1

Green Roof/ Cool Roof Proposal

Summary

- Cool roofs and green roofs are proposed as possible roof options for the grocery store and the

commercial building

- For the commercial building, a cool roof with acrylic white paint coating is recommended.

- For the grocery store, three roofing options have been proposed:

1. Cool roof for the full roof area

2. Half and half cool roof and green roof

3. Green roof for the full roof area

- With option 1 of having a complete cool roof for the commercial building and the grocery store,

energy reduction of 1.7% can be achieved in comparison to an untreated roof, with no

installation/material cost due to the Pittsburgh Cool Roof initiative described later in the report.

- With option 3 of installing a complete green roof over the grocery store, an energy reduction of

2.4% can be achieved in comparison to a standard untreated roof. Although installing a green

roof costs approximately $15-$22 per square foot, the vegetables grown on this roof can bring

in revenue to the store.

- Another option to reduce the installation cost of a green roof would be to implement this as a

student learning project where students can help in the plant installation and help reduce labor

costs.

Assumptions

The rooftop assembly options could take advantage of any combination of white roof or green roof

options. The plans below describe the three roofing options:

Option 1: Cool Roof

Figure 1: Option 1 - Cool roof for the full roof area; Option 2 – Half and half cool roof and green roof

2

Figure 2: Green roof for the full roof area

Figure 3: Recommended option 2 for roof design

We recommend option 2 for maximum rooftop production of edible plants for the grocery, while

maintaining easy roof access and drainage in the rear of the building. This also allows space for

additional planters of vegetables if desired, with green walls to the rear of the building near the lift

access.

Roofing background information:

1. Cool roofs

Conventional roofs are typically dark and retain sunlight as heat. When the temperature rises, these

dark roofs absorb heat, which increases roof and building temperatures, building cooling costs, and local

temperatures in urban settings because of the urban heat island effect. These effects can be reduced by

painting roofs with a white coating, which reflect the suns heat instead of absorbing it.

3

Advantages of cool roofs:

- Cool roofs reduces cooling costs

- Cool roofs increases roof durability

- Cool roofs reduces greenhouse gas emissions and pollution by lowering the demand for energy

use

2. Green roofs

Types of Green roofs:

1. Extensive Green roofs: These roofs are generally very shallow in depth of soil or growing media

which is usually 3-6 inch although they can be even 1 inch in depth. Extensive roofs are primarily

used for their environmental benefits such as storm water management and insulating

properties. They do not require irrigation except during the initial growth period and require

little or no maintenance. They are usually not intended to be accessed directly for use as a

garden or open space, by paved walkways and seating areas.

The lack of consistent supplemental watering, shallow soil depth and exposure to intense and

desiccating sunlight and wind require vegetation capable of surviving these harsh, dry

conditions. Generally, plants used for this are known as succulents. Sedums are most often used

for these conditions. Maintenance required for extensive roofs is initial hand watering during

installations and establishments. Occasional weeding, fertilizing and spot repair is required.

2. Intensive roofs: These roofs systems have greater depth of soil or growing medium which allows

for greater diversity in size and type of vegetation. The growing medium is typically 6-8 inches

and can go upto 15 feet or more. Ideally, these green roofs have relatively flat roof surfaces (1-

1.5%) or mild roof slope percentage of 3%. Pathways, terraces, water fountains, ponds and

other architectural features result in beautiful and dramatic spaces that can often be accessed

by people.

Since intensive roofs have greater depth compared to extensive roofs, they are capable of

storing water for longer periods. For this reason, intensive roofs have additional layers such as

protection boards and water retention mats that are usually included in the design to prevent

the roof from any leakage. Due to the increased number of layers intensive roofs are expensive

and require higher maintenance.

4

Figure 4: Types of vegetation for green roofs (Adapted from International Green Roof Association)

Special factors for green roof design

1. Load/weight requirements:

The load on a green roof can be of three forms-

- Dead load: actual weight of materials used to construct the roof

- Live load: weight added to the dead load as a result of use of space such as people moving on and off

the roof.

- Other loads: impact of winds, snow or seismic action.

Therefore, the design of a green roof must allow for a safety factor. The total weight of all built

components as a result of all loads must be less than the maximum load permitted by codes. In most

constructions, the majority of the weight is supported at the parapet walls and at points directly over

the intersections of structural beams.

Material Load Requirements

Conventional Roof 7-10 psf

Drainage Layer (Saturated) 2-3 psf

Soil Media (Saturated) 60-95 lb/ft3

Plants 2-3 psf

2. Leak detection:

One of the important steps in the construction of a green roof is to perform the leak detection test.

Methods used to perform the leak detection test are:

- Flood test: Upon completion of the waterproofing layer, verifying water tightness can be accomplished

by flooding the roof to a certain depth. With thermoplastic non-adhered singly ply assemblies, cuts are

made at low points following the flooding to determine if moisture has entered below the membrane

during the flood test. This test can be very time consuming and does not give the exact locations of the

leaks.

- Electric field vector mapping (EFVM): This method involves the installation of waterproofing over a

conductive deck, such as steel or re-inforced concrete. Points of water entry through the membrane

appear as electrical grounds on the surface and can be mapped manually using a voltmeter and quickly

isolated.

5

Considerations for Sustainability

1. Roof Insulation

Cool roof

For all assemblies, a high performance insulation system will be employed.

Figure 5: Recommended Roof section with insulation

The roof assemblies can be modified to include 3” of polyisocyanurate insulation (R-19 continuous)

placed above roof deck and 3” of ccSPF (R-19) on the underside of the roof deck after it has been

repaired to create a total roof assembly of R-38. White TPO membrane or Acrymax material can be

applied over the polyisocyanurate insulation to provide a reflective, “cool-roof” rated weather tight

assembly.

Assembly with Green Roof

The same insulation method will be used for semi-intensive

green roof, with an addition of the items above the insulation:

• Drainage medium/root barrier

• Growing medium (6-8in)

o soil in planting areas

o mulch in pathways

• Vegetation

2. Material selection and its environmental impacts

With the advancement in green roof technology, the products used for green roof construction are eco-

friendly products which have zero environmental impacts.

6

Recommendations for green roof materials:

1. Growing media: Rooflite intensive certified growing media

(http://www.rooflitesoil.com/rooftop-farming)

2. Drainage System: Rooflite drain

Recommendations for cool roof coatings:

1. Field Applied Acrylic coating by Acrymax Technology – Bright white

(http://www.acrymax.com/roof-coatings.html)

2. Field applied Acrylic coating by Acrylabs – Bright white

(http://www.acrylabs.com/Roofing_Systems_Products.php)

3. Energy Consumption:

1. Designing a cool roof for the full roof area for the commercial building and the grocery

store, energy reduction of 1.7% can be achieved in comparison to an untreated / dark roof,

with no installation/material cost due to the Pittsburgh Cool Roof initiative described later in

the report under Roofing costs.

2. Designing a complete green roof over the grocery store, an energy reduction of 2.4% can be

achieved in comparison to a standard untreated roof/dark roof.

Resources

Case Studies

Case Study 1: Green roof- Eagle Street Rooftop Farm, Brooklyn, New York

Operation and Ownership:

- Eagle street rooftop farm is a 6000 square foot green roof organic vegetable farm located on a

warehouse rooftop in Greenpoint, Brooklyn.

- The farm is installed on a building which is owned by siblings Gina and Tony Argento of

Broadway Stages, a Greenpoint based sound stage company with a longstanding history of

community investment. Broadway stages financed the installation.

- Goode Green designed the green roof and installed the base system and growing medium.

Design and Installation:

- Comprised of 2” built-up components: polyethelene, drainage mat and retention and separation

fabrics

- Growing media components: mixture of compost, rock particulates and shale.

- Contains a water retention layer, which can hold upto 1.5” of rain and help in the reduction of

stormwater runoff

- Reduction in cooling costs by helping to cool the warehouse below

- Installation cost: $10 per square foot

- Low cost due to: the three story building and open expanse of roof were very accessible and

recycled materials such as rafters were utilized for edging

7

Farm design and setup:

- Arranged into 16 north – south beds measuring 30” to 4’Growing media components: mi in

width and divided down the middle by a single long aisle.

- The beds have a soil depth of 4 – 7” and the aisles were filled with mulched bark

- Initial irrigation was provided via black plastic drip lines using city tap water

- Currently, the farm relies on hand watering for seedlings and transplants and rainwater for

established plants

Farm Produce:

- In the first season, the farm grew over thirty types of produce, from watermelon to cabbage

- In 2012, the farm focused on a selection of hot peppers to begin product development of a

Brooklyn-based hot sauce

- Heat, soil depth and soil quality affect the capacity of the farm and the most botanically

successful crops for health and high yield are hot peppers, cherry, tomatoes and sage.

Case Study 2: Green walls - Edible garden - Pizzeria Mozza - Los Angeles

Project:

• Vertical garden at the Pizzeria Mozza in Los Angeles – to provide on site greens and herbs for the

restaurant

• Designed by Tournesol Siteworks

• Green wall technology

o Elmich Vertical Greening Modules

o Netafim in-line drip irrigation

o Battery-powered timer/valve attached to nearby water source

o Edible plants include several types of herbs, rosemary along the sides and lettuces and

cabbage in the opening on top.

o Walls units are 8” thick. Total wall dimensions are 12’ wide x 10’ tall

Climate Viability:

• The same system used in LA for food has been used at the Seward Child Care Center in Minneapolis

(Climate Zone 4A), showing that it is also viable in colder climate like Pittsburgh (Zone 5A)

• Both projects use the VGM-10 living wall modules with an 8″ soil profile, which has kept their plants

from going through a dramatic freeze-thaw cycle.

• Minneapolis project lost several, but not the majority of plants over the first winter installed, those

lost were replaced

Installation Process:

8

• All modules are shipped flat and assembled on site, keeping shipping costs down and conserving

space and energy.

• Assembled modules are filled with soil, and plants inserted into openings in the fabric

• Modules are left flat for several weeks at the beginning of growth

• Driplines are attached, and they continue to grow for an additional 2 weeks at a slight tilt.

• Racking is installed and the panels can be attached to a vertical wall.

Product Specifications:

• VGM system is “100% recycled plastic planting module, attached to stainless steel rails mounted to a

wall or structure.”

• Each rail is attached to brick with two 1/2 x2” lag bolts

• Total saturated weight of system should never exceed 50lbs/cu.ft.

Additional Benefits

• Reduces heat gain on south facing walls

9

• Provides rain screen like benefits to exterior finish

• Easily constructible, and installable with typical methods

Double-sided Green wall Option

• Same system can be used free standing with possible application at the rear

of the building to provide visual and physical boundaries to the rooftop.

• This example uses the same VGA units in a double-sided modular living wall

at the Sheraton Delfina, Santa Monica

• Important considerations – possible doubling of weight to 100lbs/cu.ft in

double sided, rooftop location.

Roofing Costs

Cool Roof

Cool Roofs, the newest servePGH initiative, is now making resources available to nonprofit

organizations to coat their own roofs, helping them to save on energy costs and lower their carbon

footprint. In an effort to expand the Cool Roof's impact, nonprofits may apply for materials and

resources to coat their rooftops at no cost.

10

To be eligible for Cool Roofs, nonprofit organizations must commit to both engaging volunteers to carry

out the coating process and reporting utility information, in exchange for in-kind materials and technical

assistance. Nonprofits must also demonstrate that their roof meets the appropriate guidelines for

coating. An eligible roof will receive: reflective paint/primer, rollers and other paint supplies, technical

assistance from the Mayor’s Office of Sustainability and Energy Efficiency, and supplies for volunteers

such as sunglasses and safety guides.

Green roof

According to current research, the approximate cost for green roof construction is between $15-$20 per

square foot. This can be reduced by adding educational/community work by school students or the

community. By educating students and the community to help sow the vegetation during the green roof

construction, the labor and construction costs can be greatly reduced.

Drawings of application in the building

Planting beds

• 4,524 sqft of area within the parapet walls – all to be mulched

• 1,620 sqft of planting beds – extensive soil

50 linear feet green wall

• 20 linear feet @ 10’ high on south facing façade

• 30 linear feet, double sided on rear of building

o At 100psf – rear walls could total over 9000lbs wet

11

Grocery Store Equipment: Lifts

Lift to be provided to allow access to the storage area within the store as well as up to the rooftop.

Considerations

• Access to the lift platform from the rear, side, and front depending on level being accessed

• Height adjustable to ground floor, street level, and rooftop

• Lift will be located near existing roof drain, which may need to be rerouted

• Ramp for access should be provided at roof level to load items over parapet

12

Plan (Option 3)

Detail (all options)

13

Bibliography

Farm, E. S. (n.d.). Retrieved 2013, from http://rooftopfarms.org/

International Green Roof Association, I. (n.d.). A Quick Guide to Green Roofs. Retrieved from

http://www.igra-

world.com/links_and_downloads/images_dynamic/IGRA_Green_Roof_Pocket_Guide.pdf

Ramesh, S. (2011). Design Principles and case Study Analysis of Low Impact Development Practices -

Green Roofs, Rainwater Harvesting and Vegetated Swales. Blacksburg: Virginia Tech Libraries.