Heating, ventilating and air-conditioning (HVAC) typically accounts for 30% to 50% of commercial building energy use. Small commercial buildings often use oversized and inefficient rooftop air handling units (RTUs) to provide both air conditioning and ventilation. A conversion strategy to reduce energy consumption is the installation of a very high efficiency dedicated outdoor air system (DOAS) to provide ventilation with a separate heat pump system to provide heating and cooling. Decoupling the heating and cooling from ventilation allows for improved energy efficiency and control of space conditions. Upgrades to mechanical systems can also improve the indoor air quality (IAQ) and comfort through control of carbon dioxide (CO2) concentrations, dry bulb temperature, and relative humidity (RH). A pilot study of eight buildings was conducted to investigate the potential benefits of replacing existing RTUs with high efficiency heat recovery ventilators (HRVs) and air source heat pumps in the Pacific Northwest. This report contains results for a subset of seven buildings for which data is available. The building energy use before and after the conversion was determined using utility data, energy modeling and monitoring. Indoor environmental conditions were measured at hourly intervals for up to one year postconversion using CO2, temperature, and RH sensors. The data was analyzed to determine changes in energy use and IAQ before and after the conversion. This paper presents the pilot building results pre- and post-conversion. While several factors need to be in place to ensure optimal performance and cost effectiveness, the pilot shows that replacing RTUs with DOAS systems in existing commercial buildings can both reduce energy use as well as improve indoor environmental conditions. This conversion type is viable for a wide variety of building types and scale-up of the retrofits has the potential to significantly improve a previously underserved segment of the building stock. Presented by James Montgomery at the 15th Canadian Conference on Building Science and Technology.

1. 1
Energy and Indoor Air Quality Impacts of
DOAS Retrofits in Small Commercial Buildings
15TH CANADIAN CONFERENCE ON BUILDING SCIENCE AND TECHNOLOGY
NOVEMBER 7TH, 2017
PRESENTED BY:
JAMES MONTGOMERY, PHD

2. 2
 Background
 Methodology
 Results
 Lessons Learned (to date)
Outline

3. 3
Background

4. 4
Pilot Project Overview
 Early pilot work funded by the Northwest Energy Efficiency
Alliance (NEEA)
 New high efficiency Heat Recovery Ventilation (HRV) unit
 Vertical mounting for existing RTU ductwork
 1000 cfm max flow
 Greater than 80% sensible heat recovery efficiency

5. 5
Pilot Project Overview
 Target Building Sector:
 Small commercial (< 25,000 ft2)
 Includes small office, retail, schools, restaurants, small
assembly
 Makes up approx. half of the commercial building floor area in
the Pacific Northwest.
 Smaller HVAC systems; typically not engineered.

6. 6
Pilot Project Overview
Ventilation +
Heating (or Cooling)
Outdoor
Air
Return Air
Exhaust
Air
Packaged Rooftop Unit

7. 7
Pilot Project Overview
Dedicated Outdoor Air System
Outdoor Air
Ventilation Exhaust
Air
Heat Recovery
Exhaust Air
Heat Pump
Zone-Level
Heating (or
Cooling)

8. 8
Pilot Projects
 8 pilot projects to date
#4 Office
Libby MT#6 Office
Seattle WA
Dorm #8
Darby MT
#1 Office
Portland OR
#3 Restaurant
Corvallis OR
#5 Restaurant
Portland OR
#2 Office
Corvallis OR
#7 Office
Seattle WA

9. 9
# Location
Building
Type
Occupied Hours
Conditioned
Area, ft2 (m2)
1 Portland, OR Office M-F, 7am-6pm
11,600
(1,080)
2 Corvallis, OR Office M-F, 8am-5pm
13,200
(1,225)
3 Corvallis, OR Restaurant
Su-W, 11am-11pm
Th-Sa, 11am-12am
1,600
(162)
4 Libby, MT
Office w/
Garage
M-F, 9am-5pm
5,600
(520)
5 Portland, OR Restaurant
M-F, 11am-9pm
Sa-Su, 9am-9pm
1,150
(110)
6 Seattle, WA Office M-F, 9am-5pm
5,900
(550)
7 Seattle, WA Office M-F, 8am-5pm
24,300
(2,260)
Wide range
of climates
Applicable to most
building types
Size ranges from
~1,150ft2 to 24,300ft2

10. 10
Pilot Project Overview
 PART 1: Establish Baseline Conditions
 PART 2: Calibrate Baseline Energy Model
 PART 3: DOAS Conversion
 PART 4: Establish Post-Conversion Conditions
 PART 5: Calibrate Post-Conversion Energy Model

11. 11
Methodology

12. 12
Pre-Conversion Baseline Model Calibration
 Calibration based on monthly electricity and natural gas bills
0
10
20
30
40
50
60
70
80
0
2
4
6
8
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
OutdoorDryBulb(°F)
EUI(kBtu/ft2)
CVRMSE: 2.1 (elec) / 6.4 (gas)
NMBE: 3.8 (elec) / 2.1 (gas)
Coefficient of Variation of the Root Mean Squared Error (CVRMSE) < 10% and Normalized Mean Bias Error (NMBE) <
5% as per ASHRAE Guideline 14 for calibration of whole building energy simulation to monthly utility data.
Actual Elec/Gas (2014) Modeled Elec/Gas (2014)

13. 13
Post-Conversion Comparison
 Comparison of modeled TMY to actual post-conversion use
 Re-calibration done after 1-year post-conversion data
0
10
20
30
40
50
60
70
80
0
2
4
6
8
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
OutdoorDryBulb(°F)
EUI(kBtu/ft2
)
Modeled Elec/Gas (TMY) Actual Elec/Gas (2016/17)
Avg Monthly Temp (2016/17) Avg Monthly Temp (TMY)
Actual Elec/Gas (2016/17) Modeled Elec/Gas (TMY)

14. 14
Monitoring Equipment
 Energy Data
 Utility Billing
 Electricity Sub-metering
 Indoor Environmental Quality
 Carbon Dioxide
 Temperature
 Relative Humidity

15. 15
Air Leakage Testing
 Conducted pre- and post-conversion
 US Army Corps of Engineers (USACE) test protocol

16. 16
 Energy Savings
Summary of Project Results

17. 17
Summary of Energy Savings
 Pre and Post-Retrofit energy end use breakdown compared
Offices Restaurants
0
50
100
150
200
250
300
350
EUI(kWh/m2)
Fans
Cooling
Heating
Other
PRE-CONVERSION
POST-CONVERSION
NOT
MODELLED
0
500
1000
1500
2000
2500
3000
3500
4000
EUI(kWh/m2)

18. 18
Summary of Energy Savings
Pre,
kBtu/ft2
(kWh/m2)
Post,
kBtu/ft2
(kWh/m2)
Savings
Pre,
kBtu/ft2
(kWh/m2)
Post,
kBtu/ft2
(kWh/m2)
Savings
1
Portland,
OR
Office
48
(153)
14
(44)
71%
63
(200)
29
(91)
54%
2
Corvallis,
OR
Office
33
(103)
25
(80)
22%
57
(180)
50
(158)
13%
3
Corvallis,
OR
Restaurant
313
(990)
146
(461)
53%
1,082
(3,418)
914
(2,890)
15%
4
Libby,
MT
Office/Garage
84
(265)
45
(141)
47%
105
(333)
66
(209)
37%
5
Portland,
OR
Restaurant
193
(609)
58
(182)
70%
773
(2,444)
638
(2,017)
17%
6
Seattle,
WA
Office
19
(60)
10
(33)
45%
42
(133)
34
(106)
20%
7
Seattle,
WA
Office TBD TBD TBD TBD TBD TBD
22% to 71% 13% to 54%

19. 19
 Air Leakage
Summary of Project Results

20. 20
Air Leakage Testing
 Typical leakage ~0.2 to 0.5 cfm/ft2 @75Pa (1.0 to 2.5 L/s·m2)
 Building #3 (restaurant) was an outlier <1.6 cfm/ft2 @75Pa (8.1 L/s·m2)
due to kitchen equipment openings
 51% decrease in Building #4: removal of two swamp coolers
 23% increase in Building #6: difficulty sealing ductwork between floors
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
EnclosureAirLeakage
(cfm/ft2@75Pa)
Pre-conversion
Post-conversion
NotTested

21. 21
 Temperature
Summary of Project Results

22. 22
0
20
40
60
80
100
120
60
70
80
90
100
OutdoorDryBulb(°F)
InteriorTemperature(°F)
Office 6 Office 3 Reception Outdoor Dry Bulb
Post-conversion
Pre-conversion
HVACConversion
Drybulb Temperature – Building #2 – Office, Oregon
 Primary use: confirm space setpoint/setback being met
 Secondary use: troubleshooting and optimizing operation
 Initially tight control of space temperature
 Occupant adjustments causes deviation
 Spaces deviate but small temperature band in each

23. 23
0
20
40
60
80
100
120
60
70
80
90
100
OutdoorDryBulb(°F)
InteriorTemperature(°F)
Back Front Outdoor Dry Bulb
Post-conversionPre-
conversion
HVACConversion
Drybulb Temperature – Building #3 – Restaurant, Oregon
 Primary use: confirm space setpoint/setback being met
 Secondary use: troubleshooting and optimizing operation
 Significant daily variations in space temperature
 Challenges maintaining setpoint during summer

24. 24
 Carbon Dioxide
Summary of Project Results

25. 25
0
20
40
60
80
100
120
0
400
800
1200
1600
2000
2400
2800
OutdoorDryBulb(°F)
CO2Concentration(ppm)
Open Office Private Office Garage
Post-conversionPre-conversion
HVACConversion
Building #4 – Office, Montana
 Pre-conversion ventilation system provided good IAQ
 Reduction in peak CO2 concentration post-conversion

26. 26
0
20
40
60
80
100
120
0
400
800
1200
1600
2000
2400
2800
OutdoorDryBulb(°F)
CO2Concentration(ppm)
Back Front Outdoor Dry Bulb
Post-conversionPre-
conversion
HVACConversion
Building #3 – Restaurant, Oregon
 Pre-conversion CO2 variation is significant, concentration
often in excess of 1,000ppm
 Post-conversion concentration shows minor reduction in peak
concentration
 Greatest concentration is after HRV operating hours (staff
clean-up)

27. 27
Carbon Dioxide Concentration
Project
Number
Occupancy
Frequency
above
1000ppm
Pre
Frequency
above
1000ppm
Post
Average
Occupied Pre
Average
Occupied
Post
1 Office N/A 0.2% N/A 500
2 Office 0.7% 0.1% 615 565
3 Restaurant
23% 15%
900 740
4 Office/Garage
2.6% 0.1%
620 545
5 Restaurant
7.2% N/A
760 N/A
6 Office N/A 0.0% N/A 500
7 Office 0.0% 2.7% 480 560
Project
Number
Occupancy
Frequency
above
1000ppm
Pre
Frequency
above
1000ppm
Post
1 Office N/A 0.2%
2 Office 0.7% 0.1%
3 Restaurant
23% 15%
4 Office/Garage
2.6% 0.1%
5 Restaurant
7.2% N/A
6 Office N/A 0.0%
7 Office 0.0% 2.7%
Project
Number
Occupancy
1 Office
2 Office
3 Restaurant
4 Office/Garage
5 Restaurant
6 Office
7 Office
0% to 24%
0% to 15%
480 to
900ppm
500 to
740ppm

28. 28
Lessons Learned

29. 29
Lessons Learned
 Successful DOAS conversion depends on several
factors, including:
 Reduction in ventilation air volumes; demand controlled
ventilation (DCV)
 Very low ventilation fan power (0.5 Watts/cfm or less)
 Very high ventilation heat/energy recovery efficiency
 Can be a challenge due to limited equipment meeting
required specifications
 Implementation has led to a number of lessons
learned:

30. 30
Air Leakage
 Commissioning of HRV airflow at diffusers found rates up to 25% below
design conditions
 Initial solution from contractors was to increase the airflow rate at the
HRV until space supply flowrates were met
 Root cause identified to be air leakage at ductwork at fittings
 Challenges repurposing existing ductwork due to the leaks
 Care required at new duct joints

31. 31
Contractor Education
 Several pilots initially specified old equipment capacity
 Relied heavily on design assistance from heat pump equipment
suppliers
 Typically leads to extra features
 Tools and/or technical support for selecting proper equipment
required for broad scale implementation

32. 32
Occupant Education
 Operation changes required to account for the separation of the ventilation
from A/C
 Occupants initially hesitant to adjust setpoint temperature despite
dissatisfaction with the indoor temperature
 Others made changes without understanding the impact
 Proper instruction around the intended system operation and periodic follow-
up is required to ensure both comfort and energy goals are achieved

33. 33
Discussion + Questions
FOR FURTHER INFORMATION PLEASE VISIT
 www.rdh.com
 www.buildingsciencelabs.com
OR CONTACT US AT
 jmontgomery@rdh.com