HVAC Systems Selection

The HVAC Systems Selection Category should be viewed as an "advanced" version of the HVAC Systems Design Category; the primary difference is that in lieu of just selecting a system based on "designer experience", the student design team is required to perform a life cycle cost analysis to select the system that provides the lowest life cycle cost, all while staying in budget.

Similar to the HVAC Systems Design category, each team is required to determine the buildings cooling and heating loads in order to determine the capacities of the buildings HVAC systems: cooling and heating plants, air distribution system and equipment, and hydronic/steam piping systems as determined by the team.

Each student team should conduct a life cycle cost analysis comparing several HVAC Systems. The HVAC system(s), either single or multiple systems included in the analysis are the systems that they feel best serves all of the buildings spaces based on the Recreation Center’s operation.  The swimming pool filtration treatment system is not a part of his design competition; however, the environmental control of the natatorium space is included and the use of recovered energy for pool water heating is encouraged.

ASHRAE student teams located outside the USA and Canada may locate the Recreation Center in the capital of the student’s country, IE: Students from Mexico may use Mexico City.  Building criteria and design assumptions to remain the same for all building sites, with the exception of the climate information.  Student teams should determine whether the buildings envelope as designed complies with ASHRAE Standard 90.1-2004.

Each student team will look at each of the nine broad categories of criteria to be considered in comparing HVAC systems.  The first three categories of requirements are gates – yes or no questions.  The system must meet the performance requirements, must provide the required capacity and must fit the space available.

The next six criteria are comparisons. Some systems cost more to install; some cost more to run, some less; and so on.  Each criterion will have a different weight or importance.  The goal of the HVAC system selection process is to identify and evaluate how well each potential system meets the overall weighted criteria for the project. 

The HVAC selection criteria are the following:
1) Performance requirements

a) Must be able to meet design criteria

i) Comfort:  Temperature/Humidity – ASHRAE Standard 55-2004.
ii) Ventilation – Meet or exceed the requirements of ASHRAE Standard 62.1-2004
iii) Energy Consumption – 20% less than ASHRAE Standard 90.1-2004 using the Performance Rating Method as described in Appendix G.     
    (1) Energy consumption should be modeled using software modeling tools such as the following:

(a) Trane TRACE 700
(b) DOE 2.1
(c) eQUEST
(d) Carrier HAP

iv) Sound

    (1) Office area – RC 35N
    (2) Lobby/corridor area – RC 45N
    (3) Gym/Pool/Locker rooms/kitchen – RC 50N

2) Capacity requirements

a) Yes/No
b) Must be able to meet peak gain/loss

i) Indoor design conditions
ii) Outdoor design conditions –refer to Exhibit 4
iii) Internal heat gains

3) Spatial requirements

a) Yes/No
b) Must fit in available space

i) Mechanical rooms
ii) Shaft space
iii) Height above ceiling
iv) Floor space
v) Building height limits
vi) Maintenance access

4) First cost (30% of weight)

a) Relative
b) Spend all that is necessary but no more
c) Trade-offs with other criteria
d) Very owner or project variable

5) Operating cost (30% of weight)

a) Relative
b) Trade-offs, especially with first cost
c) Not just energy

i) Water and sewer
ii) Water treatment
iii) Labor – operating and maintenance
iv) Life cycle – discount rates (7.0%), interest rates (6.0%), replacement costs, annual inflation 3.5%.
v) Load profile dependency

6) Reliability (5% weight)

a) Relative
b) Very project dependent

i) Value/cost of downtime
ii) Mean time between failure vs. mean time to repair

c) Life safety
d) Effect of failure on building’s operation

7) Flexibility (5% weight)

a) Relative
b) Skill level required
c) Location of maintenance activity
d) Preventive maintenance
e) Breakdown repair

8) Sustainability (30% weight)

a) ASHRAE’s GreenGuide – David Grumman
b)  US Green Building Council Rating System v2.2

The final HVAC System Selection for the building shall address the following major design goals:

• Low 20 year life cycle cost
• Low environmental impact
• Comfort and health
• Creative high performance green design
• Synergy with architecture

Criteria and goals are not the same thing.  Criteria are different aspects of what the system does.  They measure system performance.  Goals are defined by what the owner and designer wish to achieve with the system (low operating costs, low first cost, etc.).  Goals tell us how important each of the criteria is relative to the other criteria.

Exhibits
Exhibit 1
Refer to  Exhibit 1 for judging criteria for the Student System Selection Competition.

Exhibit 2
 Architectural Drawings in AutoCAD Format (ZIP)

Exhibit 3
 Architectural Drawings in PDF Format (ZIP)

Exhibit 4 
Refer to Exhibit 4 for Design Information and assumptions.