Time lag and decrement factor in CIBSE and UNI-EN-ISO 13786

[PierNick]

Hi everyone, I have some problems to understand how apache calculates the "decrement factor time lag" (in italian "sfasamento")

I compared the "decrement factor time lag" of my opaque construction, calculated in the CIBSE list of derived parameters of APACHE, with the "decrement factor time lag" of the same construcion, calculated with the UNI-EN-ISO 13786.

With CIBSE: 11.00 Hrs
With UNI-EN-ISO 13786: 23,7 Hrs

..can someone help me to understand it?

bye,

PN

[PCully]

Hi,

All I can really advise here is that you compare the two calculation methodologies in use here and see where the discrepancy comes in.

The VE uses methods for the calculation of admittance and decrement factors layed out in CIBSE Guide A (2006), Appendix 3.A6 and chapter 5.7 so you can start there and compare to whatever EN-ISO method you used.

Phil