Ground U-values in Criterion 2 of Part-L BRUK report
Posted by Andy Tindale on 23-Apr-09 04:42 PM

Ground floor U-values used in constructions adjacent to ground can either be entered as being corrected for 3-D conduction effects or not and the setting to define whether the U-value is corrected or not is set on the Constructions dialog for ground floor constructions.
For uncorrected ground floor U-values, SBEM automatically corrects the U-value based on the floor area of the building and the external wall perimeter length using the equations in BS EN ISO 13370 prior to carrying out calculations and Criterion 2 checks. So in cases where an uncorrected U-value has been used you will find that the U-values reported by SBEM in the Criterion 2 section of the BRUKL report will be corrected and will seem not to agree with uncorrected U-value you entered. For small buildings the correction can be significant.

If you carry out the correction yourself (possibly using the BRE U-value calculator) you will find that the U-values reported under Criterion 2 of the BRUKL report do match with entered values.