TGD L 2011 – D.5 – Treatment of thermal bridging in DEAP calculation

D.5 Treatment of thermal bridging in DEAP calculation Heat loss through thermal bridging is taken account of in the DEAP calculation. Two alternative methods of accounting for heat loss are possible: – (a) Heat loss through thermal bridging can be accounted for in terms of a fraction (y) multiplied by the exposed surface area of the building. Where Acceptable Construction Details for sections 1 to 6 in the 2011 edition of the document “Limiting Thermal Bridging and Air Infiltration – Acceptable Construction Details” are used for all key junctions the value of (y) can be taken as 0.08. Where this is not the case, but this method of accounting for thermal bridging is used, the default value of (y) is taken to be 0.15. (b) Values of can be determined from the results of numerical modeling, or they can be derived from measurement. The linear transmission heat loss coefficient (HTB) can then be calculated directly and included in the DEAP calculation. Values of are given in Tables D1 to D6 of this Appendix for Acceptable Construction Details and for Appendix 2 of the 2011 edition “Limiting Thermal Bridging and Air Infiltration – Acceptable Construction Details” to allow this approach to be used for these details. Where Section 3 – internal insulation details are used the psi values given in Table D6 may be used.

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