Super Energy Efficient 

Design (S.E.E.D.) Home 

Evaluation

A. German, B. Dakin, C. Backman, E. Weitzel, 

and D. Springer

Alliance for Residential Building Innovation (ARBI)

December 2012
NOTICE

This report was prepared as an account of work sponsored by an agency of the United 

States government. Neither the United States government nor any agency thereof, nor 

any of their employees, subcontractors, or affiliated partners makes any warranty, 

express or implied, or assumes any legal liability or responsibility for the accuracy, 

completeness, or usefulness of any information, apparatus, product, or process 

disclosed, or represents that its use would not infringe privately owned rights. Reference 

herein to any specific commercial product, process, or service by trade name, trademark, 

manufacturer, or otherwise does not necessarily constitute or imply its endorsement, 

recommendation, or favoring by the United States government or any agency thereof. 

The views and opinions of authors expressed herein do not necessarily state or reflect 

those of the United States government or any agency thereof.

Available electronically at http://www.osti.gov/bridge

Available for a processing fee to U.S. Department of Energy

and its contractors, in paper, from:

U.S. Department of Energy

Office of Scientific and Technical Information

P.O. Box 62

Oak Ridge, TN 37831-0062

phone: 865.576.8401

fax: 865.576.5728

email: mailto:reports@adonis.osti.gov

Available for sale to the public, in paper, from:

U.S. Department of Commerce

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone: 800.553.6847

fax: 703.605.6900

email: orders@ntis.fedworld.gov

online ordering: http://www.ntis.gov/ordering.htm

Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste
iii

Super Energy Efficiency Design (S.E.E.D.) Home Evaluation

Prepared for:

The National Renewable Energy Laboratory 

On behalf of the U.S. Department of Energy’s Building America Program

Office of Energy Efficiency and Renewable Energy

15013 Denver West Parkway

Golden, CO 80401

NREL Contract No. DE-AC36-08GO28308

Prepared by: 

A. German, B. Dakin, C. Backman, E. Weitzel, and D. Springer

Alliance for Residential Building Innovation (ARBI)

Davis Energy Group, Team Lead

123 C Street

Davis, California 95616

NREL Technical Monitor: Cheryn Metzger

Prepared under Subcontract No. KNDJ-0-40340-00

December 2012
iv

[This page left blank]
v

Contents

List of Figures ............................................................................................................................................ vi

List of Tables .............................................................................................................................................. vi

Definitions.................................................................................................................................................. vii

Foreword................................................................................................................................................... viii

Acknowledgements ................................................................................................................................. viii

1 Introduction........................................................................................................................................... 1

1.1 Background and Motivation ................................................................................................1

1.2 Objectives and Research Questions.....................................................................................2

2 Project Description............................................................................................................................... 3

2.1 Energy Efficiency Measure Details.....................................................................................4

Thermal Envelope................................................................................................................6

Mechanical Systems.............................................................................................................7

Lighting and Appliances......................................................................................................8

Photovoltaic System.............................................................................................................8

2.2 Preliminary Savings and Cost Estimation............................................................................9

3 Methodology ....................................................................................................................................... 10

3.1 General Technical Approach .............................................................................................10

3.2 Measurements....................................................................................................................10

Monitoring Data Points......................................................................................................10

Short Term Tests................................................................................................................10

3.3 Equipment..........................................................................................................................13

Data logger Specifications.................................................................................................13

Modem Specifications .......................................................................................................13

3.4 Computation of Monitoring Variables...............................................................................14

4 Results................................................................................................................................................. 16

4.1 System Commissioning .....................................................................................................16

4.2 Short Term Test Results.....................................................................................................17

4.3 Monitoring Results and Discussion ...................................................................................17

Whole Building Performance and Comparison .................................................................17

Load Reduction Strategies.................................................................................................19

4.4 Cost Effectiveness and Marketability ................................................................................21

5 Conclusions and Recommendations ............................................................................................... 24

References................................................................................................................................................. 25

Appendix A: Floor Plan and Construction Details................................................................................. 26

Appendix B: Mechanical System Controls Schematic.......................................................................... 28

Appendix C: Short Term Testing and Commissioning Results ........................................................... 29
vi

List of Figures

Figure 1. Schematic of mixed mode cooling system .............................................................................. 2

Figure 2. Completed S.E.E.D house .......................................................................................................... 3

Figure 3. SIP wall installation..................................................................................................................... 6

Figure 4. Insulation installed below slab (left) and PEX tubing laid out for radiant heating and 

cooling delivery (right)......................................................................................................................... 6

Figure 5. West elevation showing sun screen over window and air-to-water heat pump................... 7

Figure 6. Hydronic equipment and piping installed in the garage......................................................... 8

Figure 7. The 3kW photovoltaic system ................................................................................................... 9

Figure 8. Monitoring sensor location schematic ................................................................................... 12

Figure 9. S.E.E.D. house 9-month electricity use by end-use .............................................................. 18

Figure 10. Pie chart showing percentage of total 9-month electricity use by end-use ..................... 18

Figure 11. Comparison of 9-month monitored electricity use with BEopt estimate.......................... 19

Figure A - 1. Floor plan............................................................................................................................. 26

Figure A - 2. Wall, roof, and foundation details ..................................................................................... 27

Figure A - 3. Mechanical system controls schematic ........................................................................... 28

Unless otherwise noted, all figures were created by the ARBI team.

List of Tables

Table 1. Building Energy Efficiency Measures ........................................................................................ 5

Table 2. Monitoring Points List................................................................................................................ 11

Table 3. Sensor Specifications ................................................................................................................ 14

Table 4. Results of Short Term Tests...................................................................................................... 17

Table 5. Energy and Building Load Savings Comparison of Load Reduction Measures ................. 20

Table 6. S.E.E.D. Home Measure Costs .................................................................................................. 22

Table A - 1. Hydronic System Flow Rate with Various Zones Calling ................................................. 29

Unless otherwise noted, all tables were created by the ARBI team.
vii

Definitions

ACH50

AHRI

ARBI

AWHP

Air changes per hour at 50 Pascals

Air-Conditioning, Heating, and Refrigeration Institute

Alliance for Residential Building Innovation

Air-to-water heat pump

Btu

CARB

COP

DEG

British thermal unit

Consortium for Advanced Residential Buildings

Coefficient of performance

Davis Energy Group

DHW Domestic hot water

DX

ECM

Direct expansion

Electronically commutated motor

EER

ERV

Energy efficiency ratio

Energy recovery ventilator

HERS

HSPF

Home Energy Rating System

Heating seasonal performance factor

HVAC Heating, ventilation, and air conditioning

kWh

PSC

PV

Kilowatt-hour

Permanent split capacitor (motor)

Photovoltaic 

RCS

S.E.E.D.

SEER

SHGC

SIP

Reverse cycle chiller

Super Energy Efficient Design

Seasonal energy efficiency ratio

Solar heat gain coefficient

Structurally insulated panel
viii

Foreword

The “Super Energy Efficient Design” (S.E.E.D) home being evaluated under this project is a 

1,935 ft2, single-story spec home located in Tucson, Arizona. This prototype design was 

developed with the goal of providing an exceptionally energy efficient yet affordable home. The 

design includes numerous aggressive energy features intended to significantly reduce heating 

and cooling loads, such as structurally insulation panel (SIP) walls and roof, high performance 

windows, an energy recovery ventilator (ERV), an air-to-water heat pump with mixed-mode 

radiant and forced air delivery, solar water heating, and rooftop photovoltaic (PV) system. 

Source energy savings are estimated at 45% over the Building America B10 Benchmark. This 

project provides an opportunity to evaluate the commercial viability of these aggressive energy 

measures in a hot-dry climate.

The Alliance for Residential Building Innovation (ARBI) team used system commissioning, 

short term testing, long term monitoring and detailed analysis of results to identify the 

performance attributes and cost effectiveness of the whole house measure package. System 

monitoring was initiated in the summer of 2011 and the home was occupied in August, 2011. 

Results are presented from nine months of data collection. Actual post construction costs were 

obtained from the builder, and a cost effectiveness analysis was completed to evaluate 

commercial viability. Energy use was compared to BEopt model estimations, and annual cost 

benefits are determined relative to the builder standard. 

Acknowledgements

Davis Energy Group would like to acknowledge the U.S. Department of Energy Building 

America program for their funding and support of development of this technical report as well as 

research that informed it. In addition, we would like to thank builder Michael Ginsburg of La 

Mirada Homes for his ongoing cooperation throughout the design, construction, and monitoring 

stages of this project. 
1

1 Introduction

1.1 Background and Motivation

The “Super Energy Efficient Designed” (S.E.E.D.)1 home being evaluated under this project is a 

1,935 ft2

, single-story spec home located in Tucson, Arizona. The builder, Michael Ginsburg of 

La Mirada Homes, developed this prototype design with the goal of providing exceptionally 

energy efficient yet affordable homes and to determine which technologies and strategies will 

cost effectively accomplish this goal. The numerous aggressive energy efficiency measures that 

are incorporated into the S.E.E.D House contribute significantly to source energy reductions with 

an estimated 45% savings over the Building America B10 Benchmark (Hendron et al, 2010). 

Envelope measures significantly reduce the heating and cooling load and include structurally 

insulated panel (SIP) walls with added exterior foam, SIP roof panels, high performance low-E 

vinyl framed windows with a low solar heat gain coefficient (SHGC), appropriate shading by 

overhangs and exterior screens, and a fully insulated slab floor. The mechanical system consists 

of an air-to-water heat pump (AWHP) with a mixed-mode delivery system that delivers hot 

water through radiant floor tubing embedded in the slab, and chilled water through a 

combination of a small fan coil and the floor tubing. An energy recovery ventilator (ERV) is 

installed to provide filtered fresh air while minimizing the associated heating and cooling 

penalties of bringing in outside air. A solar water heating system with electric backup provides 

water heating and a rooftop photovoltaic (PV) system offsets utility electricity use. These 

measures, and specifically the package of measures, have the potential to lead to market-ready 

solutions that cost effectively provide comfort in homes with efficient, healthy, safe, and durable 

operation. Through detailed monitoring, this project affords the opportunity to evaluate the 

commercial viability of these energy measures in a hot-dry climate with an acute focus on the 

mixed-mode chilled water cooling delivery.

While the focus is on evaluation of measures specific to new construction single family 

residences in hot-dry climates, many of the energy efficiency measures are appropriate for 

various climate regions and in multifamily construction. The Building America Standing 

Technical Committees on Enclosures, Space Conditioning, and Analysis Methods have identified 

several gaps and barriers related to high performance building envelopes and HVAC and 

delivery systems. These outline the need for:

• Effective air tightness strategies

• Low cost space conditioning distribution strategies for low load homes

• Availability and documented performance of high efficiency, small capacity heating and 

cooling equipment for low load situations

• Better evaluation of alternative space conditioning systems (i.e. hydronic delivery).

Following on favorable results from a 2007 Building America study in Borrego Springs, 

California (Springer et al, 2008), the Davis Energy Group (DEG) was interested in using this 

house for further evaluation of mixed-mode chilled water cooling delivery. In the Borrego 

Springs test, two nearly identical homes were equipped with the same model 13 SEER 

condensing unit, one connected to a conventional DX evaporator coil and ducted distribution 

 1 http://lamiradahomes.net/lamirada_homes_seed.htm
2

CONDENSING

UNIT

EVAPORATOR

FAN COIL

RADIANT DISTRIBUTION

(Plate Heat

Exchanger)

(Tubing in Slab Floor)

Return

Air

Supply

Air

Figure 1. Schematic of mixed 

mode cooling system

system, and the other to a refrigerant-to-water heat 

exchanger with mixed-mode distribution. During the test 

period from July through September 2007, energy efficiency 

ratios (EERs) of 5.1 and 10.3 were measured for the standard 

system and the chilled water system, respectively. It was 

theorized that the reduced “thermal lift” resulting from the 

relatively high evaporator temperature of the chilled water 

system was responsible for the substantial reduction in 

compressor power.

For heating and cooling, the S.E.E.D. home incorporates an 

Aqua Products AWPH (“reverse cycle chiller”) connected to 

a distribution system that consists of a small fan coil piped in 

series with the radiant floor (see Figure 1). The fan coil is 

included primarily to provide latent cooling during humid 

conditions. This system design is being evaluated in detail under 

ARBI Task 2, Project 1: Air-to-Water Heat Pumps with MixedMode Delivery.

1.2 Objectives and Research Questions

The primary objective of this study is to determine how well the high performance envelope and 

innovative cooling system interact to cost effectively reduce cooling energy use in this hot-dry 

climate. Efforts are made to answer the following research questions in this report.

1. Does the house meet the design expectations for energy efficiency, cost effectiveness,

and marketability? 

2. How effective is the combination of the high performance envelope, ERV, and other 

measures at minimizing the heating and cooling load, and what are the energy savings?
3 

2 Project Description

The 1,935ft2 S.E.E.D. house is located in Tucson, Arizona, which is in a hot-dry climate (IECC 

Climate Zone 2), at 2,400 ft elevation. The heating and cooling degree days for Tucson are 1,578 

and 3,017, respectively (65° base). While the early summer is characteristically hot and dry, the 

monsoon season of late summer brings frequent rain and associated higher humidity. Figure 2

shows a picture of the completed house. See Appendix A and Figure A - 1 for a schematic floor 

plan.

 

Figure 2. Completed S.E.E.D house

During 2009 and 2010, DEG worked with La Mirada to provide HVAC and radiant design 

assistance, assist in selection of the energy efficiency measures, and model the house using 

EnergyGauge for evaluation relative to Building America Benchmark goals. DEG also assisted 

the builder in properly evaluating heating and cooling loads and duct sizing using ACCA Manual 

J and D methodologies so that equipment oversizing was avoided and proper system airflow was 

assured. The builder made the decision to use SIP walls and roof panels early in the design 

process. The SIP wall and roof panels are highly compatible with flat-roof Southwest 

architecture, simplify construction, and can potentially have a lower finished cost than frame 

walls and trusses.

As the builder wanted to pursue the idea of including solar space heating, TRNSYS simulations 

were conducted to estimate the feasibility and energy use implications of options, including solar 

water heating, and solar water heating plus space heating. This analysis showed that the space 

heating component was not cost effective. The resulting report convinced the builder to provide a 

solar water heater that would only serve domestic water heating loads. This report is included as 

an appendix in the Building America Test Plan (ARBI 2011). 

The builder was also interested in eliminating ducting and planned to use radiant floor heating, 

but was unsure how best to deliver cooling. DEG recommended the use of an AWHP with a 

mixed-mode delivery system that utilizes a small fan coil and a radiant floor cooling system for 

distribution for the following reasons:
4

• The flat roof design and lack of an attic allows little room for ducting; the small fan coil 

allowed use of small ducts that could fit within framing and soffits.

• Heat pump heating is the logical choice in an all-electric house.

• The exposed concrete floor facilitates the use of radiant cooling and improves the 

efficiency of radiant heating due to the lower resistance to upward heat flow and more 

moderate water temperatures.

• The water-based system with buffer tank and thermal energy storage in the floor slab can 

accommodate very low heating and cooling capacity without resulting in equipment 

short-cycling.

• The hydronic fan coil provides insurance against indoor humidity build-up and 

consequent floor condensation, and helps return higher temperature water to the 

evaporator in summer and lower water temperature in winter, resulting in improved heat 

pump performance.

Construction of the house began in March 2010. Walls were raised in July and the house was 

completed in April 2011. Monitoring of the house and the building mechanical systems has been 

initiated and will continue for a period of at least one year.

2.1 Energy Efficiency Measure Details

Table 1 summarizes the energy efficiency measures incorporated in the S.E.E.D. House.
5

Table 1. Building Energy Efficiency Measures

Measure Specification

Basic Building Characteristics

Building Type / Stories Single Family, 1 story

Conditioned Floor Area 1935

Number of Bedrooms 4

Envelope

Exterior Wall Construction 4.5 in. SIP Walls

Exterior Wall Insulation 4.5 in. SIP Panels (R-27) + R5 exterior foam insulation

Foundation Type & Insulation Slab-on-grade w/ R-10 below slab and R-7 at edge

Roofing Material & Color 3-ply built-up roof with CRCC Rated Cool Roof

Ceiling Insulation 6.5 in. R-41 SIP Panels

Roof Deck Insulation R-41

Radiant Barrier No

House Infiltration - Blower Door Test 2.4 ACH50

Thermal Bypass Inspection - QII Yes

Thermal Mass 5 in. thick exposed concrete floor

Glass Properties: U-Value / SHGC

All Windows 2-Pane Low-E, Low SHGC Vinyl 0.29 / 0.21

HVAC Equipment

Heating Type & Efficiency Heat Pump, 9 HSPF

AC Type & Efficiency HP, 13 SEER, 11 EER

Heating & Cooling Distribution Radiant floor & ducted

Duct Location & Insulation In Conditioned Space, R-6

Verify Duct Leakage Yes, <6%

Verify Cooling Right Sizing Yes

Ventilation Cooling n/a

Mechanical Ventilation ERV, Ducted

Water Heating Equipment

Water Heater Type & Efficiency Electric Storage, RE 0.96

Tank Capacity/Gallons 80 gallon

HW Distribution Time, Temp Recirculation, Master bath only

Solar Water Heater Type & Solar Fraction Active / Closed Loop / 58% SF

Appliances & Lighting

EnergyStar Appliances Dishwasher/Fridge/Washer

Dryer Fuel Electric

Oven / Range Fuel Electric

Fluorescent Lighting Package 100% Flourescent

PV System

PV Solar System Type & Capacity 3.4 kW DC system
6

Figure 3. SIP wall installation

Following is detailed information on individual measures that were selected, with discussion of 

their tradeoffs as appropriate.

Thermal Envelope

Walls/Roof: Polyurethane foam core SIPs are used for both the exterior wall and the roof. The 

SIPs construction was chosen for its thin 

profile and high R-value and to minimize 

thermal bridging, reduce the amount of 

wood used for framing, and reduce 

infiltration. The walls consist of 4.5 in.

panels at R-27 plus 1 in. of R-5 exterior 

foam sheathing and 2 × 2 interior furring 

for electrical wiring. The roof is 6.5 in.

SIP panel roof at R-41 with a 3-ply built 

up cool roof. The SIP roof panels have 

structural beam support resulting in solid 

foam panel-to-panel connection. While 

SIPs are currently more expensive than 

traditional wall framing, they require 

significantly less labor to install and reduce 

the risk of onsite installation defects. Additionally, they increase occupant comfort due to 

reduced infiltration and thermal bridging. Figure 3 shows the installation process for the walls.

Slab Foundation: The finished concrete floor surface reduces cost, facilitates the use of the 

thermal properties of the slab, and also matches the Southwest décor. R-10 rigid insulation is 

installed continuously below the slab and R-7 at the slab edge to reduce losses through the 

radiant heating and cooling (see Figure 4).

Figure 4. Insulation installed below slab (left) and PEX tubing laid out for radiant heating and 

cooling delivery (right)

Windows: High performance, vinyl-framed, argon gas-filled dual pane windows with a U-Factor 

of 0.29 Btu/hr-ft2-°F and a solar heat gain coefficient (SHGC) of 0.21 were specified and 
7

Figure 5. West elevation showing 

sun screen over window and air-towater heat pump.

installed. The house design also includes porches, screens, and overhangs to minimize direct 

solar gains through the windows year round (see Figure 5).

Air Tightness: The builder’s intention was to attain a leakage rate of 5.0 ACH50 or lower by 

carefully caulking plates and other leakage points and by furring out exterior walls to create a 

chase for wiring and piping that are within the thermal and air barrier envelope. The tested 

ACH50 was 2.4. Extremely tight houses can present indoor air quality concerns if adequate 

mechanical ventilation is not provided; mechanical ventilation compliant with ASHRAE 62.2 

(ASHRAE 2010) is provided via an ERV delivering 

filtered outdoor air throughout the house.

Mechanical Systems

Heating and Cooling: Both space heating and 

cooling are provided by the AWHP. Heating is 

delivered through the radiant floor while cooling is 

delivered via both the fan coil and radiant floor. The 

fan coil is sized to provide about half the required 

cooling capacity. The AWHP, manufactured by 

Aqua Products, consists of a 13 SEER Ruud heat 

pump perched on a module that contains the 

evaporator coil and temperature controls. Because 

the Ruud is installed with a non-matched heat 

exchanger coil it is not AHRI rated. Average rated 

efficiencies for this unit with a matched standard 

indoor evaporator coil are 11 EER and 9 HSPF. 

Figure 5 shows a picture of the installed unit. Chilled 

or hot water is piped first to a small fan coil to provide latent and sensible cooling (the fan is 

designed to only operate in the summer; however, an installed valve allows for fan coil bypass in 

any mode). The water is then delivered to the radiant floor tubing, which will provide the bulk of 

the sensible cooling and all of the heating. Piping chilled water to the fan coil first warms the 

water entering the slab and removes moisture in the supply airstream, reducing the risk of 

condensation on the floor surfaces. The fan coil is located in an insulated closet and all ductwork 

is in conditioned space. Figure 6 shows the installed hydronic equipment and piping. The small 

tank on the far right is the buffer tank for space conditioning. The large storage tank in the 

middle, with the drainback tank above it is for the solar domestic hot water (DHW). The 

hydronic fan coil can be seen on the far left in the closet.
8

Figure 6. Hydronic equipment and piping installed in the garage

Fresh Air Ventilation: An UltimateAir RecoupAerator ERV provides mechanical ventilation. 

The ERV exhausts air from the bathrooms, laundry and main room and supplies filtered outdoor 

air through the central heating and cooling duct system. 

Water Heating: An 80-gallon storage tank is heated by a drainback solar water heater connected 

to an internal coil, and is supplemented by a 4500 W element located in the top of the tank. The 

solar water heating system includes one 4 ft × 10 ft flat plate collectors mounted at a 45 degree 

slope facing south, and the drainback tank is located above the storage tank (see Figure 6). Based 

on TRNSYS analysis, the solar heater should be able to provide nearly all of the hot water needs. 

Lighting and Appliances

The S.E.E.D. house uses hard-wired fluorescent linear fixtures and CFLs for all hard-wired 

lighting. The dishwasher and builder-supplied clothes washer are ENERGY STAR® rated. The 

builder is also providing a central switch to disable non-critical consumer electronics throughout 

the house when not in use. 

Photovoltaic System

A grid-connected 3.4 kW PV (DC) solar electric system is installed and is expected to produce 

most of the electrical energy used by the house on a net annual basis. While the PV system costs 

more than any one of the efficiency measures alone, it is a critical feature for the builder to 

determine the PV sizing required to achieve net zero energy and to help sell the home in the 

target market. 
9

Figure 7. The 3kW photovoltaic system

2.2 Preliminary Savings and Cost Estimation

An evaluation was completed using BEopt v1.1 that predicts source energy savings for the 

S.E.E.D. House of 45% and 73% over the BA B10 Benchmark without and with PV, 

respectively. Savings over the regional standard are similar at 42% and 71% without and with

PV, respectively. Arizona does not enforce a statewide energy code but allows individual 

municipalities to adopt and implement local codes. The city of Tucson enforces the 2006 

International Energy Conservation Code (IECC) with certain local amendments. The “Regional 

Standard” energy savings reflect this baseline.

The building was modeled in BEopt using the specifications listed in Table 1; however, 

limitations due to BEopt capabilities and unknown operational efficiencies include the following:

• The AWHP seasonal efficiency is unknown. BEopt is only able to model air-to-air heat 

pumps. For modeling purposes, the rated efficiency of the Ruud heat pump was used.2

• The efficiency of the mixed-mode heating and cooling delivery system is unknown. 

Ducted distribution was modeled in BEopt with ducts located in conditioned space (per 

design).

 2 Performance of the air-to-water heat pump is being calibrated using monitoring data and TRNSYS under ARBI 

Task 2, Project 1: Air-to-Water Heat Pumps with Mixed-Mode Delivery.
10

3 Methodology

3.1 General Technical Approach

The general approach of this research plan is to employ system commissioning, short term tests, 

long term monitoring, and detailed analysis of results to identify the performance attributes and 

cost effectiveness of the whole house measure package. Due to funding constraints, system level 

analysis was not conducted under this project. HVAC system design is being evaluated in detail 

under ARBI Task 2, Project 1: Air-to-Water Heat Pumps with Mixed-Mode Delivery.

The team verified control settings for the heating, cooling, and ventilation systems, and checked 

the operation of the heat pump, controls, zone valves, fan, and other components. Long-term 

monitoring is used to provide “continuous commissioning” and to identify failure of any 

components. DEG also verified that the builder has complete documentation on all systems, 

including installation, maintenance, and operation manuals, ready for conveyance to the owner.

Monitoring data is carefully reviewed and analyzed in an effort to respond to the research 

questions and to identify sources of energy savings, such as from reduced heating and cooling 

load, improved equipment efficiency, etc. Actual post-construction costs are obtained from the 

builder, and a cost effectiveness analysis is completed to evaluate commercial viability. 

Monitored energy use is compared to BEopt model estimations and annual cost benefits are 

determined relative to the builder standard. Nine months of occupied data are collected and 

evaluated for this analysis.

3.2 Measurements

The site is equipped with a data logger and modem for continuously collecting, storing, and 

transferring data via telephone lines or cellular communications. Sensors are scanned every 15 

seconds, and data is summed or averaged (as appropriate) and stored in data logger memory 

every 15 minutes.

Monitoring Data Points

Table 2 lists all the measurement points that are monitored on a continuous basis. Key water side 

data points are shown in the piping diagram in Figure 8.

Short Term Tests

The DEG team and the HERS Rater collected additional data from the following short-term tests

to support the calculations described in this test plan and facilitate answering the research 

questions. The tests are outlined below:

• A blower door test using standard protocols.

• A duct blast test to measure duct leakage (all ducts are in conditioned space).

• A water flow test to measure flows with different zone valves operating and with the fan 

coil bypassed.

• The air handler was tested to measure airflow, verify correct tap settings, and measure 

blower power.
11

• Heat pump circulation, solar loop, and hot water recirculation pumps measured to 

quantify power consumption.

Table 2. Monitoring Points List

Abbrev. Description Location Sensor Type Sensor Mfg./Model

TAO Temp, air, outdoor Northwest side of covered 

rear patio, in shade, on under 

side of patio roof

RTD, 4-20ma

RMYoung 41372LF RHO RH, air, outdoor RH, 4-20ma

TAI1 Temp, air, indoor, East West Wing, next to T1, 

outside Bath 2, mount 

approx. 4 ft 6 in. high 

RTD, 4-20ma

Vaisala HMW60

RHI1 RH, air, indoor, East RH, 4-20ma

TAI2 Temp, air, indoor, Living Great Room, next to T2, on 

west wall of Dining area, 

mount approx. 4 ft 6 in. high 

RTD, 4-20ma

Vaisala HMW60

RHI2 RH, air, indoor, Living RH, 4-20ma

TAI3 Temp, air, indoor, Master Bed Master Bedroom, next to T3, 

on south wall, mount approx. 

4 ft 6 in. high 

RTD, 4-20ma

Vaisala HMW60

RHI3 RH, air, indoor, Master Bed RH, 4-20ma

TAS Temp, air, AH Supply Supply Plenum, Mech Rm RTD, 4-20ma

Vaisala HMD60

RHS RH air, AH Supply RH, 4-20ma

TAR Temp, air, AH Return Return Plenum, Mech Rm RTD, 4-20ma

Vaisala HMD60

RHR RH air, AH Return RH, 4-20ma

TWHL Temp, Water, Heat Pump Leaving Air Handler, Mech Rm Immersion TT Thermex

TWFS Temp, Water, Floor Supply Air Handler, Mech Rm Immersion TT Thermex

TWHE Temp, Water, Heat Pump Return Mechanical Room Immersion TT Thermex

TWCS Temp, Water, Cold Water Supply Mechanical Room Immersion TT Thermex

TWHO Temp, Water, DHW Supply Mechanical Room Immersion TT Thermex

TSF1 Slab bottom temp - zone 2 Living - floor surf near Tstat Contact TT Omega

TSF2 Floor surface temp - zone 2 Above insulation near Tstat Contact TT Omega

TSF3 Below slab insulation temp - zone 2 Below insulation near Tstat Contact TT Omega

TAERVS Temp, air, ERV Supply ERV Closet RTD, 4-20ma

Vaisala HMD60\

RHERVS RH, air, ERV Supply RH, 4-20ma

TAERVO Temp air ERV Entering (Outdoors) ERV Closet RTD, 4-20ma

Vaisala HMD60 RHERVO RH, air, ERV Entering (Outdoors) RH, 4-20ma

EHP Energy, Heat Pump At Outdoor Unit Power Meter Wattnode/WNB-3D-240-P

EHSE Energy, Total House Main Service Panel Power Meter Wattnode/WNA-1P-240P-PV

EWH Energy, WH Electric Element Mechanical Room Power Meter Wattnode/WNA-1-P-240P

EFAN Energy, Air Handler Fan Air Handler, Laundry Power Meter Wattnode/WNA-1-P-240P

EERV Energy, ERV ERV Closet Power Meter Wattnode/WNA-1-P-240P

EPV Energy, PV System Main Service Panel Power Meter Wattnode/WNA-1P-240P-PV

FWS Flow, Heat Pump System Mechanical Room Flow meter Onicon F-1300

EGEN Energy, House to Grid Main Service Panel Power Meter Wattnode/WNA-1P-240P-PV

SPC Status, HW Recirc Pump Mechanical Room Current Status Mtr Hawkeye

FWC Condensate Flow Mechanical Room RainGauge

SZ1 Zone 1 Status Mechanical Room Current Status Mtr Hawkeye

SZ2 Zone 2 Status Mechanical Room Current Status Mtr Hawkeye

SZ3 Zone 3 Status Mechanical Room Current Status Mtr Hawkeye

FWD Flow, Domestic Hot Water Mechanical Room Flow meter Dwyer
12

Figure 8. Monitoring sensor location schematic
13

3.3 Equipment

Data logger Specifications

Data Electronics data loggers are used to collect and store monitoring data. A Model DT-800 is 

used for this site. Analog inputs are single-ended type (all referenced to ground). Digital inputs 

are used for power monitors and status signals; high speed counter inputs are used with water 

flow meters. The data loggers are provided with an RS232 communications interface and battery 

backup. They also include integral cold junction circuitry for direct measurement of Type T 

thermocouples.

Manufacturer: dataTaker, Inc.

Model: DT-800

Analog Inputs: Up to 36 single-ended and 24 double-ended

Digital Inputs: 16 total, 8 bidirectional, 1 kHz

Analog Accuracy: 0.02% of reading plus 0.02% of full scale.

Memory: 2 MB flash, 4 MB SRAM, 24 system variable registers

Modem Specifications

The Datataker RS232 port is connected to a Hayes compatible modem. Modem settings are 

established using the following commands:

E0 Commands not echoed

M0 Quiet mode 

L0 Low ring volume

&D0 DTR ignored

&R0 CTS tracks RTS when modem is on-line

&N6 Communication at 9600 Baud Rate

&S0 Forces DSR signal high

S0=1 Auto answer mode, one ring

\N2 Reliable mode only

&W0 Saves active profile 0

A 9-to-25 pin RS232 cable (modem - DCE) with connections as shown on Page 13 of the 

Datataker Manual (Version 3.1) is used to connect the modem to the Datataker.

Standard specifications for the sensor types used are listed in Table 3. Sensor selection was based 

on functionality, accuracy, cost, reliability, and durability. Specific model numbers are listed as 

examples; similar models by other manufacturers may be used. Signal ranges for temperature 

sensors correspond approximately to listed spans.
14

Table 3. Sensor Specifications

Type Application Mfg/Model Signal Span Accuracy

RTD Outdoor temp and 

RH RM Young 41372LF 4-20 mA 14 - 140°F ±0.5F

0 – 100% +2%RH

RTD Indoor / Duct 

temperature / RH Vaisala HM*60 4-20 mA 23 - 131°F ±1.5%

0 – 100% +2%RH

Type T 

Thermocouple

Immersion Water 

temperatures

Gordon Watlow Type 

T special limits

~11mV 

@ 500oF

Range = 0.4% -328 to 662oF

Surface / Air 

temperatures Omega -99 to 500 oF

24VAC Relay

Fresh air damper 

status, zone 

damper status 

Hawkeye dry 

contact n/a n/a

Small power 

monitor

Fan and condenser 

power

WattNode 

pulse CTA/40 ±0.5%

WNA-1-P-240-P

Large power 

monitor

Total house power, 

PV production

Watt Node 

pulse CTA/60

CTA/120 ±0.5%

WNB-3D-240-P

Flow meter Water flow Onicon F-1300 pulse varies by meter ±0.5%

Pyranometer Insolation LiCor Analog varies by sensor ±5%

3.4 Computation of Monitoring Variables 

Whole house electricity use and PV electricity production: Energy supplied to the house and 

energy produced by the PV system are measured by two power meters and used to identify total 

house electric use.

End-use electricity use: Electric use of the water heating system includes the electric water 

heater, hot water recirculation pump, and solar collector pump. Recirculation pump energy use 

(Erecirc ) is calculated based on pump status and a one-time measurement of pump power as in 

Equation 1. The solar collector pump power was not monitored but is estimated based on PV 

array operation and rated pump power. PV power production was used as an indicator of when 

the pump would be available to operate based on collector temperatures. Based on the relatively 

low system recovery loads, a factor of 50% was applied to the available hours to account for 

times when the tank setpoint was met. Total DHW electricity use is calculated using Equation 2.

Equation 1: Erecirc = SPC * Precirc / 1000 * 15 min * 1 hour / 60 min (kWh)

Equation 2: Edwh = EWH + Erecirc + Esolar pump (kWh)

Where: SPC = recirculation pump status (% run time of 15 min monitoring period)

Precirc = recirculation pump power (W) = 38 W

EWH = electric use of water heater heating element and solar pump (kWh)

Total power input to the heating and cooling system is the sum of that of the outdoor compressor 

unit, the circulation pump, and the indoor fan. Circulation pump energy use (EPUMP) is 

calculated based on heat pump status and a one-time measurement of pump power as in Equation 
15

3. Heat pump status is calculated as a part load factor within the data logger program by filtering 

on heat pump system flow, FWS. Total heat pump electricity use is calculated using Equation 4.

Equation 3: EPUMP = PLEHP * Pcirc / 1000 * 15 min * 1 hour / 60 min (kWh)

Equation 4: Ehp = EHP + EFAN + EPUMP (kWh)

Where: PLEHP = heat pump part load factor (% run time of 15 min monitoring period)

Pcirc = heat pump circulation pump power (W) = 150 W

EHP = heat pump energy (kWh)

EFAN = air handler fan energy (kWh)

ERV energy use is continuously monitored and is used to further disaggregate building 

electricity use. Emisc, which includes appliance, lighting and miscellaneous electric load (MEL) 

energy use, is calculated as the difference between total building electricity use and DHW, 

HVAC, and ERV electricity according to Equation 5.

Equation 5: Emisc = EHSE – Edhw – Ehp – EERV (kWh)

Where: EHSE = total house electricity use (kWh)

EERV = ERV electricity use (kWh)

Additional data: Outdoor temperature and relative humidity are monitored on site. 
16

4 Results

The following results are from evaluation of the S.E.E.D. house, with a focus on whole building 

performance and cost effectiveness.

4.1 System Commissioning

Major commissioning tasks were conducted over two days in April, 2011. The focus of the trip 

was to verify correct operation of the mechanical systems, specifically the heat pump, verify 

correct operation of the monitoring equipment including sensors and communications, and take 

one-time measurements of pertinent data points.

Integrating the zoning, the hydronic and air systems, and heat pump in both heating and cooling 

required some creative on-site revisions to the original design as well as troubleshooting. 

Although efforts were made to use off-the-shelf components, this was not possible in all 

instances. A custom control box was constructed to communicate between the zone thermostats, 

the zone valve controller, the heat pump, and the fan coil. The TACO zone controller is designed 

for heating-only systems; it is not capable of controlling heating and cooling. A residential zone 

control may have worked, but the defrost control may not have been compatible with the AWHP

equipment. A relay was installed to open all floor zone valves when a defrost signal is received 

from the heat pump allowing the heat pump to absorb heat from the entire slab instead of from a 

single zone.

The Aqua Products controls require that a heating call be received from a single zone to activate 

the reversing valve in heating. Therefore, the living room zone was selected as the master zone 

and has to call for heating for either of the other two zones to receive heating. For cooling, the 

controls were able to be set up such that a call for cooling from any zone would initiate heat 

pump operation. 

There was some difficulty wiring the pump into the Aqua Product controls. It was expected that 

if the pump relay output was wired directly to the unit it would operate whenever there was a call 

for heating or cooling; however, at start-up it was found that the pump was not operating at all. A 

second relay was installed between the zone controller and the heat pump. A control schematic 

can be found in Appendix B.

A zone bypass was installed on the radiant floor system to maintain a minimum flow rate 

through the heat pump when only one zone is calling. The monitoring equipment was used to 

verify both pump flow and power under different scenarios. Both flow and power remain 

relatively constant regardless of the number of zones calling.

One-time HERS tests, including duct and building envelope leakage testing, were completed by 

HERS raters contracted by the local utility (Tucson Electric Power). DEG also conducted testing 

to verify fan coil airflow, fan coil power, and pump power. Refer to Appendix C for testing and 

commissioning results.

Cooling operation began with using the floor only for delivery and the air handler turned off. The 

air handler was enabled later in the summer to test mixed-mode delivery performance for 

comparison. During the local monsoon season, the builder discovered that the condensate pan 
17

had been installed incorrectly at a slight slant, not allowing the condensate to drain and causing it 

to pool in the pan. This water then re-evaporated into the supply airstream, resulting in the reintroduction of humidity to the space. Once the issue with the condensate pan was identified, the 

builder fixed the problem by leveling the pan, which facilitated proper drainage, and indoor 

relative humidity decreased. However, relative humidity never exceeded 60% during this period, 

and the occupants did not express any discomfort.

4.2 Short Term Test Results

Following are results of short term tests conducted either by DEG or Tucson Electric Power. Test 

results showed alignment with design expectations. 

Table 4. Results of Short Term Tests

Short Term Test Results

Blower Door Infiltration 2.41 ACH50

(1.48*10-4 SLA)

Duct Blaster Leakage 5.7% (46 cfm)

Cooling Airflow 831 cfm

Heat Pump Circulation Pump 150 W

DHW Recirculation Pump 38 W

Solar System Pump 137 W

4.3 Monitoring Results and Discussion

Whole Building Performance and Comparison

Nine months of monitoring data during occupied times was available for this report (August 

2011 - April 2012). While the monitoring period began before August, the house was unoccupied 

and some of the systems were not operating. The data was analyzed to evaluate electricity use by 

end use, evaluate percent of total building electricity covered by the PV system, and compare 

monitored data to BEopt estimations. Figure 9 shows monthly electricity use by end-use 

including monthly PV system production. Electricity use in August is twice as high as most other 

months due to very high cooling loads. Daily average temperatures ranged from 84o

F to 95oF 

during this month, much higher than other months in the monitoring period. 

Throughout the nine-month period, the 3.4 kW PV offset 71% of total house electricity use. Over 

the course of a year, this percentage may increase since the nine-month period did not cover 

summer, during which time increased solar radiation is available. However, high cooling loads in 

June and July may dampen any gains from increased PV production.

The pie chart in Figure 10 breaks down the relative contribution of each end use over the ninemonth monitoring period. Almost half of total electricity is attributed to lighting, appliances, and 

MELs. Cooling represents 25%, which is a substantial portion considering that most of the 

monitored months with cooling loads are in the swing season. Over half of the heat pump 

cooling energy was expended in August. 
18

Figure 9. S.E.E.D. house 9-month electricity use by end-use

Figure 10. Pie chart showing percentage of total 9-month electricity use by end-use

0

200

400

600

800

1,000

1,200

1,400

August-11 September-11 October-11 November-11 December-11 January-12 February-12 March-12 April-12

Electricity Use (kWh)

App, Ltg, MEL ERV

DHW Heating

Cooling PV Production
19

Figure 11 provides a comparison of monitored energy use with estimates from BEopt. Heating 

and cooling energy use is removed for this comparison since BEopt limitations do not allow for 

accurate modeling of the strategy used in the S.E.E.D. house. While it is a 4-bedroom home, 

there were only one to two occupants for the majority of the monitoring period (two occupants 

during August through December; one occupant from January through April). The BEopt model 

was updated to reflect two bedrooms and similarly two occupants, based on occupancy 

calculations in the House Simulation Protocols (Hendron et al, 2010). After accounting for 

occupancy, monitored data shows about one third less electricity use for all non-HVAC/DHW 

loads than BEopt predicts. ERV use was 27% less than estimated and DHW use was three times 

greater. While the DHW solar collector pump was not monitored and therefore a portion of the 

405 kWh is an estimate, the pump contribution was relatively minor next to the winter electric 

resistance heating. BEopt modeling predicted very little backup water heating. However, while 

monitoring data confirmed this was the case during the summer, fall, and spring, electric 

resistance DHW energy use increased during the winter months as the solar resource and output 

of the solar water heater is reduced. Total DHW electricity use in December was 100 kWh. Total 

monitored and BEopt electricity (including HVAC) were within 2% of one another.

Figure 11. Comparison of 9-month monitored electricity use with BEopt estimate

Load Reduction Strategies

The S.E.E.D. house incorporates a number of energy efficiency measures designed to 

significantly reduce the heating and cooling load on the building, consequently reducing energy 

use and allowing for equipment downsizing. These measures include high R-value SIP walls and 

roofs, high performance low-E windows, slab insulation, air sealing, ducts in conditioned space, 

and an ERV. BEopt was used to investigate the benefits of these various measures by estimating 
20

cooling and heating loads and total energy use percent reductions. The base case used for 

comparison purposes was the B10 Benchmark applied to a home with geometry, orientation, and 

window area of the S.E.E.D. house. Table 5 shows that the most considerable savings from an 

envelope measure are achieved through increasing wall performance from R-13 to almost R-34 

through the use of SIP walls. However, moving ductwork to conditioned space provides even 

greater savings accompanied by significant building load reductions. Parametric run #8 packages 

all the envelope measures together (runs 2-6) resulting in 13% total source energy savings. 

Adding ductwork in conditioned space to the envelope package increases savings to 18% with an 

over 50% reduction in both heating and cooling loads. Instead of a 4-ton unit heat pump in the 

base case, a 2-ton unit can be used and was installed. Heat pump capital cost saving, estimated at 

approximately $925, helps offset incremental costs for the envelope measures. As a comparison, 

forgoing the load reduction measures and installing a high efficiency heat pump (12.5 EER and 

9.0 HSPF) results in 4% source energy savings.

Table 5. Energy and Building Load Savings Comparison of Load Reduction Measures

Parametric 

Run Description

Total 

Source 

Energy

(kBtu/yr)

% 

Energy 

Savings

Heating 

Load

(kBtu/h)

Cooling 

Load

(Tons)

% 

Heating 

Load 

Savings

% 

Cooling 

Load 

Savings

1

BA B10 

Benchmark 

(BC)

201 - 55 3.7 - -

2 BC + SIP walls 188 6% 45 3.1 17% 16%

3 BC + SIP roof 

w/ single ply 197 2% 51 3.5 7% 7%

4

BC + underslab 

& edge 

insulation

199 1% 54 3.7 2% 2%

5 BC + Low-e 

windows 198 2% 53 3.6 4% 3%

6

BC + reduced 

infiltration (2.4 

ACH50)

197 2% 51 3.5 6% 5%

7

BC + ducts in 

conditioned 

space

187 7% 41 2.7 25% 29%

8 Envelope 

Package 175 13% 35 2.5 36% 33%

9

Envelope 

Package + Ducts 

Inside

164 18% 25 1.7 54% 55%

BEopt modeling does not predict any energy benefit through use of an ERV compared to a 

standard exhaust mechanical ventilation system. While there is a decrease in heating energy use 

during the winter, the increased fan energy use results in a net increase in electricity. Monitored 

results of the ERV show average power consumption of 50 Watts when delivering 75 to 80 cfm 
21

and a sensible effectiveness approaching 80% as the temperature difference between indoors and 

outside increase with decreased effectiveness at lower temperature differences.

4.4 Cost Effectiveness and Marketability

The builder’s cost-effective model was to offset the incremental cost of energy efficiency 

measures with cost savings by using basic instead of mid-range or high-end finish products. The 

money invested in tight, insulated enclosures and high efficiency mechanical systems is 

countered by savings from installing base model cabinets, no floor coverings, no tile work or 

granite, fewer accessories, reduced landscaping, etc. Additional detail on this can be found on the 

builder’s website3

. 

Table 6 summarizes as-built cost data provided by the builder for the energy efficiency measures 

incorporated in this project. Incremental costs are based on the builder’s standard elements that 

would be included in a house that the builder normally would construct. Base case costs are 

estimated primarily from contractor bids and provided by the builder. In some cases where data 

was not available, costs were taken from the BEopt cost database. 

Including the cost of the PV system and net utility incentives and tax credits, the total estimated 

incremental cost is around $38,000. Not including PV, the estimated incremental cost is just over 

$32,000. Through a combination of local utility incentives and available state and federal tax 

credits, the builder was able to offset most of the cost of the PV system. As discussed previously, 

the builder offset some of the incremental costs associated with the building efficiency measures 

by specifying basic finish products. The cost savings to the builder via this strategy are not 

presented in Table 6 except when the cost trade is within the same product. For example, cost 

savings for lighting and appliances were achieved by specifying lower cost lighting fixtures and 

base model appliances. Through the trade-off of features and reducing his profit margin from 9% 

to 5%, the builder was able to price the home at $5,000 over what he would normally sell a 

comparable house without any of the energy features.

While in a good housing market this should be an effective marketing strategy, the Tucson real 

estate market continues to suffer greatly since the market crash. Average sale prices of single 

family homes in Tucson are down 17% over the past year4 with an average sale price in 

September, 2011 of $120,000. The trend is similar across low, medium, and high range homes. 

The builder placed the S.E.E.D. house on the market upon completion of construction. While his 

project has received a lot of interest and press within the community, he did not receive any 

serious offers. Because he reduced his profit margin to 5% to sell at almost the same price as a 

similar home without the energy features, he does not have as much flexibility to drop the price, 

which could help sell the home in the current market. After a couple of months he moved in 

himself and has been occupying the home since. As the market improves, the expectation is that 

energy efficiency, especially in middle income homes, will become a much stronger selling 

point. 

 3 http://www.lamiradahomes.net/lamirada_homes_cost_effective.htm

4 http://www.zillow.com/local-info/AZ-Tucson-home-value/r_7481/. Accessed 12/08/11.
22

Table 6. S.E.E.D. Home Measure Costs

Component Builder Standard

Base Case As Built BaseCost

As-Built

Cost

Incremental

Cost

Exterior Walls 2 × 6 frame, R-19 batt 4.5 in. SIP + 1 in. ext. foam $34,800 $48,219 $13,419 Roof Truss, R-30 blown-in 6.5 in. SIP 

Slab No insulation Edge and underslab 

(Creatherm) $2,675 $2,675

4 in.SlabMonoPour w/ slab 

rebar

5 in.Slab/Ftg&Stm no slab 

rebar $15,000 $16,345 $1,345

Windows U-value/SHGC = 0.4/0.3 U-value/SHGC = 0.29/0.21 $3,800 $4,272 $472

Envelope Sealing Standard caulking and 

sealing Extra caulking and sealing $0

HVAC 7.7 HSPF/13 SEER, 4-ton Aqua Products RCS, 2-ton $13,652 $25,026 $11,374

Reverse Cycle Chiller n/a 13 SEER / 8.5 HSPF

included

above

included

above included above

Air Handler 1600 cfm, Ruud or equal MagicAire DUC08, 800 

cfm

Ducting 1600 cfm system, R-8 ducts 800 cfm system, R-6 ducts 

in conditioned space

Radiant Floor/Manifolds none Per plan

Zone Controls/Valves none Per plan

Mechanical Ventilation Exhaust fan, 50 cfm ERV $462 $2,441 $1,979

Water Heating 50 gal. electric, EF = 0.904 Electric, EF = 0.96 $610 N/A -$610

Solar Water Heating None

80 gallon drainback, single 

tank, 1-4x10 Eagle Sun 

AE-40 collector

$4,331 $4,331

Hot Water Recirculation None Pump, time/temp control $400 $400

Lighting 66% incandescent 100% fluorescent $2,350 $1,870 -$480

Appliances Standard efficiency

ENERGYSTAR

refrigerator, dishwasher, 

clothes washer

$6,000 $3,536 -$2,464

PV System None SunPower 3.4 kW DC $24,045 $24,045

Less Utility Incentives / Tax Credits ($18,236)

Total Costs $76,674 $114,924 $38,250

From a perspective of construction, performance and operation, the S.E.E.D. home has met the 

builder’s expectations. He was very happy with the construction of the building envelope, and 

the performance of the building during the hot summer exceeded his expectations. Monitoring 

data shows favorable results in terms of system operation and overall energy use. He has been 

disappointed with the marketability of the home, but at this point attributes it to the current 

market conditions, not the features of the home. 

Savings over the builder standard, as specified in Table 6, were evaluated using BEopt. 

Estimated annual source energy savings are 37% and 74% without and with PV, respectively. A 

cost effectiveness analyses was conducted assuming the costs in Table 6 and annual utility 

savings based on BEopt. This analysis assumes that the incremental cost of the energy efficiency 

measures will be wrapped up into a homeowner mortgage at an interest rate of 5.5% and a loan 

term of 30 years. Utility savings are estimated using average utility rates and escalation rates for 
23

electricity and natural gas of 4% in Arizona A real discount rate of 3% is used. Based on these 

assumptions, the $38,250 incremental cost is not justified and results in a negative average 

annual cash flow of $361. However, a positive average annual cash flow is achieved if the 

incremental cost can be reduced to around $30,000, which is reasonable based on a mature 

market cost analysis conducted for the AWHP strategy alone5. 

In another analysis, when the actual additional cost to the buyer of $5,000 is used, the average 

annual cash flow is positive at $1,120. If the builder were to increase his profit margin back to 

9%, increasing the additional cost to the buyer up to $24,000, the annual cash flow to the

homeowner would still be $265. 

 5 Savings are achieved through reductions in radiant floor costs primarily justified by labor savings and elimination 

of the ducted system. Preliminary analysis has shown that in a hot-dry climate the fan coil is not necessary for 

dehumidification purposes and that the radiant floor can deliver all necessary cooling without risk of floor 

condensation.
24

5 Conclusions and Recommendations 

Whole building energy performance based on nine months of data is better than expected. Total 

electricity use (before PV generation) is within 1% of BEopt estimates and the 3.4 kW PV 

system offset 71% of total house electricity use; actual PV production was 14% greater than 

what BEopt estimated. Good building envelope design and distributed thermal mass all 

contribute to reducing the need for space cooling and providing superior indoor comfort.

The builder’s cost-effective model was to reduce the incremental cost of energy efficiency by 

using basic finish products and reducing his profit margin. These trade-offs allowed the builder 

to price the home at $5,000 over what he would normally sell a comparable house without any of 

the energy features. Using annual energy savings based on BEopt modeling, this incremental 

cost would result in a positive average annual cash flow to the homeowner of $1,120.

While this strategy has not yet been successful in the current Tucson real estate market, which 

has been hit hard by the market crash, the authors theorize that this strategy may be very 

effective in the future as utility costs increase, time-of-use pricing becomes more prevalent, and 

zero net energy homes are encouraged or mandated through regional and/or national energy 

policy. During difficult economic periods, buyers are very focused on price and, as a result, often 

do not consider the performance of the home.

Without considering the builder’s cost tradeoffs, relatively small reductions in incremental cost 

are necessary to make the whole building energy efficiency package cost effective. Significant 

cost reductions in the AWHP are achievable if the technology can gain larger market penetration 

and acceptance. Further cost savings could be achieved with the elimination of ducted 

distribution for cooling. Due to the prototype nature of this project, the HVAC system costs were 

much higher than would be expected if installed by a contractor more familiar with this strategy. 

Contractor familiarity is expected to increase in the future as radiant systems gain greater market 

acceptance due to their comfort and efficiency benefits. Other potential cost savings may 

include: a) heat pump water heating or condensing gas technologies for water heating in place of 

solar water heating; b) less expensive heat recovery products and climate-specific evaluation to 

identify the most cost-effective mechanical ventilation strategies; and c) other methods of 

achieving high R-value walls and roof other than high cost SIP assemblies.
25

References

ACCA (2006). “Manual J Residential Load Calculations, Eighth Edition.” Air Conditioning 

Contractors of America.

ACCA (2009). “Manual D Residential Duct Systems.” Air Conditioning Contractors of America.

AHRI (2005). ANSI/AHRI Standard 1060. “2005 Standard for Performance Rating of Air-to-Air 

Exchangers for Energy Recovery Ventilation.” Air-Conditioning, Heating, and Refrigeration 

Institute. 

ARBI (2011a). “Draft Technical Report: Air-to-Water Heat Pumps with Mixed-Mode Delivery”. 

Prepared for Building America by the Alliance for Residential Building Innovation. December, 

2011.

ARBI (2011b). “Test Plan: S.E.E.D. House, La Mirada Homes”. Prepared for Building America 

by the Alliance for Residential Building Innovation. August, 2011.

ASHRAE (2004). ANSI/ASHRAE Standard 152-2004. “Method of Test for Determining the 

Design and Seasonal Efficiencies of Residential Thermal Distribution Systems.” American 

Society of Heating, Refrigeration, and Air-Conditioning Engineers. 

ASHRAE (2010). ANSI/ASHRAE Standard 55-2010. “Thermal Environmental Conditions for 

Human Occupancy.” American Society of Heating, Refrigeration, and Air-Conditioning

Engineers. 

Hendron, R.; Engebrecht, C. (2010). Building America House Simulation Protocols. Golden, 

CO: National Renewable Energy Laboratory. NREL/TP-550-49246. 

Springer, D.; Eastment, M.; Dakin, W.; Rainer, L. (2008). “Comparative Performance of Four 

Prototype Mechanical Systems in a Desert Climate.” ASHRAE Paper #SL-08-061. June, 2008.
26

Appendix A: Floor Plan and Construction Details

Figure A - 1. Floor plan
27

Figure A - 2. Wall, roof, and foundation details
28

Appendix B: Mechanical System Controls Schematic

The control diagram and associated description for the heat pump and zone control are shown in 

Figure A - 3.

Figure A - 3. Mechanical system controls schematic

ZONE VALVES

1

TACO ZVC403

ZONE VALVE CONTROL

END

SWITCH N/O COM N/C 1 2 3 4

ZONE 1

1 2 3 4

ZONE 2

1 2 3 4

ZONE 3

T T

ZONE 1

T T

ZONE 2

T T

ZONE 3

R C

2 3

H

M

L

C

FAN

MOTOR

BLACK

BLUE

RED

FAN COIL

WHITE

DESCRIPTION OF OPERATION

Z1 Z2 Z3 R/ES ES C

HEAT PUMP

OMROM MY3-AC24(S)

3PDT 24VAC RELAYS

INTERFACE BOX WITH

H

E

A

T

C

O

O

L

C Y1

W1

R C

AQUA PRODUCTS RCS

R W2 Y B/O R W Y R W Y

ZONE1

GREAT ROOM

ZONE 2

M. BEDROOM

ZONE 3

W. BEDROOMS

THERMOSTATS

PUMP RELAY

PUMP

120 V

N

L1

240V

POWER

L1

L2

HEATING: A heating call from the Zone 1 

master thermostat activates the interface 

relay, causing the heat pump to operate in 

heating mode. On a call for heating from

any thermostat, the "W" signal passes

through the interface relay to the zone control.

The zone control opens the corresponding

zone valve. When the zone valve is open the

zone control end switch signals the "Y/W"

input to the heat pump, causing it to run in

heating mode. The zone control relay enables

the fan coil to operate (if the manual switch

is in the on position).

COOLING: The Zone 1 master thermostat

is set to "Cool" causing the heat pump to

operate in cooling mode. On a call for

cooling from any thermostat, the "Y" signal

passes through the interface relay to the

zone control. The zone control opens the

corresponding zone valve. When the zone

valve is open the zone control end switch

signals the "Y/W" input to the heat pump,

causing it to run in cooling mode. The zone

control relay simultaneously starts the

pump and activates the fan coil relay,

causing it to run the fan. The manual switch

can be used to disable the fan coil.

RELAY

ZONE CONTROL

C R Y/W CL HT DEF

Y W R Y W R

THERMOSTATS A/H

W2 Y B/0 R W C

ZONE 1 ZONE 2 ZONE 3 AUX HT

R1

R2

DEFROST

6

2 4

5

1 3

R

C

W1

W2

G

6

5

4

3

2

1

W2

W1

C

CBC2

TB2

1

2

3

4

L1

FAN

L2

240 VAC

MANUAL

FAN SWITCH

DEFROST: On receiving a

defrost signal from the heat

pump the interface control

will open all zone valves,

allowing the heat pump to

obtain defrost cycle heat

from the entire slab.

RED

BRN

ORN

VIO

BLK

BLK

YEL

RED

VIO

ORN

BRN

L2

L1

CBC1 BLK

RED

RED

BLK

RED

RED

STRIP HEAT SECTION

BRN

ORN

NOTE: MEASURE VOLTAGE

BETWEEN 'C' LEG OF FAN COIL

TRANSFORMER & 'C' LEG AT

INTERFACE BOX BEFORE

CONNECTING TO TB2 TO

INSURE THEY ARE IN PHASE.

REVERSE 24V WIRES AS NEEDED.

R

C

EMERGENCY HEAT: On a

2nd stage heat call from the

Zone 1 thermostat (only), the

interface box signals the

fan coil relay to activate

strip heat and run the fan 

at medium speed.

Set Zone 1 thermostat

changeover switch to 'B'.

NOTE: DISCONNECT

TRANSFORMER FROM

TERMINAL.

S.E.E.D HOUSE MECHANICAL SYSTEM CONTROLS 4/7/11
29

Appendix C: Short Term Testing and Commissioning Results

SYSTEM/SENSOR COMMISSIONING

Preparation and Base Load Measurement

 Shut off breakers for water heater element, refrigerator, microwave, range, washing 

machine, and PV system.

 Run hot water tap (bathtub) to deplete solar storage (didn’t do)

 Shut off the ERV.

 Unplug solar pump.

 Unplug recirc pump.

 Wait 5 minutes while base load is being measured.

Verify Hydronic System Operation

 Install flowmeters and recharge system

 Review control wiring, verify transformer in zone control is disconnected

 Disconnect heat pump compressor from contactor

 Unplug heating pump from switched outlet and plug into live outlet.

 Set all thermostats to cool and power up heat pump

 Verify pump operation

 Set up logger to read flow and set logger spans correctly

 Manually open Zone 1 (guest bedrooms) and wait 5 minutes while pump power and flow 

are recorded

 Manually open Zone 2 (living) and wait 5 minutes.

 Manually open Zone 3 (master bedroom) and wait 5 minutes.

 Adjust bypass valve to ensure a minimum flow of 5gpm in all zone calling scenarios

Table A - 1. Hydronic System Flow Rate with Various Zones Calling

Zones Calling Flow Rate 

(gpm)

All open 6.21

Zone 1 only 5.72

Zone 2 only 5.69

Zone 3 only 5.69

Zone 1 & 2 only 5.74

All closed 5.65

DHW Pump Power Tests

Solar Pump (could not test – leak in solar collector)

 Plug in the solar pump.

 Wait 5 minutes (after pump starts running)
30

 Unplug and turn off water.

Recirc Pump

 Plug in recirc pump and set to “manual on.”

 Wait 5 minutes while pump power is recorded.

Air Handler Airflow Tests

To check supply/return temperature calibration:

 Turn on switch at fan coil.

 Unplug the pump from live outlet.

 Close coil bypass valve (noting original position).

 Activate Living Room thermostat in cooling mode (verify fan operation)

 Wait 5 minutes while supply/return sensors are checked.

To measure airflow:

 Plug the pump into the switched outlet.

 Set Living Room thermostat to heat and raise temperature until it turns on the heat pump.

 Manually close the zone valve for the Living Room.

 Wait 15 minutes or until supply/return temperature difference stabilizes.

Restore System

 Set Living Room thermostat to 78 (cooling mode). 

 Reset the position of the coil bypass valve.

 Turn on breakers that were turned off in Step 1, Preparation.

 Plug in the solar pump.

 Turn on the ERV.

 Set recirc pump to “timer.”

HERS TESTS

Duct tightness test

 Test total duct leakage 24 supply/22 return: 46 cfm total leakage

Blower door 

 Test building leakage with blower door (CFM50 < 1935) 750 CFM50

One Time Measurements

 Verify fan coil airflow 831 cfm

 Measure solar pump power 137 Watts

 Measure heat pump circulation pump power 150 Watts

 Measure DHW recirculation pump power 38 Watts
DOE/GO-102012-3701 ▪ December 2012

Printed with a renewable-source ink on paper containing at 

least 50% wastepaper, including 10% post-consumer waste.