The condition where one substance incorporates another substance. In energy auditing and building science, we’re usually talking about water/vapor and porous building materials like wood, brick and concrete.

Air Conditioning Contractors of America

ACH is an acronym for Air Changes per Hour and is a measurement of air infiltration. It is the total volume of air in a home that is turned over in one hour.

One substance producing a surface bond with another.

A substance or mixture (in the case of epoxy) for joining two materials together.

Like absorption, condition where one substance incorporates another substance, in this case concentrated on the surface.

Air Barrier or Air Shell or Air Control Layer
The portion of the building enclosure which controls air flow. Comprised of low air permeance materials.

Air Barrier Component
Elements such as windows, doors and service entries inserted and sealed into the building enclosure. Air barrier components should be ‘Air Impermeable’ defined as allowing less than 0.02 L/(s x m2) air permeance at 75 pascals pressure difference.

Air Barrier Material
A material designed to be the primary air barrier in a building enclosure. Air Barrier materials should be ‘Air Impermeable’ defined as allowing less than 0.02 L/(s x m2) air permeance at 75 pascals pressure difference. See, we don’t just make this stuff up. This is not ‘Nam, there are rules, Dude.

Air Impermeable Material
A building material which allows less than 0.02 L/(s x m2) air permeance at 75 pascals pressure difference. These materials are used as part of the air barrier in the building enclosure.

Air Infiltration
Air leakage into conditioned space. This is natural, unplanned (and generally unwanted) allowance of unconditioned external air into the conditioned internal space.

Air Leakage
Unwanted air flow through the conditioned space. This is natural, unplanned (and generally unwanted) air flowing in and out of the building enclosure. Air leaking out is called exfiltration and air leaking in is called infiltration.

Air Permeable Material
A building material which allows more than 0.02 L/(s x m2) air permeance at 75 pascals pressure difference. These are structural materials which can be part of the building enclosure but are not intended as part of the air barrier.

American Lung Association. Long associated with the building industry and improving interior air quality.

The American Society of Heating, Refridgeration and Air Conditioning Engineers. ASHRAE is an international technical society for all individuals and organizations interested in heating, ventilation, air-conditioning, and refrigeration.

Naturally occurring fibrous minerals that because of their extreme durability and fire resistance were used extensively in residential and industrial construction. The inhalation of asbestos fibers can cause serious illnesses such as asbestosis, lung cancer and mesothelioma.

Backer Rod
A narrow foam rod installed in a joint or seam to eliminate air leakage. Combined with caulking this can form an air tight and water tight seal.

Balloon Framing
A method of building framing where the walls are framed from long continuous wall studs that run from the sill plate to the roof eaves. Floors, windows and other fixtures are built around the continuous framing.

Band Joist
Located atop the foundation wall, the vertical lumber element to which the basement floor joists are attached forming the first floor. This can be a major source of air infiltration even in modern construction.

The below ground level foundation of a building, often used for storage and utility space.

Most commonly referring to caulk beads, used for sealing small gaps in framing and structural elements.

One of the main structural elements in the building enclosure, traditionally wood though it can be a wide variety of building materials.

Below Grade
In building terms, grade is the ground level. Therefore, below grade…below ground level. All in the name.

Gas produced by the microbial breakdown of organic matter. Primarily comprised of methane, biogas can be harnessed as an energy source.

Ironic name (now former name) for the defense contractor, no? It is residential and commercial post-usage water carrying organic materials, usually waste (food, garbage, restrooms, etc.)

Blower Door
A blower door is a vinyl sheathed aluminum frame which houses a powerful fan and pressure sensor. The frame is adjustable to different door frame sizes. Auditors use blower doors to test building tightness and identify air leaks.

Blower Door Test
Run by an energy auditor, the blower door depressurizes the house to measure air tightness and identify air leaks. A blower door test can also be run during weatherization work for contractors to find areas to be addressed.

The core of a water-based heating system. A boiler heats water which is carried through structures via a steam or a hot water distribution system. Steam systems have higher heating requirements (because of the higher operating temperature of steam vs. water). Almost any fuel sources are options but the most common in North America are oil and natural gas boilers.

Borate/Boric Acid
Borates are a class of chemicals added to cellulose as a fire retardant and anti-pest treatment. Borates are created from boron and are also used as treatments for wood and lumber.

Brownfields are former industrial sites, often that have been environmentally compromised. Brownfields usually require environmental reclamation work prior to being used in other capacities.

AKA Building Science Corporation. We like these guys.

BTL (Building Tightness Limit)
The same as Minimum CFM50. It is possible to increase the airtightness of a building to the point where natural air change rates (from air leakage) may not provide adequate ventilation to maintain acceptable indoor air quality. To help evaluate the need for mechanical ventilation in buildings, national ventilation guidelines have been established by ASHRAE.

British Thermal Unit. A measure of heat equal to the amount of energy to raise 1 pound of water by 1 degree Fahrenheit.

Building Enclosure
A snazzier name for building shell. The structural layer, thermal, vapor and air control layers which separate the exterior, unconditioned environment from the interior, conditioned space.

Building Envelope or Building Shell
The shell of a building that defines the division between the interior, conditioned space and exterior unconditioned space. Consists of an air, vapor and thermal barrier, a water control plane and the structural elements which include the foundation (or slab), the exterior walls and roof.

Building Tightness Limit
The limit as blower door tested that a building can be tightened before mechanical ventilation needs to be added to maintain sufficient fresh breathable air.

Computer Aided Design. Programs used in building design.

Cape Cod
A very popular style of house originating in 1700s New England. They are characterized by a steep pitched roof, a 2nd floor with half-height knee walls, full end gable walls and in older construction, a centrally located chimney. Modern variants tend to locate the chimney on one gable end. Cape Cod houses enjoyed a resurgence in popularity during the 20th century with rising demand for affordable housing options.

Ironically (yes, this is irony), the difficulty of airsealing a Cape’s 2nd floor and heavy omnipresent Cape Cod sea breezes make Capes a challenge to heat when located in their eponymous locale.

Capillary Action
The directional movement of liquids through a porous material, driven by molecular forces. Due to capillary action, liquids can move against gravity or other driving forces.

Capillary Break
A water impermeable material that acts as a barrier between two porous or permeable ones.

Carbon Cap and Trading
A proposed system where limits are set (that would be the ‘Cap’ part) on carbon emissions. Entities who stay below the carbon emission limits will earn credits they can sell to those entities who emit more than the carbon limit (aaaand..that’s the Trade part).

Carbon Footprint
Total carbon dioxide (some measures include all greenhouse gases) emissions produced by an individual, group or event. This can be by transportation, food consumption and most any economic activity. Emissions for all GHG are usually measured in carbon dioxide equivalents.

Carbon Neutral
OK, so you’ve figured out your carbon footprint. Being carbon neutral means reducing your carbon footprint to zero through energy efficiency, renewable energy and carbon offsets.

Carbon Offset
Carbon offsets are purchases to, wait for it, offset someone’s carbon emissions. An example would be paying for a planted tree which would remove carbon dioxide form the atmosphere.

Carbon Tax
A system regulating carbon emissions by placing a tax on the combustion of fuels that release carbon into the atmosphere.

A landscaped drainage, directing rain water downhill toward a nearby lake or stream.

Cathedral Attic
A vaulted ceiling where the insulation has been installed along the roof deck. This makes the attic conditioned space, allows for its use as storage and improves the performance of any hot water piping or ductwork

One of several types of joint sealant. Typically refers to silicon based caulking today but the term dates back to mixtures of hemp fibers and pine tar used to water seal boats.

Cavity Wall
A form of wall assemblies where a hollow space is built between two masonry skins. The dead air space provides some insulating value and acts as moisture drainage. Also commonly called a ‘double wythe masonry wall’.

Combustible Area Zone (CAZ)
The CAZ is the area which houses the appliances that heat the home through combustion, such as a boiler or a furnace. Typically located in the basement, they can also be located in other areas such as garages or portions of the main floors. The CAZ needs to maintain a minimum pressurization to avoid spillage, back drafts, or other hazards.

In some instances, the amount of mechanical ventilation running in the home can de-pressurize the CAZ too much for the appliances to maintain proper safety specifications which are currently -3 to -5 Pascals (Pa).

CAZ Worst Case Depressurization Test
A combustion appliance test evaluating the potential for backdrafting flue gases. An auditor first creates the ‘worst case depressurization’ (activating exhaust fans and closing door to produce the highest negative pressure in the house). He then visually assesses the flue gas spillage and tests the flue gas pressure with a pressure guage.

In other words, if you turn on every fan in the house, will you start sucking smoke out of your furnace?

California Energy Commission which because of California’s size often sets energy standards throughout the country

Cellulose Insulation
Cellulose is one of the more common and least expensive forms of insulation. Cellulose is shredded paper typically with boric acid as a flame retardant and anti-pest treatment. Cellulose can be blown loosely over flats or densepacked in wall cavities to achieve approximately R-3 to 3.5 per inch. Cellulose retards but does not stop air movement.

Cement Board
A combination of fibrous materials and cement formed into 4’x8′ sheets. Often used as tile backing board in high moisture locations like bathrooms.

Central Heating
Another one of those, ‘it’s all there in the advertising’ items. Central heating is a heating system that heats the house from one central location. Note we didn’t say ‘centrally located’ which can be an issue with central heating (systems set up in one corner of a residence making it difficult to reach the opposite corner)

Central heating systems heat the entire house from a single point, for example furnaces or boilers. These types of heating systems are generally more efficient than point source heating systems, but they also usually utilize fossil fuels for combustion.

Cubic Feet per Minute. The volume measure for air flow in building science.

This is the airflow (in Cubic Feet per Minute) needed to create a change in building pressure of 50 Pascals. CFM50 is the most commonly used measure of building airtightness and represents a fictional wind blowing on all sides of the structure at approx. 20 mph.

It is possible to increase the air-tightness of a building to the point where natural air change rates (from air leakage) may not provide adequate ventilation to maintain acceptable indoor air quality. To help evaluate the need for mechanical ventilation in buildings, national ventilation guidelines have been established by ASHRAE.

Chimney Balloon
Chimney balloons are inflatable heavy plastic gauge balloons that can effectively seal unused chimney chases.

See siding. The outer covering of a residence. Provides improved aesthetics and acts as weather protection.

When water moves from a vaporous state to liquid. Occurs when surface temperatures drop below the dew point.

Conditioned Space
The space within the building enclosure that is being environmentally controlled.

Cooling Degree Days or CDD
A measure of a building’s cooling load in a particular location.

The decay of metal by elements in its environment.

What your concrete foundation does after being poured into forms. This is a chemical process where the material (in this case, concrete) sets.

Deep Energy Retrofit
A turbo charged version of a typical retrofit. A deep energy retrofit is one where the goal is achieving 50-75% reduction in energy use. This usually involves very high levels of insulation, enormous reduction of air leakage and window replacement (yes, I said it).

To dry out air in a conditioned space, usually using a mechanical system to remove water.

Dew Point
The temperature at which the water vapor in humid air will transition to liquid.. Solids below the dew point will cause vapor to condense on its surface.

Domestic Hot Water

The movement from greater concentration toward lesser concentration of molecules through a medium.

Drainage Plane
Downward sloping planes of water resistant (though not necessarily impermeable) materials allowing the drainage of storm waters away from the structure.

Drip Edge
A construction detail that directs water away from the building.

What you think your concrete foundation does after being poured into forms (it actually cures). This is a physical process where the material (in this case, concrete) dries out by evaporation.

Sometimes also shown as SEER. Stands for Energy Efficiency Rating, used to measure the efficiency of air conditioners. More efficient ACs have a higher SEER/EER number.

The leftover mineral salts found after moisture evaporates. In buildings, usually seen on the surface of concrete and brick in higher moisture environments.

Embodied Energy
Embodied energy is the entire energy input of a product or service. This covers the product’s entire lifecycle from the raw materials through disposal.

In building science, a material’s ability to emit radiation (usually referring to heat and light). Emissivity runs from e = 0 (perfect reflection of radiations) to e = 1 (no emissions at all). The darker and duller the surface the closer emissivity will be to 1 and conversely the more reflective a surface the closer to 0.

This is mostly discussed with window glazings in construction. Low-e window glazings reflect a higher percentage of heat and light.

The ability of one system to exert force over a distance on another system (not what you thought at all, was it?). Most commonly stated in Joules.

Energy Audit
Energy audits are assessments of the insulation, air leakage, moisture, air quality and heating systems in your home. Done responsibly, an audit should account for each factor and how they interact.

Energy Efficient Mortage / EEM
A variation on the standard mortgage where energy costs and projected savings are accounted for as part of the house’s operating costs. By acknowledging the lower overall costs , lenders can provide a higher level of financing than normally possible.

Energy Factor
Part of the Energy Star program, used as a standard for household appliance efficiency. Appliances such as water heaters, washers, dryers and dishwashers are rated, comparing energy consumed vs. energy used.

Energy Recovery Ventilator
Also abbreviated as ERV, this is a mechanical system that recovers heat and moisture while exchanging internal air for fresh external air.

Energy Star
Standard for energy efficiency in many consumer products. First developed by the US Dept of Energy, it has since evolved into an international standard for efficiency.

Energy Star Homes
A residential program implemented by the EPA and Dept of Energy that maintain an energy efficiency standard 15% higher than that of the International Residential Code.

Energy Star Windows
Similar to Energy Star homes, Energy Star provides a minimum performance standard for windows. These standards vary by climate zone.

Otherwise called the building shell or building envelope, this is the separating barrier between conditioned and unconditioned space. Consists of a structural element and a vapor, thermal and air barriers and usually a drainage plain.

U.S. Environmental Protection Agency. Another group we like.

Expanded Polystyrene Insulation. When we start using your Dunkin’ Donut cups for insulation.

Equivalent Leak Area
Closely related to blower door testing, effective leak area is the area of air leaks in a structure. This is a excellent shorthand to communicate the magnitude of air leakage problems to homeowners.

Evacuated Tube Solar
A solar collector (usually solar hot water) that uses glass tubes that have been vacuum sealed. They are typically coupled with either water or glycol as a heating medium and a reflective collecting surface to direct heat. Evacuated tube systems generally perform better during winter than flat plate solar collectors.

Expanded Polystyrene or EPS
This is the white beaded ‘styrofoam’ most people are familiar with (think Dunkin Donuts coffee cups). It is typically formed into rigid foam boards and has a higher vapor permeability than either XPS or Polyisocyanurate (foil faced). EPS would need to be paired with a vapor barrier in building shell applications.

I used this term a lot…it is air flowing out of a building, driven by pressure and temperature. In residential audits, most commonly found as attic exfiltration driven by the stack effect.

External Insulation Finishing System or EIFS
As the name implies (or actually just says), EIFS combine insulation and siding to form the traditional insulation and water control element of a building enclosure.

Expansion Joint
The process of selecting players from opposing teams for the purpose of creating a new sports franchise. Wait…that’s an expansion draft. An expansion joint is a one which allows for the temperature driven expansion and contraction of two building materials. They can also abate damage from ground movement or traffic.

The aesthetic and protective exterior of a building.

All those things we use in your house to attach things to other things. Nails, screws, etc.

Faucet Aerator
A mesh screen found at the tip of modern faucets. Rather than coming out in a stream, the aerator spreads the flow into droplets. This improves flow, reduces splashing and saves water.

Finished Floor Area

Fiberglass Insulation
Fiberglass consists of extremely fine glass fibers, used in making various products, such as yarns, fabrics, insulators, and structural objects or parts. As an insulation, it is cost effective, temperature resistant and equally effective in most climates. The main drawback is that it does not stop air flow in any way. Unless paired with an effective air barrier, fiberglass insulation won’t function at the advertised R-value.

Fiberglass Faced Gypsum Board
A form of gypsum board (drywall) that has been treated and covered with a glass fiber surface to resist moisture. Used under brick, EIFS, stucco and many other sidings.

A building material for directing exterior water away from the building. Occasionally used in other capacities such air sealing chimney enclosures.

Flat Plate Solar Collector
One of the main types of solar collectors, usually used for hot water or space heating. A flat plate solar collector circulates a heating medium (glycol, water or air) through a flat metal plate. Compares with an evacuated tube solar collector. Flat plate collectors perform better in direct sunlight and are more common in southern climates. Conversely they perform less effectively during the winter.

Fly Ash
Fly ash is one by-product of burning coal that has been adapted by the concrete industry. Fly ash can cheaply (and energy effectively) act as a bonding agent in Portland concrete while improving overall quality.

Fossil Fuels
Non-renewable energy source created through geologic forces from ancient biomass. A primary source of pollution, examples include petroleum, coal and natural gas.

Framing Member
One of the wood or steel elements that comprise the building enclosure. Includes studs, rafters, joists, storm braces or top and bottom plates.

Freeze Thaw Cycle
One of the mechanisms for breaking down building materials (as well as naturally occurring rocks and minerals). High moisture levels must be present where the freezing and thawing of moisture in the material matrix cause structural damage.

French Drain (sometimes called a Dutch Drain)
A exterior perimeter drain around a building. These drains help reduce basement moisture problems by moving rain water away from the foundation.

The material in question easily fragments and powders, possibly becoming airborne. Most commonly refers to asbestos and vermiculite but equally applicable to fiberglass and rockwool.

Fuel Cell
A modern electric no-emission solution for fossil fuel problems (most often discussed with cars). Fuel cells generate electricity through a simple hydrogen-oxygen reaction. Advocates of nuclear, wind and solar power are fascinated by the potential of fuel cells to displace gas-driven vehicles.

Gallons Per Flush or GPF
Required reading material for any men’s room urinal. Gallons per flush is a standard measure for water consumption in toilets. This can be modified by the addition of a dual flush system or with a efficient model, limited to 1.28 gallons or less.

Also called a Dutch Gambrel, a popular house style in North America characterized by a symmetrical roof with two pitches. The top roof section has a more shallow pitch and the lower section is steeper.

Global Warming
The global incremental increase in average temperature, often attributed to man-made contributions to the greenhouse effect.

Ground level in relation to the building.

Grade Beam
A reinforced concrete foundation member used for load support in loose soil environments. Designed to distribute the load of the building to reinforced bearing points.

Water collected from residential outflow excluding toilets (see blackwater). Compared to blackwater, graywater is not very contaminated.

Green Electricity
Renewably produced electricity. This can include some sources of hydroelectric, photovoltaic panels, reflective solar power plants, wind farms and recycled biomass plants.

Green Mortgages
Also called energy efficient mortgages. This is were the bank or mortgage company allows a customer to assume a larger loan, understanding that an energy efficient residence has energy costs.

Green Roof
A controversial approach to building efficiency, a green roof is one where the surface is covered with flora. It helps insulate the roof (reducing winter heating loads and summer cooling loads) and absorbs some water. The questions lay in the wisdom of introducing a huge water-retaining biomass into the roof system for functions which white paint and insulation do better.

A marketing practice where companies attempt to portray their products as beneficial to the environment. An example is that many video game companies no longer include paper manuals, claiming it is to reduce paper usage.

Gut Rehab
All in the name. Renovation where a building is gutted, down to the stud walls. All interior walls and fixtures are removed, leaving only the structural elements of the building shell.

Habitable Space
The space within the building enclosure where folks sleep, dine, cook etc. on a continual basis.

Within landscaping, areas where manmade elements such as roads, concrete or brick have been included. They are covering the natural soil. Hardscaping is particularly useful in high traffic areas or in achieving designs (such as a water fountain) that would be difficult with natural landscaping.

HCFCs otherwise called the not at all horrifying sounding HydroChloroFluoroCarbons. More commonly known by the trademarked name Freon, HCFCs are useds as liquid coolant in refrigerators and can contribute to damage of atmospheric ozone. Woohoo.

Top framing members over all building egresses (primarily windows and doors).

Heat Exchanger
A system which transfers heat usually for the retention of a greater portion of domestic heating. Air to air heat exchangers capture a portion of outgoing heat by transferring it to the incoming air flow. Water heat recovery systems do the same for a water medium, capturing some of the potentially wasted outgoing heated water and preheating incoming water.

Heat Gain
The amount of heat gained within a conditioned residential space from non-heating system sources. This includes sunlight, body heat, incandescent lights and the heat radiating from an active boiler/furnace.

Heat Island Effect
Also known as the Urban Heat Island, the phenomena where urban centers are significantly warmer than the surrounding rural areas. The main cause is the dominant use of solar absorptive materials in urban construction. This includes dark colored roofing shingles, asphalt roads, parking lots and dark colored building sheathing.

Heat Recovery System
A system which extracts heat from outgoing hot water lines to retain a greater portion of domestic heat. The captured heat can preheat incoming cold water.

Heating Load
Heating load is the maximum number of BTUs the heating system will need to provide for a comfortable interior temperature. The load is calculated on a worst case scenario (in other words, the coldest it is likely to ever get in your area).

Home Energy Rating System. HERS is a residential energy efficiency scoring system. Existing homes are scored on a scale where 0 indicates a net zero energy use home and 100 represents an ‘American Standard Building’. The lower the score the more efficient the building. In 2009, the Department of Energy created a new scale, the EnergySmart Home Scale which subtracts HERS Index scores from 100 (making 100 a net zero energy home and higher scores better).

High Efficiency Toilets
Toilets with a max 1.3 gallons per flush of water volume. After passing the Energy Policy Act of 1992, limits were placed on the total water volume for flush toilets. This lead to the emergence of HETs.

Home Performance With Energy Star
One of the national weatherization programs in the U.S. The program concerns itself with energy efficiency contractors trained in proper assessment of home performance. The program is overseen by the EPA and Department of Energy.

House wrap
I love the hard ones. A variety of exterior wraps for the house, acting as the water drainage plane.

High Performance Lighting

U.S. Department of Housing and Urban Development

An acronym that stands for Heating, Ventilation, and Air Conditioning. This refers to all of your building’s major mechanical systems.

Hydronic System
Sometimes called Forced Hot Water. This is a mechanical conditioning system which uses water for transporting heat through the building.

A tool for measuring and recording air humidity levels.

Indoor air quality. In auditing, IAQ figures prominently in ensuring sufficient fresh breathable air, reasonable humidity levels and freedom from mold and chemicals.

Ice Dam
A fossil fuel powered way to remove snow from your roof. Ice dams are a lip of ice that forms on the outside edge of a roof. When large enough, water can pool behind the lip, possibly causing roof leaks and water damage. When an upper portion of the roof is above the freezing point (melting snow) and a lower portion is below freezing, ice dams can form.

ICF or Insulated Concrete Forms
A method of building insulated building foundations. Insulated forms are assembled and constructed for the foundation framing. Polystyrene foam (either EPS or XPS) is used for the exterior and interior walls of the forms. Concrete is poured into the gap, solidifying the foundation.

An open cell spray foam insulation. Icynene foam uses water during its application instead of pentane or other ozone damaging chemicals. It has a fairly high vapor permeability making high humidity and moisture environments problematic.

International Energy Conservation Code. The international code standard for energy use in construction.

Infrared Thermometer
A thermometer which uses the infrared spectrum to detect surface temperatures at a distance. This is a useful tool for homeowners to do their own home energy investigations without the much more substantial investment of an infrared camera.

Infill Building Site
A building lot bordering other already developed lots. Usually formed by parceling off smaller lots from a larger one in an urban setting.

Incoming Solar Radiation. A portmanteau of this phrase, it refers to total surface solar energy over a given time period. It is most commonly stated as watts per square meter or kilowatt hours per square meter per day.

A converter changing direct current (DC) electricity into alternating current (AC). A integral component to most photovoltaic systems, they can customize output to any necessary voltage or frequency.

Where Superman is from. Duh. Also, a colorless, odorless, tasteless noble gas used in fluorescent lighting and gas fill in some modern windows.

Kyoto Protocol
International treaty made in 1997 agreeing to the global reduction of greenhouse gases. It covers most major sources of greenhouse pollutants.

Landfill Gas
Methane and other gases produced by the action of microorganisms within landfills. They are increasingly being harnessed to produce clean energy (not ‘green’ energy since the fuel source is not renewable but dependent on human waste production) and capture the potent greenhouse gas methane.

Latent Heat
The heat (energy) in a system that is not observable as a change in temperature. Examples include vapor condensing from air or ice melting into water. In both cases, the material stays the same temp until the latent heat is expended (the ice entirely melted). Compares with Sensible Heat.

LED bulbs
Light emitting diode. LEDs are extraordinarily long lasting and very efficient relative to either incandescents or CFLs. LEDs produce light with a semiconductor ‘filament’ instead of the standard metal one.

Yet another sexy acronym, this one standing for Leadership in Energy and Environmental Design. This program from the United States Green Building Council sets standards for green building design and construction.

Log Cabin
A cabin built from logs. Simple, no? Log cabins built with modern materials balance an authentic feel with providing a comfortable modern conditioned space.

Low E Coating
Low E coatings are designed to allow sunlight in but block/reflect a higher degree of solar heat. Low E or low emissivity coatings are a thin, silvery metal layer on the window pane. Very useful in sunny climates to reduce cooling loads by limiting solar heat gain.

Low Emissivity
See Low E Coating directly above. We’re basically talking about the same thing.

Low Flow Showerhead
Showerhead with less than the 2.5 gpm water flow.

Mechanical Ventilation Requirements: This is the amount of air needed to maintain the Minimum CFM50. It can be achieved through a variety of means such as an exhaust fan or Heat Recovery System, but is needed to maintain occupancy and building safety.

Net Metering
For homeowners with renewably produced electricity, net metering credits the homeowner when they produce more electricity than they use. The excess is sold back to the local electric companies.

Net Zero Home
A home or building which produces as much energy as it consumes. This is usually achieved by high levels of thermal resistance, limited air leakage and renewable energy sources.

Off Gassing
Off gassing are the chemical vapors released from paints, finishes and other materials into the home. This is an indoor air quality issue and must be considered as the building envelope is tightened.

Off Peak Electricity
Off peak electricity is the period of time, usually night, when there is less demand for electricity. Utilities often charge reduced rates for off-peak usage.

On Demand Hot Water
A mechanical system which delivers hot water ‘on demand’. Clever name, no? This reduces heat loss when there is no hot water use since the system does not maintain a reservoir of pre-heated water.

Oriented strand board. Also known as waferboard or sterling board. Made by orienting strands of wood slivers and compressing them, end of Terminator-style, into a board. OSB use has exploded in the last 30 years, largely supplanting plywood and planed lumber in building shell construction.

Outdoor Resets
Outdoor resets are similar to Temperature Controls but regulate the combustion unit by comparing output to the outside temperature.

A variant of oxygen molecules found in the earth’s atmosphere. It is very important for life on earth as the atmospheric ozone layer blocks potentially dangerous solar UV rays.

A unit of pressure equivalent to one newton per square meter.

Passive Heating
Heating systems for a house that lack a active mechanical component. Usually some variant of solar heating (solar hot air, thermal masses or solar heat gain).

Passivhaus Standard
A modern ultra-high efficiency construction standard overseen by the Passivhaus Institut (clever name) in Germany. The standard mandates very high levels of thermal resistance, very low air transported heat loss and high performance windows.

See one entry up. A house (or haus) that meets the Passivhaus standard. As the title implies, the goal with a Passivhaus is massive reduction of energy use without active renewable systems.

Passive Solar
Utilizing solar in passive manner such as with thermal masses or solar light tubes instead of actively with photovoltaic panels or solar hot water systems.

Passive Ventilation Stack or System
A sub-slab ventilation system which help direct radon gas out of the house instead of lingering beneath (and sublimating through) the basement slab.

This is the amount of time it will take to recoup the costs vs. savings. (Costs/Savings)

Peak Oil
The point in time when maximum global oil production is reached and then begins to decline. This is based on the observed production of individual oil fields and witnessing the same peak and decline of production in larger geographical regions.

The terminology ‘Peak _____’ has been widely adopted in conversations about finite recoverable resources.

Also abbreviated as PV. Usually references photochemical cells which generate electric current when under direct sunlight.

Platform Framing
A method of light frame construction where each floor is built independently. The walls are assembled with a footer, header and vertical wall studs and tied together at corners. Shear strength is added with the addition of plywood or OSB sheathing.

Polyisocyanurate foam insulation. This is a closed cell solid foam insulation. It usually comes with foil backing. Polyiso can act as an air barrier and has the highest R-value (R-7 per inch) of any common insulating material. However, it does not hold up under direct sunlight and does degrade to approximately R-6 after 5-10 years.

Post and Beam Construction
A style of framing using heavy timber fastened with mortise and tenon joints. Characterized by heavy thermal bridging and hurricane/storm braces for torsional strength.

Post Consumer Waste
Reclaimed waste products collected through a wide variety of recycling and material reclamations. The materials were once intended for consumer use.

Power Vented Exhaust
A combustion system’s gas vent that is coupled with a fan system to expedite the removal of flue gases.

Programmable Thermostat
A thermostat which allows for setting different room temperatures over periods of time. One of the most cost effective ways to reduce your heating bill.

A measure of the resistance of an insulating or building material to heat flow, expressed as R-11, R-20, and so on; the higher the number, the greater the resistance to heat flow.

Radon is a radioactive, colorless, odorless, tasteless noble gas byproduct of uranium decay. Radon is a common problem in Maine and other New England states and it is a significant cancer risk.

Radon Mitigation
Radon mitigation are mechanical systems designed to reduce radon levels in residences. Usually this involves ventilating below the foundation slab.

Ranch style houses were first built in the US in the 20s, rapidly gaining in popularity during the post-War boom. They are typically single story with a shallow roof line, hip roofs and simple layouts in the living spaces.

Recycled Content
The amount of recycled material in a product. Determined by % of weight that is recovered material.

Renewable Energy
Energy which comes from natural sources such as wind, sun and hydro. These sources naturally replenish. Compare to non-renewables like coal, natural gas and oil.

Renewable Resource
A naturally occurring resource which is stably and sustainably replenished over time. Examples include solar power, hydro or any type of biomass like lumber or cork.

Increasing the energy efficiency and structure of an older building.

Return on Investment
This is the return on the dollar for money spent. (Savings/Costs).

A fibrous insulation very similar in structure to fiberglass. It is made from spun melted rock and can be found as batts or loose fill. Rockwool is used for insulation, fire proofing and in non-energy fields as a medium for hydroponic plant growth.

Roofing Felt
A waterproof roofing layer made of paper infused with bitumen (basically tar).

Salvaged Material:
Building materials reclaimed from unused or demolished buildings.

Savings to Investment Ratio
This is a metric showing what the lifetime savings versus cost of a proposed piece of efficiency work. It is the Return on Investment multiplied by the number of years the repair will be in effect, usually standardized to 30 years. In efficiency programs, this is often one factor considered by banks to determine the feasibility of a repair before offering loan money.

Sealed Combustion
A means of providing air for heating and hot water appliances where the combustion air and post-combustion flue gases are both piped outside. Usually done through a concentric vent where both intake and exhaust run in the same pipe.

Seasonal Energy Efficiency Ratio or SEER
A measure for the energy efficiency of cooling units. The SEER rating is determined by dividing the cooling BTUs produced by the energy used in watt-hours. The higher the SEER, the more efficient the cooling unit.

Sensible Heat
The heat (energy) exchanged that affects only the temperature. Compares to latent heat which is the heat (energy) that is not observable as a change in temperature. Examples include vapor condensing from air or ice melting into water. In both cases, the material stays the same temp until the latent heat is expended (the ice entirely melted).

Sewage Biogas
Gas produced by the microbial breakdown of sewer transported organic materials. Primarily comprised of methane, biogas can be harnessed as an energy source.

The exterior layer of the building envelope installed over the stud walls. Historically this has been planed lumber boards but in the 20th century this has been supplanted by plywood and later oriented strand board (OSB).

The outer covering of a residence. Provides improved aesthetics and acts as weather protection.

Sill Plate
Located atop the foundation wall, the bottom horizontal lumber to which the basement floor joists are attached. This forms the first floor. The sill plate can be a major source of air infiltration even in modern construction.

Slab On Grade
More commonly known as a slab foundation. A very simple, cost effective alternative to a full basement, slab concrete is poured directly into an excavated mold.

Solar Gain
The energy gained (usually we’re talking about heat) from sunlight.

Solar Heat Gain Coefficient or SHGC
SHGC is an abbreviation seen on window performance labels. It shows the percent of solar heat allowed through the window.

Solar Window Screen
A modified external window screen designed to block a higher percentage of solar gain heat. This can help reduce a building’s summer cooling load.

Spray Foam
A polyurethane-based insulation that is applied via spraying on the insulating surface. The two main flavors are a denser impermeable closed cell foams and a less dense semi-permeable open cell foam.

Stack Effect
Ahh…stack effect. One of the main drivers of air transported heat loss in homes. Warm air naturally drifts upward within the building envelope. This updraft grows stronger as the indoor-outdoor temperature difference grows (the stack draft will be much stronger if outdoor temp is 20 F compared to 50 F). This thermal updraft finds every crack and seam to escape in the building’s peak. The updraft also creates a corresponding negative pressure, pulling in cold air at the building’s base.

Structural Insulated Panels or SIPs
A building panel made of rigid foam board between two layers of oriented strand board (OSB). SIPs integrate several elements (structure, thermal barrier and air barrier) into one panel. SIPs buildings are among the tightest, most energy efficient conventionally available.

A wood beam used in residential construction.

Sun Tunnel or Solar Tube
A form of passive solar lighting. Solar tubes or sun tunnels are tubes which run from the roof and terminate in a globe which diffuses the light through an interior room.

A resource, energy or material which can be extracted and used in a manner which is viable over an indefinite period. Compare with finite resources like petroleum.

Tankless Coil
A tankless coil is a means of producing hot water with boilers where the water heating coil is immersed directly in the combustion water heating chamber. This is a very inefficient way to produce hot water as it requires the entire boiler to fire year-round.

Temperature Controls
Temperature controls monitor the heating distribution system’s return and supply lines. By examining the difference in temperature between the departing and returning supply, it closely controls the boiler/furnace output.

100,000 BTUs. Often used to standardize the comparison of different energy sources. When used for home heating and hot water, natural gas is delivered in therms.

Thermal Barrier
The temperature control layer of the building envelope. AKA Insulation.

Thermal Bridging
The movement of heat across a building assembly through a poorly insulated section, often compromising thermal performance of the wall assembly. The most common example is vertical wall studs in a building wall.

Thermal Envelope
Same as thermal barrier. The temperature control layer of the building envelope. AKA Insulation.

Thermal Imaging Camera
Infrared camera. A camera which uses the infrared spectrum. Thermal cameras are a mainstay of the auditing industry as they can detect gaps in insulation, air infiltration and water leaks.

Thermal Mass
A key element to one form of passive heating. Thermal masses are typically very large chunks of a material capable of absorbing a great deal of heat energy. Examples would be a large granite block or concrete slab.

Top Plate
The stud board that forms the top of a wall in platform framed construction.
Tight Construction
Houses built with high levels of insulation and low levels of air infiltration.
The inverse of R-value. Another measure of the thermal resistance (actually thermal conductance but it’s so often conflated with R-value, we might as well call it resistance) of a building assembly or insulating product, most often used with windows.
Urea Formaldehyde
The base for older formulations of spray foam insulation and a binder for particle board and OSB.

Unvented roofs are those which do not have an active ventilation system. More and more modern construction use unvented roof designs. In cold climates, this requires that the interior air barrier (or other condensing surfaces) stay warmer than the dew point so as to avoid condensation. This makes venting which is intended to transport moisture out of the building unnecessary but requires controlling interior moisture sources.

Vapor Barrier
Building shell layer which controls/prevents the diffusion of water vapor through it.

Most modern residential construction ventilates the roof & occasionally the basement. The main goals with ventilated roofs are controlling roof temperature, extending the life of roof sheathing and, during the winter, slowing the melting of snow. A desired benefit is controlling moisture. A roof ventilation system usually consists of continual venting along the roof edge (known as soffit or edge vents), channel vents running along the roof deck (known as channel or proper vents) leading to either a ridge vent (running the length of the roof peak) or gable end vents.

More acronym fun, standing for Volatile Organic Compound. VOCs are carbon-based organic (I know that’s redundant) compounds which can evaporate at room temperature. Found in many home products, they can contribute to air quality issues.

EPA program to promote efficiency with faucets, showers and other plumbing water sources.

Material additions to the seams of doors and windows to reduce the leakage of interior conditioned air.

Wind Washing
Wind washing is wind driven air movement through the insulation. This can significantly impair the insulation’s effectiveness. Typically occurs along exposed building edges such as eaves.

A form of landscaping that minimizes the need for irrigation.

Extruded Polystyrene foam insulation. This foam board insulation has advantages in that it is water resistant, can act as an air barrier and has higher insulating values (R-5.5 to R-6.5 per inch) than other common insulating materials.

{ 2 comments… read them below or add one }

odor removal Cincinnati September 2, 2011 at 12:24 am

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Erik North September 2, 2011 at 2:12 am

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