space: an enclosed space within a building that is cooled by a cooling system whose sensible output capacity exceeds 5 Btu/ h.ft2 of floor area.
2. heated space: an enclosed space within a building that is heated by a heating system whose output capacity relative to the floor area is greater than or equal to the criteria in Table 3.1
3. indirectly conditioned space: an enclosed space within a building that is not a heated space or a cooled space, which is heated or cooled indirectly by being connected to adjacent space(s) provided:
1. the product of the U-factor(s) and surface area(s) of the space adjacent to connected space(s) exceeds the combined sum of the product of the U-factor(s) and surface area(s) of the space adjoining the outdoors, unconditioned spaces, and to or from semi-heated spaces (e.g. corridors) or
2. that air from heated or cooled spaces is intentionally transferred (naturally or mechanically) into the space at a rate exceeding 3 ach (e.g., atria).
Cool Down: reduction of space temperature down to occupied setpoint after a period of shutdown or setup.
Degree-Day: the difference in temperature between the outdoor mean temperature over a 24-hour period and given base temperature. For the purposes of determining building envelope requirements, the classifications are defined as follows:
Cooling degree-day base 65ºF (CDD65): for any one day, when the mean temperature is more than 65ºF, there are as many degree-days as degrees Fahrenheit temperature difference between the mean temperature for the day and 65ºF. Annual cooling degree-days (CDDs) are the sum of the degree-days over a calendar year.
Heating degree-day base 65ºF (HDD65): for any one day, when the mean Temperature is less than 65ºF, there are as many degree-days as degrees Fahrenheit temperature difference between the mean temperature for the day and 65ºF. Annual heating degree-days (HDDs) are the sum of the degree-days over a calendar year.
Design Conditions: the set of temperature, humidity and wind conditions that are used to estimate the heat loss and heat gain for a dwelling.
Design Energy Cost: the annual energy cost calculate for a proposed design.
Design Professional: an architect or engineer licensed to practice in accordance with applicable state licensing laws.
Distribution System: Conveying means, such as ducts, pipes, and wires to bring substances or energy from a source to the point of use. The distribution system includes such auxiliary equipment as fans, pumps, and transformers.
Dual-Purpose Water Heater: a single water heater appliance used as a heat source for a heating system and for supplying potable domestic hot water. Only certified dual-purpose water heaters should be used for both purposes.
Note: a dual-purpose water heater is also referred as a “combo unit”.
Efficiency: performance at specified rating conditions.
Energy Factor (EF): a measure of water heater overall efficiency.
Fuel: a material that may be used to produce heat or generate power by combustion.
Heat-Distribution Unit: equipment that releases heat from steam or heated water into the space to be heated.
Note: typical examples include baseboards, convectors, radiators, engineered component radiant panels, and fan coils.
Heat Source: a device that provides heat to a hydronic distribution system.
Hydronic: of or relating to a heating or cooling system that transfers energy by circulating a fluid through a system of pipes.
Hydronic Solution: the fluid in the hydronic system.
Note: the fluid can be water or a solution containing chemicals such as glycol.
Hydronic System: of or relating to a heating or cooling system that transfers energy by circulating a fluid through a system of pipes utilizing mechanical systems, including but not limited to renewable and non-renewable energy sources, energy recovery, associated equipment and appliances for space heating or cooling; potable water heating; non-potable water heating; swimming pool heating or process heating; and solar thermal systems; snow melt; frost protection; dehumidification; humidification.
HVAC System: the equipment, distribution systems, and terminals that provide, either collectively or individually, the processes of heating, ventilating, or air conditioning to a building or portion of a building.
Infiltration: the uncontrolled inward air leakage through cracks and crevices in any building element and around windows and doors of a building caused by pressure differences across these elements due to factors such as wind, inside and outside temperature differences (stack effect), and imbalance between supply and exhaust air systems.
Labeled: equipment or materials to which a symbol or other identifying mark has been attached by the manufacturer indicating compliance with specified standards or performance in a specified manner.
Open System: a piping system, conveying potable water or a hydronic solution, that is open at some point to the atmosphere.
Proposed Building Performance: the annual energy cost calculated for a proposed design.
Radiant Heating System: a heating system that transfers heat to objects and surfaces within the heated space primarily (greater than 50%) by infrared radiation.
Radiant Panel: a tube or piping configuration installed for the purposes heat radiation into a specific space.
Note: examples include in-floor, in-wall, and in-ceiling radiant layouts.
Rated R-Value of Insulation: the thermal resistance of the insulation alone as specified by the manufacturer in units of h.ft2 ºF/Btu at a mean temperature of 75 ºF. Rated R-value refers to the thermal resistance of the added insulation in framing cavities or insulated sheathing only and does not include the thermal resistance of other building materials or air films (See thermal resistance).
Reset: automatic adjustment of the controller setpoint to a higher or lower value.
Service Water Heating: heating water for domestic or commercial purposes other than space heating and process requirements.
Service Water Heater: an appliance intended for the heating of water for plumbing services (as distinct from water for space heating).
Setback: reduction of heating (by reducing the setpoint) or cooling (by increasing the setpoint) during hours when a building is unoccupied or during periods when lesser demand is acceptable.
Setpoint: point at which the desired temperature (ºF) of the heated or cooled space is set.
Slab-On-Grade-Floor: that portion of a slab floor of the building envelope that is in contact with the ground and that is either above grade or is less than or equal to 24 in. below the final elevation of the nearest exterior grade.
Heated slab-on-grade floor: a slab-on-grade floor with a heating source either within or below it.
Unheated slab-on-grade floor: a slab-on-grade floor that is not a heated slab-on-grade floor.
Solar Energy Source: source of thermal, chemical, or electrical energy derived from direct conversion of incident solar radiation at the building site.
System: a combination of equipment and auxiliary devices (e.g. controls, accessories, interconnecting means, and terminal elements) by which energy is transformed so it performs a specific function such as HVAC, service water heating, or lighting.
System Design: the layout and specification of all components, and heat-distributions means and methods.
Thermostat: an automatic control device used to maintain temperature at a fixed or adjustable set-point.
Warm-Up: increase in space temperature to occupied set-point after a period of shutdown or setback.
Water Heater: vessel in which water is heated and is withdrawn for use external to the system.
Zone: a heat-distribution loop or system of loops that has a separate control means, independent from control means of other distribution loops, for automatically regulating its heat output.
