Conservation of fuel and power: Approved Document L, Volume 2 — Buildings other than dwellings

AA O N L I N E V E R S I O N Thermal bridging Occurs when part of a thermal Thermostatic room controls A device or system element has significantly higher heat transfer than that automatically controls the output of the materials surrounding it. heating and/or cooling emitters to control the temperature in each room (or, where justified, a *Thermal element Defined in regulation 2(3) and 2(4) heating zone) independently where heating and/or as follows. cooling is provided by a fixed building service. 2(3) In these Regulations “thermal element” Total useful floor area The total area of all means a wall, floor or roof (but does not include enclosed spaces, measured to the internal face of windows, doors, roof windows or roof-lights) the external walls. When calculating total useful which separates a thermally conditioned part of floor area, both of the following should be taken the building (“the conditioned space”) from— into account. a. the external environment (including the • The area of sloping surfaces such as staircases, ground); or galleries, raked auditoria and tiered terraces b. in the case of floors and walls, another part of should be taken as their area on plan. the building which is— • Areas that are not enclosed, such as open i. unconditioned; floors, covered ways and balconies, should be ii. an extension falling within class 7 of excluded. Schedule 2; or NOTE: This area is the gross internal floor area iii. where this paragraph applies, conditioned as measured in accordance with the Code of to a different temperature, Measuring Practice by the Royal Institution of Chartered Surveyors (RICS). and includes all parts of the element between the surface bounding the conditioned space and the U-value A measure of the ability of a building external environment or other part of the building element or component to conduct heat from a as the case may be. warmer environment to a cooler environment. It is expressed as the quantity of heat (in watts) 2(4) Paragraph 2(3)(b)(iii) only applies to a building that will flow through 1m2 of area divided by the which is not a dwelling, where the other part of difference in temperature (in degrees K) between the building is used for a purpose which is not the internal and external environment. The unit is similar or identical to the purpose for which the W/(m2·K). conditioned space is used. Weather compensation A system which enables Thermal envelope The combination of thermal the operating flow temperature of a heating system elements of a building that enclose a particular to be varied. An external sensor communicates conditioned indoor space or groups of indoor spaces. with one inside the boiler. The temperature is Thermal separation Occurs where a building and a varied by either of the following. conservatory or porch are divided by walls, floors, • Modulating the heat generator output (direct windows and doors to which one of the following acting). applies. • Using a mixing valve to adjust the flow • The U-values are similar to, or in the case of a temperature to the heat emitters. newly constructed conservatory or porch not exceeding, the U-values of the corresponding Wet heating system When a heating appliance (usually a boiler) produces hot water which is exposed elements elsewhere in the building. distributed around the building to heat emitters. • In the case of a newly constructed conservatory or porch, windows and doors have similar draught-proofing provisions as the exposed windows and doors elsewhere in the building. 9900 AApppprroovveedd DDooccuummeenntt LL VVoolluummee 22,, 22002211 eeddiittiioonn BBuuiillddiinngg RReegguullaattiioonnss 22001100 O N L I N E V E R S I O N