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
Building America Team Meeting
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
Building America Team Meeting
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.
Building America Team Meeting
Initial Evaluation - Technical
IBACOS Quality Assessment Results
• Two days of site evaluations.
• Overall score 3.2 (scale of 0 to 4)
– “Low Risk” Category
Building America Team Meeting
Initial Evaluation - Technical
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
Building America Team Meeting
Initial Evaluation - Technical
Best Practices Observed:
– Grade I fiberglass batt installations.
– R-13 cavity + R-4 continuous exterior
insulating sheathing.
– Good air sealing of the enclosure.
Building America Team Meeting
Initial Evaluation - Technical
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.
Building America Team Meeting
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.
Building America Team Meeting
Plan 200
Building America Team Meeting
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
Building America Team Meeting
Prototype – Design Strategies
• 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.
Building America Team Meeting
Prototype – Design Strategies
• 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.
Building America Team Meeting
Prototype – Design Strategies
• 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.
Building America Team Meeting
Prototype – Design Strategies
• Additional wall R value was achieved by using Johns
Manville Spider® blown in fiberglass.
Building America Team Meeting
Prototype – Design Strategies
• 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
Building America Team Meeting
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.
Building America Team Meeting
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
Building America Team Meeting
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.
Building America Team Meeting
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