We have been using Trace 3D+ for the load calculation for one of our actual projects. In order to be more confident in the 3D+ outputs and compare the two tools side by side, we created a separate Trace 700 model for comparison, and here are what we noticed:

* For a seasoned user, creating the model from scratch in both tools took about the same time. For complicated shape buildings, 3D+ takes bit more time because the software will re-generate the entire model if any changes have been made.
* The 3D+ load calc results are sensitive to some other inputs such as internal loads, # of occupant, etc.
* To be focusing on building skin load, we removed all internal/misc loads; ventilation; infiltration; etc., and the load calc results of 3D+ and 700 compared favorably for this medium mass building. The room cooling load differences range 5~15% with 3D+ loads are usually lower, total building cooling load difference is ~10%.
* Plenum definition will have some sizable impacts on the room cooling load results.
* There is an almost 1/3 increase in the overall building cooling load running the exactly same model in the newer 3D+ v4.01.97 compared with result using v3.20.18, the difference is because of the Air Correction category shown in the System Cooling Checksums output. Trane CDS Help explained that this is because of the EnergyPlus simulation engine update.

Thank you,

S O N G Z H A N G, P H. D., P. E., L E E D B D + C
Sr. Energy Engineer
Southland Engineering
22340 Dresden Street, Suite 177
Dulles, VA 20166
Office: 703.834.5570
Fax: 703.834.5572