ASHRAE Journal - February 2014 - 54

TECHNICAL FEATURE

common architectural oversights
the CxA should look for include:
* Infiltration rates that exceed accepted industry standards;
* Improperly specified vapor/air
barriers;
* Poorly defined thermal breaks at
windows, doors, walls, and rooflines;
and
* Improperly located equipment
(which can transmit noise or vibrations to occupied spaces).
Table 1 is a sample checklist of the
primary architectural elements the
CxA should review during DPC.

Mechanical Systems Review

TABLE 1 Sample checklist of the primary architectural elements the CxA should review during DPC.

Roof "R" values, penetrations, reflectance, exterior wall insulation, perimeter slab insulation, and vapor

1 barrier designs must match the energy/mechanical model and be appropriate for the building application and

geographic location.

Window and door "U" values and shading coefficients must match the energy/mechanical model and be
appropriate for the building application and geographic location.

Spaces that require special equipment (such as computer rooms, elevator equipment rooms, kitchens, labs,
etc.) must be properly identified.

Thermal breaks at windows and door frames, roofs, and walls must be clearly defined and appropriate for the
building application and geographic location.

Vapor/air barriers that separate exterior conditions from conditioned interiors must be clearly defined and
appropriate for the building application and geographic location.

The building's life-safety plan must clearly define egress, wall types, and any special system requirements
(such as smoke exhausts, controls, or pressurization). Review all applicable drawings to cross-check
mechanical and electrical systems that relate to the overall life-safety plan and the building's air-distribution
requirements across rated partitions.

The locations specified for generators, air handlers, chillers, cooling towers, and pumps must meet all of the
owner's requirements for aesthetics, noise, vibration, and maintenance.

The project specifications for entry/exit infiltration rates must reflect the correct pressure (example: ASTM
Standard E1677-11 calls for a pressure of 0.30 inches H2O [75 Pascal]).

A modern building incorporates
Wall/roof, wall/floor, window, louver, and door caulking and sealing specifications must be able to achieve the
9
specified leakage rate.
a broad spectrum of unique com10 Envelope leakage testing procedures must be properly specified per appropriate NEBB or ASTM standards.
ponents and control sequences.
As a result, its mechanical sys11 Structural bracing for mechanical equipment must be clearly specified and depicted.
tems are often more technically
complex than its architecture, so there's a lot that can
TABLE 2 Sample checklist of the primary mechanical component specifications
go wrong.
the CxA should review during DPC.
Some of the more common mechanical issues the CxA
HVAC system specifications must be appropriate for the application and
1
geographic location.
should check for include:
Conditioning and zoning considerations (exposure, size, use, and occupancy)
* Incorrectly specified HVAC systems;
2
and thermostat locations must be appropriate for the application.
* Improperly defined zones;
3 System diversity must be within acceptable ranges for actual building operations.
* Total variable air volume (VAV) that exceeds air-handling unit (AHU) capacity, does not match the sum of the
Airflow volumes for supply and return air diffusers/grilles must match both
4
terminal devices and the central air equipment.
individual components, or is outside industry-acceptDiffuser sizing and capacity must produce adequate throw within allowable
able limits;
5
noise criteria.
* Equipment velocities, pressure drops, or installation
System flows must match equipment and system design and rated capacities
6
techniques that do not meet industry standards;
while meeting general industry-accepted practices for size and application.
* Improperly calculated energy balances (in which the
Building pressurization airflows must account for exhaust and allowable leak7
components supplying the boilers, chillers and air hanage at designed wind velocities.
dlers do not correctly match the specified pumps, cooling
Pipe and duct velocities must be consistent with the OPR, the BOD, and ap8
plicable industry standards.
coils, reheat coils, and filters); and
Equipment, coil, terminal inlet/outlet flow velocities, and pressure drops must
* Improperly specified start-up, flushing, and com9
be within acceptable industry ranges.
missioning procedures.
The inlet and outlet configurations of fans, pumps, coils, filters, and other
10
Table 2 is a sample checklist of the primary mechanical
equipment must not cause reductions in airflow volume.
component specifications the CxA should review.
11 Ducts and piping must be consistent with industry best practices.

Control Sequence Review
Control sequences are normally unique to each building, and must be analyzed to determine their appropriateness for each application. Common control sequence
issues include:
54

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FEBRUARY 2014

* Sequences written in complex or confusing language;
* Contradictory or inconsistent requirements;
* Sequences that describe opening control requirements but fail to describe shutdown requirements;
* No instructions for power or equipment failure;

ASHRAE Journal - February 2014

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