Problems with THERM 7.4 and ENISO10077-2

[lad...@bba.star.co.uk]

Dear THERM creators

Please find attached a letter of concern regarding your THERM software and its compliance with European Standard ENISO10077-2.

We are a Notified Body in Europe, accredited to using your THERM software to this test method and I would welcome your comments on this please.

With thanks

~LUKE~

[Tom Foster]

Of interest to one major set of Therm users, as software accedited for use in PassiveHouse calculations, I took it upon myself to forward the letter to Peter Warm, one of UK's PassiveHouse Certifiers; this is their comment:

"EN ISO 1077 applies to the calculation of the thermal performance of doors windows and shutter, and the changes referred to in the letter appear to relate to the frame cavity algorithms used for these calculations. We need to look into this further, but it does not seem at first glance that this will have an impact on the use of Therm for other thermal modelling."

[pete warm]

I would like to add a further comment to this thread. We are Passsivhaus Certifiers based in the UK and we have a strong investment in THERM (thanks guys!) probably exampled best by our online tutorial for using THERM:   http://www.carbonlitetraining.co.uk

The proposed changes in the EN 10077-2 appear to relate mostly to the calculation of heat transfer in cavities.  In many respects this has to be welcomed as the proposals appear to tighten up this important part of the calculation methodology; in particular the use of iterative calculations so that the new standard appears to use the iteratively derived cavity boundary temperatures and cavity equivalent conductances, which is obviously better than the current CEN approach of assigning a fixed temperature difference of 10K across all cavities. Other changes relate to the calculation in an iterative fashion to allow the direction of heat transfer to be determined, which again affects the cavity equivalent conductance.

I would have thought that this would be requiring a major change to the software, no?

In relation to the use of THERM for the calculation of psi values for  building assemblies, without significant cavities, I can not see the changes to EN 10077-2 will make significant difference to the results. Having said that, if there appears to be a divergence between Northern American and .European calculation methodologies we will all suffer!

So, Dear THERM creators, your considered response would be welcome.    In an attempt to make life easier I attach a copy of the proposed standard.

Thanks for your creation!, peter warm

[Tom Foster]

Great Pete - good to see you (or your team) active on this forum