Basis of Design - ASHRAE Journal, October 2013

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Technical vs. Process Commissioning
Basis of Design
The basis of design (BOD) document provides building designers and engineers with an effective tool they can use to clearly present—to the owner,
commissioning agent (CxA), contractors, suppliers, and any other third
parties—the decision, assumptions, and specifications that are being used to
develop the construction documents for a project.
The BOD transforms the raw data from the owner’s project requirements
(OPR) document (the “what”) into a detailed, technical, actionable plan (the
“how”) that will meet the owner’s objectives—which will also help avoid the
“scope creep” that can derail the project schedule and lead to budget overruns.
Understanding the Basis of Design
ASHRAE defines the BOD as “a document that records
the major thought processes and assumptions behind
design decisions made to meet the owner’s project
requirements (OPR).” The design team uses the BOD
document to show how their assumptions and specifications will enable the completed project to satisfy the
requirements listed in the OPR document. The previous
article in this series (ASHRAE Journal, August 2013) noted
that the owner can use a well-crafted OPR document as a
checklist or “scorecard” to verify project success.
The BOD document needs to be created early on: after
the schematic design is completed, but before creating the actual design development documents. That’s
because the BOD must explain the decision processes
behind the design, essentially “translating” the owner’s
*This is the third in a series of articles that explain the technical commissioning process for new
buildings. The series (and the first article) is titled “Technical Commissioning: The Commissioning
Process that Works.” Some of these articles’ content is based on ASHRAE Guideline 0-2005, The
Commissioning Process (published 2005) and the National Environmental Balancing Bureau (NEBB)
Whole Building Systems Technical Commissioning Procedural Standards Manual (revised April
2013). In addition, some of the information in this article has been taken from an unpublished NEBB
standard titled NEBB Standard Owner’s Project Requirements (OPR) Guideline (June 20, 2011). This
article also draws upon an unpublished “sample” OPR document created by NEBB for the fictional
“ABC Headquarters Office Building” (Jan. 2, 2011).
vision into practical design criteria—and improving
the communication process between all parties during
the design phase. As noted in the previous article, the
USGBC has made the OPR and BOD documents mandatory for all LEED-NC certified projects (LEED 2009).
Unfortunately, the BOD document is too often forgotten until after the design process. Then something is
thrown together—which ends up of no use to anyone.
Without a BOD document, the CxA cannot fully understand and act upon the design team’s actual intentions.
Some Practical Considerations
To help ensure easy understandability by the most readers, write your BOD document in layman’s terms (whenever possible). Use lots of charts, tables, detailed lists, and
graphs. If photos best explain what you want to convey,
include them, along with clear and detailed captions.
Every member of the design team should be a part of
preparing the BOD document and then maintaining it
throughout the design process. It’s not a job for a juniorlevel designer or intern. You’ll also need to involve the
architectural team, as well as the mechanical, plumbing, and electrical engineers. And don’t forget specialty
ABOUT THE AUTHORS Vince Briones, P.E., is senior program manager at Atkins in Austin, Texas, and Dave McFarlane is a principal project director at Atkins in Fort Myers, Fla.
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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.
••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
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.
Early in the design phase—and after
Servicing and
••Equipment mounting. All floor-mounted equipment shall rest on a 3-in.-thick (minimum)
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
••Control standards. Smoke detection and emergency automatic controls shall conform to
approval were noted in the BOD.
the latest National Electrical Code (NEC) NFPA 90A and NFPA 72 standards.
and Fire
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
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TABLE 2 Sample indoor design criteria.
All Spaces (Except
Utility Spaces And
Data Center)
Occupied: 75
Night Setback: 81
Occupied: 70
Night Setback: 63
+0.01 to Hall
30 in Offices &
Conference Room
30 in Open Cubicles
Utility Spaces (Such
as Electrical &
10 Above Ambient
+0.01 to Hall
Data Center
(No Night
35% (Summer &
(No Night
+0.01 to Hall
[Adapted from NEBB’s unpublished sample OPR document (Jan. 2, 2011), p. 14. Vibration values based on Sound and Vibration Design and Analysis; NEBB, 1st Edition (1994).]
And the later in the design phase
that the owner calls for changes,
the more expansive they become—
and the more frustrated the owner
TABLE 3 Sample lighting and electrical design criteria.
Building the Document
••Controls. The entire facility shall be on a timed lighting control system with photocells.
Lighting shall also be controlled manually by local switches that have motion-controlled
occupancy sensors.
••Lighting fixtures in offices, cubicles, conference rooms, break rooms, utility rooms, the
lunchroom, and the data center shall be recessed, high-efficiency linear fluorescents with
energy-saving, low-mercury lamps. Lobby lighting shall use metal-halide lamps, LED (lightemitting diode) downlights, and LED accent lights. Restrooms shall have LED downlights.
••Exit signage and emergency lighting shall be equipped with a 90-minute emergency
battery pack. Exit signs shall use LED illumination.
••Light levels setpoints (in foot-candles) shall be 40 fc; except in the data center and
mechanical, electrical, and storage rooms, which shall be 30 fc.
••Lighting heat gain. The heat gain from lighting fixtures shall be obtained from the lighting
power density factors defined in the latest version of ANSI/ASHRAE/IES Standard 90.1, and
shall be based on the actual lighting installed in the building.
To ensure the BOD meets all of
the owner’s needs and desires, it
should address in detail the design
elements identified in both the RFP
and the OPR. Hopefully, the OPR
captured all of the owner requirements in the RFP, but it’s a good idea
••Lighting elements/power density. All exterior lighting shall employ LED lamps, and shall
be designed to use less than at least 25% of the allowable lighting-power density based upon
to review the OPR against the RFP.
the latest version of ANSI/ASHRAE/IES Standard 90.1.
Project description. As noted in
••Zones of illumination. All site lighting shall have minimal trespass over the property line. All
exterior lighting shall comply with LZ3 zone requirements as defined by the latest version of
the previous article, the OPR must
serve as the source document for
••Fixtures shall be either pole- or wall-mounted, with angled shade to reduce light pollution.
Total lumens above 90 degrees from nadir shall be less than 5%.
the BOD. So the first major section
of the BOD should be a restatement
••Design codes. The electrical design shall comply with the Minnesota Building Code, all
applicable local codes, and the requirements of the latest version of NFPA 70.
of the OPR’s project description—an
••Building utilization voltage shall be 277/480 volt, 3-phase, 4-wire. The calculated service
overview of the building’s purpose
size shall be 1,250 amperes.
••Grounding shall be in accordance with the latest version of NFPA 70, article 250. Raceway
and essential functions. Be sure to
systems shall be concealed, except in mechanical and utility areas.
include the data from the key charts
and tables in the OPR that will drive
the design team’s efforts, such as the space utilization
purposeful intent to preserve the owner’s requirements
table, the outdoor design criteria table, the indoor
in its design efforts.
design considerations table, and the complete, updated
Codes, standards, and specifications. Like the OPR,
list of all authorized vendors, suppliers, and contractors. the BOD states that the building must comply with all
You’ll also need to include an updated project schedapplicable federal, state, regional, county, city, and local
ule in the BOD, and this section of the document is a
codes, standards, and specifications.
good place to display it. By capturing the overall project
But unlike the more general statements in the OPR docdescription and key related information from the OPR
ument, the BOD must include specific details for all of the
document, the design team demonstrates not only its
applicable codes and specifications that must be satisfied
clear understanding of the project’s purpose—but its
by every project discipline—that way both the design and
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the construction teams can take them
TABLE 4 Sample building envelope design criteria.
all into consideration. The sample
HVAC criteria here are based on stan••Fenestration percentage. The percentage of glass on the building’s exterior shall be 40%.
dards adopted by Minneapolis.
••Window specifications. All exterior windows shall be specified to help prevent unwanted solar
heat gain in summer, while still harnessing direct solar radiation in winter. Visible light transmitWhile the OPR might generally
tance (VLT) shall be at least 0.75.
state that “the building will meet
••Insulating value. The U-value of all exterior windows shall be at least 0.55.
all applicable ASHRAE standards,”
••The solar heat gain coefficient (SHGC) of all exterior windows shall be 0.40.
the BOD must be more specific—so
••Interior wall panels shall be 5/8-in.-thick gypsum board over metal framing (16 in. on
the designers know exactly which
••Exterior curtain wall assemblies shall be double-pane insulated and fully climate-appropriate.
code to follow in their designs. As a
••Insulating value. The maximum U-value of all exterior walls shall be 0.032.
result, the BOD might state that the
building “shall meet or exceed ANSI/
••Framing. The roof shall be metal-framed.
••Overlayment material shall be ¼-in.-thick protection board.
ASHRAE Standard 62.1-2010.”
••Moisture barrier shall be either white thermoplastic polyolefin (TPO) membrane or GalRoof
By specifying the exact codes and
valum® deck.
standards required, the BOD identi••Insulation shall be entirely above deck with continuous layers of open-cell foam as needed to
achieve a minimum rating of R-30.
fies how the design team will meet the
owner’s requirements. In addition, a
careful delineation of codes and standards not only helps
only minimally addressed in the previous article, that
prevent “cutting corners,” but also helps answer questions
doesn’t mean it shouldn’t be a key element of the BOD.
about why something was designed in a certain manner.
As with every aspect of the BOD, defining the envelope
HVAC design. The BOD must explain how the buildcriteria must be a team effort. For example, a key enveing’s HVAC systems will be designed in accordance
lope design element is establishing the sealing levels
with the project RFP, the OPR, and all applicable codes,
that will achieve the owner’s desired infiltration rate—
standards, and regulations—as well as any other essenwhich is data that should come from the architect. Although a
tial design criteria (which should also be described in
mechanical engineer or energy modeler can evaluate
the BOD). For example, the sample OPR in the previous
the performance of various building materials, they may
article called for “total energy consumption of less than
not understand the physical or budgetary impacts of (for
70 kBtu/ft2 per year.” The BOD must explain how the
example) changing a roof’s insulation specification from
components will meet this requirement (Table 1).
R-20 to R-40 (see Table 4 for sample criteria).
Indoor and outdoor design. The OPR should include
Utility baselines. The BOD should include projected
detailed charts that describe the owner’s expectations
monthly utility baselines for electrical, gas, and water
for the building’s interior and exterior environments
usage. These baselines—which you can extract from the
(temperature, humidity, CO2 levels, etc.). The BOD must OPR—will provide a starting point for whatever monitoring
restate those considerations and refine them as needed. tool the owner wants to use to track resource consumption.
For this series we’re assuming our sample building
Additional energy-usage factors. The BOD must also
is being constructed in Minneapolis; so its indoor and
address any other systems or equipment that will affect
outdoor design criteria are based on ASHRAE data for
the building’s energy use, such as loads for occupants,
Minneapolis (see Table 2, Page 78, for sample criteria).
miscellaneous equipment, and any specialty areas such
Lighting and electrical systems. The previous article
as kitchens, fitness rooms, and server rooms.
made little mention of owner’s lighting expectations; but
Sustainability goals. A key element of the BOD is a
those specifications must be thoroughly documented in
description of the owner’s sustainability goals. Typically,
the OPR and BOD. Certainly, the building owner wants
this includes the owner-mandated LEED rating, as well
to maximize light output for occupant comfort. But the
as the version of LEED to be used in the project. The
owner also wants to minimize energy use and maintedescription should include specific details, such as:
nance requirements. So the BOD must give the design
“The facility is required to achieve LEED-NC Gold rating
team the needed data to translate the owner’s desires into
under LEED Version 3.0.”
actionable design (see Table 3, Page 78, for sample criteria).
LEED certification is not the sole responsibility of the
Building envelope. While the building envelope was
design team—every party and person involved in the project
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must actively support the owner’s efforts toward LEED
certification. LEED certification is definitely a chain that
is only as strong as its weakest link.
Maintenance staff training. The requirements for the
owner’s staff training that are defined in the OPR must
be included in the BOD. Be sure to include details that
show the amount of time that will be spent on training
and the types and methods of training that are planned.
Project delivery, budget, and milestones. It’s important to describe the project delivery method the owner
intends. This could be a bid plan and specification,
design-build, gross maximum pricing, or other method.
Also include descriptions of the budget, all known
required meetings, and project milestones—all of which
should be obtainable from the OPR document.
Additional design concerns. Many other design
concerns must be captured in the BOD. Space doesn’t
permit us to mention them all, but be sure to describe
any BIM requirements, all specialized software (such as
simulation tools for energy modeling), coordination of
work between the various engineering disciplines, any
desired measurement and verification programs, and
any QC or QA processes the owner wants.
Commissioning requirements. If the building isn’t
properly commissioned, you probably won’t end up with
a truly satisfied owner. So capture and update all of the
commissioning requirements, and build the CxA’s building-specific requirements into the BOD. The commissioning scope of work table and the commissioning phases
and responsibilities table should be key parts of the BOD.
To ensure the building’s ongoing optimal performance,
consider adding to the project plan a comprehensive
annual “commissioning check-up.”
Like the OPR, the BOD is an interactive tool that must
be revised as the owner and design team make decisions.
Especially as the project evolves, and budget and time
constraints enter the picture, you’ll need to adjust the OPR
and the BOD documents. Remember, the owner’s requirements drive the basis of design; not the other way around!
So don’t view the BOD as a burden. View it as a key element in an effective communication process—the kind
of process that will help ensure that the owner’s voice is
heard accurately—which is how the owner will end up
with a building that meets expectations.
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