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Glossary of Terms

Topher Belknap

Airkrete Insulation:
Insulation made from Magnesium Silicate, which is white, and similar in consistency to meringue cookies. It is foamed into place, and needs to be supported until it dries. R-value around 4 per inch of thickness.
Blower Door Test
An integral part of an energy audit. A fan is placed in a door, and air is evacuated from the building. Measurements are taken to determine the amount of air leakage that would be expected under normal circumstances. This is often joined with a tour of the building to discover where all those leaks are.
Cellulose Insulation
Insulation made from ground up paper products and impregnated with Borates to repel pests and fire-proof it. Usually installed by blowing with a large machine. In can be packed tight in closed spaces (4 lbs per cubic foot which prevents settling issues), or installed fluffy on top of things, or even sprayed with glue into open walls. R-value is around 3.5 per inch of thickness depending on how it was applied.
Dew Point
A measure of the amount of moisture in the air. It is defined as the temperature at which the moisture in the air would start to condense. A very important concept for buildings; see also Relative Humidity.
A building standard for renovations. The renovation version of the Passivhaus standard, slightly more lax in some aspects.
Expanded Polystyrene Insulation (EPS)
A foam board insulation, usually white and seemingly made of small beads, used for picnic coolers. R-value around 4 per inch.
Extruded Polystyrene Insulation (XPS)
A foam board insulation, often blue or pink. R-value around 5 per inch of thickness.
Fiberglass Insulation
Fibrous insulation available in batts or blown in small clumps. The most common sort of insulation in most houses. It has an R-value around 3 per inch.
Icynene Insulation
A professionally applied two-part spray foam insulation. Useful for air sealing and insulating in the same process, more expensive obviously.
Insolation (note the 'o', not a 'u')
The amount of sun which strikes a particular location, often generalized over a geographic area (i.e. does not include local shading).
Any material which significantly reduces the transfer of heat through a surface.
Foamed Glass Insulation
Insulation similar in many ways to pumice. Made from recycled glass, foamed, and formed into small rocks, or blocks. R-value around 3.5 per inch of thickness.
Home based renewable electrical energy connected to the public utility electric lines. See also: Net Metering.
Heat Pump
A machine for moving heat, by compressing a fluid. Air conditioners, refrigerators, dehumidifiers are all heat pumps. They can also be used as heating systems in many configurations, air-to-air, water-to-air, water-to-water; air source, or ground source (often mislabeled Geo-thermal).
Heat Retaining Ventilation System (HRV)
A machine for supplying the required fresh air to a house, while keeping as much of the heat contained in the outgoing air as possible. There are various styles, such as heat exchange models, and paired reversing fans.
Hygrometer (Humidity Guage)
An important tool for homeowners involved in energy efficiency changes to monitor their changing environment, and ensure that no dangerous conditions occur. This measures the amount of moisture in the air, expressed as the relative humidity.
Infrared (IR) Camera
A useful part of an energy audit. It is a camera sensitive to radiation below the visible portion, and can be used to 'see' small variations in the surface temperature of surfaces. Used to determine presence of insulation in walls, detect cooling of surfaces due to air leakage (especially in conjunction with a blower door test), and make cool-looking pictures of houses. Does not work well with windows, metal, and some other surfaces.
A type of heat pump, usually air-to-air, where the compressor section is distant from air handler. A single compressor may be set up to run multiple in-room heater/coolers.
Net Metering
A financial arrangement with a public utility where the utility is required by law to pay ratepayers for any electricity they generate, up to the amount they use (on a yearly basis).
A building standard originated in Germany. It is a performance rather than a prescriptive standard, so it has room for innovations. The basic idea is super-insulating surfaces, reducing thermal bridging, seal air leaks, and using high performance windows, all simulated in a computer before it is built, to meet certain energy metrics.
A system for creating landscapes that mimic nature while producing food for humans.
A foam board insulation, usually yellow, and often having aluminum foil on the faces. R-value around 7 per inch.
PhotoVoltaic (PV)
A system for converting sunlight into electricity. Often we are talking about large panels mounted on a roof or structure. They can be part of a stand-alone system, connected to the pulic utility grid, or both.
A measure of the resistance to heat of a material or assembly. This is the inverse of the heat conduction, and in house terms generally higher is better. Often when discussing materials R-value will be given as a per inch value. Units are (feet² • hour • °Fahrenheit) / BTU. [Note well: there is a metric version which is different but not always differentiated.]
Relative Humidity
A measure of the amount of moisture in the air. the percentage of moisture compared to the maximum air of the given temperature can hold. See also Dew Point.
Roxul (Rockwool) Insulation
Insulation made from slag from foundries and fibered basalt. R-values around 3 per inch of thickness.
Solar Pathfinder
A useful tool used in energy audits. It measures the amount of solar energy that a given location gets based on determining the location of various shade producing things in the vicinity. The amount of sun is determinable to the month and hour of the day.
Vaguely, more insulation than is traditional. Usually no effort is made to optimize or match the amount of insulation to other aspects of the building (contrast with Passivhaus).
Thermal Bridging
The reduction in insulation value in a building assembly caused by the lower R-value of structural members. A standard 2x6 wall for example, contains 10% of its area as wood studs, rather than insulation.
Whole-Wall Coefficient
The reduction in insulation value in a wall assembly due to normal door and window support structures. Expressed as a percentage of a full wall insulation R-value.
U-value (or U-Factor)
A measure of heat conduction. The inverse of R-value, it says how much heat moves through a surface of a given size, per hour, based on the difference in temperature between the two sides. Units are BTU / (feet² • hour • °Fahrenheit). [Note well: there is a metric version which is different but not always differentiated.]