green roofs: hard data to support the hype

AIA Pittsburgh

A217

Green Roofs: Hard Data to Support the

Hype Green_BP16

Eric French, Mark Zavislak, John Buck,

Darla Cravotta April 21, 2016

Credit(s) earned on completion of

this course will be reported to AIA

CES for AIA members.

Certificates of Completion for both

AIA members and non-AIA

members are available upon

request.

This course is registered with AIA

CES for continuing professional

education. As such, it does not

include content that may be

deemed or construed to be an

approval or endorsement by the

AIA of any material of construction

or any method or manner of

handling, using, distributing, or

dealing in any material or product. _______________________________________

____

Questions related to specific materials, methods,

and services will be addressed at the conclusion

of this presentation.

This presentation is protected by US and International Copyright laws.

Reproduction, distribution, display and use of the presentation without written

permission of the speaker is prohibited.

© Allegheny County, Civil & Environmental Consultants, Eisler Landscapes

Copyright Materials

INTRODUCTION

Green roofs are said to last longer, reduce

energy costs, absorb storm water, improve air

quality and help to lessen the heat island effect.

In 2010 Allegheny County set out to test most of

those claims by installing four different types of

green roof systems on half of the County Office

Building roof, leaving the remainder for

comparison. An important part of the installation

was an extensive data collection system.

Members of the team will explain the project

concept and present that data in terms of water

infiltration and thermal analysis showing what

has been learned to date from the different roof

types.

INTRODUCTION

Course

Description

Learning

Objectives

1. Understand the composition of

different types of green roofs;

2. Explain the performance differences

in green roof types;

3. Present issues in the maintenance

and construction of green roofs; and

4. Substantiate the advantages of a

green roof with hard data.

At the end of the this course, participants will be able to:

INTRODUCTION

Client:

Allegheny County, Pittsburgh, PA

Location:

Allegheny County Office Building 542 Forbes Avenue, Pittsburgh PA, 15219

Support From:

Penn State Engaging Pittsburgh

Pennsylvania Environmental Council

Conservation Consultants, Inc.

3 Rivers Wet Weather (www.3rww.org )

USDOE and Federal Stimulus funding (ARRA)

Overview

Pittsburgh, PA

INTRODUCTION

http://www.3rww.org/

Overview

8,400 SF of 20,000 SF

conventional roof converted

to green roof in June 2010

About 2/3 roof unchanged -

conventional “control” roof

Continuous monitoring of

weather, temperature and

water relationships using 95

sensors linked to internet

Total Project Cost (Including

Monitoring and Educational

Components): $621,000

Pittsburgh, PA

INTRODUCTION

Building Program

Educate and lead by example (83 of 130 local municipalities with CSOs)

Reduce Storm water Runoff and Combined Sewage Overflows (CSOs)

Cool – Reduce “Urban Heat Island Effect”

Improve building performance by demonstrating benefits of green roof.

Extend roof life Beautify

INTRODUCTION

Building Program

INTRODUCTION

ACOB Project Execution Team:

Allegheny County – Darla

Cravotta, Rich Fitzgerald

Cuddy Roofing (A Scalo

Company) – Prime Contractor

Eisler Landscapes – Green

Roof Design and Installation

Civil & Environmental

Consultants – Monitoring

System, Engineered Soil Design

IDC Architects

Allegheny County Office Building

Structural Limitations

TYPICAL GREEN ROOFS

Types of Green

Roofs Used at

ACOB

1. Tray Extensive (4” soil,

pre-grown sedum)

2. Extensive (4” soil,

sedum sod or spriggs)

3. Semi-Intensive (~6” soil,

plugs and pots)

4. Intensive (>8” soil,

plugs and pots)

TYPICAL GREEN ROOFS

Types of Green

Roofs

TYPICAL GREEN ROOFS

Credit: http://greensulate.com/services/design-consult/

Types of Green

Roofs

TYPICAL GREEN ROOFS

Credit: http://www.archtoolbox.com/materials-systems/site-landscape/green-roofs.html

Benefits:

• Easy to design

• Great for small areas

Types of Green

Roofs

TYPICAL GREEN ROOFS

Credit: http://www.archtoolbox.com/materials-systems/site-landscape/green-roofs.html

Benefits:

• Reduced costs

• Flexibility

Design

DESIGN AT ACOB

Installation

DESIGN AT ACOB

DESIGN AT ACOB

Installation

DESIGN AT ACOB

DESIGN AT ACOB

Installation

One Year Later

INSTALLATION AT ACOB

INSTALLATION AT ACOB

One Year Later

Monitoring

Stations

Monitoring Program

Monitoring weather, temperature and water

relationships using 95 sensors linked to

internet

Monitoring System

Features

• Microclimate and design differences

considered

• “High” and “Low” slope positions

monitored

• 95 temperature, moisture, and weather

sensors monitored

• Real-time internet-accessible data

• Transfer relevant data to inspire,

educate, advance state of art

Monitoring Program

Monitoring

Locations

H

Extensive

(4”) H H

H H

L

L

L L

L

L

L

Intensive

(8”)

Semi-

intensiv

e (6”)

Monitoring Program

Monitor Locations

Legend

Climate

Control Roof

Green Roof

Sheltered

Sheltered

Exposed 40%

Cooler

Monitoring Program

Monitor Locations

text

text

Extensive

Sod Roof (4”)

Tray

Extensive (4”)

Intensive &

Semi-Intensive

(~6-10”)

Monitoring Program

Membrane Leak Detection (EFVM) (not shown: ceiling T/RH monitoring sensors)

Monitoring Equipment

Drainage Wetness

Sensor


Lateral Drains to Roof Drains

(Over Composite Drainage Blanket)


Sensor Wires in

Conduit


Wire Shelves to Support Microcosms

and Closed-Cell Styrofoam for

Lightweight Contouring


Dielectric Moisture Sensor

(Decagon EC-5)


Control Roof

Measurements

Roof Surface

Temperature

Solar Radiation

Air

Temperatures

at 6”, 18” a.g.l. Roof Wetness


10” 6.5”

4” Control

Microcosms Comparisons

in Same Microclimate

Highly-monitored

miniature green roof

alternatives

Set in same

microclimate

Interpretive display

value

Drainage directly

measured


Highly-monitored miniature

green roof alternatives, with

interpretive display value

Set in same microclimate

95 Sensors Measure:

Runoff from soil surface

Percolation to drainage

blanket

Soil Moisture (3 depths)

Soil Temperature (3

depths)

Solar radiation, air

temperature, rainfall

A. Soil Runoff

B. Soil Drainage

C. Soil Drainage

Lysimeter

A

B C

Microcosms Comparisons

in Same Microclimate


Cooler Roof

Temperatures

Results

40oF

Cooler!

Cooler Roof

Temperatures

Results

Peak Summer Surface Temperatures: Green Roof 35-

60oF Cooler

Building Peak

Temp. Delay

Building City

Modified Bitumen Roof

Modified Bitumen Roof

Vegetated Soil

Shaded, Vegetated Soil

Vegetated Soil

Unvegetated Soil

Vegetated Soil and Hardware

IR Thermography

11:16 AM

April 15, 2016

(Air Temp 65.6oF)

IR Thermography (108.4oF) at Sp1

Agrees with Roof Sensor (108.7-112.5oF)

Cooler Roof

Temperatures,

Heat Flux

Results

Carnegie Mellon Univ. Student Analyses of

Temperature Flux Differences (Wang and Becker, 2011, David Dzombak, Ph.D. Advisor)

Considered insulation components and temperature gradients

across green roof and control roof layers to calculated heat flux

Found Greatest Energy Benefit in Warm Weather – Cooler Roof

Temperatures Reduce Heat Gain to Building (75.3% difference in

heat flux (gain) between green and control roofs in June-August)

Found Modest Energy Benefit in Cold Weather (8.2% difference in

heat flux (loss) between green and control roofs in November 2010-

April 2011)

Evaporative cooling vs. insulation?

For Further Inquiry: Can measure soil evaporative water loss.

Heat Loss (+) and Gain (-), MJ/M2

Results

Wang and Becker, 2011, David Dzombak, Ph.D. Advisor

Green Roof Hydrologic

Monitoring

Results

Forecasting Stormwater Capacity:

Monitoring green roof soil moisture and roof

runoff

Can forecast how much stormwater green roof

soils can absorb

Water Balance

Monitoring

Results

Monitoring Rainfall & Runoff vs. Soil Water Content

Green Roof Soil Moisture

Storage Relationships

Results

Monitoring Green Roof Soil Stormwater Storage

Rainfall (blue), Roof Drainage (red) and Soil

Volumetric Moisture Content with Depth

Results

Runoff Delay

Runoff R

eduction

Rainfall, Roof Drainage & Soil Moisture

Relationships

Results

Rainfall, Roof Drainage & Soil Moisture

Relationships

Results

00.10.20.30.40.50.60.70.80.91

0

0.2

0.4

0.6

0.8

1

1.2

1.4

8/31/11 0:00 9/10/11 0:00 9/20/11 0:00 9/30/11 0:00

So

il W

ate

r S

tora

ge

(vo

lum

etr

ic)

Inc

he

s o

f R

ain

fall

or

Ro

of

Dra

ina

ge

Date / Time

Total Rainfall During Rain EventTotal Roof Drainage During Rain EventTotal Apparent Soil Water Storage (0-7" BGS)

Rainfall and Roof Drainage Main Roof

Microcosms (inches)

Results

4.46

5.75

4.1

1.92

3.13

4.36 4.4

3.89

0

1

2

3

4

5

6Rainfall(inches)

4" Soil RoofDrainage(inches)

6.5" SoilRoofDrainage(inches)

10" SoilRoofDrainage(inches)

Runoff Reduction Main Roof Microcosms

(inches)

Results

4.46

5.75

4.1

1.92

3.13

4.36 4.4 3.89

0

1

2

3

4

5

6

7

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

4" Soil %RunoffReduction

6.5" Soil %RunoffReduction

10" Soil %RunoffReduction

Rainfall

Real-Time Data, Outreach

http://gis.cecinc.com/AlleghenyCounty/index.html

Results

Monthly Stormwater Performance

August 1, 2014 to July 30, 2015

% Avoided

Runoff 4" Soil

(Extensive)

% Avoided

Runoff 6.5"

Soil (Semi-

Intensive)

% Avoided

Runoff 10" Soil

(Intensive)

Average 48.9 77.1 91.3

Minimum 15.4 28.8 70.4

Maximum 98.2 100.0 100.0

Stormwater Performance

Results

Monthly avoided stormwater runoff: ~15-100%

depending on month and soil thickness -

underestimated in winter (snow under-

measured)

Annual avoided stormwater runoff: ~50-90%

depending on month and soil thickness -

underestimated in winter (snow under-

measured)

Outreach

Results

http://www.alleghenycounty.us/allegheny-green/energy-conservation/green-roof.aspx

Demonstration increased public awareness of

green roofs for stormwater management

Continuously updated performance data for

green roofs in our region (5 years)

Data increases confidence of design

community and regulators








Costs, Energy Savings

Results

Normal costs for green roofs start at $22/SF

for sedum built up roof system

Total Project Cost (Including Monitoring and

Educational Components): $621,000 (about

$74/SF)

Cost Savings: 10-20% reduction in overall

heating/cooling costs; close to $7,000 savings

in July 2010 (vs. a cooler July 2009)

Thank you for your interest!

Questions?

This concludes The American Institute of Architects

Continuing Education Systems Course

Eric French - [email protected]

John Buck – [email protected]

Darla Cravotta - [email protected]

Mark Zavislak- [email protected]

green roofs: hard data to support the hype

Data & Analytics