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Glossary

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glossary-a AIR EXCHANGE RATE Either m3/h or in fractions of the total volume of the house per hour. You need a certain rate of air changes for health reasons (fresh air, counter-act summer overheating) and to avoid excess moisture in the home, but excessive and/or uncontrolled air changes means loss of energy.AIR LEAKAGE is the uncontrolled movement of air in to and out of a building which is not for the specific and planned purpose of exhausting stale air or bringing in fresh air.

AIR TIGHTNESS TESTING See Pressure test.

APEX/PEAK The uppermost point of a truss.

ASYMMETRIC TRUSS A truss with two rafters meeting at the APEX, having a different pitch on both sides.

ASYMMETRIC TIMBER FRAME A timber frame wall system where the frame is constructed using two vertical studs, inner and outer, of different sizes.The inner and outer studs form the insulation space, structural loads are mainly carried by the larger stud.

ATTIC TRUSS/ROOM-IN-THE-ROOF A special roof truss forming the top storey of a dwelling. Characterised by a central habitable area free of web members with large timber members elsewhere. May have to be assembled partly on site because of transport difficulties.

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glossary-b   BALLOON FRAME Uncommon build type in the UK for timber frame whereby the panels are built to roof/wallplate level and the floor is then hung internally from plates or hangers.BATTENS Small timber members spanning over trusses to support tiles, slates, etc.

BEARER A member designed to distribute loads onto a number of trusses or studs.

BEARING The part of a truss receiving structural support. This is usually a WALLPLATE but can be an internal wall etc.

BINDER A longitudinal member nailed to trusses to maintain correct spacing.

BIRDSMOUTH A notch in the underside of a loose rafter to allow a horizontal seating at a point of support (not normally used on trussed rafters except with a raised tie feature).

BLOCKING AND BRIDGING (STRUTTING) BLOCKING Solid pieces of timber in short lengths fixed between floor joists at ends of spans to prevent any movement.

BOBTAIL See STUB END.

BOTTOM CHORD/CEILING JOIST/TIE The lower member of a truss, normally horizontal, which carries the ceiling construction, storage loads and water tank.

BRACING/ WIND BRACING Lengths of timber used to brace components together to distribute loads more evenly throughout the structure to counteract forces such as wind loads.

BREATHER PAPER A man made material such as woven polypropylene, generally stapled to the outside face of an external timber frame panel. It allows water vapour to pass through from the inside to the outside of a timber frame wall, but resists the passage of water in the opposite direction

BREATHING WALL (PANELVENT/ BITVENT) These boards manufactured from wood chips, selected wood waste and forest thinnings have been designed as a sheathing board for the timber frame industry and a sarking board in most forms of construction. In normal situations they do not require a breather paper or vapour barrier. This allows moisture migration from the inside to the outside of the structure.

BREDEM Building Research Establishment Domestic Energy Model. Estimating cooking, lights, appliances and hot water use and working out heating demands using RDSAP or SAP.

BREEAM Building Research Establishment (BRE) Environmental Assessment Method. It is the widely used environmental assessment method for buildings, which takes a wide range of sustainable aspects into consideration. It sets standards for best practice in sustainable design and is a measure used to describe a building’s environmental performance.

BRICKWORK COURSING Ecoframes ensure wherever practicable to position openings in timber frame such as windows and doors and soffit lines to brickwork coursing. This is to enable complete bricks to line up with the openings to avoid the bricklayers having to cut more bricks than is necessary.

BRICKWORK LINTELS Galvanised steel lintels that are fixed to the external timber frame panel and support brickwork / blockwork over window / door openings in timber frame.

BRIDGING Solid pieces of timber generally at mid spans of floor joists to prevent distortion/twisting of timber.

BUILDING DESIGNER The person responsible for the structural stability and integrity of a building as a whole.

BUILDING REGULATIONS An area of building control that states how a building should be constructed to ensure safe and healthy accommodation and the conservation of energy. This form of control is administered by the relevant local authorities, to whom an application must be made and permission received (generally a conditional approval) before work is started. Ecoframes supply structural drawings and engineering for building control approval for the structural shell which are generally completed approximately 2 weeks before the delivery of the frame. The client or client’s Architect makes the main application before work on site begins.

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glossary-c   CAMBER An upward vertical displacement built into a truss in order to compensate for anticipated deflection caused by applied loads.
 CANTILEVER The part of a structural member or TRUSS which extends beyond one or both of its bearings.

CARBON FOOTPRINT A measure of the impact our activities have on the environment through CO2 emissions. It relates to the amount of greenhouse gases produced in our day-to-day lives through burning fossil fuels for electricity, heating and transportation etc. The carbon footprint is a measurement of all greenhouse gases we individually produce and has units of tonnes (or kg) of carbon dioxide equivalent.

CAVITY BARRIER Either timber/wire reinforced mineral wool blanket or polythene sleeved mineral wool used to seal off the cavities into zones

CEILING JOIST See BOTTOM CHORD.

CHEVRON BRACING Diagonal bracing nailed to the truss in the plane of specified webs to add stability.

CHORDS Refer to the Top and Bottom Chords which are respectively the RAFTER and CEILING TIE.

CHP Combined Heat and Power. A replacement for boilers with economic and environmental benefits, simultaneously producing heat and power.

CLS Canadian Lumber Size– generic term for timber used to construct timber frame panels.

CONCENTRATED LOAD A load applied at a point.

CONCRETE SCREED An in situ flooring of cement mortar laid to an accurate flat surface by screeding. Screeds are laid on the structural floor and usually have no reinforcement – in a timber frame situation it would be laid after the structural shell has been erected (generally approx 65mm deep).

COP Coefficient of Performance. E.g. a COP of 3.5 means that (at e.g. at 10ºC outside temperature and DHW temperature of 40ºC) the device (e.g. heat pump) will use 1kW for every 3.5kW put out.

CPSU Combined Primary Storage Units – a boiler with a thermal store all in the same casing.

CRIPPLE RAFTER/JACK RAFTER An infill rafter completing the roof surface in areas such as the corners of hip ends.

CRIPPLE STUD A short stud that is connected to a full height stud to form a bearing for a horizontal lintel for a window or similar opening.

CSH or CfSH Code for Sustainable Homes. Valid in England, Wales and Northern Ireland.

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glossary-d   DAMP PROOF COURSE (DPC): A strip of impervious material that sits underneath the timber frame soleplates or brickwork / blockwork to keep out moisture. The dpc at ground level excludes rising damp but they are also used to divert rain out of the cavity, to drain through weepholes at the lintel above door or window openings. Dpc comes in preformed rolls and made of flexible materials such as bitumen-polymer, Polythene or pitch-polymer.DAMP PROOF MEMBRANE (DPM) A wide layer of impervious material such as mastic asphalt or a polythene (Build Regs specify 1200g or 300μm) sheet underlay beneath a ground slab to create a waterproof skin. A surface damp proof membrane can also be used such as is supplied with a floating floor.

DEFLECTION The deformation caused by the loads.

DER Dwelling Emission Rate (annual CO2 per sqm) due to space heating, water heating, ventilation and internal lighting minus any CO2 emissons saved by any generation of electricity.

DESIGN LOAD Collectively the loads for which the unit is designed. These consider the duration of the loads -long term, medium term, short term and very short term.

DHW Domestic hot water.

DIFFERENTIAL MOVEMENT Timber being a natural resource is prone to some shrinkage across the grain although it is stable in the longitudinal section. An allowance is made in the floor where joists do have to lye across the grain. The difference between the timber frame movement and that of the external brickwork is the differential movement.

DORMER HOUSE/BUNGALOW Also sometimes known as a one and a half storey house or room in the roof bungalow. This is where the roof space is utilised by using Attic Trusses or similar. The rooms on the first storey will have sloping ceilings and either dormer windows or velux type roof lights to allow light into the rooms.

DORMER WINDOW a roof window, built into the slope of the roof, where the window frame itself is vertical. Usually surmounted by a small pitched roof in the classic interpretation.

DPC –  See DAMP PROOF COURSE

DPM –  See DAMP PROOF MEMBRANE

DUO/DUAL-PITCH TRUSS A truss with two top chords meeting at an apex and not necessarily being at the same pitch on both sides.

DWANGS See NOGGING.

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glossary-e   EAVES The line where the rafter meets the wall – The eaves are the roof overhang (usually clad in fascia and soffit) which protects the brickwork, or other external cladding from rain. It generally allows air ventilation to the roof void while keeping out insects and other animals.EAVES/ HEEL JOINT The part of the truss where the rafter and the ceiling tie intersect. This is usually where the truss is supported.

ENVIRONMENTAL IMPACT (EI) rating. Based on estimated annual CO2 emmissions per sqm due to space heating, hot water heating, ventilation and internal lighting – minus any CO2 emissions saved by any generation of electricity. Figure between 1 and 100+, rounded to the next integer, with the higher the number the better the standard. EI rating of 100 corresponds to zero net CO2 emissions. May also be expressed in bands (like SAP).

EMBODIED ENERGY Energy used to produce a building material, including its transport.

ENGINEERING/ ENGINEERS CERTIFICATE Ecoframes employs structural engineers (all NHBC registered) to provide structural information on the size and nature of the various components that make up structural timber frame kit. Structural calculation, assembly drawings and details are supplied by Ecoframes for submission to the Local Authority by the client or the client’s representative. N.H.B.C. HB353B Certificate/Engineers Structural Certificate, provided by Ecoframes.

EPBD Energy Performance in Buildings Directive. EU requirement for each EU member state to implement:

EPC Energy Performance Certificate. Issued by the OCDEA. Energy rating ”as built” (i.e. including actual – not planned – figures and components). Benchmark or energy performance & recommendations for cost effective improvement of energy performance. To be included in the HIP.

ER The Energy Rating (ER) value is calculated using a formula that balances a product’s U-value with its potential solar heat gain coefficient (SHGC) and its airtightness. The higher the number, the more energy efficient the product.

ERECTION/ INSTALLATION The on site construction of the timber frame structural shell by a specialised team that usually include for thier own mechanical handling and accommodation whilst working. A structural shell for an average 3/4 bed house will generally take approximately 7 – 10 working days to erect.

EUROCODE 5. The new structural design code for timber which is replacing BS5268

EXTENDED RAFTER/RAISED TIE TRUSS A truss which is supported at a point on the extension of the rafter, beyond the point where the bottom chord meets the top chord.

EXTERNAL JOINERY The windows and doors etc. produced from high quality planed timber.

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glossary-f   FABRICATOR A company engaged in the design & manufacture of Engineered Timber Products i.e.roof trusses, timber frame homes, metalweb joists & glulam trusses etc… FASCIA/BARGE & SOFFIT A board which is generally timber set on edge along the eaves. This covers the rafter ends and will usually carry the gutter. Bargeboard – As above but used on the sloping areas of the roof. They are fixed in pairs along the edge of the gable to cover the roof timbers and protect them from rain. They can be ornately carved or moulded if required to create a feature. Soffit board – A horizontal sheet fixed under the eaves, concealing the rafters and the underside of the roofing. It runs between the back of the fascia and the face of the outer wall. The soffit can be either flat or sloping.

FASTENER See CONNECTOR PLATE/NAIL PLATE.

FINK TRUSS Named after the original designer. A duopitch truss, the two top chords having the same pitch and the webs forming a letter W. The most common truss type used for dwellings. Use of this type of truss prevents effective use of the roof space or attic.

FIRESTOPS Cavity barriers such as flexible mineral fibre strips in polythene sleeves required at junction of separating and compartment wall and external wall with roof.

FLOOR JOISTS A wooden (or steel) beam which directly supports flooring in common with other joists (or a ceiling lining as a roof joist) Types of floor joists generally used by Ecoframes are:- SOLID TIMBER- Treated softwood floor joists  at 400, 450 or 600 mm centre spacings. The cross sectional sizes usually used are 195 x 54mm, 195 x 70mm, 220 x 45mm and  ‘I-JOIST’ /Metal Web joists of varying sizes.

FRENCH HEEL A heel joint where the top chord sits on the top of the bottom chord.

FSC Forest Stewardship Council is an international, non-governmental organisation dedicated to promoting responsible management of the world’s forests. Mark that indentifies sustainably grown timber.

FUEL POVERTY Households with energy costs that exceed 10% of their income.

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glossary-g   GLULAM Large section timber material for structural applications. It is an engineered product built up by gluing together layers of timber boards with staggered joints in lengths up to 13.5 metres.G-VALUE Solar heat gain coefficient (SHGC). Measure of the solar heat passing through a window, which can be harvested for heating up a dwelling. The value is influenced by the panes of glass and coating, which absorb and reflect heat. E.g. a g-value of 0.6 means that 60% of heat passes through the glass/ window.

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glossary-h   HANGER A metal component designed to provide a connection between a truss or other component and its support.HEAD BINDER Horizontal timber member that ties together individual wall panels.

HEAT EXCHANGER Used in MVHR systems to transfer heat from the extract air to the supply air; also used to transfer heat from heat pumps or solar collectors to heating systems and domestic hot water.

HEAT LOAD this measures the capacity of the space heating system required to maintain comfortable indoor temperatures at any one time, specified in Watts per square metre of treated floor area, or W/m2. For a house with, for example 110m2 treated floor space, if the annual space heat requirement is at the maximum of 15kWh/(m2a), the energy consumption for heating would be 1,650 KWh over an entire year. See space heat requirement.

HEAT PUMP A device extracting heat from a source of a lower level of temperature (e.g. outside air or ground) and ”pumping it up” to a higher, used for space heating and DHW (domestic hot water). With some, the process can be reversed to extract heat from the building (air conditioning).

HEEL/EAVES JOINT The part of a truss where the top and bottom chords intersect, normally where a truss is supported.

HIP BOARD A raking member extending from ridge to corner in hip end construction.

HIP CORNER A corner turn in a building incorporating a hip end.

HIP END An alternative to a gable end. The end wall is finished to the same height as the adjacent walls. The roof inclines from the end wall usually at the same pitch as the main trusses. See HIP SET.

HIP Home Information Pack. Since 14 December 2007 every home put on the market, no matter what size, must have a Home Information Pack. It brings together valuable information at the start of the process – such as a sale statement, local searches and evidence of title. The Pack also includes an Energy Performance Certificate with advice on how to cut CO2 emissions and fuel bills.

HORN/NIB The projection of the bottom chord of a trussed rafter built into masonry as a bearing. Used on monopitch and stub end trusses.

HRV Heat Recovery Ventilation, see MVHR.

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glossary-i   I BEAMS/ENGINEERED TIMBER JOISTS These generally use laminated veneer lumber flanges, routed to accommodate an OSB centre web. They can accommodate larger spans than standard joists and are a lightweight, uniform product. Advantages include reduced shrinkage, cupping, bowing, twisting and splitting that can be associated with standard joists.IMPOSED LOAD The load produced by occupancy and use including storage, inhabitants, moveable partitions and snow, but not wind. Can be long, medium or short term.

INSULATION The materials used in walls / floors and roof space to create a warm structure to satisfy the clients requirements and comply with part L of the building regulations .There are 3 main physical types of insulation: Fibrous, Foamed Boards and Multi foil—all with their own advantages and disadvantages. Fibrous include: Mineral Wool, Polyester Fleece, Hemp, Flax, Woodfibre, Cellulose Fibre (Warmcel) and Sheep’s Wool. Rigid Boards include. Polystyrene Slab (Jablite), Poyurethane Foam, Phenolic Foam. Multi-foils include such things as Actis Tri-iso. These insulants come in a variety of forms such as Loose Fibres, Batts, Rolls, Rigid Boards and Sheets. There are also other Hi-tech insulation systems such as Vacuum Insulated Panels (VIP’s) and Aerogels.

The various advantages and disadvantages of the different types will not be discussed here although it is worth mentioning that it is an important area, well worth discussing. Ecoframes generally favours the use of fibrous Insulants in preference to Oil-based foams.

INTERNAL MEMBER/WEB A timber member used to transmit forces between chords.

INTERNAL PARTITIONS Timber wall panels between rooms that are prefabricated and generally without sheathing unless required for engineering purposes

INTERSECTION The area where one roof meets another

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glossary-j   JOIST HANGERS Galvanised steel hangers that can be nailed to timber or other materials that floor joists sit into for supportreturn to top of page
   
glossary-k   KING POST Internal vertical member of a roof truss which connects the APEX to the bottom chord/ceiling tie on a truss.return to top of page
   
glossary-l   LAMBDA (λ) The Lambda value is the intrinsic figure for the thermal conductivity of a material. The unit is W/(mK). If the figure high, e.g. 220W/(mK) for aluminium, then the material is a good conductor of heat. If it is low, e.g. 0.035W/(mK) for silk, then the material makes a good thermal insulation.LATENT HEAT CELLS High-performance thermal stores, which operate with phase changing material. Ideal for small units or where there is not much space for a heat store (can e.g. be placed in the corner of a roof).

LIVE LOAD A term often used instead of IMPOSED LOAD.

LONGITUDINAL BRACING Component of STABILITY BRACING.

LOOSE TIMBER Members not forming part of a truss but necessary for the formation of the roof. See JACK/CRIPPLE RAFTER.

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glossary-m   M CONNECTOR PLATE/FASTENER/NAIL PLATE Metal plate having integral teeth punched from the plate material. Used for joining timbers in one plane with no overlap. Supplied by system owners and the subject of an Agrement Certificate. Not usually for site application.MOISTURE RESISTANT CHIPBOARD (V313) This is manufactured mostly from softwood forest thinnings and timber waste from sawmills or manufacturing processes. Ecoframes always use the moisture resistant form that is generally recommended for bathrooms and other potentially wet areas.

MONOPITCH TRUSS A truss in the form of a right-angled triangle, having a single top chord.

MVHR Mechanical Ventilation with Heat Recovery, also called HRV. Controlled exchange of air which requires a high standard of air tightness. Up to 90+% of energy can be recovered that would otherwise be lost in during the air exchange process.

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glossary-n   NAIL PLATE See CONNECTOR PLATE.NATIONAL HOUSE BUILDING COUNCIL – NHBC (NHBC / NHBC Builder) An organisation that encourages better house building. It has a register of reputable house builders and includes services such as conciliation between builders and purchasers, the NHBC Warranty, ten year insurance on new houses and advice on proper site practices. ECOFRAMES™ will provide a suitably signed engineers certificate for the timber frame structure if the NHBC route is chosen by the client for insurance and warranties.

NHER National Home Energy Rating. A Metric to compare the Energy Running costs of houses. A figure between 0 (= a tent with an electric fire) and 20 (= Significant local generation of electricity, zero running costs), based on annual fuel running costs per sqm and using standard occupancy conditions and deflated three year average fuel prices.. Includes SAP plus cooking and appliances but is based on actual location. Most new homes are around 9.

NODE Point on a truss where members intersect.

NOGGINS (PLASTERBOARD) A horizontal member fitted between 2 studs, Joists or Trusses generally to supply a fixing for plasterboard.

NOTCHING & DRILLING (FOR SERVICES) It is important the joists and studs are notched and drilled for services (to run cables and pipes through) in areas indicated by the supplier only. Notching and drilling zones will be indicated by the manufacturer in their standard details so as not to impair the structural integrity of the structure.

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glossary-o   ORIENTED STRAND BOARD (OSB) Timber board generally used to sheath external panels of timber frame. It is manufactured by flakes of timber ’snowed’ into a mat using a small electrical charge so the resulting board has a specific strength.OVER FASCIA VENTS An eaves vent that runs along the top of the fascia. They can have different size openings depending on the ventilation requirements of the roof (generally 10 – 25mm).

OVERHANG Measurement on plan from the intersection point of the underside of top and bottom chords to the end cut of the rafter.

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glossary-p   PADSTONE A reinforced member/area built in a wall to distribute the pressure from a concentrated load onto a larger area of wall.PANEL CONSTRUCTION In a panel system the structural studs are spaced at 400 / 600mm centres and carry the loads down to the foundations via the soleplate. Timber frame external walls (and internal loadbearing) are required to carry the dead and imposed loads acting on the structure and transmit them to the foundations. On average the panels can vary from around 2 metres in length upwards if a crane is being used on site.

PARALLAM: This is a beam created from shards of timber formed longitudinally in line with the length of the beam. This product is stronger than conventional timber and is generally used as lintels above windows or beams in floor zones.

Part F …of Building Regulations. Requirements for Northern Ireland to meet Energy Performance levels.

Part L1A …of the English Building Regulations. Requirements for England and Wales to meet Energy Performance levels.

PART PROFILE See STUB END.

PARTY FLOOR A separating floor between flats that has to perform similar duties to the party wall above. A party floor has to give more consideration to impact sound insulation as well as airborne sound.

PARTY WALL / COMPARTMENTATION A separating wall between two dwellings that must fulfil two main requirements 1, To reduce the passage of sound between the dwellings to levels set out in part e of the building regulations. 2, To comply with regulations as to give adequate fire protection between the buildings right up to the roof and through the cavities. Timber frame party walls perform well above building regulation requirements and the main components that improve sound and fire insulation is the type and mass of plasterboard used, the addition of insulation and adequate cavities between structures.

PASSIVHAUS. A type of construction concept pioneered by Dr Wolfgang Faus.

PEA Predicted Energy Assessment. Issued by the Plan Assessor. For new homes sold from plan; to be included in the HIP and to be replaced by ”as built” EPC within 15 working days of completion.

PEAK See APEX.

PERMISSIBLE STRESSES Design stresses for grades of timber published in BS5268:Part 2 .

PHASE CHANGING MATERIAL Material that absorbs heat to a certain temperature and releases heat at a certain temperature. Used to store heat e.g. during sunshine and release the heat again when the temperatures drop. E.g. paraffin is a phase changing material, which has a 4 times better heat storage capacity than water for a certain temperature range. Used in heat storage cells or plaster board. See latent heat cells and thermal mass.

PHI The German Passivhaus Institute.

PHPP Passivhaus Planning Package. A very accurate energy assessment tool for consultants and architects. It goes along with the design process of the building and is used in the certification process of passive houses.

PHVP Passivhaus Pre-Planning. The simplified version of PHPP, including (more) standard values to get approximate results in the planning phase.

PITCH The angle of the chord (usually rafter) to the horizontal measured in degrees.

PLAN ASSESSOR Certified / authorised to assess plans for new buildings and issue PAEs as well as giving advice on energy performance improvements.

PLATE LOCATION/POSITION TOLERANCE Acceptable deviation from specified location. Design allowance is 5mm in both orthogonal directions. May be specified greater.

PLATE See CONNECTOR/NAIL PLATE.

PLATFORM FRAME Most timber frame construction in the UK is generally platform frame. It is where a structure is built sequentially upwards in platforms (floor by floor).

PLYWOODS These consist of an odd number of thin layers of timber with their grains alternating across and along the panel or sheet. They are then glued together to form a strong board which will retain its shape and not have a tendency to shrink, expand or distort. Generally used for floor decking or as sheathing boards.

POST & BEAM CONSTRUCTION Differing Timber frame construction method to the panel construction that ECOFRAMES generally use. It is where heavy structural Glulam or timber posts and beams are used (generally 150 x 150mm or larger) to transfer all the loads of the structure down to the foundations.

PRESSURE TEST Also called air permeability test. This measures the air tightness of a building (m3/h at 50Pa) and is needed for the EPC.

PSI (Ψ) The PSi-value is related to the lambda-value (also in W/(mK)), but in this case it denotes the thermal conductivity of an assembly of materials, e.g. the edge of a window glazing panel, where glass sheets, one or more spacers and the window frame, with one or more different material, come together. It describes therfore the thermal bridging of that detail. The higher the figure, the higher the heat loss through that detail. Figures of 0.01W/(mK) and smaller are considered “thermal-bridge-free” and this is what detailed planning of a Passive House is aiming for. [Can they? Surely this would mean that heat flows in the opposite direction? ]

PURLINS Horizontal heavy section timber, steel or glulam that run at right angles to the underside of the roof rafters. They carry the load of the roof to the gable ends of a house and also generally supported on internal panels which transfer the loads to the foundations.

PV Photovoltaic. Generation of electrical power from (sun) light.

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glossary-q   QUARTER POINT The point on the rafter where an internal member/web connects in a ‘FINK’ type trussed rafter. QUEEN POST Internal member (web) which connects the APEX & CEILING JOIST/TIE to a third point on a TRUSS.

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glossary-r   RACKING RESISTANCE The wall panel studs (generally set at 600mm centres) carry the vertical loads from the floor / roof down to the foundations. The studs must be restrained using a sheet material such as plywood or oriented strand board to provide resistance to racking and stiffen the structure.RADON A naturally occurring radioactive gas formed as a result of the radioactive decay of uranium, which is more or less present in all rocks and soils. It can accumulate in buildings and can be harmful to the health of the inhabitants. Constant ventilation, e.g. through MVHR systems, decreases the accumulation of radon gas drastically.

RAFTER DIAGONAL BRACING Component of STABILITY BRACING.

RAFTER/TOP CHORD A sloping roof beam that generally runs from eave to ridge. Most roof elements are generally pre-fabricated trusses but rafters are used for infilling and for other areas where prefabrication is not practical. This term can also be applied to the principal rafter of a truss.

RAISED TIE TRUSS See EXTENDED RAFTER TRUSS.

RDSAP Reduced Data SAP. Survey system used to produce EPCs for existing homes.

REDUCING TRUSSES See VALLEY FRAMES.

REMEDIAL DETAIL A modification produced by the Trussed Rafter Designer to overcome a problem with the trussed rafter after its manufacture.

RENEWABLE ENERGIES Thermal and electrical energy derived from sources other than fossil fuels (oil, gas and coal).

RETURN SPAN The span of a truss being supported by a girder truss.

RIAS Founded in 1916 as the professional body for all chartered architects in Scotland and is the foremost architectural professional institute in the country dealing with architecture and the built environment.

RIBA The Royal Institute of British Architects is the UK body for architecture and the architectural profession.

RIDGE BOARD Timber running along a ridge and sandwiched between oncoming loose rafters.

RIDGE The line formed by truss apexes.

ROOF DESIGNER The person responsible for the design of the roof as a whole so that it is stable in itself and is capable of transmitting wind forces on walls and roof to suitable buttressing walls. The Roof Designer is appointed by the Building Designer or can be the Building Designer himself.

ROOF TRUSS These are triangulated plane roof frames designed to give clear spans between the external supporting walls. They are delivered to site as prefabricated components and fixed to wall plates generally at 600mm centres. They receive lateral stability through wind bracing timbers that are fixed through them to bind them together.

ROOM-IN-THE ROOF See ATTIC TRUSS.

R-VALUE The R value or R-value is a measure of thermal resistance of materials. The R-value is independant of the thickness of the material. The higher the R-Value number, the more insulative the product is. R-value is the reciprocal of U-value.

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glossary-s   SAP Standard Assessment Procedure for new homes. Independed of location (using a ”standard location”) and including lights, heating and hot water but not cooking and appliances. Rating scale is from 1 to 100+ with the higher the number the lower the fuel running costs. 100 corresponds to zero running costs, so the rating can be over 100 if surplus energy is exported.
 SARKING A material such as plywood or OSB applied to the upper surface of rafters on a roof to give a continuous panel support. A system that is used as standard in Scotland, but uncommon in England and Wales.

SCAB Additional timber connected to a truss to effect a splice, extension or local reinforcement.

SCAFFOLDING These are temporary working platforms erected around the perimeter of a building to provide a safe working place at a convenient height. With timber frame the scaffolding is generally erected around three sides of the building before the kit is delivered. It is then enclosed at a suitable time. The scaffolding is erected far enough away from the external wall panels so it can stay up throughout the build for use by bricklayers and roofers etc.

SETTING-OUT-POINT The point on a truss where the undersides of the top and bottom chords intersect.

SHEATHING Boards laid side by side – tongued and grooved boarding is used for flooring (generally 18 or 22mm moisture resistant chipboard/OSB or plywood) and close boarding for timber frame panels and roofs (9mm OSB or plywood generally used for panels)

SHGC Solar heat gain coefficient; see G-value.

SKEW NAILING Driving nails at angles into the surfaces to be joined. A method of fixing trussed rafters to wall plate by use of nails applied through chords.

SOFFIT Board fixed underneath EAVES overhang along the length of the building to conceal timbers.

SOLAR HEATING Generation of hot water (and in some cases additional space heating) through sunlight.

SOLEPLATE A horizontal timber member fixed to the ground floor slab to which the wall panels are then nailed to. It is generally treated with a powerful preservative.

SOLEPLATE LAYOUT One of the first jobs to be done by ECOFRAMES after receiving an order is to issue a soleplate layout. This is an accurately dimensioned drawing for the ground workers to set out the foundations precisely. It indicates the load bearing and non-loadbearing panels. It is important that the foundations are constructed accurately to the timber frame soleplate to ensure a successful and smooth running project.

SOLEPLATE TIES/ FIXINGS The soleplate fixings serve two purposes, to locate the plates accurately during construction setting out the superstructure. They also transfer wind loads down to the foundations once the building is completed. The soleplates may be fixed by shot-firing through the timber into the concrete slab or using stainless steel soleplate fixing shoes. Soleplates may also be fixed to brickwork substructures using stainless steel straps.

SOUND INSULATION The reduction of the sound transmission from one space to another especially significant through walls and floors between separate dwellings (see party wall / party floor)

SPACE HEAT REQUIREMENT this measures the amount of energy that is needed to maintain a comfortable indoor temperature, usually specified in kilowatt hours per square metre of treated floor area per year, or kWh/(m2a). See heat load.

SPAN Span over all wall plates. The distance between the outside edge of the two supporting wall plates and sometimes equal to overall length of bottom chord.

SPANDREL PANEL Timber frame triangular panel forming gable wall above ceiling line.

SPLICE A joint between two in-line members employing a metal connector plate or glued finger joint.

SPREADER BEAM See BEARER.

STABILITY BRACING An arrangement of loose timbers installed in the roof space to provide lateral support to truss members and to the trusses.

STICK BUILD A method of timber frame where a structure is built on site from loose materials as opposed to in the factory. This type of construction is more common in the United States and Canada than in Britain.

STRAP Metal component designed to fix trusses and wall plates to walls. Heavy duty type for lateral fixing and standard used for holding down.

STRUT Internal member connecting the third point and the quarter point on a FINK TRUSS.

STUB END A truss type formed by the truncation of a normal triangular truss.

STUDS A vertical timber (generally 95 x 45mm or 145 x 45mm) that form the wall panels and is the height of the required wall.

SUPERCHORD A means of providing deep chord members by connecting together two members at there edge using Gang-Nail connector plates, us

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glossary-t   TANK PLATFORM & WALKWAY Timber bearers and floor decking such as chipboard or plywood that are installed in the roof space to form a walkway and take the load of the storage water tank.TCB – THERMAL CAVITY BARRIER A non combustible material (generally flexible mineral fibre strips in polythene sleeves) which cuts off the path of smoke and fire. It is mainly used vertically either side of party walls and up the lengths of the eaves on gable ends.

TEMPORARY BRACING An arrangement of diagonal loose timbers installed for safety during erection. Often incorporated with permanent STABILITY BRACING.

TER Target Emission Rate (CO2). The DER must not exceed the TER for a notional dwelling of the same size and shape.

THERMAL ENVELOPE In contrast to the building envelope. It sets the boundaries for the insulation and airtightness line between the inside and outside of a building. E.g. a cold loft is outside the thermal envelope.

THERMAL IMAGING Survey which detects thermal losses through a buildings fabric.

THERMAL MASS The capacity of the structure of a building to store heat. Helps to level out indoor temperatures and reduces the risk of overheating in summer. Concrete, stone or phase-changing materials all have a high thermal mass.

THERMAL STORE Used to store heat for hot water and/or space heating.

TIE See BOTTOM CHORD

TIMBER STRESSS GRADING The classification of timber into different structural qualities based on strength.

TOP CHORD/ RAFTER See RAFTER.

TOP PLATE Horizontal timber rail that ties together studs in a wall panel.

TOSH NAILING See SKEW NAILING.

TRA Trussed Rafter Association. Organisation which represents the truss industry.

TRADA QUALITY ASSURANCE SCHEME Formalised method of quality control in the manufacture of trusses administered by the Timber Research and Development Association.

TREATMENTS OF TIMBER Timber used in the structural shell is sufficiently treated against insect attack and general decay and comply with the requirements of the N.H.B.C. and the Building Regulations 1995.

TRIMMER Cross member between joists or studs to form an opening. A typical example is to trim out an opening in a floor around a staircase.

TRUSS CLIP A metal component designed to provide a structural connection of trusses to wall plates, to resist wind uplift forces and to eliminate the disadvantages of skew nailing.l

TRUSS SHOE A metal component designed to support and provide a structural connection/support of a truss to a girder or beam.

TRUSS/TRUSSED RAFTER A lightweight framework, normally triangulated, spaced at intervals generally not exceeding 600mm and made from timber members of the same thickness fastened together in one plane by metal fasteners or plywood gussets.

TRUSSED RAFTER DESIGNER The person responsible for the design of the trussed rafter as a component and for specifying the points where bracing is required.

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glossary-u   U VALUE A measure of the rate of heat transfer through a building component, such as window or wall by the means of convection, conduction and radiation. Units = W/(m2K). The smaller the u-value, the better the insulation. UKTFA Timber Frame Association. Organisation which represents the timber frame industry.

UNIFORMLY DISTRIBUTED LOAD (UDL A Load that is uniformly spread over the full length of a member.

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glossary-v   VALLEY BOARD A raking member from ridge to corner in valley construction.VALLEY FRAMES A set of diminishing trusses that will infill an area of roof between two different roof directions.

VALLEY JACK TRUSSES A set of diminishing trusses that will infill an area of roof between two different roof directions.

VALLEY SET A set of diminishing trusses that will infill an area of roof between two different roof directions.

VAPOUR BARRIER Usually a layer of polythene, ECOFRAMES generally use125mu, supplied in rolls which is installed to restrict the passage of water vapour, e.g. on the inside of external wall panels on the warm side of insulation.

VERGE The line where the trussed rafters meet a gable wall.

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glossary-w   WALKWAY See TANK PLATFORM.WALL CAVITIES The void between the timber frame wall panel and the external skin such as brickwork or blockwork. The standard timber frame cavity is 60mm below dpc and 50mm above as 10mm is used up by the external sheathing board of the timber frame. WALL PANEL THICKNESSES External wall panels generally consist of 95×45mm or 145×45mm timber studs, a 10mm sheathing board, breather paper and tape that is factory fixed. The internal panels are usually studwork (some internal panels are sheathed with a 10mm board for engineering purposes) The 145mm external panels are used instead of the 95mm so that higher insulation values can be achieved)

WALL PLATE A timber member laid along and fixed to the supporting walls on which the roof trusses bear. Not less than 75mm wide.

WALL TIES Stainless steel brackets and nails installed to tie back and brace the external brick or block cladding to the timber frame. Polypropylene tape fixed to the outer face of external wall panels indicate where the studs are so that the ties can be fixed back at approximately 5 per m2. Wall ties provide lateral restraint but do not carry the weight of the wall which is self supporting.

WARRANTIES OF TIMBER FRAME House builders are required to get adequate insurance and guarantees on what they are building whether it is through the NHBC or through a company such as Zurich Municipal. Structural calculation, assembly drawings and details are supplied by Ecoframes for submission to the Local Authority by the client or the clients representative. N.H.B.C. HB353B Certificate/Engineers Structural Certificate, provided by Ecoframes.

WEB LONGITUDINAL BRACING A component of STABILITY BRACING.

WEBS Timber members that connect the rafters and the ceiling tie together forming triangular patterns which transmit the forces between them.

WIND BRACING An arrangement of loose timbers or other structural system installled in the roof space to form diaphragms in the planes of the rafters and ceiling ties to transmit wind forces to suitable shear walls.

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glossary-x    
   
glossary-y   Y VALUE A notional additional U-value, spread uniformly over the whole thermal envelope.return to top of page
   
glossary-z   ZERO ENERGY BUILDINGS (ZEB) or net zero energy building is a general term applied to a building’s use with zero net energy consumption and zero carbon emissions annually.return to top of page