ashrae hq renovation library/about/new hq/ashrae-hq-hva… · hvac option 1: all-air tzhp system...

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)