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This thread was originally posted in the other place, and is a team effort to collect together as many acronyms and abbreviations used in the building trade as we could. If you know of any abbreviations missing, or think there should be a correction to the list, then post them as a reply to this topic and one of the moderators can edit the original list to keep it all up together. AAV = Air Admittance Valve. (Sometimes referred to as a Durgo Valve.) AAV (alternative) = Automatic Air Vent. ACH = Air Change [per] Hour AIUI = "As I understand It". AONB = Area [of] Outstanding Natural Beauty Article 4 Direction = Removes Permitted Development (PD) rights. (See: http://www.brighton-...cle-4-direction ) ASHP = Air Source Heat Pump (And see also: http://www.planningp...ects/heatpumps/ ) BC / BCO / BI = Building Control / Building Control Officer / Building Inspector (Often prefixed with LA = Local Authority, as in LABCO.) BR = Building Regulations (Regs) CIL = Community Infrastructure Levy (= a charge levied by a LA based on the sq.m of a property. Note: self-builds are exempt.) CO = Conservation Officer. (Now often designated: Heritage Officers. Specialized - although often not particularly qualified - planning officers working in a local authority Conservation/Heritage department. Have the power to over-rule BC where the Regs are concerned if a proposal is considered likely to impact on the "historic character" of a building, whether Listed or not, or in a Conservation Area.) {Listed Building, see: http://www.planningp...ing_consent.pdf } {Conservation Area, see: http://www.planningp...ns/conservation } CU = Consumer Unit CCU = Cooker Connection Unit CWS = Cold Water Storage [tank]. (Large plastic tank often in attic.) CYL Stat = hot water cylinder thermostat for control of DHW temperature. DeltaT = ΔT (Greek symbol Δ =delta in Greek alphabet) Temperature difference. (In the building context usually referring to the difference in temperature across a wall when discussing the effectiveness of insulation.) DG = Double Glazing (Sometimes referred to in shorthand as 2g = double glazed; 3g = triple glazed. Also expressed as 'd/g') DCW = Domestic Cold Water DHW = Domestic Hot Water DNO = Distribution Network Operator (electricity supply) DPC = Damp Proof Course DPM = Damp Proof Membrane EA = Environment Agency EDPM = Roofing membrane. (EPDM rubber (ethylene propylene diene monomer (M-class) rubber), a type of synthetic rubber,) EPC = Energy Performance Certificate (See: https://www.gov.uk/b...ce-certificates ) EPS = Expanded Polystyrene Insulation EV - Expansion Vessel EWI = External Wall Insulation F&E = Feed and Expansion tank. (Small plastic tank often found in attic alongside CWS.) FCU = Fused Connection Unit FWIW = "for what its worth". (As in: "That's my opinion FWIW.") FYI = For Your Information. (Now often seen in formal letters since they took the form of emails, and especially in the header of an email forwarded to keep someone "in the loop".) GCN = Great Crested Newt GSHP - Ground Source Heat Pump HC or VHC = heat capacity/volumetric heat capacity ICF= Insulated Concrete Formwork IGU = Insulated Glazed Unit (industry term for double or triple glazing) IMHO = "in my honest opinion." (Alternative: "in my humble opinion.") IIRC = "If I remember correctly." IWI = Internal Wall Insulation KISS = Keep It Simple Stupid. (Usually expressed as: "Stick to the KISS principle.") LA = Local Authority LBC = Listed Building Consent. (Needed to carry out work on any Listed building, whether domestic or commercial, privately or publicly owned, which is protected by law because of its historic significance, whether by age or architectural importance attested to by English Heritage.) (See also: Listed Building, above.) LPA = Local Planning Authority LPG = Liquefied Petroleum Gas M&E = Mechanical and Electrical MCB = Miniature Circuit Breaker MDPE = Medium-density polyethylene also referred to as Alkathene. Pipe used to carry mains water and gas, usually buried underground. MI = Manufacturers Instructions MVHR = Mechanical Ventilation [with] Heat Recovery. NPPF = National Planning Policy Framework OEM = Original Equipment Manufacturer OLIVE = Compressible copper ring accompanying threaded plumbing fittings that compresses around the pipe when the fitting is tightened to form a watertight seal. Often reinforced with PTFE tape [see below]. OSB = Orientated strand board Party wall = An internal wall common to two properties. (Not always a contentious issue, but see: http://www.planningp...on/partywallact ) PDR = Permitted Development Rights. (Sometimes just 'PD'. See: http://www.planningp...ssion/permitted ) PGM room stat = Programmable room thermostat: selects both operating times and temperatures. PI = Professional Indemnity (Insurance) PINS = Planning Inspectorate PME = Protective multiple earthing PIR = Rigid Polyisocyanurate Insulation PoE (or POE) = Power over Ethernet. Enables power to be provided to the device (phone or a network camera) using the same cable as that used for network connection. PRV = Pressure Relief Valve PRedV - Pressure Reducing Valve PHE - Plate Heat Exchanger PTFE (tape) = (polytetrafluoroethylene) Tape used to seal threads and joints (e.g. around olives in compressions fittings) in plumbing. Also known as Teflon tape outside the UK PUR = Rigid Polyurethane Insulation PV = Photovoltaics e.g. Roof Solar panels R-value = Thermal resistance [insulation] (the higher the better) RCD = Residual Current Device RCBO = Residual Current circuit Breaker with Overcurrent protection RDF = Refuse Derived Fuel RTFM = Read The Flipping Manual. (The polite version; the less inhibited version is usually expressed with the 'F' meaning what you think it means.) SAP = Standard Assessment Procedure (See: https://www.gov.uk/s...sment-procedure ) (See also: https://www.bre.co.u...P-2012_9-92.pdf ) ( https://www.gov.uk/g...t_file_2012.pdf ) SAPV - SunAmpPV SE = Structural Engineer SEPA = Scottish Environmental Protection Agency SFCU = Switched Fused Connection Unit SHC = Specific Heat Capacity (heat is another word for energy, don't confuse with temperature) SIPs = Structural Insulated Panels SSSI = Site of Special Scientific Interest Stat = Thermostat. (Room stat = wall mounted thermostat/central heating control.) SUDs = SUSTAINABLE URBAN DRAINAGE [system] SVP = soil vent pipe. SWA = Steel Wire Armoured (cable) SWMBO = She Who Must Be Obeyed (Attributed to "Rumpole of The [Old] Bailey", who used the phrase when referring to his wife, but actually from Rider Haggard's "She": https://www.youtube....h?v=bS5YmETSVCI ) TAF = Temporary Amphibian Fence TBH = "to be honest" (As in: "TBH I don't know.") TBF= "to be fair" (As in: "TBF to the builder, he hadn't a clue.) T&E = Twin and Earth (cable) TF = Timber Frame (form of house construction) T&G = Tongue and groove. (Often given in lower-case: t&g.) T&PV = Temperature & Pressure [relief] Valve TS = Thermal Store UFH = Under Floor Heating. (Also expressed as 'Underfloor Heating' but usually still given as UFH.) U-value = Rate of transfer of heat [insulation] (get it as low as possible, below 0.15 if you can) UVC = Unvented Cylinder VCL = Vapour Control Layer WUFI = "Wärme und Feuchte instationär" - Heat and Moisture transfer analysis XPS = Extruded Polystyrene Insulation ZV = Zone valve, motorised or other. (Directs heating medium to wherever needed according to programmed requirements.) UNITS OF MEASUREMENT L x W x H = Length times width times height. (But note that when giving dimensions for windows and doors ALWAYS follow the convention of width first, following by the height.) J = joule (not Joule) W = watt h = hour s= second k = kilo (thousand) kW = kilowatt kWh = kilowatt hour kWp = kilowatt peak (Solar installations - literally peak output.) m = metre (not meter) m2 = square metre (not metre squared) t = time T = temperature °C = Celsius or Centigrade K = kelvin (not °K or degrees Kelvin) k or k often means conductivity R = resistivity U = 1/R g = gram kg = kilogram (the odd SI unit, use it) J/(kg.K) = J/(kg.K) = J.kg-1.K-1 W/(m2.K) = W/m2.K = W.m-2.K-1 f(x) = function of x. (Common usage in thermal and stress calculations as well as statistics.) e = Exponent (1+1/1!+1/2!+1/3!+1/4!...) how things heat up and cool down, how fast things grow, π = pi ratio of a circles diameter to its circumference