Thermal Bridging Details
Thermal bridging details are available from:
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Source
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Scope
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Comments
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1
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14 junctions: walls/walls (corners, party), walls/floors (ground, separating, non-separating) wall/roof (eave, gable), sill, jamb, lintel.
6 inner leaf block types: ( 3 aircrete, 3 aggregate blocks)
3 wall types: cavity full fill insulation, cavity partial fill, solid wall external insulation
Range of Insulations
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Many of these also include fire detailing info. and notes on compliance with acoustic robust details
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2
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14 junctions: walls/walls (corners, party), walls/floors (ground, separating, non-separating) wall/roof (eave, gable), sill, jamb, lintel.
3 inner leaf block types: (3 aggregate blocks)
2 wall types: cavity full fill insulation, cavity partial fill
Range of Insulations
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Data is split by different wall types. Then for each wall type each junction has a detail/certificate for the three generic aggregate block types and all insulation types and thicknesses. Data is a subset of source 1. Onsite checklist provided
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3
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14 junctions: walls/walls (corners, party), walls/floors (ground, separating, non-separating) wall/roof (eave, gable), sill, jamb, lintel.
3 inner leaf block types: (3 aircrete)
3 wall types: cavity full fill insulation, cavity partial fill, solid wall
Range of Insulations
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Data presented in downloadable pdf books and arranged as source 2. Details include fire stop details. Details provided can accommodate RDL acoustic requirements. Books include guidance checklist for construction
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It is suggested that sources 2 and 3 are used during the design process as they more simply enable comparisons.
The psi values from sources tabled above are more accurate than those available in SAP 2012 Appendix K. and take account of the high standard of thermal performance. They enable SAP assessors to fully optimise fabric performance calculations and demonstrate compliance without recourse to more expensive solutions. Their use can also help avoid the need for renewables.
In Building Regulation terms, Part L1A 2013 (section 3.9) requires that buildings are constructed so that there are “no reasonably avoidable thermal bridges” at junctions. It provides guidance on acceptable sources of psi-values for inclusion in SAP calculations, these being:
1. To use construction joint details and their attendant Psi-values included in DCLG Approved Construction Details or those formally recognised by DCLG. (DCLG approved Construction Details are available but are considered to be out of date and lack details of the psi values, so are of limited use with SAP, which required this information. It is understood that these will not be updated)
2. To use details and Psi-values modelled by a person with suitable expertise and experience, who can demonstrate competence in using the software and in correctly interpreting BR497 guidance. (Signposts to these are provided above)
3. To use in the absence of modelled details the default Psi-values included in SAP 2012 Appendix K.
4. To avoid calculating the energy loss from individual junctions completely by using a conservative energy loss value for the dwelling (a y-value of 0.15) in the SAP calculation. (It should be noted that this option is highly punitive in terms of its impact on heat loss, which is significantly increased and should therefore be avoided).