Tristan's profile - activity

The project is referencing 90.1-2007

Hello All,

A colleague of mine out west is working on a LEED compliance model for a new hospital and has raised some interesting questions regarding how baseline HVAC systems are to be modeled under Appendix G. Details of the situation are as follows:

• ASHRAE 90.1 defines “residential” spaces as: Spaces in buildings used primarily for living and sleeping. Residential spaces include, but are not limited to…hospital patient rooms…
• Table G3.1.1A indicates that for residential spaces with fossil fired heat our baseline system should be “Sys-1 PTAC”
• The ASHRAE PTAC system from the system library (model is being prepared in IES-VE, though this applies to most defaults of this system) has no explicit MUA system, nor is it described in the standard what form this system should take. Having no central MUA system in the baseline will overly penalize the design as there will be nowhere to take into account the high static pressures associated with filters, heat recovery, etc.
• The ASHRAE PTAC system from the system library (model is being prepared in IES-VE) has no explicit MUA system, nor is it described in the standard what form this system should take. Having no central MUA system in the baseline will overly penalize the design as there will be nowhere to take into account the high static pressures associated with filters, heat recovery.
• Given the configuration of a PTAC system as described if OA is ducted directly into each zone at 6+ ACH then over the course of each iteration the zone will be completely filled with unconditioned OA.
• The high OA/ACH requirements would seem to trigger the requirement for Exhaust Air Energy Recovery as indicated in G3.1.2.10. Again this would require some manner of central MUA system to simulate.

If any of you have been down this road before with a hospital project with more than 20,000 ft2 of patient rooms then your guidance would be greatly appreciated.

Many thanks in advance!