Glossary

adobe Building material made of earthen clay and straw, often in brick form, unfired. 

air barrier A home’s airtightness is the greatest indicator of its energy use for heating and cooling. Aside from air infiltration, this barrier needs to manage moisture to avoid condensation turning into mold, rot, and structural damage.

air changes per hour When the total volume of air in a house is completely replaced with outside air within a specific amount of time, it is called x number of air changes per hour at 50 pascals of pressure (ACH50).

air stratification Heated air rises so that the warmest air is at the top and cooler air is at the bottom. Think of a house with two stories and a basement – the basement is the coolest.

alternative building blocks These could be thought of as “cement blocks”, but with a difference. They can contain recycled polystyrene, recycled wood-fiber, or extra air to make them light.

berm To help moderate temperature, redirect winds, reduce the snow and ice build up on the north side of buildings, or even to dampen the noise, earth is mounded against the walls or even on the roof. This MUST be designed for by an engineer.

british thermal unit (BTU) The measure of the quantity of energy; the heat necessary to raise one pound of water 1° Fahrenheit. It is equal to 252 calories or approximately the same amount of heat emitted by a kitchen match.

cellulose An affordable and effective insulation made from recycled newspaper with non-toxic borates added as pesticide and fire retardant.

chimney effect When air (or gas) is heated, it tends to rise and when cooled, it tends to sink. This is due to lower density when warmed, compared to the density of the surrounding air. This is used to help cool buildings when windows are open at the top of the house – the warm air rises and creates a negative pressure which brings in cooler air up from the bottom.

clerestory The earliest example of this is Luxor, Egypt. When vertical windows are placed high enough up, they let in light. These are not windows intended for viewing, but rather windows to bring heat and light into the building.

conduction The transfer of heat between objects by direct contact. It is passed from molecule to molecule by rapid vibrations.

conductive heat loss When heat passes through building materials, from the inside to the outside.

construction waste reduction The use of construction materials in such a way that there is very little waste by the use of efficient dimensioning and the use of any scrap material (rather than using a new piece of material and cutting it down to size). This practice also uses recycled materials.

continuous insulation (CI) An uninterrupted layer of insulation installed across all structural framing members without thermal bridges. It is placed on the exterior, interior, or within an assembly to block heat loss and condensation, meeting modern energy codes for high-efficiency buildings.

convection Heat is transmitted from a warmer surface to a cooler surface by air or liquid movement. Warm air rises because it expands. As it cools, it shrinks and drops causing thermosiphoning.

daylighting A design component that uses natural light in as many places throughout a house as possible to reduce the use of electrical lighting.

direct gain This is the basis of passive solar heating. It is where sunlight enters the building from a south facing window (in the northern hemisphere) and strikes a high density mass. The heat will be absorbed in the mass and released when the air temperature drops lower than the temperature of the mass. 

duct sealing Sealing up all the leaks at joints and seams, and plugging all the other holes helps with furnace efficiency.

earth sheltering Uses the earth to berm earth up to the tops of walls, or even on the roof, to help moderate the outside temperatures against the walls or the roof of habitable spaces.

efficient lighting The most efficient light fixtures are Light Emitting Diodes (LED's), followed by Compact Fluorescent Lamps (CFL's). Incandescent light bulbs, the most common bulbs for over a century, use lots of electricity and do not last very long. They are considered to be inefficient.

embodied energy The energy used by the individual building materials, from the time of the natural resource acquisition to manufacturing, production, and finally, to product transportation and delivery.

Energy Rating Index (ERI) Is a whole-house performance score used in building codes like the International Energy Conservation Code. On this scale, a score of 100 matches a 2006 reference home, and a score of 0 means a net-zero energy home.

EnergyStar rating A program regulated by the federal government that evaluates the energy efficiency of a building, light fixture, appliances, etc.

engineered composite wood Made from recycled or reconstituted wood, these products are laminated or ‘finger-jointed’. Manufactured wood makes for a more consistent product with better strength. This would also include laminated veneer lumber (LVL), oriented strand board, (OSB), and manufactured joists.

efficient glazing Double or triple-layered glass units used in contemporary window systems. The most energy-efficient type of glass for double and triple glazing is low emissivity (low-E) glass. See low-E glass.

heat gain The temperature of a space increases when something that emits heat is added to the space. This could be sunlight, people, appliances, machines, lights, or even a heat sink.

heat recovery ventilator (HRV) A way to bring fresh air inside. This process uses air that will be expelled from the home to warm it, before expelling the stale air.

heat sink Heat can be stored in materials (or thermal mass) and radiated again to the surrounding area as needed. This heat source also adds to heat gain.

HERS Ratings The Home Energy Rating System (HERS) Index is the standard by which a home’s energy efficiency is measured. It’s also the nationally recognized system for inspecting and calculating a home’s energy performance. The HERS Index measures a home’s energy efficiency. When you’re selling your home, a low HERS Index Score can command a higher resale price. And when you’re buying a home you can anticipate the costs of energy bills and efficiency upgrades.

house wrap or WRB This material is wrapped around all the walls of the home, preventing air from passing through it, thereby avoiding a ‘drafty’ house. Also known as weather resistant barrier.

infiltration heat loss When there are cracks around doors, windows and outlets (among other places), then cold outside air can come in and warm inside air can get outside in winter, or the reverse in summer.

internal heat gain Heat is generated by people, cooking, lights, hot water, etc, which adds to the heat of the room.

indirect gain system When a dense heat-absorbing material is placed between the source of the heat and the space needing the heat.

indirect mass When using materials like concrete, water, brick, stone, adobe, etc., the air heats up, penetrates the materials and is stored within it. When the air temperature is cooler than the mass temperature, the heat is then released.

low-E glass A thin metal coating lets in short wave solar energy but blocks long wave thermal energy.

low flow toilets A toilet that uses roughly 1½ gallons of water, or a dual flush system that uses less water for a liquid flush than for a solid waste matter flush.

low-e windows The “e” stands for emissivity. The glass is coated with a nearly invisible layer that helps improve thermal performance by reducing the flow of heat from inside to outside or outside to inside.

mass wall This wall generally faces south, and is made of a high density material, that stores heat from the sun or the surrounding air. When the air temperature drops to a lower temperature than the wall, the idea is that the wall radiates heat back into the space. It is a passive way to heat a house.

net zero energy home A house that produces as much energy as it consumes.

natural convection The movement of heat through the movement of air or water.

optimum value engineering (OVE) Homes tend to be ‘overbuilt’ by using too much lumber. Using OVE techniques allows lumber to be reduced without compromising the home’s structural elements. It saves on material costs, labor costs, and gives a higher insulation value due to less wood and more insulation.

passive cooling The use of a ‘thermal chimney’ to draw the air from the lowest point of the house, which is generally cooler, to the highest point of the house. Many times the windows are placed at the top of the thermal chimney so hot air can be expelled, thereby pulling cool air up.

Passive House (PHI or Phius) The Passive House approach (not the same as ‘passive solar’) creates durable, resilient buildings that slash heating energy use by as much as 90% and dramatically reduce operational carbon emissions. Passive House design tools and methods make these energy performance gains predictable. You know what performance to expect with a certified Passive House. Most importantly, Passive House buildings create healthy, comfortable, and quiet interior environments, full of clean, filtered fresh air.

passive solar Uses the sun to help heat buildings. It is necessary, in order to have true passive solar heating, to have a reasonable amount of thermal mass within the building, both indirect mass and sunstruck mass. No mechanical systems are used and the building itself is the heating system. Building orientation, site selection, materials and design allow the collection, storage and distribution of the sun’s heat.

payback The length of time it takes to recoup the cost of the improvement in energy savings. If you were to spend an extra $3k on additional insulation, weather stripping and caulking, while reducing your heating and cooling bills by $600 annually, it would take five years to pay off the $3k investment. After that you are earning money. Well, not really, but you get the idea.

photovoltaic Also known as PV or Solar Cells. Light is converted to electricity in DC voltage stored in a battery array, directly used in the house, or sold back to the utility company. These systems can be either off the grid, meaning that they are not hooked up to a company that supplies electricity, or grid tied, where the electricity can be sold back to the utility.

R–value The “R” stands for resistance (ie, resistance to heat loss). When used in referring to insulation, the higher the number means that the wall, roof, or floor is less likely to allow heat to move through. The insulating ability of material(s) to prevent the migration of heat from warm to cold is rated numerically and is expressed as 1/U. The higher the number means the slower heat loss, which is a good thing.

SHGC - solar heat gain coefficient Is the fraction of solar radiation admitted through a window, door, or skylight, either transmitted directly and/or absorbed, and subsequently released as heat inside a home. The lower the SHGC, the less solar heat it transmits.

solar thermal heating system This system works similarly to domestic hot water with collectors and a storage tank. But here the hot liquid is sent directly through a hot water baseboard in each room. A backup system for solar thermal would be a boiler.

solstice – winter & summer The longest day of the year - summer solstice - is June 22. The shortest day of the year - winter solstice - is December 22. The summer solstice offers 15 hours of sunshine, and the winter solstice provides 9 hours and 20 minutes of sun.

south orientation The longest side of a house faces anywhere from 15° east to 15° west of true south. This optimizes using the sun’s energy.

straw bale construction Bales of straw have an R-value of at least 45, therefore this type of home needs very little backup heating. They are stuccoed on the outside, plastered on the inside, are fire resistant, and have very deep window sills. They are made from the waste products of harvested crops.

structural insulated panel system (SIPS) Sheets of OSB are the ‘bread’ of a sandwich: extruded or expanded polystyrene sheets. The pieces are assembled in a factory, each with labels that instructs the house to fit together as a puzzle. The home’s walls can generally be erected in three days, depending on the floor plan’s complexity.

sunspace A room positioned along the south side of a building collects solar heat that will be used to heat itself or another space. It moves heat into another space by using convection currents, radiant heat or fans.

thermal break Since heat is conducted from one material to another, we need to provide a material between the two to stop the transmittance. Because this material does not conduct heat very well, It is used when chimneys and associated heat sinks exit the room’s heated areas, or even a concrete slab border where it touches the foundation walls. It stops the heat from ‘leaking’ out of a space.

thermal bridge Is a spot in a building’s thermal envelope where heat moves fast. It happens when a material that conducts heat well (like steel, or concrete) cuts through the insulation.

thermal envelope The physical barrier that separates the heated or cooled indoor space from the unconditioned outdoors. It functions like a protective shell, controlling the transfer of heat, air, and moisture.

thermal mass The use of very dense materials with highly-specific gravity, such as concrete, water, brick, stone, adobe, etc. When struck by sunlight, they absorb heat and later release it when the air temperature is cooler than the mass. In general, the more thermal mass in a house, the more stable the interior temperature.

thermal radiation Heat transfer between objects by electromagnetic radiation.

trombe-michel wall First used in 1881 by someone named Morse, it was popularized by Felix Trombe and Pierre Michel. It consists of a glass wall, an airspace of a few inches, and a mass wall of concrete, or filled concrete block. This wall can be vented or non-vented. The ‘outside’ is painted a very dark color to increase temperatures. Heat is absorbed by the thermal mass during daylight hours, then released when the air temperature is lower than the wall temperature.

U-Factor (Uf) ) Often referred to as U-value, is the opposite (reciprocal) of R-value (U = 1/R). It is the rate of heat loss or gain through a building component—most commonly a window, door, or skylight assembly. A lower U-factor means better insulating properties and less heat transfer.

vapor barrier Vapor barriers are best used to protect a home from rising damp and water below the slab or under the home. This material can also protect against radon. Vapor barriers were once commonly used in walls in ceilings, but it is now recommended to use materials for the building envelope that allows condensation to safely dry out. 

VOC Volatile Organic Compounds are organic chemicals that have a high vapor pressure at room temperature and offgas. 

weather stripping When you add materials around the openings of doors and windows, you prevent air leaks and moisture from coming in.

xeriscaping This is the use of native plants and vegetation, which, in our climate, means drought tolerant. This type of vegetation needs very little, if any, water to survive. However, it might take a year or more to establish the plants. But after that, they should be okay and not need anything but the minimum amount of water.