Environmental Design Solutions Limited (EDSL) was formed in 1989 to commercially develop Tas Software. EDSL sells Tas software and consultancy services using Tas. EDSL believe that the mixing of development, consultancy and software support leads to a focused software product, with quality support available to end users.

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In-depth empirical validation can be viewed on the Tas Engineering sub-pages.

EPC and Part L

Tas was the first DSM to be approved for Part L2 and EPC. Tas can be used to assess building levels 3, 4 and 5.

BEEM Checklist

Tas is recognised as Building Energy and Environmental Modelling (BEEM) software suitable for calculating building performance and predicting energy usage.

ASHRAE 140-1

Tas has completed all the building envelope and HVAC equipment performance tests as required by ASHRAE 140-1 (2004) and by ASHRAE 140-1 (2007).

EN ISO Standards

Tas 9.3.0 has demonstrated compliance with BS EN ISO standards 13791, 13792, 15255 and 15265.

3D CFD Analysis

EDSL offer a consultancy service in 3D CFD analysis, which uses in-house tools not currently available for purchase.


Tas Daylight has been validated against test case results in the CIE 171:2006 Technical Report.