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