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17 April, 2019
ASHRAE HQ HVAC System Updates
4.17.2019
17 April, 2019
TZHP
Ceiling fans
(bidirectional)
Overhead air
distribution
Operable windows for
natural ventilation
HVAC Option 1: All-Air TZHP SystemTZHP – Thermodynamically Zoned Heat Pumps
System Type
Rooftop Packaged Thermodynamically Zoned
ASHPs with DOAS, enthalpy heat recovery,
DCV, and a desiccant wheel
Air Distribution Options
Overhead, Mixed Air
Mixed-Mode Ventilation
Operable windows and atrium exhaust
Ceiling fans with reverse control
Night-Flush / Airside Economizer
Fan-assisted night flush
17 April, 2019
DOAS
With enthalpy heat recovery and DCV
Option 1A: Add desiccant wheel
Option 1B: Add DX Trim Coil
CW Terminal Unit Options
Radiant Ceiling Panels
Sensible Fan Terminal Units
Heat Pump Options
Option A: Air-Cooled HP
Option B: Water-Cooled HP
Option C: Ground-Source HP
Night-Flush & Mixed-Mode Ventilation
See Previous
DOAS
Radiant Sails
Ceiling fans
(bidirectional)
FCU
HVAC Option 2: Hydronic SystemsDOAS with Hydronic Terminal Units DOAS distribution
Option C
Geo/Lake exchange
Heat pump
Option B
Cooling tower
Option A
Air-Cooled
17 April, 2019
All-Air TZHP vs. Hydronic System
29.3
24.8
20.5
16.715.6
0
5
10
15
20
25
30
ASHRAE 90.1-2016
BASELINE
RECOMMENDED
ENVELOPE
STRATIFIED
PROGRAM
OPTIMIZED
ALL-AIR SYSTEM
PASSIVE
NIGHT FLUSH
ACTIVE
NIGHT FLUSH
ATRIUM
INTERVENTION
DOAS + CHW
TUS + ASHP
PASSIVE
NIGHT FLUSH
ACTIVE
NIGHT FLUSH
ATRIUM
INTERVENTION
FANS PUMPS COOLING HOT WATER HEATING LIGHTING PLUG LOADS
ANNUAL SITE ENERGY USE
AN
NU
AL S
ITE E
NER
GY U
SE
INTEN
SIT
Y (
KB
TU
/FT²/
YEA
R)
Path to NZE Recap
NZE Target 21.4 kBTU/ft2/yr
Stretch Target 15.0 kBTU/ft2/yr
Option 1: All-Air TZHP System Option 2: Hydronic System
17 April, 2019
Potential Night-flush Impact
29.3
24.8
20.5
16.7 16.615.6 15.5
0
5
10
15
20
25
30
ASHRAE 90.1-2016
BASELINE
RECOMMENDED
ENVELOPE
STRATIFIED
PROGRAM
OPTIMIZED
ALL-AIR SYSTEM
PASSIVE
NIGHT FLUSH
ACTIVE
NIGHT FLUSH
ATRIUM
INTERVENTION
DOAS + CHW
TUS + ASHP
PASSIVE
NIGHT FLUSH
ACTIVE
NIGHT FLUSH
ATRIUM
INTERVENTION
FANS PUMPS COOLING HOT WATER HEATING LIGHTING PLUG LOADS
ANNUAL SITE ENERGY USE
AN
NU
AL S
ITE E
NER
GY U
SE
INTEN
SIT
Y (
KB
TU
/FT²/
YEA
R)
Passive Night Flush
• HVAC fans operating
• 10PM - 5AM, April – September
• 55ºF < OAT < 70ºF
• Highly thermally massive concrete slabs
pre-cool office spaces
• Strategy reduces EUI by 0.1 kBtu/sf
• Reduced cooling EUI
• Fan EUI penalty for nighttime fan
operation
Option 1: All-Air TZHP System Option 2: Hydronic System
17 April, 2019
29.3
24.8
20.5
16.7 16.617.3
15.6 15.5 16.1
0
5
10
15
20
25
30
ASHRAE 90.1-2016
BASELINE
RECOMMENDED
ENVELOPE
STRATIFIED
PROGRAM
OPTIMIZED
ALL-AIR SYSTEM
PASSIVE
NIGHT FLUSH
ACTIVE
NIGHT FLUSH
ATRIUM
INTERVENTION
DOAS + CHW
TUS + ASHP
PASSIVE
NIGHT FLUSH
ACTIVE
NIGHT FLUSH
ATRIUM
INTERVENTION
FANS PUMPS COOLING HOT WATER HEATING LIGHTING PLUG LOADS
ANNUAL SITE ENERGY USE
AN
NU
AL S
ITE E
NER
GY U
SE
INTEN
SIT
Y (
KB
TU
/FT²/
YEA
R)
Potential Night-flush Impact
Active Night Flush
• HVAC fans and cooling coils operating
• 10PM - 5AM, April – September
• 55ºF < SAT < 70ºF
• Active cooling engaged at night
(nighttime COP > daytime COP)
• Strategy increases EUI by 0.6 kBtu/sf
• Cooling EUI penalty (cannot
provide enough pre-cooling to
overcome daytime cooling needs)
• Fan EUI penalty for nighttime fan
operation
Option 1: All-Air TZHP System Option 2: Hydronic System
17 April, 2019
Atrium Impact
29.3
24.8
20.5
16.7 16.617.3
14.715.6 15.5 16.1 14.5
0
5
10
15
20
25
30
ASHRAE 90.1-2016
BASELINE
RECOMMENDED
ENVELOPE
STRATIFIED
PROGRAM
OPTIMIZED
ALL-AIR SYSTEM
PASSIVE
NIGHT FLUSH
ACTIVE
NIGHT FLUSH
ATRIUM
INTERVENTION
DOAS + CHW
TUS + ASHP
PASSIVE
NIGHT FLUSH
ACTIVE
NIGHT FLUSH
ATRIUM
INTERVENTION
FANS PUMPS COOLING HOT WATER HEATING LIGHTING PLUG LOADS
ANNUAL SITE ENERGY USE
AN
NU
AL S
ITE E
NER
GY U
SE
INTEN
SIT
Y (
KB
TU
/FT²/
YEA
R)
Atrium Intervention
• Atrium model updated to match current
proposed design
• Reduced atrium height
• Reduce atrium glazing
• Additional overhangs
• Atrium peak load reduced by more than
50%
• Overall EUI reduced by 1-2 kBtu/sf
Option 1: All-Air TZHP System Option 2: Hydronic System
17 April, 2019
Life Cycle Cost Analysis (LCCA): HVAC Options A & B
-$1,400,000
-$1,200,000
-$1,000,000
-$800,000
-$600,000
-$400,000
-$200,000
$0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Years
Cumulative Cost Difference OPTION 1 - ALL-AIR SYSTEM (TZHP):
• First Cost $1,856,000
• Replacement Cost $281,500 every 15 years
• Maintenance $28,600 per year
• Life-Cycle Cash Flow (NPV): $5,179,476 ($1,032,241 less money
spent than Option 2 over a 30 year period)
OPTION 2 - HYDRONIC SYSTEM:
• First Cost $2,913,000;
• Replacement Cost $322,700 once at 25 years;
• Maintenance $41,200 per year
• Life-Cycle Cash Flow (NPV): $6,211,718 ($1,032,241 more
money spent than Option 1 over a 30 year period)
