Retrocommissioning of Existing Buildings

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Retrocommissioning of Existing

Buildings

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Presenters

Manus McDevitt, PE, LEED AP

Principal

Sustainable Engineering Group,

Madison, WI

Alex Harris,

Engineer

Sustainable Engineering Group,

Madison, WI

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• Understand the motivation and methods for

accomplishing Retrocommissioning (R-Cx)

• Appreciate the value of Retrocommissioning

by considering several case studies

• Recognize some typical issues uncovered by

Retrocommissioning

Learning Objectives

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What is Retro-Cx?

The process of optimizing the

performance of an existing building

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Retrocommissioning Benefits

• Improve building performance

• Provide appropriate training

to O&M staff

• Improve occupant comfort

• Improve system reliability

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Commercial

Industrial

Transportation

Residential

Buildings

Environmental Impact of Buildings

U.S. Energy Consumption by Sector – 2000

98.5 Quadrillion Btu

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When is Retro-Cx Appropriate?

When there is a good chance of success!

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Approach - Overview

1. Gather Information

2. Identify improvements

3. Monitor implementation

4. Functional testing

5. Update documentation, train operators

6. Final report

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From Stakeholders

From DocumentationFrom Observation

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Deliverables

• Operational Intent

– Narratives of facility functional use

– Verifiable performance criteria

– Stakeholder requirements for

• usability, operability, maintainability, functionality

• Basis of Operation

– Documents current building operation

• Installed equipment database

• Control sequences

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10,000SF Office Building Energy Use

Mid-West US (Chicago)

Space Heating,

32%

Space Cooling,

8%

Ventilation , 5%

Water Heating ,

10%

Lighting , 26%

Other, 19%

Building Energy Usage

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Approach - Overview






6. Final report

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2. Identify Improvements

• Can the system meet your requirements?

– If so, tune the system to meet your needs

• Examples: Calibrate sensors, adjust control sequences, repair or

replace equipment

– If not, re-design the system as required

• Costs and savings for each improvement

– Prioritize

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Deliverable

• Facility Optimization Study

– Narrative and technical evaluation of each improvement opportunity

– Estimate of project costs

– Analysis of utility savings and other benefits

– Includes:

• Discussion of documentation improvements

• Discussion of training needs

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Audit / Investigation Phase

• Collaborate with facilities

team to identify opportunities

• Review building drawings

and documentation

• Performance testing of

building systems

• Develop list of recommended

improvements

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Potential Measures

• Operational

– Equipment schedules, set points,

• Maintenance

– Valve and damper control issues

• Design

– Identify space function changes, control optimization

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Common Problems Identified

• Time clocks disabled

• Control sequences not optimized

• Energy Management Systems not understood or fully utilized

• Controls/sensors/actuators out of calibration

• Ventilation excessive

• Documentation & training inadequate

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VAV Scheduling

15 kW

Fan Savings

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VAV Scheduling

0

200

400

600

800

1000

1200

8/14/13 8:00:00 PM CDT 8/14/13 10:30:00 PM CDT 8/15/13 1:30:00 AM CDT 8/15/13 5:00:00 AM CDT

Tota

l VA

V B

ox

Reh

eat

(kB

tu/h

r)

AHU-14/15 VAV Box Reheat

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Data Room Setpoints

Data room set-

points are too tight

for temperature and

humidity, leading to

excessive energy

use.

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Adjust CRAC Set Points

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Adjust CRAC Set Points

Annual kW-Hr

Savings

Annual Savings Implementation

Cost

Simple Payback

150,000 $10,391 $50 2 days

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AHU Chilled Water Valve Control Issue

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Cooling Tower Exhaust Dampers & Ductwork

Supports have rusted

out and fell into tower

Dampers linkages are corroded

and not functional

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Disconnected Actuator

Disconnected

actuator is causing

cooling tower to run

at the same time as

boiler. We are heating

the water, only to

reject the heat to the

outdoors

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Cracked Heat Exchanger

There is risk of

carbon

monoxide being

blown into the

occupied

space. Unit

was shutdown

and gas line

shut-off to unit.

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Duct to Nowhere

Supply duct is

blowing into

plenum space.

This area was

remodeled and

drop ceiling

added, but the

duct was never

capped, as

shown on

remodel plans.

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Poor Sensor Location

Heat pump

serving this

space is always

in cooling, even

though the

room

temperature is

65°F.

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Approach - Overview






6. Final report

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3. Monitor Implementation

RCx provider’s role varies depending on

1. Needs of the client

2. Number and complexity of improvements

3. Type of improvements

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Approach - Overview






6. Final report

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4. Functional Testing

• RCx provider’s role varies

• Verify the performance of building systems

• May use statistical sampling

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Approach - Overview






6. Final report

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5. Documentation & Training

• Update documentation

– Drawings

– O & M manuals

– Operating sequences

– Equipment database

– Maintenance schedules

• Schedule training

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Approach - Overview






6. Final report

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6. Final Report

• Based on the Facility Optimization Study

– Includes discussion of implemented projects and testing

– Reference document for future projects and operations

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Persistence

Phase:

Verify

Persistence

of Savings

(Optional)

Implementation Phase:

Implement Selected

Measures & Verify Actual

Savings

Audit Phase:

Complete Audit &

Quantify Measures

Qualify

Customer

& Submit

Application

Focus on Energy RCx Process

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Medical Clinic

• Established in 1996

• 22 Clinics

• 2 million+ outpatient visits

• 1 South Park Street

• 174,000 ft2

• 6 OR’s

• 2 MRI’s

• 392 kBtu/ft2-yr (source)

Medical Clinic, Madison, WI

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Medical Clinic

Proposed Phase Workbook

Description

Electric

Energy

Savings

(kW-hr)

Electric

Demand

Savings

(kW)

Natural

Gas

Savings

(Therms)

Measure

Installatio

n

Incentive

($)

Energy

Cost

Savings

($)

Measure

Cost ($)

Simple

Payback

(Years)

M1On all air handlers, increase economizer

switchover from 51.5°F to 68°F 101,130 - - N/A $7,079 $100 0.0

M2Modify air handler schedules 123,599 - 5,727 N/A $10,617 $100 0.0

M3 Replace RTU-2 Control Board 44,800 - 5,880 N/A $6,570 $500 0.1

M4Replace 52W Incadescent Bulbs with

CFL's 6,841 1.8 -134 N/A $231 $200 0.9

M5Install lighting occupancy sensors on

Floors 5, 6, 7 and lower level 19,314 - -358 N/A $1,098 $9,100 8.3

Proposed Phase Savings

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Medical Clinic

Project Summary

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Medical Clinic

Persistence CheckGreat Persistence:

• Controls programming changes

• VFD Installs

• Equipment Upgrades

Poor Persistence:

• Schedule modifications

• Set point modifications

• Fixing valves / equipment

(Grease Fan BRGS Yearly!!)

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Medical Clinic

Performance Since Implementation

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100

200

300

400

500

600

700

1 2 3 4 5 6 7 8 9 10 11 12

Ele

ctr

ic C

on

su

mp

tio

n (

MW

-hr)

Month of year (January = 1, December =12)

Monthly Electric Consumption

2009 2010 2011 2012 2013-Pre RCx 2013 2014

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Portfolio Manager Tracking

Before After

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Medical Clinic

Review of Incentives Paid Out

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Medical Clinic

Evaluate Economics

• Savings

$66,000/yr utility cost avoidance

• Expenses

$50,000 study cost

$30,000 implementation cost

• Incentive

+$63,000 incentive

• Simple Payback = 0.3 years (after incentive)

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505 Passenger Vehicles / Year

62,000 trees grown for 10 years

121 Homes / Year

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Solar Equivalent of Electric Savings

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Retro-Cx Effort at Area School

• Built in 1960’s

• Several additions in 1980’s and 1990’s

• Total area of 250,000 ft2

• 30 Air Handling Units

• Mix of Constant Volume

and VAV

• 7 Boilers and 2 Chillers

Main concern is

energy consumption

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• A heating system controller was installed to allow for proper sequencing of all boiler units.

• The hot water system has been modified to allow for variable flow operation.

• Schedules have been modified to reflect space occupancy patterns for each air-handling unit zone.

• Economizer modes have been modified to improve comfort and energy efficiency

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• Existing chillers are being replaced with more efficient, variable flow and smaller capacity models.

• Computer labs and the IT room have been removed from main chilled water system and are now cooled by independent cooling units, which results in a shorter seasonal operating window for the chillers and improves comfort in winter.

New

Old

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Airflow checking and rebalancing results in enhanced

occupant comfort and potentially lower operating costs


• Staff have reported problems with “stuffiness” in several spaces

• Perimeter areas of Office and Guidance spaces too cold in winter

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Savings of about $30-50,000 / year in gas


Normalized Gas Use Comparison

0

5000

10000

15000

20000

25000

30000

35000

October November December January February March

Ga

s U

se

(T

he

rms)

)

2005

2006

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Savings of about $10-20,000 / yr in electricity


Electric Use Comparison

0

50000

100000

150000

200000

250000

October November December January February March

Ele

ctr

ic U

se

(kW

h)

)

2005

2006

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OLD NEW

Electric Use (kWh) 11,000 1,900

Electric Demand (kW) 18 3

• Existing roof-mounted chilled water pipe insulation is badly deteriorated

• It is being replaced with thicker aluminum shielded, weather-resistant insulation

Savings of about $500 / yr

Savings due to improved insulation

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Annual estimated savings:

$40,000 to $70,000

Estimated cost to realize savings:

~$35,000

Payback period: 6-10 months

Bonus: Improved comfort and operation!

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Life After Retrocommissioning

• RCx Process

• RCx Results

• Life After RCx

• Next Steps

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Portfolio Manager Tracking

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Continuous Commissioning Tools

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Continuous Commissioning Tools

• BAS Integrated Continuous Commissioning Tools

– “Building Analytics”

– “Building Management Performance Analytic Tools”

• Provide following capabilities

– Equipment and system fault detection and diagnostics

– Ongoing commissioning including optimization of building control

– Demand response

– Performance benchmarking

• Typically Cloud Based

– Monthly subscription fee

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LEED EB RCx

• Credits for:

– Documenting building operations and benchmarking performance

– Retrocommissioning audit phase

– Implementing identified retrocommissioning measures

– Ongoing commissioning

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What Can YOU Do?

• Benchmark your facilities

• Set goals

• Put an energy plan together

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Complete the RCx Process!

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Developing an Energy Plan

Retrocommissioning of Existing Buildings

Education

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