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Lot Specific HVAC Design for Multi-Configuration Homes
Aaron Holden – Design Manager
Directions:
Step 1) Stand across street from home and hold this card at arm’s length.
Step 2) Pick the AC capacity of the cutout your home fits in.
2 Tons 3 Tons 4 Tons
What Has Changed?
Design Conditions Field Conditions
What Has Changed?Load Comparison
-
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
Axis
Title
Infiltration
Doors
Ventilation
Internal
Ceilings
Walls
Ducts
Windows
30 Year Old Home 2009 Code Built Energy Star Home
Regional Differences - Loads
0 10000 20000 30000 40000 50000
Coronado CA
Phoenix AZ
Denver CO
Houston TX
Orlando FL
Sensible Latent
0 10000 20000 30000 40000 50000
Coronado CA
Phoenix AZ
Denver CO
Houston TX
Orlando FL
Total Heat
Coronado, CAPhoenix, AZ
Denver, CO
Houston, TX
Orlando, FL
Actual capacity depends on design conditions.
36 kBTU/h 36 kBTU/h 36 kBTU/h
Atlanta95 F
Phoenix108 F
Chicago85 F
33.2 kBTU/h 31.4 kBTU/h 34.8 kBTU/h
Regional Differences - Capacities
Room ARoom B
Room CRoom D
300
320
340
360
380
400
420
440
460
N NE E SE S SW W NW
Roo
m A
irfl
ow in
CFM
Multi-Configuration Design Complexity:Solar Orientation
House #1: Concentrated
Glazing
Room A
Room B
Room C
Room D
Load Varies Greatly with Orientation
Room Airflows Aligned
15
20
25
30
35
40
N NE E SE S SW W NWLo
ad in
kB
TUh
N
S
EW
Room Level Airflow
Load Distribution Airflow Distribution
Location%
AirflowAirflow (CFM)
Room A 10% 200 Room B 5% 100 Other 85% 1,700 Total Equipment Airflow 100% 2,000
Multi-Configuration Design ComplexityOptions Livable Sqft Glazing Sqft # of Bedrooms
Standard 2693 399 4
Elevations 0 5 0MSGD at Dining 0 42 0MSGD at Great 0 34 0Glass Block at Master Bath 0 12 0Bay Window Owners Suite 24 15 0Dining Extension 24 0 0AV Build-in 29 0 0Bed and Bath ILO Tandem Garage 187 20 1Guest Suite - W/ SGD at Deck 413 9 1Bed ILO Loft 0 0 1Max WC Configuration 3370 536 7
Options Livable Sqft Glazing Sqft # of BedroomsStandard 2693 399 4Max WC Configuration 3370 536 7Delta 677 137 3
Multi-Configuration Design Complexity
0 10000 20000 30000 40000 50000
Cooling BC
Cooling WC
Walls
Glazing
Doors
Ceilings
Infiltration
Ducts
Ventilation
Internal Gains
Multi-Configuration Design Complexity
OPTIONS!!!
Plans Options Option Combinations
Load Configurations
Room-levelTarget Airflows
1 6 64 x 16 = 1,024 x 15 = 15,360
1 15 32,768 x 16 = 524,288 x 15 = 7,864,320
“Layer Cake” HVAC Design
BaseBase
BaseBase
BaseBase
BaseBase
Opt. 1
Opt. 1
Opt. 1
Opt. 1
Opt. 1
Opt. 1
Opt. 1
Opt. 1Opt. 2
Opt. 2
Opt. 2
Opt. 2
Opt. 2
Opt. 2
Opt. 2
Opt. 2Opt. 3Opt. 3
Opt. 3
Opt. 3
Opt. 3
Opt. 3Opt. 3
Opt. 3Opt. 4
Opt. 4 Opt. 4
Opt. 4
Opt. 4
Opt. 4Opt. 4 Opt. 4
Opt. 5 Opt. 5 Opt. 5
Opt. 5Opt. 5 Opt. 5
Opt. 5Opt. 5
2.5 ton
3.0 ton
3.5 ton
20,000
22,000
24,000
26,000
28,000
30,000
32,000
34,000
36,000
38,000
N NE E SE S SW W NW Eqpt
Heat
Loa
d/Ca
paci
ty (B
TUh)
Results
155 162
22 16
2009 2010 2012 2013
Airbalance Requests
Triple Win: Lot-Specific Design
Improve Energy Efficiency
Enhance Homeowner Comfort
Reduced Costs
Plug-N-Play Ductwork: Delivering Comfort in Low-Load Homes
Tim Beggs, Manager, Innovation
WHY?Business Case
Conventional Ductwork: Issues + Limitations
• Poor layout practices• Typically routed through
unconditioned space• Leaky, requiring secondary sealing• Hard to install properly
with available labor • Inadequate access to adjust and
maintain• Not well-integrated into architecture
Low Load Homes: Less Air, Delivery Challenges
• Below 10 btu/hr/ft2
• Poor air distribution, throw, mixing• Comfort performance issues• May impede acceptance of “high
performance” homes
WHAT?Proposed Solution
Plug-n-Play Concept
• Small diameter• Home run manifold
arrangement• Kit of parts• Intuitive design
methodology
Performance and Integration Impacts
Plug-n-Play System Conventional Residential Duct System
Low pressure drop at small sizes Low pressure drop at larger sizesSeals well and easily Seal integrity is questionableThermally resistive duct wall Requires insulationRight-sized for small-capacity HVAC equipment
Overkill for low load homes
Fits within framing Requires soffitsHome run arrangement possible Trunk and branch or extended
plenum required
Constructability and Cost Impacts
Plug-n-Play System Conventional Residential Duct System
Lower installed cost Higher installed costFew unique components, 1 or 2 sizes
Multiple sizes and SKU’s
Semi rigid for quicker, easier installation
Rigid, multi-step installation, extended site time
Simple connections, attachments Extra steps for joints and takeoffsSuitable for burdened labor market Requires greater skillsSimplicity Complexity
HOWWe Got Here
Field Data Collection
Lab Testing
Performance Simulations Design Methodology
Revealing a Gap in Material Availability
Define the acceptable characteristics of• Pressure drop• R-value• Mass• Durability• Cost• Rigidity / Flexibility• Flame spread• Smoke development• Incremental tube sizes; every 1/10th inch?
NEXT STEPS
Time and Motion Study
Ongoing Project Work
• Characterize the pressure and airflow relationships for small diameter ducts and fittings
• Characterize the installed performance of the Plug-n-Play system
• Compare performance to traditional air distribution system approaches
• Define range of application for the system in terms of home size, load, load density, and climate
• Identify acceptable material properties
Ongoing Project Work
• Address code compliance further• Analyze cost and installation impacts• Cooling season evaluations• Finalize design methodology• Develop installation guidance• Secure interest from a builder and
manufacturer