hot dry / mixed dry prototypes, wathen – castanos hybrid ... · –dmaic (define, measure,...

Hot Dry / Mixed Dry Prototypes

Wathen –Castanos Hybrid Homes, Inc.

Duncan Prahl, RA

Sr. Research Associate, IBACOS Inc.

DOE Quarterly Meeting, Denver, CO

July 21, 2010

Building America Team Meeting

Wathen Castanos Hybrid Homes, Inc.

• Company Profile:

• ~180 Homes per year in Clovis / Fresno CA

• First-time, Move-up and Empty-nester buyers

• House sizes from 1100 to 2700 square feet

• Started high performance homes in 2006

• Current standard practice ~ 48% WRT BA Benchmark

• Currently 36 employees


Initial Evaluation - Mapping and Gap Analysis

2 days- mapped operational activities in 5 areas:

– Planning and Development, Product Design and Purchasing,

Home Sales and Marketing, Construction, and Customer

Care

– Identified key strengths and gaps as a builder of high

performance homes

– Strong corporate culture, trade relationships, brand

awareness, and reputation

– Integrated Design Process

From this activity 6 work improvement

groups were identified


Work Improvement Groups (WIG’s)

• Company had to invent a new operational

model

– Company reduced staff by 2/3 from 2007 - 2009

• Developed cross functional teams to

address highest value gaps

• Training was provided to company and

trades on Building Science, Quality

Management, and Quality Tools

– DMAIC (Define, Measure, Analyze, Improve,

Control) process for WIG’s

• Applied for National Housing Quality Award

in 2010, received site visit by judging panel.


Initial Evaluation - Technical

IBACOS Quality Assessment Results

• Two days of site evaluations.

• Overall score 3.2 (scale of 0 to 4)

– “Low Risk” Category



Best Practices Observed:

– Excellent HVAC duct installation.

– High efficiency equipment

– 92 AFUE furnace

– 14 SEER air conditioner

– Zoned distribution

– Rinnai tankless, gas fired water

heaters



Best Practices Observed:

– Grade I fiberglass batt installations.

– R-13 cavity + R-4 continuous exterior

insulating sheathing.

– Good air sealing of the enclosure.



Energy Performance of Existing Practices (Jan 2010):

– 48% above Building America Benchmark.

– Participating in Builder’s Challenge, California Build it Green,

& ENERGY STAR.

– 30% beyond 2008 CA Title.

– Average duct leakage <5%.

– Average building tightness < 3.5 ACH50.

– Taking advantage of every tax incentive and energy rebate

available to offset all energy upgrades.

– Homes marketed competitively at $/sq. ft. for region.


Prototype – Design Strategies

Wathen Castanos Hybrid Homes Inc. wanted to roll out a

fresh product offering for a community development,

“Loma Vista”.

• Plan #200 is a 2000 square foot, 3 bedroom ranch

style home.

– IBACOS encourage the builder to consider moving the HVAC

system and ducts to inside conditioned space.

– The cost to do a conditioned attic proved too high for the

builder’s price point.

– Very concerned about marketability of 8’ ceilings in areas of

the house.


Plan 200


Prototype – Specification Package

The point deficiency to get

from 48% to 50% beyond

BAB would have to be made

up in system efficiency and

an enhanced building

enclosure.

Net positive cash flow to the

consumer of ~$935 / year

Rating for this design

package:

RESNET HERS Index - 53

CA HERS I – 46

CA HERS II – 68

(see barriers…)

Component 2010 Base Package Prototype

Concrete Slab Uninsulated Uninsulated

Exterior Walls

2x4 16" o.c. R-13 + R-4 cont. sheathing (R19 knee walls)

2x4 16" o.c. R-15+ R-4 cont. sheathing (R19 knee walls)

Roof

Attic floor - R-38 + Radiant Barrier

Attic floor - R-49 + Radiant Barrier

Exterior Doors R-4 R-4

Windows U-.34, SHGC-.25 U-.32, SHGC-.25

Building Air Tightness 3.5 ACH50 2.7 ACH50

Mechanical Ventilation Exhaust with pressure relief Exhaust with pressure relief

Heating 92 AFUE 94.7 AFUE

Cooling 16 SEER 18 SEER

Ductwork R-8 in unconditioned R-8 in unconditioned

Water Heater Tankless, gas .82 EF Tankless, gas .98 EF

Appliances All Energy Star All Energy Star

Fluorescent Lighting 100% 100%

Photovoltaic System variable 3.7 kW

% Better than Building

America Benchmark48.4% 52.6% & 70% w/PV



• This demonstrates their

commitment to taking

this specification

package to community

scale production

• Wathen Castanos Hybrid Homes has been adamant

that the resulting prototype product would still fit into a

price point that would be competitive in their market.



• Strategies to achieve a tighter building envelope (to get

from 3.5 to below 3.0)

– Addition of seal sill that layer up under stucco weep screed.

– Glued drywall to top and bottom plates & around openings.



• Builder was already:– Sealing all penetrations through plates and enclosure.

– Sealing all window and doors between R.O.s and frames.

– Sealing all penetrations through the drywall.

• Actual blower door test results indicate a total leakage rate of 2.7 ACH50. Not amazing, but not bad for California, open frame construction.



• Additional wall R value was achieved by using Johns

Manville Spider® blown in fiberglass.



• Though attic insulation was increased to R-49 (from R-38) raised heel trusses were priced but not included.

• Some designs require raised heels for aesthetics


Design Challenges & Barriers

System Sizing

• Initial modeling indicated that a 2 ton AC was sufficient.

– Total cooling load was 20,888 Btuh

• The builder wanted to use the Bryant Evolution system.

• The 2 ton was discontinued and a 2 ½ ton wasn’t

available.

• Therefore a 3 ton system was installed.

• Again, the industry is faced with manufacturing split AC

systems that are high efficiency and small enough for

low load, high performance homes.


Challenges and Barriers

• Bringing Ducts inside conditioned space– Aesthetic concerns

– Footprint of the HVAC unit

– Noise concerns

• How much is enough?– 50% package is possible, but incremental step above 48%

builder standard practice is marginal.

– Even if we “threw everything at it” we’d only be getting in the mid 50% savings

• CA HERS I, II & RESNET Ratings– T-24 vs. 2006 IECC reference homes

– States rights vs. national uniformity


Buyer response

• Since the opening of this home, WCHH has offered a PV package as an included upgrade. Buyers can opt for any other options instead. The majority are taking the other options.

• “The home is efficient enough, I’ll take the granite countertops.” is the common response to this offering.

• The 3.7 kW photovoltaic system cost $13,940 with a

rebate of $7709 for a final cost to the builder of $6231

to the builder.


Next Steps

• Implement a model Quality Management System

within the organization

– Way to document and standardize procedures for HP

homebuilding

– Identify operational best practices for translation to other

building companies

– Track operational metrics to demonstrate benefits of making

HP a basic operational strategy

• Evaluate Prototype

– Are incremental strategies enough to maintain market

leadership?

– Re-evaluate systems strategies


Questions?

Duncan Prahl

412-999-8434

[email protected]

hot dry / mixed dry prototypes, wathen – castanos hybrid ... · –dmaic (define, measure,...

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