ASHRAE Journal - October 2013 - 77

Technical FeaTure
Fea

disciplines or consultants such as
fire protection, security, and audio/
visual providers.
You should factor BOD maintenance into your project schedule.
Then update the document at regular milestones, such as the 30%, 60%,
90%, and 100% stages of submitting
construction documents.

A Case in Point

table 1 Sample HVAC design criteria.
Item

Building
Ventilation

DesIgn CrIterIa

• Minimum ventilation rates shall be 5 cfm per person and 0.06 cfm/ft2 of building surface;
the ventilation rate for the entire building shall be 3,000 cfm. Building ventilation rate shall
meet the minimum requirements of the latest version of ASHRAE Standard 62.1.
• Inside pressure. Ventilation and air conditioning systems shall maintain a positive pressure
of 0.02 in. inside the building (compared to the exterior) to minimize air and dirt infiltration.
The volume of fresh air shall be sufficient to maintain positive pressure inside the facility
(compared to outside).
• Infiltration/exfiltration offset. An additional amount of conditioned air shall be included to
offset the effects of infiltration and exfiltration. The allowable leakage rate at 50 Pa shall be
0.2 cfm/ft2 of building surface; maximum infiltration wind speed shall be 15 mph.
• Air filtration. Air-handling units shall include two stages of filtration: The pre-filter shall
have a maximum efficiency reporting value (MERV) of 8 (per ASHRAE Standard 52.2-2007),
and the final filter shall have a value of MERV 13. Units shall be sized and selected with
respect to the dirty filter condition. Filters shall be of medium efficiency (30%), as defined
by the latest version of ASHRAE Standard 52.2. There shall also be adequate space for filter
removal and replacement.
• Outside air intakes shall be a minimum of 10 ft above the ground and a minimum of 15
ft away from any exhaust-air discharge openings or plumbing vents. Intakes shall be sized
so free-air velocities fall below 500 fpm. Intakes shall be equipped bird screens, and with
weatherproof and sand-removing louvers.

Misunderstanding a project’s design
intent is one of today’s most common
construction-related challenges. And
one of the greatest benefits of the BOD
document is that its clear presentation of the owner’s design intent helps
• Noise levels. HVAC-generated noise shall not exceed NC 45 in the data center, NC 35 in
protect the owner, the design team,
circulation areas, and NC 30 in open offices, private offices, and conference rooms.
HVAC Noise
• Duct velocities for systems of 2 in. of pressure and lower shall not exceed 1,200 fpm;
the engineers, and the contractors
Limitations
velocities for systems greater than 2 in. shall not exceed 2,400 fpm.
from confusion, misunderstandings,
• Fluid flow and pipe velocities shall be less than 6 fps for pipes less than 4 in. in diameter;
and lost revenue.
for pipes larger than 4 in., velocities shall be less than 8 fps.
We once worked on a museum
• Minimal service interruption. The design shall enable the building’s main HVAC
equipment to be serviced, maintained, and repaired with minimal interruption to building
project for which the primary exhibfunctions.
its were to be marble sculptures.
• Shutoff valves shall be provided at each coil.
Equipment
Early in the design phase—and after
Servicing and
• Equipment mounting. All floor-mounted equipment shall rest on a 3-in.-thick (minimum)
Access
concrete housekeeping pad. The design shall employ vibration-isolating elastomeric pads to
much debate—the owner’s authoreduce transmitted vibration.
rized representative approved a wet• Accessibility. There shall be 3 ft of access space around each piece of mechanical equipment, as well as enough space to allow coils to be to be removed and replaced.
pipe sprinkler system to save money.
The discussion and the decision’s
Smoke
Detection
• Control standards. Smoke detection and emergency automatic controls shall conform to
approval were noted in the BOD.
and Fire
the latest National Electrical Code (NEC) NFPA 90A and NFPA 72 standards.
But shortly before the projPrevention
ect went out for bid, one of the
museum’s user groups protested that future exhibits
result, the designers were able to charge a fair price for
could require a dry-pipe fire protection system. The
the required redesign services.
group also cited the museum’s own design-standards
Different Needs, Different Documents
documents, which mandated dry-pipe fire protection.
Sometimes architects and engineers confuse the BOD
The use group further maintained that the fire protecdocument with the narratives they create during project
tion engineer should have known about the dry-pipe
pursuit. Design professionals sometimes say, “We don’t
mandate, and should have included such a system as
need to produce an additional document. We’ve already
standard practice. But no one could recall why a wetprovided the owner with an RFP-based narrative that
pipe system had been specified.
describes our design plan.”
Good news: Because the project had a thorough BOD
It’s essential to understand that the RFP, the early
document that clearly identified the wet-pipe system
design narratives, the OPR, and the BOD are all differchange during the design, the fire protection engineer
ent documents that serve different purposes. Without this
was able to clearly show the owner how the wet-pipe
understanding, the design team can be well into the
decision was made. The owner then authorized the
design process before the owner realizes the project has
return to a dry-pipe system, and agreed that the design
taken a turn that deviates from his or her requirements.
team should not be expected to “eat” the change. As a
O ct O b e r 2 0 1 3

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ASHRAE Journal - October 2013

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