Green Home Definitions

Here is a list of words and phrases that you might hear one of our Building Science and Systems Professionals using when talking about your home. View pictures of the equipment used in a home energy audit.
 
 

ACCA Manual J:

Air Conditioning Contractors of America.  Manual J® is the industry standard for HVAC residential load calculation methods.  This manual is required by most building codes around the country.

ACH:

Air changes per hour (flow compared to volume)

AFUE rating:

The US Department of Energy's Fuel Utilizaton Efficiency and represents optimum burner efficiency.

Ambient Air:

The air around you.

ASHRAE standard:

The American Society of Heating, Refrigerating and Air Conditioning  Engineers who write the standards for heating, ventilation, air conditioning and refrigeration systems.

Band-joist:

Horizontal member that forms the perimeter of a floor system in which the floor joists tie in.

BAS:

Building Airflow Standard. The BAS is based on ASHRAE ventilation standard 62-89 that requires a minimum of 15 cubic feet per minute (cfm) per person or .35 air changes per hour based on the volume of the home.

Base pressure:

A standard used in determining gas' volumes, expressed in PSIG, ounces of water column or ounces per square inch.

Blower door:

A piece of equipment that tests the air leakage of the envelope.   Blower door is a diagnostic tool designed to measure the airtightness of building and to help locate air leakage sites. A blower door consists of a calibrated fan for measuring an airflow rate, and a pressure-sensing device to measure the air pressure created by the fan flow. The combination of pressure and fan-flow measurements are used to determine the building airtightness. The airtightness of a building is useful knowledge when trying to increase energy conservation or decrease indoor air pollution, or control building pressures.

BTU:

A BTU is defined as the amount of heat required to raise the temperature of one pound of liquid water by one degree from 60° to 61° Fahrenheit at a constant pressure of one atmosphere.

CAZ:

Combusition Appliance Zone.  A zone in the house that contains a combustion appliance. CAZs need not be heated. For example, a garage with a combustion-fired furnace or water heater is a CAZ.  Exception: A zone with an appliance that has an isolated combustion path preventing mixing of room air and combustion air is not considered a CAZ.

CFM:

Cubic feet per minute. A rating that expresses the amount of air a blower or fan can move.  The volume of air (measured in cubic feet) that can pass through an opening in one minute. 

CO:

Carbon Monoxide

Carbon monoxide:

Carbon monoxide, with the chemical formula CO, is a colorless and odorless, tasteless, yet highly toxic gas. Its molecules consist of one carbon atom covalently bonded to one oxygen atom.

Carbon Dioxide:

Carbon dioxide (chemical formula: CO2) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom.  It is a gas at standard temperature and pressure and exists in Earth's atmospere in this state.  It is currently at a globally averaged concentration of approximately 387 ppm(parts per million) by volume in the Earth's atmosphere.

Chimney:

A chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere.

Combustion Appliance:

Combustion appliances are those which burn fuels for warmth, cooking, or decorative purposes.  Typical fuels are gas, both natural and liquified petroleum(LP), kerosene, oil, coal and wood. Examples of the appliances are space heaters, ranges, ovens, stoves, furnaces, fireplaces, water heaters and clothes dryers. 

Combustion Appliance Zone (CAZ):

A zone in a home that contains a combustion appliance.

Combustion analyzer:

A device used to measure the steady-state efficiency of combustion heating units.  The combustion appliance has reached "steady state."

Condensing Coil:

Where refrigerant gives up its heat and changes from a gas to a condensate.

Conduction:

Conduction is the direct flow of heat through a material resulting from physical contact. The transfer of heat by conduction is caused by molecular motion in which molecules transfer their energy to adjoining molecules and increase their temperature.

Convection:

The transfer of heat through a fluid (liquid or gas) caused by molecular motion.

Crawl spaces:

Unoccupied areas between the living space and the ground.

Cumulative leakage test:

This test represents the effective leakage of all the holes in the ductwork added together.

Dew point:

Change from a vapor to a liquid.

Diffusion:

The process in which there is movement of a substance from an area of high concentration of that substance to an area of lower concentration. 

Dilution Air:

Air that enters a draft hood or draft regulator and mixes with the flue gasses.

DHW:

Domestic hot water heater

Draft:

The vent pressure of a natural draft appliance.

Draft diverter:

A device fitted in the flue way of a gas appliance to prevent updraft, downdraft, or the secondary flue blockage from obstructing the escape of combustion gases.

Duct:

A pipe, tube or canal which carries air or liquid from one place to another, as in heating and air-conditioning ducts.  Ducts are used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. These needed airflows include, for example, supply air, return air, and exhaust air. Ducts also deliver, most commonly as part of the supply air, ventilation air. 

Duct blaster:

The piece of equipment used to measure effective air flow through the ducts.

Energy:

Any source of useable power.

Evaporator Coil:

Where refrigerant collects heat and changes it from a condensate to a gas.

Exfiltration:

Uncontrolled leakage of conditioned air from inside the home to the outside.

Exhaust fan:

A fan that moves air out of an enclosure.

Exhaust Fan Flow Meter:

A device that measures the pressure across a hole of specific size.

External static pressure:

The resistance of all components outside the appliance cabinet.

Floor joists:

Horizontal boards laid on edge resting on the beams or walls that provide the main support to the floor.

Flow Hood Testing:

A flow hood is used to test the airflow from individual registers.  The device is tightly positioned over a register, as sensors measure the flow pressure and convert it to cfm.

Flow Plate Testing:

A calibrated device that is installed in the vicinity of the fan cabinet to measure effective flow of air across the cooling coil.

Flue:

A flue is a duct, pipe, or chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors.

HDD:

Measures annual heating loads.

Heat Exchanger:

A device used to transfer heat from a fluid (liquid or gas) to another fluid where the two fluids are physically separated.

Hygrometer:

Measures the relative humidity of various building zones.

HVAC:

Is an acronym that stands for "heating, ventilating, and air conditioning."  A system that provides heating, ventilating, and/or cooling within or associated with a building.

IAQ:

Indoor Air Quality 

Inerstitial Zones:

Inside hollow walls such as wall cavities, floor cavities and chases.

Manometer:

A device that measures duct pressure.

Monoxor:

Portable CO Tester measure ambient and stack carbon monoxide levels from 0-2000ppm.

MSDS:

Material Safety Data Sheets 

NFPA:

National Fire Protection Association sets the standards for vent design.

NFRC:

The National Fenestration Rating Council (NFRC) is a 501 (c) 3, non-profit organization that provides performance ratings on windows, doors and skylights.  It is strictly an educational organization and provides the public with the information needed to make more informed choices.

OSHA:

Occupational Safety and Health Administration: a government agency in the Department of Labor to maintain a safe and healthy work environment.

Pascal:

Standard unit of air pressure measurement. Approximately 1/250-inch water gauge.

Pilot Light:

A pilot light is a small gas flame, usually natural gas or liquefied petroleum gas, which is kept alight in order to serve as an ignition source for a more powerful gas burner.

Phantom Load:

Energy that is being used even when the appliance is off.

Plenum:

The supply plenum is located directly over the heat exchanger/cooling coil and serves as the distribution center for ducts carrying conditioned air to the zones of the building.  The return plenum serves as the central collection area for air returned from the building for  conditioning.  Properly designed plenums distribute an even pressure to ductwork that assures each duct moves a portion of the distribution air.

Power:

The rate at which work is performed or energy is transmitted, or the amount of energy required or expended for a given period of time.

Pressure Boundary:

The primary air enclosure boundary separating conditioned air and unconditioned air. Typically defined by the air barrier system.

Psychrometric chart:

A chart that provides an intrepretation of when air of a certain moisture content will reach dew point (change from a vapor to a liquid).

ppm:

parts per million

Radiant Barriers:

Reflective surfaces, positioned to intercept the flow of radiant energy.

Radiation:

Energy that is radiated or transmitted in the form of rays or waves or particles.

Radiant heat:

Heat transferred from one body to another which are not in contact (ie, from the sun to a roof).

Radon:

A potentially dangerous soil gas that moves into the building from the soil under and around the foundation.

Return Air:

Air that has circulated through a building as supply air and has been returned to the HVAC for additional conditioning or released from the building.

R-Value:

An expression of the thermal resistance of a material or a group of materials.  R-values are the common term for insulation value for the general public.

SEER:

Seasonal Energy Efficiency Rating.  The energy efficiency rating in BTU's of heat removal per watt of appliance.

Serpentine heat exchanger:

A tube heat exchanger that makes approximately four passes back and forth so the combustion gases can give up more heat.

Single stage, multiple stage or variable rate:

The types of gas valves.

SHGC:

The Solar Heat Gain Coefficient (SHGC) measures how well a window blocks heat from sunlight. Look on the NFRC label for the rating.

Soffit:

The visible underside of structural members such as staircases, cornices, beams, a roof, overhang or eave.

Spalling:

Flaking of the outer face of masonry, often caused by expanding moisture in freezing conditions.

Spillage:

The measurement of CO that spills out of the flue upon start up of a combustion appliance.

Square footage:

Figured by multiplying the length times the width.  Also called "area".

Stack Effect:

Stack effect is the movement of air into and out of buildings, chimneys, flue gas stacks, or other containers, and is driven by buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature and moisture differences. The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect is also referred to as the "chimney effect", and it helps drive natural ventilation and infiltration.

Steady state:

The point where the combustion appliances have reached equilibrium in the combustion process.

Surface area:

Sum of all conditioned surface areas,including all below grade surfaces that are defined within the thermal envelope

Supply:

The conditioned air is distributed throughout the home using a system of rigid and flexible duct, collectively referred to as ductwork. Ductwork is a circulatory system that uses supplies to feed air into a room and returns to complete the circuit back to the air handler.  Adequate and properly placed returns will keep closed room from becoming pressurized which limit the entrance of supply air in the room.

Temperature rise:

The temperature difference between the supply and return air in the plenums.

Thermal Barrier:

Material used in conjunction with polyurethane foam that is designed to inhibit the rise in temperature of the foam during a fire in order to delay the foam's involvement in the fire.

Thermal Boundary:

The insulation and building materials that surround the conditioned areas of a building and help to maintain the temperature of the conditioned areas.

Thermal Envelope:

The building's exterior shell: walls, foundation, floors, ceiling, windows, doors, and roof.

Thermostatic Expansion Valve:

A thermostatic expansion valve (TXV) is a precision device used to meter the flow of liquid refrigerant entering the evaporator at a rate that matches the amount of refrigerant being boiled off in the evaporator.

Therms:

1 therm = 100,000 BTU;  24,500,000 BTUs = 245 therms of gas

Ton:

The BTU's required to melt one ton of ice

U-Value:

An expression of the hourly BTU loss through one square foot of building material or building system, for each degree of temperature difference from one side to the other.  U=1/R

Under-vented combustion appliance:

An appliance where the vent system is not substantial enough to completely handle the exhaust products.  The distinguishing characteristic of an under-vented draft-hooded appliance is the spillage of flue gases that occur after 60 seconds of operation.

Vapor barrier:

A waterproof material or film placed between a heated area of the home and an area that is not heated to prevent moisture from seeping between the two areas.

Vent:

A hole for the escape of gas or air.

Vent pressure test:

An analytical expression of the strength of the vent system, expressed in inches of water column or Pascal of pressure.

VOC's:

Volatile organic compounds refer to a wide group of carbon-based compounds that diffuse readily into the air. They include cleaners, deodorizers, solvents, wood finishes, insectides. They are also a major component in many building materials including plywood, fiberglass, insulation, PVC's and plastics.

Volume:

The volume of any solid, liquid, or gas is how much three-dimensional space it occupies, often quantified numerically. Figured by multiplying the length times the width times the height.

Weep-screed flashing:

Allows moisture to exit the building while allowing air to enter.

WRT:

With reference to. When measuring pressure differences, one zone is the reference zone. Pressure measured in the other zone is WRT the reference zone.