ASHRAE 140-1 Envelope and HVAC equipment performance results for Tas 9.1.x
Tas version 9.1.x has completed all the building envelope and HVAC equipment performance tests as required by ASHRAE 140-1 (2004).
The required output and documentation, as well as the Tas models actually used, can be downloaded here:
Of the results required for Section 5.2 output, Tas is out of range on only seven occasions.
Although not required by 140-1 a brief explanation of these results is given here.
In test 440 Tas is out of range by only 0.5% and this test was also not completed by all packages
(less comparative data). It's also clear from the comparative results that only two packages account for
radiation exiting back out through the window rigorously (test 440 has highly reflective internal surfaces
meaning radiation will 'bounce' many times increasing the loss of radiation). These three results are very
tightly packed at 3.967, 3.975 and our result at 3.949 MWh.
The other six out of range tests are all free float cases where we are consistently very slightly cooler
than the range allows. This is due to Tas employing a sophisticated radiation back loss model that
incorporates cloud data and humidity to predict a more accurate 'sky temperature'. We have confirmed this
by modifying the back loss model to be typical and all six cases then fall within range. Because of good
empirical agreement of this back loss model in the past, we prefer to retain it and fall out of range in
these cases.
No bugs were found in Tas during this testing.