Radiator reflector
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A radiator reflector is a thin sheet or foil applied to the wall behind, and closely spaced from, a domestic heating
radiator Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics. A radiator is always a ...
. 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 A radiant barrier is a type of building material that reflects thermal radiation and reduces heat transfer. Because thermal energy is also transferred by conduction and convection, in addition radiation, radiant barriers are often supplemented wit ...
and is intended to reduce energy losses and hence decrease fuel expenditure.


Effectiveness

Studies based both on modelling and experiments have demonstrated modest improvements in energy losses through the walls of houses through this method. Harris shows that plain aluminum foil was only "marginally" less effective than a proprietarily-shaped foil that claimed to avoid temperature stratification. Harris reports that "reductions in the overall energy consumption of the estroom of up to 6% were recorded by installing lainfoil behind a radiator, while the heat loss through the area of wall immediately behind the radiator fell to less than 30% of the original value". In his 3m cubed test room with a 1 x 0.5 m radiator and walls of average U value 0.44 W/m2K, he found that for a radiator temperature of 43 °C the heat flux through the wall behind the radiator reduced from 7.1 to 3.1 W/m2. Note that the average heat loss in the room was not reduced by such a large percentage as only part of the surface of the room was covered by radiators. He concludes that "in the test room used, which is the size of a small bedroom or sitting room, the total energy saved in a typical year in the UK’s climate would be of the order of 60 kWh". Baldinelli et al. support these findings and note that their "results show how the performance of the reflecting panel depends strictly on the insulation level of the external wall facing the radiator; more specifically, efficiency increases when the thermal resistance decreases, reaching energy savings of up to 8.8% in worst insulation conditions." Although the foils are termed "reflectors", they do not have much effect on radiated heat or its reflection. As radiators work at a relatively low temperature, the
Stefan–Boltzmann law The Stefan–Boltzmann law describes the power radiated from a black body in terms of its temperature. Specifically, the Stefan–Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths ...
The
Stefan–Boltzmann law The Stefan–Boltzmann law describes the power radiated from a black body in terms of its temperature. Specifically, the Stefan–Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths ...
states that the effectiveness of a thermal radiator is proportional to the fourth power of its
absolute temperature Thermodynamic temperature is a quantity defined in thermodynamics as distinct from kinetic theory or statistical mechanics. Historically, thermodynamic temperature was defined by Kelvin in terms of a macroscopic relation between thermodynamic wor ...
. A hot-water radiator at has only 1/4 the radiated power of a stove at , or 1/16 that of a radiant element at
means that they are weak radiators of heat. Most heat from a domestic radiator is as
convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...
currents of heated air. Where a reflector foil also has some insulating ability against
conduction Conductor or conduction may refer to: Music * Conductor (music), a person who leads a musical ensemble, such as an orchestra. * Conductor (album), ''Conductor'' (album), an album by indie rock band The Comas * Conduction, a type of structured f ...
(i.e. losses through the wall), it may have some useful effect. This is most pronounced when the wall itself has poor insulation performance: in a wall constructed to modern standards of insulation, even this effect may be reduced to a negligible benefit. The effect of placing a 10mm combined insulation and reflection behind radiators is about the same as that of 15mm insulation without a reflective layer. When the wall thickness behind the radiator is at minimum 1980 German standards this will reduce total heat losses of a building by about 4%. For a (by 1980s standards) well-insulated building heat losses can be reduced by about 1.6%.N. König: "Der Einfluß von wäremreflektierenden Folien in Heizkörpernischen auf den Heizenergieverbrauch eines Hauses" https://www.ibp.fraunhofer.de/content/dam/ibp/de/documents/Publikationen/IBP-Mitteilungen-optimiert/058.pdf A more effective
DIY "Do it yourself" ("DIY") is the method of building, modifying, or repairing things by oneself without the direct aid of professionals or certified experts. Academic research has described DIY as behaviors where "individuals use raw and semi ...
radiator reflector is a thin insulating layer (against conduction) of a lightweight insulator such as
expanded polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
foam veneerWidely sold in 2mm sheet rolls as an insulator beneath
wallpaper Wallpaper is a material used in interior decoration to decorate the interior walls of domestic and public buildings. It is usually sold in rolls and is applied onto a wall using wallpaper paste. Wallpapers can come plain as "lining paper" (so t ...
.
or 3mm
polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...
foam, as used for
laminate flooring Laminate flooring (also called floating wood tile in the United States) is a multi-layer synthetic flooring product fused together with a lamination process. Laminate flooring simulates wood (or sometimes stone) with a photographic applique la ...
underlay.


Commercially available products

There are only two radiator reflectors approved for use in the UK Government's
Carbon Emission Reduction Target The Carbon Emission Reduction Target (CERT) in the United Kingdom (formerly the Energy Efficiency Commitment) is a target imposed on the gas and electricity transporters and suppliers under Section 33BC of the Gas Act 1986 and Section 41A of the E ...
(CERT) Scheme administered by
Ofgem , type = Non-ministerial government department , nativename = , nativename_a = , nativename_r = , logo = Ofgem logo.svg , logo_width = 124px , logo_caption = , seal = , seal_width = , seal_caption = , picture = , picture_widt ...
(the UK Regulator of energy companies) – Radflek and Heatkeeper (also called Novitherm).


See also

* U value


References

{{DEFAULTSORT:Radiator Reflector Residential heating appliances Energy conservation Building insulation materials