A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent material, a sash set in a frame in the opening; the sash and frame are also referred to as a window. Many glazed windows may be opened, to allow ventilation, or closed, to exclude inclement weather. Windows may have a latch or similar mechanism to lock the window shut or to hold it open by various amounts.
In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.
Thermal insulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.
In building design, thermal mass is a property of the mass of a building that enables it to store heat and provide inertia against temperature fluctuations. It is sometimes known as the thermal flywheel effect. The thermal mass of heavy structural elements can be designed to work alongside a construction's lighter thermal resistance components to create energy efficient buildings.
In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions. The measure is therefore equally relevant for lowering energy bills for heating in the winter, for cooling in the summer, and for general comfort.
Cordwood construction is a term used for a natural building method in which short logs are piled crosswise to build a wall, using mortar or cob to permanently secure them. This technique can use local materials at minimal cost.
In thermodynamics, the heat transfer coefficient or film coefficient, or film effectiveness, is the proportionality constant between the heat flux and the thermodynamic driving force for the flow of heat. It is used in calculating the heat transfer, typically by convection or phase transition between a fluid and a solid. The heat transfer coefficient has SI units in watts per square meter per kelvin (W/m2/K).
Heating degree day (HDD) is a measurement designed to quantify the demand for energy needed to heat a building. HDD is derived from measurements of outside air temperature. The heating requirements for a given building at a specific location are considered to be directly proportional to the number of HDD at that location.
Superinsulation is an approach to building design, construction, and retrofitting that dramatically reduces heat loss by using much higher insulation levels and airtightness than average. Superinsulation is one of the ancestors of the passive house approach.
Building insulation is material used in a building to reduce the flow of thermal energy. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation. Often an insulation material will be chosen for its ability to perform several of these functions at once.
Solar gain is the increase in thermal energy of a space, object or structure as it absorbs incident solar radiation. The amount of solar gain a space experiences is a function of the total incident solar irradiance and of the ability of any intervening material to transmit or resist the radiation.
Sol-air temperature (Tsol-air) is a variable used to calculate cooling load of a building and determine the total heat gain through exterior surfaces. It is an improvement over:
A thermal bridge, also called a cold bridge, heat bridge, or thermal bypass, is an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer. Thermal bridges result in an overall reduction in thermal resistance of the object. The term is frequently discussed in the context of a building's thermal envelope where thermal bridges result in heat transfer into or out of conditioned space.
Pipe Insulation is thermal or acoustic insulation used on pipework.
Window insulation film is a plastic film which can be applied to glass windows to reduce heat transfer. There are two types in common use designed to reduce heat flow via radiation and convection respectively.
Window insulation reduces heat transfer from one side of a window to the other. The U-value is used to refer to the amount of heat that can pass through a window, called thermal transmittance, with a lower score being better. The U-factor of a window can often be found on the rating label of the window.
A radiator reflector is a thin sheet or foil applied to the wall behind, and closely spaced from, a domestic heating radiator. The intention is to reduce heat losses into the wall by reflecting radiant heat away from the wall. It is a form of radiant barrier and is intended to reduce energy losses and hence decrease fuel expenditure.
Insulating glass (IG) consists of two or more glass window panes separated by a space to reduce heat transfer across a part of the building envelope. A window with insulating glass is commonly known as double glazing or a double-paned window, triple glazing or a triple-paned window, or quadruple glazing or a quadruple-paned window, depending upon how many panes of glass are used in its construction.
Dynamic insulation is a form of insulation where cool outside air flowing through the thermal insulation in the envelope of a building will pick up heat from the insulation fibres. Buildings can be designed to exploit this to reduce the transmission heat loss (U-value) and to provide pre-warmed, draft free air to interior spaces. This is known as dynamic insulation since the U-value is no longer constant for a given wall or roof construction but varies with the speed of the air flowing through the insulation. Dynamic insulation is different from breathing walls. The positive aspects of dynamic insulation need to be weighed against the more conventional approach to building design which is to create an airtight envelope and provide appropriate ventilation using either natural ventilation or mechanical ventilation with heat recovery. The air-tight approach to building envelope design, unlike dynamic insulation, results in a building envelope that provides a consistent performance in terms of heat loss and risk of interstitial condensation that is independent of wind speed and direction. Under certain wind conditions a dynamically insulated building can have a higher heat transmission loss than an air-tight building with the same thickness of insulation. Often the air enters at about 15 °C.
Quadruple glazing is a type of insulated glazing comprising four glass panes, commonly equipped with low emissivity coating and insulating gases in the cavities between the glass panes. Quadruple glazing is a subset of multipane (multilayer) glazing systems. Multipane glazing with up to six panes is commercially available.
