Preparation for a fan pressurisation test
The pressurisation test must be carried out on the completed building. Details of the recommended test procedures and the instrumentation are given in CIBSE TM 23 21 . The following points relate to preparation of the building and the Determine the exact boundaries of the external envelope of the building that is to be tested. Service spaces such as boiler rooms, lift rooms or rooms housing switch gear, may be taken as outside the space to be tested. Adjoining buildings, connected for example...
Values of fc
The correction factor for the glazing blind combination, fc, may either be selected from Table 13.2, or obtained from the appropriate shading coefficients. The shading coefficients for various glazing and shading device combinations Table 13.2 Correction factor for glazing blind combinations. Glazing blind combination from inside to outside 0.95 0.62 0.66 0.92 0.60 0.62 0.69 0.47 0.50 0.56 0.37 0.39 0.57 0.47 Blind clear reflecting Blind clear absorbing Blind low-e clear Blind low-e reflecting...
Origins of the CPR method for office buildings
The three principal sources relevant to the CPR method are Energy Consumption Guide 19 Energy use in offices ECON19 54 . This provides benchmarks for energy consumption which have been derived from surveys of operational office buildings. Energy assessment and reporting methodology EARM office assessment method 45 . This provides a technique for estimating operational energy consumption, and comparing actual performance with ECON 19 benchmarks. CIBSE Guide Energy efficiency in buildings 36 ....
Example Solid ground floor over clay subsoil with vertical edge insulation
The floor in Fig. 6.2 is provided with vertical edge insulation instead of all-over insulation. The insulation is to a depth of 750 mm, and the insulation is 75 mm thick with a thermal conductivity of 0.040 W mK. The resistance of the insulation layer is From Example 6.1, the perimeter to area ratio of this floor is 0.57, and its uninsulated U-value is 0.74 W m2K. We require the edge insulation factor from Table 6.2, and it is necessary to interpolate between the columns for Rins 1.5 and Rins...
The elemental method for dwellings
In the elemental method, compliance is demonstrated by specifying Maximum U-values for walls, floors and roofs Maximum area-weighted U-values for windows, doors and rooflights Maximum combined area of windows, doors and rooflights Minimum boiler efficiencies for the heating system boiler the SEDBUK rating, or Seasonal Efficiency of a Domestic Boiler in the UK . The maximum U-values allowed by the elemental method are shown in Table 2.1, and are illustrated in Fig. 2.2. If an element is exposed...
The importance of thermal bridges
Thermal bridges are areas of increased heat flow across otherwise thermally insulating materials or constructions. They are a particular problem in building construction because it is rarely possible to provide a perfectly continuous and unbroken layer of insulation around the whole of the space which is to be insulated. In addition to the increased heat flow, a thermal bridge also has an effect on surface temperatures, creating in winter a drop in surface temperature on the inner warm side of...
Conservatories 1
Roof spaces adjacent to a room in a roof. Xhese values, which are shown in Xables 5.3 and 5.4, can also be applied to similar situations in other buildings. For other unheated spaces it may be possible to calculate Rextra from where AINX is the total area of the elements separating the internal heated space from the unheated space, and AEXX is the total area of the elements separating the unheated space from the outside. However, if this formula yields a result for Rextra greater than 0.5 W...
Example calculation
Part of the top floor of a college building is used as a studio for student art classes. The room is 14m x 7m on plan, with a floor to ceiling height of 3 m. One of the long walls is an external wall facing south-west with four windows, each 2.5 m wide by 1.5 m high. The window frames have a framing ratio of 20 of the window area. Daylight along the long internal wall is provided by a line of six horizontal rooflights, each 1m square, with a framing ratio of 25 . The centre line of the...
The target Uvalue method for dwellings
In order to demonstrate compliance using the target U-value method, it is necessary to calculate and compare two U-values. The first, UT, is a target U-value. This is a theoretical index which is calculated from an initial basic formula, and which is then adjusted to allow for any design features that affect the energy consumption of the dwelling. The second, UAVG, is the area-weighted average U-value of the actual dwelling, taking into account all exposed surfaces including walls, floors,...
Infrared thermography
Infrared thermography uses specially designed infrared video or still cameras that convert the infrared radiation into images that show surface heat variations. The technique has applications in a variety of fields, including medicine, electrical installations, cold storage facilities, etc. When applied to buildings, it can be used to examine the whole or part of the exterior envelope, or it can be used to look at surface temperatures within a building. When used to identify thermal bridges, it...
Example calculations for roofs
Example 4.1 Pitched roof with insulation between the joists Figure 4.2a shows insulation laid between the ceiling joists of a pitched roof which is covered with 19 mm roof tiles. The maximum U-value allowed by the elemental method is, from Table 2.1, 0.16W m2K, and it is required to determine the necessary thickness of insulation. First, from Table 4.5, there is a AU correction of 0.01 W m2K. The design or 'look-up' U-value is therefore a Insulation between ceiling joists a Insulation between...
Q CPR Calculations Methods for Office Buildings
The carbon performance rating CPR calculation method is a simple technique, derived from three sources, for assessing the amount of carbon emitted into the atmosphere in units of kgC m2 year. It is used within the elemental method for assessing the contribution to carbon emissions arising from the operation of mechanical ventilation and air conditioning systems. It is also used in the whole-building method for offices in order to assess the total emissions due to mechanical ventilation, air...
auau R
In this wall, the fixing of the mineral wool insulation in its timber sub-frame is such that there is no air movement on the warm side, but there are some air gaps penetrating the insulation layer. As the air gaps are in the mineral wool and timber sub-frame, Rl Rit 1.815. Referring to Table 5.1, the correction for air gaps is level 1, and so AU11 0.01. With RT 3.170, the correction is thus As this is less than 3 of U, it may be ignored. The final U-value is rounded to two decimal places Figure...
Thermal bridging causes and avoidance
Thermal bridges in construction elements are due to a variety of causes, the most common being Timber, concrete or steel columns, joists or battens in a wall or roof Fixing and jointing details around the edge of openings Metal ties, staples, nails, etc. which penetrate an insulation layer, either to hold the insulation in place or to improve stability between the components on either side of the insulation layer Internal corners between walls, or walls and floors, or walls and ceilings. The...
Background theory
The lower the U-value of a construction element, the more significant is the effect of thermal bridging on the calculation of the U-value. Consequently it is usually necessary to include thermal bridging in the calculation method. The theory is based on the calculation of thermal resistances. For a single layer of material, the thermal resistance R is given by where d is the thickness of the layer in metres, and X is the thermal conductivity. The combined resistance of several materials depends...
Windows doors and rooflights Xyd
When available, manufacturers' certified U-values by approved methods of measurement or calculation should be used. If these are not available, values for single, double and triple glazing may be taken from Tables 4.1, 4.2 and 4.3, modified where necessary for metal frames according to Table 4.4. Low emissivity low-E coatings are of two main types, 'hard' and 'soft'. If the exact value of the emissivity, sn, is not known, then for hard coatings or where the type of coating is unknown use the...
Windows doors and rooflights
The requirement does not apply to repair work on parts of these elements such as Replacing sealed double-glazing units Replacing rotten framing members. However, where these elements are to be replaced rather than repaired, it becomes necessary to provide new draught-proofed ones with either An average U-value not exceeding the appropriate value in Table 2.1, or A centre-pane U-value not exceeding 1.2W m2K. The replacement work should comply with the requirements of Parts L and N. Furthermore,...
Reasonable provision of energy meters and submeters
Reasonable provision of meters would be to install incoming meters in every building greater than 500 m2 gross floor area including separate buildings on multi-building sites . This would include Individual meters for direct measurement of the total electricity, gas, oil and LPG consumed by a building A heat meter capable of direct measurement of the total heating and or cooling energy supplied to the building by a district heating or cooling scheme. In the case of sub-metering, it would be...
Roof window
Door, glazed to more than 50 of its total area, including its frame, measured internally Space heating or hot water service boiler Part L1 applies to replacement work on controlled services or fittings when Replacing old with new identical equipment Replacing old with new but different equipment The work is solely in connection with controlled services or includes work on them. Ways of satisfying the requirements of Part L1 may depend on the circumstances of the particular case. Specific...
Introduction Ttl
The elemental method of both AD L1 and AD L2 allows any or all of the windows, doors or rooflights to have U-values which are greater than the standard maximum values, provided that compensating measures are taken. The compensation may be either a lower U-value in one element to offset a higher U-value in another, or it could be a reduction in the area of one or all of the elements. The guiding principle is that the total heat loss through windows, doors and rooflights should not exceed that...
Values for FD
Values for FD depend on a combination of plant management features and monitoring and reporting features, and must be obtained from Table 12.1. In this table, values are selected from the most relevant column. If it is appropriate to select more than one value from that column, then the final value of FD is the product of the selected values. Provision of energy metering of plant and or metering of plant hours run, and or monitoring of internal temperature in zones, plus the ability to draw...
Stack effect pressure difference
The stack effect is the pressure due to the difference between inside and outside temperatures, over a pair of openings at different heights. The natural pressure gradient in the air due to height is different inside and outside the buildings because the air density is different. The net stack effect pressure difference, Aps, between the two openings is given by where g is the acceleration due to gravity h2-h1 is the difference in height between the two openings Text and Tint are the external...
Correction for mechanical fasteners
Xf is thermal conductivity of the fastener nf is number of fasteners per square metre Af is cross-sectional area of one fastener a is obtained from Table 5.2. Table 5.2 Corrections for mechanical fasterners. Table 5.2 Corrections for mechanical fasterners. Reproduced with permission from BS EN ISO 6946 Reproduced with permission from BS EN ISO 6946 Corrections for fasteners must not be applied when The wall ties are across an empty cavity The wall ties are between a masonry leaf and timber...
The elemental method for buildings other than dwellings
In the elemental method, compliance is demonstrated by specifying Maximum U-values for walls, floors and roofs and rooflights Maximum area-weighted U-values for windows, personnel doors and rooflights Maximum combined area of windows and doors as a percentage of exposed wall area Maximum area of rooflights as a percentage of roof area Minimum performance standards for all energy consuming building services Design details to meet air leakage standards and to avoid solar overheating. With regard...
The Uvalue via an unheated space
The precise calculation of the heat flow through a building element, and then via an unheated space to the outside, requires complex procedures. These can be found in BS EN ISO 13789 10 . However, for the purposes of Part L, a simpler procedure in which the unheated space is assumed to behave like an additional homogeneous plane layer is usually adequate. With this assumption, the extra thermal resistance of an unheated space may be included in the calculation of the U-value of an element using...
Condensation and mould growth
When the temperature of an inside surface is below the dew point of the air inside a building, condensation will occur. There are several possible causes of this condition, and the increased rate of heat loss due to a thermal bridge is one of them. Conditions are rarely so bad that condensation is a permanent feature on an internal surface, and in most cases, if it occurs at all, condensation appears intermittently. Because of this it can go unnoticed and may only become obvious when mould...
AD L Section Design
The are a number of general considerations which should be applied to a building design project. These include Preparing designs for the building and its services which are appropriate to the need to achieve energy efficiency Providing information so that the performance of the building in use may be assessed Making provisions in the design of the building services installations which facilitate inspection and commissioning. Reference may be made to the CIBSE Guide on energy efficiency in...
References
BRE Building Research Establishment, Watford, Herts WD25 9XX BRECSU Building Research Energy Conservation amp Support Unit, Watford, Herts CRC Construction Research Communications Ltd, Watford, Herts WD25 9XX CIBSE Chartered Institution of Building Services Engineers, 222 Balham High Road, 1. Thermal insulation Avoiding risks. BR 262, BRE CRC, 2002. 2. Limiting thermal bridging and air leakage Robust construction details for dwellings and similar buildings. The Stationery Office, 2001. 3....