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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 1
HVAC SYSTEMDESIGN PROCESS
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 2
HVAC System Design ProcessEstablish HVAC-related owner’s project requirements (OPR: design issues/intents/criteria;
including code/standard compliance)Establish zoning requirementsMake a preliminary system selection based on the aboveCalculate preliminary design heating/cooling loadsSelect appropriate source equipment (to meet loads, intent, and context)Select appropriate distribution approach (to meet intents and to fit context)Coordinate HVAC components with other building systemsRough-size equipment (fans, pumps, valves, dampers, pipes, ducts, condensers, air-
handlers, tanks, …) Run energy analyses to optimize equipment selections and system assembliesFinal-size equipment based upon optimization studiesCoordinate final individual equipment selections into a cohesive wholeDevelop appropriate control logic and strategiesDevelop commissioning tests and checklistsWitness systems installation and verificationDevelop systems manuals for the ownerProvide benchmark performance data for the ownerConduct POE validations of systems outcomes on site
red = architect blue = engineer with architect black = engineer
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 3
HVAC System Selection Process
Carefully consider potential design issues
Clearly define design intents
Establish meaningful design criteria
Compare potential systems against criteria
Select best system
Validate system selection
collectively, the first three become the Owner’s Project Requirements (OPR) for climate control and IAQ
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 4
Common HVAC Selection Issues
• First cost• Life-cycle cost• Durability• Maintainability• Reliability• Appearance• Zoning capabilities• Flexibility• Energy efficiency• ODP and GWP
• Greenness• Noise• Space requirements• Smoke control
capabilities• Fuel options• Owner dictates• Demand charges• Many others
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 5
Common HVAC Design Intents
• “Provide” thermal comfort• “Provide” acceptable IAQ• Low first cost• Good energy efficiency• No equipment located in occupied spaces• A “green” system• Highly reliable operation• Easily maintained equipment• Low life-cycle costs• And such …
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 6
Establish Design Criteriafor Each Intent
• Low first cost means no more than $xx.xx / sq ft• Energy efficient means xx% better than the requirements of
ASHRAE Standard 90.1• Provide thermal comfort means meets the requirements of
ASHRAE Standard 55 (“bettering” this standard is not necessarily meaningful; comfort is comfort)
• Provide good IAQ means meets the requirements of ASHRAE Standard 62.1 (“bettering” is expensive to verify and may be energy intensive)
• Easy to maintain means janitorial staff can do the job• No equipment in occupied spaces means as stated• Aesthetically pleasing means meets three visual precedents
the criteria shown above are simply examples, from a world of possibilities
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 7
Selection Matrix (a design tool)
311297OVERALLRATING
7285469 **Good IAQCapabilities
5493666CleanAppearance
8081001010 *HighFlexibility
5677298Good EnergyEfficiency
4973557Low First Cost
WEIGHTEDSCORE
SYSTEM B
SCORE
SYSTEM B
WEIGHTEDSCORE
SYSTEM A
SCORE
SYSTEM A
PROJECT WEIGHT
INTENT
* most important attribute/intent; ** second most important; etc.
and the most logical system to use—in this context—is B
POSSIBLE SYSTEM “A” POSSIBLE SYSTEM “B”
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 8
Key HVAC Coordination Issues
• Equipment Locations– Source equipment (noise, maintenance access, access for
replacement, access/connection to utilities)– Condenser (must be exterior, noise, appearance, airflow, spray)– Air-handlers (length and placement of air supply and return paths,
outdoor air access, noise, vibration)– Terminal devices (maintenance access, noise, space incursion)– Outdoor air intakes (located to provide unpolluted outdoor air)
• Floor Area for Equipment– Main mechanical room(s), satellite AHU room(s), condenser
• Volume for Distribution (and for Equipment)– Ductwork (by itself and in coordination with beams, lighting
fixtures, sprinkler piping, electrical and signal runs)
• Aesthetics– Exposed elements (especially diffusers)
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 9
Desired Equipment Locations
The Architect’s Studio Companion: 3rd Ed.
this is a jointarchitectural/mechanical
decision
these 4 examples all “work” … butone will usually make more sense
in a given project context
a 5th option (not shown) wouldbe “fan room on roof”
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 10
Required Equipment Locations
zonecontrol
diffusers are laid out for
reasonable air distribution
The Architect’s Studio Companion: 3rd Ed.
box MUSTbe in this
area
undifferentiatedsupply air;
not yet controlled for specific zones
zone-differentiatedsupply air
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 11
Large Equipment
Areas
for schematic planning: can estimate central plant at 7% +/-of conditioned floor area
The Architect’s Studio Companion: 3rd Ed.
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 12
AirHandling Unit
Areas
The Architect’s Studio Companion: 3rd Ed.
USE these simple tools in studio—don’t just guess
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 13
Consider Volume (not just floor area)
The Architect’s Studio Companion, 3rd Ed.
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 14
Volumeworking in and around structure
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 15
Volume
plenums are neveras deep as they seem
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 16
Provide for Access who will know thisstuff is up there?
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 17
Estimating Duct Sizes (another option)
• For schematic design, assume 1 cfm per square foot (for an all-air system; 0.1 for an air-water system)
• Duct volume (in ft2) = airflow (in cfm) / air speed (in fpm)– cfm = cubic feet per minute (airflow rate)– fpm = feet per minute (air speed in ducts)
• Assume (as a starting point) 1000 fpm air speed– higher air speed is possible and fairly common, but it uses more
energy and generates more noise (and we’re just estimating)
• Estimate duct dimensions as needed for the area served by a given duct (main ducts, branch ducts, …)
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 18
Estimating Duct Sizes (Examples)
• For a 200 sq ft office (all-air HVAC)
– (200 sq ft)(1 cfm/sq ft) = 200 cfm– 200 cfm / 1000 fpm = 0.2 sq ft – duct size might be around 12” x 3” or 6” x 6” or ….– and a similar size return air duct may be required
• For a 3000 sq ft classroom wing (all-air HVAC)
– (3000 sq ft)(1 cfm/sq ft) = 3000 cfm– 3000 cfm / 1000 fpm = 3 sq ft – duct size might be 36” x 12”– and a similar size return air duct may be required
message: ducts can get quite large, and there are often two of them
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 19
The Aesthetics ofAir Delivery
register
diffuser
diffuser
diffuser
all devices do not have equal visual impact
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 20
The Aesthetics of Air Delivery
diffuser grille register
grille
a diffuser provides sophisticated control of air delivery; a register the same but not quite so sophisticated; a grille basically just covers up a hole
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 21
Aesthetic Potential
of ExposedSystems
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 22
The Messy Stuff Is Usually Hidden
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 23
Big Stuff: Plan for It
chiller
cooling tower
you’ve got to give innovation credit for the partially earth-bermed cooling tower
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 24
Really Big Stuff: Seriously Plan for It
< penthouse mechanical room >
OA “duct”
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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 25
Creative Design
student work: Oklahoma State University
Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 26
Creative Design
student work: Oklahoma State University