Implementing Green Rooftops at The University of Kansas

Beau Barnhart, Jessica Brooks, Colin Chilcoat,

Alicia James, Eric Simon, Ryan Surface,

Len Turi, Tommy Watgen, Reece Zwisler

EVRN 615 Environmental Studies Capstone

Dr. Kelly Kindscher

May 2012

Executive Summary

The purpose of our project was to investigate ways in which green roof installations can

benefit the University by reducing gray water runoff, decreasing energy consumption, decreasing

heat island effects, and improving the overall aesthetics of the buildings on campus. With

potentially tens of thousands of square footage available to the University for this project, we

believe green roof installations are not only achievable, but also cost effective. We realize that

green roof installations ―…require the collaboration of many professionals; the engineer,

architect, builder, and plant grower must work in concert with each other and local officials

responsible for building codes.‖1 However, coordinating the efforts of these individuals is no

different from any other building project on campus. Our project focused on three main

buildings, Nunemaker Hall, Malott Hall, and Eaton Hall. A cost analysis of Nunemaker Hall is

provided in the Appendix (Table 1).

BACKGROUND

1 http://www.rocklandcce.org/PDFs/Horticulture_Fact_Sheet_044.pdf

Long popular in Europe, green roofs have been steadily growing in popularity in the States

and several studies have been conducted recently to determine the thermal performance of green

roofs and their subsequent impact on a buildings energy performance, the results of which have

been largely positive. Germany has long been the leader in green roof construction and it is

estimated that 12% of all flat roofs in Germany are ―green.‖2 No parallels for Germany’s success

exist in the States, but Chicago is fast-tracking itself to become the ―greenest‖ city in the US.

Many of their initiatives include green roof construction and their shining example is the City

Hall building, whose green roof was completed in 2001. The 20,300 sq ft roof features 20,000

plants of more than 150 varieties, most of which are native to the region.3

Like many universities across the nation the University of Kansas has committed itself to

a sustainable future. Both faculty and students through a variety of actions on and around campus

have demonstrated this commitment. The recently published campus sustainability plan is a step

in the right direction and provides the framework for the further development of sustainable

traditions at KU. However, without action, the plan will remain just that, a framework. The plan,

specifically the section concerning campus grounds, only briefly touches on the topic of green

roofs.

While KU remains behind the frontrunners in university sustainability, it is on the right

path. A student group at Carleton College similar to the groups developed in our Capstone course

achieved their goal of installing a green roof on their campus in 2005. The 666 sq ft roof was

2 MSU Green Roof Research Program. Aug. 2006. Apr. 2012 . 3 City of Chicago. 2010. Apr. 2012

.

installed on their chemical storage building and used only plant species native to Minnesota.4

Carleton’s success is not unique, green roofs are springing up at universities worldwide. Not only

do they assist in energy savings, but they also contribute to campus beautification, which is all

too important in luring prospective students.

ENERGY SAVINGS

The University of Kansas provides heating to campus buildings by steam, which is

provided by power plants fueled by natural gas. Of our natural gas usage, 90% is used for space

heating. Additionally, 15% of our electricity use is for building cooling and heating. This

electricity and natural gas use account for 18.16% of our greenhouse gas emissions.5 Green roofs

are proven to provide heating and cooling benefits and are especially beneficial for older

buildings. New buildings are generally so well insulated that green roofs provide little added

energy savings.6 Implementation of green roofs on select campus buildings would provide

energy savings for the long-term, positively improving our environment, as well as our

pocketbook.

Data on KU buildings’ energy use per gross square foot provide a criterion to select

potential green roof locations to improve energy efficiency and savings from reducing building

heating and cooling demands. Buildings with the highest average energy use index (kBtu/GSF)

and below the average usage of a similar type of building include Nunemaker Hall, Computer

4 http://apps.carleton.edu/campus/sustainability/greenroof/

5 CAP-KU, and KU Center for Sustainability. CAP-KU: Creating a Climate Action Plan for the University of

Kansas. Rep. Print. April 2010. 6 Castleton, H.F., V. Stovin, S.B.M. Beck, and J.B. Davison. "Green Roofs: Building Energy Savings and the

Potential for Retrofit." Energy and Buildings 42.10 (2010): 1582-591. Web. 7 Mar. 2012.

.

Services Facility, Ellsworth Telecom Annex, Child Care Facility, Eaton Hall, Spencer Museum

of Art, and Carruth O’Leary Hall on the Lawrence Main Campus.7 It should be noted that some

buildings (e.g. Haworth) use a great amount of energy due to fume hoods and research

equipment.

For energy savings to be met, green roofs need to be installed by retrofitting existing

buildings with little to no roof insulation. Studies show that buildings with roofs that are well

insulated produce little to no energy savings, and newer buildings tend to be well insulated.

However, implementing a green roof on an existing building with no roof insulation has almost

halved annual energy used for heating, as well as saved 22-45% annual energy for cooling (see

Table 1).8

Roof Insulation Level Annual energy

saving % for heating

Annual energy

saving % for cooling

Total annual

energy saving

Well insulated 8-9% 0% 2%

Moderately insulated 13% 0-4% 3-7%

No insulation 45-46% 22-45% 31-44% Table 1. Castleton, H.F., V. Stovin, S.B.M. Beck, and J.B. Davison. "Green Roofs: Building Energy Savings and the Potential for Retrofit."

INSULATION

―An insulation layer is optional on any roof, and prevents water stored in the greenroof

system from extracting heat in the winter or cool air in the summer. Insulation is generally

applied on existing roofs in retrofitting projects that may require an increase in the insulation

7 CAP-KU, and KU Center for Sustainability. CAP-KU: Creating a Climate Action Plan for the University of

Kansas. Rep. Print. April 2010. 8 Castleton, H.F., V. Stovin, S.B.M. Beck, and J.B. Davison. "Green Roofs: Building Energy Savings and the Potential for Retrofit." Energy and Buildings 42.10 (2010): 1582-591. Web. 7 Mar. 2012.

.

value and is usually determined by the architect.‖9 So exactly how does a green roof reduce

energy costs? Couldn’t one simply add extra insulation and forgo the added expenditure and

maintenance of a green roof system? The following diagrams and information that supplements

them help to identify the reasons green roofs shouldn’t be thought of in ―R‖ values alone. ―R‖

values assume the restriction or resistance of heat energy flow, which is not really the effect of a

vegetative roof.

9 http://www.greenroofs.com/Greenroofs101/insulation.htm

Starting from the top,

1. Foliage – This is the most complex because it uses all methods of heat control provided by

nature – convection, evaporation, conduction, solar reflectivity, radiative heat emission, thermal

mass. Plants can also utilize extra heat conserving strategies such as defoliation during winter.

2. Stem gap – The air trapped between the foliage and the top of the planting medium provides

limited conduction and the stem itself conducts a small amount of heat between the foliage and

the roots.

3. Medium – Planting media conducts heat and often has enough thermal mass that it needs to

be taken seriously. It can also cool through evaporation when adequately moist.

4. Drain layer – The amount of heat conduction through the drain layer depends on how wet it

is. A more significant role of the drain layer can be through mass transfer - the removal of heat

from saturated media by providing a drain path for water heated within the media. As an aside,

this can also have the opposite effect in the winter by accelerating snow melt and preventing ice

damming.

5. Waterproofing – The membrane provides simple conduction and some thermal mass.

6. Insulation (if necessary) – Insulation slows heat conduction and has negligible thermal mass.

7. Roof deck – Again, the roof deck provides simple conduction but can have significant

thermal mass.

10

Now we can begin to understand that a green roof simply doesn’t resist heat loss in one

direction. The system is alive and allows for the transfer of heat in and out of the system. ―From

an energy standpoint, a green roof will have its greatest impact on a large, single or two story

building where solar heating is a major factor in the building’s energy usage, especially if

considerable heat is also generated internally. The foliage will get rid of the solar heat and the

10 http://www.greenroofs.com/archives/energy_editor.htm images and information by Christopher Wark

media will absorb and slowly release internal heat or excessive outdoor heat at night.‖11

We feel

that a building like Nunemaker Hall is the perfect candidate to take advantage of the energy

savings and environmental benefits of installing a green roof system. We realize the capital

investment by the University is large. I would propose that the University install heat sensors that

collect data from both the top of the roof and right below the deck. With that data collected the

engineering department could run models based off of different soil depths and plant

configurations to project the insulating properties of a green roof system. Projections from those

models could be correlated into overall energy conservation. Lastly, projected energy

conservation could be correlated into dollars saved based on current energy expenditures in real

dollars per kilowatt-hour.

OTHER BENEFITS

The benefits of green roofs can be numerous, but they are often relative: their success

depends on what one wants out of their green roof. Benefits outside of energy savings can be

numerous and worthwhile depending on the roof. The simple addition of plants allows for

increased photosynthesis and while the effects may be minute one cannot deny that there is an

increase in air quality in the direct vicinity of the green space. As these plants take in the carbon

dioxide in the area they will release clean oxygen and filter particulate. This benefit would be

much greater if entire regions were to install green roofs but any mitigation to anthropocentric air

pollution is a step in the right direction.

11 http://www.greenroofs.com/archives/energy_editor.htm

Green roofs also lend a hand to durability and resilience of roofs. The organic material

acts as an insulator against both hot and cold weather and reduces the amount harmful sunrays

that contact the roofing material as well as limit large temperature fluctuations.12

This leads to a

milder climate for the roofing material, which causes it to last longer with less maintenance

needed.

On top of these benefits, green roofs help to absorb some storm water runoff and put the

water to good use growing new life. Results from studies looking at water runoff associated with

green roofs show that green roofs are effective at reducing storm water runoff while also

releasing only minuscule amounts of agricultural pollutants.13

The reduction of runoff helps to

ease loads on sewer systems during precipitation events as well as help filter out pollutants.14

It can also be argued that there is a large marketing benefit to adding a green roof.

Currently, there is a large push for more environmentally friendly practices and conservation

amongst both industry and the private sector. By adding green roofs a company or university

would be able to advertise their support for the ―go green‖ effort and this could be beneficial to

profits and/or student satisfaction.

Aside from these mitigation efforts green roofs also have an inherent aesthetic value that

can be enjoyed by anyone with a view of such roofs or areas. By adding beautiful landscapes to

what would otherwise be rubberized roofing it is even possible that stress levels for employees of

overlooking buildings may decrease.

12 http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=shwart&index=an&req=5751909&lang=en 13 http://www.ncbi.nlm.nih.gov/pubmed/22244273 14 http://www.sciencedirect.com/science/article/pii/S0925857410000029

ENGINEERING

Structural considerations prior to installing a new or retrofitted green roof system

―…requires the collaboration of many professionals; the engineer, architect, builder, and plant

grower must work in concert with each other and local officials responsible for building

codes‖.15

For the sake of brevity this section will outline and define a few key elements to

consider including; live load, dead load, snow load, rain load, drainage, wind load, roof pitch,

and material choices.

Live Load:

Section 4.1 of American Society of Civil Engineers ( ASCE) defines live loads ―… those

loads produced by the use and occupancy of the building or other structure and do not include

construction or environmental loads such as wind load, snow load, rain load, earthquake load,

flood load, or dead load. Live loads on a roof are those produced (1) during maintenance by

workers, equipment, and materials, and (2) during the life of the structure by movable objects

such as planters and by people‖.16

Dead Load:

ASCE 7-05 3.1.1 defines dead load as consisting "... of the weight of all materials of

construction incorporated into the building...". 17

Items that can be considered to be dead load

include construction materials that make up the building (beams, columns, floor systems, ceiling

systems, wall systems, doors, windows, floor coverings, wall coverings, cabinets, and the like)

15 http://www.rocklandcce.org/PDFs/Horticulture_Fact_Sheet_044.pdf 16 http://civil.eng.buffalo.edu/cie429/ASCE-7-02-Live%20loads%20-s04.pdf 17 http://www.bgstructuralengineering.com/BGASCE7/BGASCE7003/index.htm

and permanently attached equipment such as heating and ventilating systems, electrical trays,

piping, etc…

After a brief phone interview with an architect at Intrinsic Landscaping in Glenview IL, I

(Len) was told ― In all my years of doing this I have only seen one commercial building that

required additional support‖. In simplified terms, almost any commercial roof can be designed in

such a way to meet ―load ―requirements for the area they are located in. With an average

minimum load rating of 40lbs psf, most commercial roofs, like those on campus, can easily

support an extensive green roof system. New buildings can easily be designed for increased roof

load capacity.

Snow Load:

Section 7.3 (ASCE) defines FLAT ROOF SNOW LOADS, pf

The snow load (pf) on a roof with a slope equal to or less than 5◦ (1 in./ft = 4.76◦) shall

be calculated in lb/ft2 (kN/m2) using the following formula:

p f = 0.7CeCt I pg

Ce = exposure factor as determined from Table 7-2

Ct = thermal factor as determined from Table 7-3

I = importance factor as determined from Table 7-4

pg = ground snow load as determined from Fig. 7-1 and Table 7-1; or a site-specific

analysis, in lb/ft2 (kN/m2)

Put more simply, ―The live load due to the weight of snow on a roof; included in design

calculations‖18

. ―Snow loads are influenced by elevation, general weather and moisture patterns,

slope direction, exposure, roof (or trail bridge) configuration, and wind direction and severity.

Overestimation of snow loads can unnecessarily increase the cost of construction.

Underestimation of snow loads can result in premature failure, high maintenance costs, resource

damage, and, in some cases, safety issues …Use International Building Code(IBC )2003 —15

psf-25 psf‖.19

Rain Load:

Defined as such, ― the amount of water that could accumulate on a roof from blockage of

the primary drainage system is determined and the roof is designed to withstand the load created

by that water plus the uniform load caused by water that rises above the inlet of the secondary

drainage systems at its design flow. If parapet walls, cant strips, expansion joints, and other

features create the potential for deep water in an area, it may be advisable to install in that area

secondary (overflow) drains with separate drain lines rather than overflow scuppers to reduce the

magnitude of the design rain load. Where geometry permits, free discharge is the preferred form

of emergency drainage‖.20

Roof Drainage:

“Roof drainage is a structural, architectural and mechanical (plumbing) issue. The

type and location of secondary drains and the hydraulic head above their inlets at the

18 http://encyclopedia2.thefreedictionary.com/snow+load 19 http://www.fs.fed.us/t-d/snow_load/ 20 http://www.ce.udel.edu/courses/CIEG407/CIEG_407_Protected/Chapter%208%20Commentary.pdf

design flow must be known in order to determine rain loads. Design team coordination is

particularly important when establishing rain loads.”21

Wind Load:

―For using the actual sustained wind speed expected (were we to actually determine it):

Force, F = A x P x Cd

A = The projected area of the item

P, Wind pressure (Psf), = .00256 x V^2 (V= wind speed in Mph)

Cd, Drag coefficient, = 2.0 for flat plates. For a long cylinder (like most antenna tubes),

Cd = 1.2. Note the relationship between them is 1.2/2 = .6, not quite 2/3‖.22

MATERIALS

The two primary choices for commercial buildings are modified bitumen, and PVC

sheeting. While both materials are currently used on campus, I believe the PVC roofing

membrane has the advantage due to its recyclability and built in resistance to root penetration.

While costs are identical and installations similar, the PVC membrane I investigated scores19

points towards LEED certification,23

which will help the University meet its LEED certification

goals.

21 http://www.ce.udel.edu/courses/CIEG407/CIEG_407_Protected/Chapter%208%20Commentary.pdf 22 http://k7nv.com/notebook/topics/windload.html 23 http://ussarnafil.webdms.sika.com/fileshow.do?documentID=1862

Modified Bitumen Overview:

―Modified Bitumen (MB) is asphalt that has had modifiers added to it to give it plastic or

rubber-like properties.‖24

Positives

Approximately 2 lbs. per square ft.

Approximately $2.50 per sq. ft. for material

15 year manufacturer guarantee

Easily repaired

Drawbacks

Torch down system, Noxious fumes from installation may disrupt class

One architect has told me that roots love this material; however, some in the field find

this to be an advantage.

No recyclability at the end of its life.

No points towards LEED certification

PVC membrane Overview:

PVC membranes are‖… Formulated for long-term, direct exposure to the elements, this

membrane is fiberglass reinforced, offering exceptional dimensional stability and a low

coefficient of thermal expansion. By fully encapsulating the fiberglass reinforcement, there is no

risk of delamination or water wicking.‖25

Positives

Has been used successfully on many projects in Chicago and around the world.

24 http://www.roofhelp.com/choices/modified/ 25 http://usa.sarnafil.sika.com/en/solutions_products/10/10sa01/choosing-a-roofing-system/thermoplastic-roof-membranes.html

Approximately 2lbs. per sq. ft.

$0.75 per sq. ft. without adhesive (if used only as a membrane on existing roof.)

Approximately $3.00 per sq. ft. if adhesive is used for permanent attachment on new

installation.

Upwards of 25 year life expectancy

Recyclable (if no adhesive is used in the application).

Root resistant

Can be used over an existing roof or on a new installation.

Points toward LEED certification depending on manufacturer

Drawbacks

Thermoplastic welding for seams may release noxious gasses like modified roofing.

PVC may not be recyclable depending on if it is permanently adhered.

DESIGN

We selected three buildings on campus as our primary sites for future green roof

installations, Nunemaker, Eaton Hall, and Mallot Hall. All of the buildings have similar

attributes. They have a flat roof, existing drains, rooftop access, and they are visible from

multiple vantage points. When selecting the proposed future sites we considered accessibility,

drainage, infrastructure, and maintenance/watering, and aesthetics.

Nunemaker Hall – 3,225 total square feet of green roof construction

Nunemaker is one of our top choices for future implementation of a green roof. This is

one of the most energy inefficient buildings on campus (See Appendix graph A). Due to the

building’s energy inefficiency, we believe, the potential energy savings provided by a green roof

installation more than offset the cost of installation and maintenance (See Green Roof Cost

Analysis of Nunemaker Hall below). The roof is visible to foot traffic walking on the Hill and to

students living in Lewis Hall. While being pleasing to look at it helps raise student awareness

about the importance of saving energy.

Possible drawbacks to this location include; shade provided by surrounding trees may

hinder growth of grasses on the structure and due to the large amount of windows on the

building, overall energy saving may be lower than anticipated.

Eaton Hall – 8,600 total square feet of green roof construction

Eaton Hall is another primary target for our proposal. This roof is very accessible, has

good drainage infrastructure, and is visible from both Learned Hall and on top of the Hill.

Another positive about Eaton is that there are several lower adjacent roofs where rainwater

collection is very feasible. If a proper pumping and water dispersal system was coupled with a

rainwater collection system it could drastically decrease the number of maintenance man-hours

per semester.

30’X60’ 1,800 sqft

40’X80’ 3200 sqft

Mallot Hall – 3,400 total square feet of green roof construction

Our final building selected for future green roof construction is Mallot Hall. This plot

distribution was selected because of the four drains, which run down the middle of the roof.

Mallot Hall shares some similarities with both Nunemaker and Eaton Hall. Mallot is one of the

most energy inefficient buildings on KU’s campus. Thus, similar to Nunemaker, it will help

justify funding from the University as a long-term investment. Mallot also has an adjacent roof,

which could have similar benefits for watering as Eaton (which was discussed in the Eaton Hall

section above). However, this location is actually better than Eaton Hall, for watering purposes,

because the adjacent roof (for possible water collection) is above the proposed green roof area

(as show by the shadow cast down near the yellow circle on the right). This means that water

could be moved passively (instead of by a pump) down to the proposed roof for dispersal. The

yellow circles depict the placement of possible water collection sites.

There are three major issues that must be considered before the construction of this

proposed site. One is that the proposed roofing area is only a fraction of Mallot’s entire roof (the

rest of the roof is occupied by large ventilation units). The implications of that mean we must

consider the realistic amount of possible energy saved. The second issue, also related to the

ventilation units, is that they are constantly blowing out air from various scientific labs within

Mallot. This creates the possibility of exposing the proposed green roof to unexpected unknown

toxins. Although exposure to toxic exhaust needs to be considered, I think since the ventilation

roof is higher and the exhaust will continue to rise and quickly disperse, and thus will not be a

major impediment. The third and final issue to be considered is evident in the picture above. It

appears as though the drain of the far right has water pooling, which means it is either the lowest

point on the roof, or that the drain is no longer working to it full capacity. Based on that

information, action should be taken accordingly, to either replace the drain or incorporate that as

the lower point in the slope aspect of the constructed plots (this should be assessed before

construction begins).

Green Roof Cost Analysis of Nunemaker Hall

Breakdown of Capital requirements: Base Cost Future savings Alternative

PVC membrane And Installation

Approx. 3225 sf @ $100.00 per sf* 1

$322,500 $193,500*2 0

Soil cost (4in depth extensive roof)*3

Approx. 45 cu yards @ 90 per cu yard

$4050 0 0

Insulation R 7.5

Approx. 219 sheets @ $13 per sheet

$2845 $ 47,600*4 0

Plant/Seedum plugs*5 $4350 0 0

Crane /Boom Truck

6 hrs @ $1000 per hr.

$6000 0 0

University labor for soil placement

And planting

$36 per hour 120 hrs*5

$4320 0 0

Engineering/recalculating existing

blueprints and load capacities

$1000 0 0

Recurring labor

2 hrs. per week@52 weeks* $32 per hr

$3330 0 0

Totals $348,400 $241,000 0

Adjusted $107,300 0 0

Offset recurring annually 0 $47,600 0

Estimated time to pay off project- 2 years

*1 This number is pricing based on material and installation. KU, having relationships with

companies like Emerald Roofing, Should be able to negotiate a better price than this.

*2 Based on a 60% increase in roof longevity. I felt doubling roof longevity as some

manufacturers’ suggest is too generous.

*3 Quick engineering note: Based on 61lbs ft

2 = 61(4in/12)= 30.4 psf dead load increase.

*4

Based on a 20% increase on energy cost Nunemaker Hall $238,000 annually26

(2008).

*5 Again, I went high on the number here. Journeyman wage for either maintenance or grounds

crew is less than $36.00 per hr. I also increased the time estimated by 25%.

*6 Again, this number is high on the wage, but actual maintenance time may increase or decrease.

SOIL

26 http://www.energy.ku.edu/data/archive/Electricity%20Reports%20thru%20Dec%2008%20AN%20-%2002%2055.pdf

When choosing a growing media for a vegetated roof there are many different

factors to consider. The most basic variable to choose is soil depth. There are two distinct types

of roofs, extensive and intensive. These two types of vegetated roofs are differentiated simply

based on the depth of the growing media, which in turn affects the type of vegetation that may be

supported. In general extensive roofs have a soil depth of less than 6 inches and intensive roofs

have a minimum depth of 6-8 inches. In comparison extensive roofs are less expensive, more

lightweight, and require less maintenance27

. Intensive roofs are more suited for rooftop gardens

as they can support a much wider range of vegetation including small trees and shrubs. Intensive

roofs will most likely require more inputs such as fertilizer, irrigation, and the growing media

will require a larger percentage of organic matter.

Growing media is typically a mixture of several materials and will contain an organic and

inorganic component. Soil organic matter (SOM) is the remnants of biotic material that is in the

process of decomposition. SOM increases cation exchange capacity, improves water retention,

and provides a supply of nitrogen, phosphorus, and sulphur to plants28

. For extensive green roofs

4-10% organic matter is common. Intensive green roofs may have plants with higher nutrient

requirements; upwards of 10-15% SOM is needed for intensive roofs. It is important to note that

SOM has a high water holding capacity and therefore increased quantities of SOM will result in

increased saturated weight. The disadvantages of increased SOM are that over time the

decomposition of organic matter causes substrate shrinkage, which can result in compaction.

27 K.L. Getter, D.B. Rowe. “The role of extensive green roofs in sustainable development HortScience”. 41 (5) (2006), pp. 1276–1285 28 J.H. Havlin, S.L. Tisdale, W.L. Nelson, J.D. Beaton. Soil fertility and fertilizers(7th ed.) Pearson Prentice Hall, Upper Saddle River, N.J. (2005)

Compaction decreases the amount of pore space through which oxygen, nutrients, and water can

travel29

. Decomposition of SOM can also result in lack of nutrients over time.

The inorganic fraction of the growing media can be derived from a variety of materials. It

is most important that the inorganic fraction be lightweight as well as containing sufficient and

large pores. The macropore structure of the inorganic fraction allows for quick drainage of water

via gravitational forces. The hydraulic conductivity of the material must be sufficient enough to

drain rapidly during a storm to prevent any ponding, which may have detrimental effects on the

vegetation and displace soil. Inorganic material can comprise up to 80-90% of the growing

media in an extensive roof and 50-70% in an intensive roof. Common materials include Perlite,

vermiculite, lightly expanded clay granules, pumice, and expanded shale.

A variety of proprietary growing media mixtures are available from companies located in

the United States. These engineered soils claim to offer a balance between sufficient drainage

and water retention properties, as well as being lightweight, and less susceptible to compaction.

However, locally derived material should be a consideration in an effort to reduce cost. Pre-

engineered soils may need to be shipped long distances, which is costly and not environmentally

friendly. The University of Kansas may have some resources of biomass useful for compost from

facilities maintenance. The University of Kansas field station could also be considered as a

resource for donor material. If native vegetation is being grown on a green roof it may be

advantageous to have the native mycorhizzea, a symbiotic fungus, from the local topsoil. Local

materials that might be used for the inorganic content include expanded clay and expanded shale;

both of these materials are present in the greater Midwest area

29 K. Handreck, N. Black. Growing media for ornamental plants and turf (3rd ed). University of New South Wales Press, Sydney (2002)

Figure 1: Provided by City of Chicago

Figure 2: Provided by City of Chicago

PLANTS

The choice of green rooftop vegetation is an important one. One must consider a number

of things when selecting the right plant cover for a green rooftop location. In general, one has to

be mindful of every aspect of the specific site (i.e.; climate, wind, annual rainfall, roof slope, soil

depth, solar access...etc.) in order to narrow down the list of prospective species30

. Our group

30 Getter, Kristin L., and Bradley D. Rowe. "Selecting Plants for Extensive Green Roofs in the United States." Michigan State University Extension 3047 July (2008): Pg 3.

decided to strictly use species that are native to not only the region of the Midwest but species

that could thrive in the environmental conditions of the Great Plains. The most successful of

species used for green roofs are looked at as ―water conservers,‖ which absorb water when

available and conserve water by closing the plants pores31

. The most reliable types of plants for

extensive rooftop gardens are succulents such as Sedums, Delosperma, Euphorbia,

Sempervivum. All of which are known for their water storage32

. On the other hand, it’s important

to avoid plants that are drought resistant with extensive roots that need to search deep into the

Earth for a source of water.

With the aforementioned factors in mind, a successful green rooftop garden is one with

species that have life longevity. It's an important aesthetic feature to consider when choosing

plant species. The University of Kansas is known for its pristine landscaping, green grasses, and

blooming flowers. Our green rooftop location would follow suit, by contributing a new aspect of

design that would allow the building structure to merge with the surrounding landscape

throughout seasonal conditions33

. In order to achieve this, ideally, the most receptive plants

would be ones that reseed themselves and spread naturally. The location, with respect to the

overall campus aesthetic is another important factor to consider. If the rooftop is more visible on

campus, more ―eye-pleasing‖ species can be selected. For example, a location with no public

access and limited public visibility would not be a location with multiple varieties of colored

species, whereas a location that can be seen by campus onlookers could take advantage of the

diversity of plant types and species.

31 "Live Roof Hybrid Green Roof System." Live Roof Design Guide. Hoerr Schaudt Landscape Architects, 2012. . 32 Getter, Kristin L., and Bradley D. Rowe. "Selecting Plants for Extensive Green Roofs in the United States." Michigan State University Extension 3047 July (2008): Pg 3. 33 Miller, Charlie. "Extensive Vegetative Roof." Whole Building Design Guide. National Institute of Building Sciences, 2 Apr. 2011. .

Our group decided to narrow in on three specific species: grasses, Sedum, and Forbs.

We’re hoping to implement a green roof where native tall and short prairie grasses are ever-

present. In regards to water retention, prairie grass has a distinctive response to restricted

precipitation and high evapotranspiration that suggests it to be ideal for the shallow well-drained

soil of an extensive green roof34

. We chose prairie grasses that increase and spread themselves

through seeding. Next, Sedums are the most seen plant cover for extensive green roofs. They’re

known for being hardy, easy to grow, and have low water reliance. Last, we chose the Forbs

species, which are non-grass prairie plants. Studies show that the success of Forbs growth

increases when grown near other grasses35

. For the optimum performance of green roofs, Forbs

should be grown alongside succulents and grasses. Below is our list of species based on our

selection criteria (See Appendix). The list indicates specific genus’ that have been scientifically

tested and recommended for green rooftops in the Midwest based on an extensive green rooftop

study carried out by the University of Michigan36

.

The amount of plant types will vary per location. If implemented, our campus' beautiful

green rooftop could easily become the home to 15-20 plant species depending on the set budget.

Another budget constraint is the technique used for planting. The green rooftop could either be

seeded cohesively or established with plugs that were grown and then planted or bought directly

from one of the regions native seed merchants. With either choice, the planting techniques are

considered to be equally successful. However, a green rooftop established with plugs would have

34 Sutton, Richard K., "Rethinking Extensive Green Roofs to Lessening Emphasis on Biomass" (2009). Landscape Architecture Program: Faculty Scholarly and Creative Activity. Paper 15. Pg 4. 35 Sutton, Richard K., "Rethinking Extensive Green Roofs to Lessening Emphasis on Biomass" (2009). Landscape Architecture Program: Faculty Scholarly and Creative Activity. Paper 15. Pg. 9. 36 Getter, Kristin L., and Bradley D. Rowe. "Selecting Plants for Extensive Green Roofs in the United States." Michigan State University Extension 3047 July (2008): Pg 5-7.

more of an immediate aesthetic and energy saving impact. Possible seed merchants include,

Stock Seed Company, Hamilton Seed Company, Sharp Seed Brothers, the Missouri Wildlife

Nursery, Northwest. Horticulture. Below are an example of the varying prices for the prairie

grasses alone, supplied by the Stock Seed Company37

. The prices are Per Live Seed (PLS) lbs.

Grass Type Price (PLS lb)

Blue Grama $24.00

Indian Grass $13.50

Prairie Dropseed $90.00

Junegrass $40.00

Side Oats Grama $14.50

Western Wheat Grass $8.50

Little Bluestem $15.50

Needlegrass $6.00

SAFETY

There are many aspects of safety to take into consideration when installing or

constructing a green roof system. Hazards most commonly associated with green roofs are those

that are common to any building/construction project located on a rooftop. Falling from the roof

is a major consideration so a harness and tie offs should be used whenever possible and

necessary. Also, when considering load capacity for the green roof it should be noted that this

capacity is for the entire project and not just the final product and measures should be taken to

ensure that this capacity is not reached or surpassed throughout the project. Public safety should

also be taken into consideration if there is going to be public access to the sight. A border fence

or barrier should be erected to keep the public from reaching the edge of the building. Another

37 "Prairie and Turf Grasses." Stock Seed Farms.

major consideration is fire safety. This is perhaps the biggest issue especially when considering

the dead and dry grasses that accumulate over time. In regards to regulations and rules for a

green roof system there are no national or state regulations on exactly what can and cannot be

done; it remains under the jurisdiction of the building code and not a separate entity. There are,

however, guidelines that can and should be taken into consideration when building a green roof.

A guideline called the ANSI/SPRI VF-1 External Fire Design for Vegetative Roofs was approved

by ANSI, American National Standards Institute, in 2010 that gives some very well put together

guidelines for Fire safety considerations. The main points highlighted in this document, among

others, are fire breaks and borders of at least 6 feet to prevent fire spread, a fire resistant and

impermeable membrane be in place under the entire roof system and readily available access to

one or more hydrants.38

MAINTENANCE

Green roofs will require periodic maintenance to insure that they stay in a good

condition. Watering is obviously one of the most important keys to good maintenance. Prairie

plants are drought tolerant and would only need water in times of droughts that last two months

or more. If plant species that are not drought tolerant, or require an irrigation system, are used

then watering will need to be done three times a week. A water source should be nearby so that

watering becomes an easier task.39

38http://www.greenroofs.org/resources/ANSI_SPRI_VF_1_Extrernal_Fire_Design_Standard_for_Vegetative_Roofs_Jan_2010.pdf 39 Markham Jared, Green Roof Maintenance and Care. “Kimberly-Clark Professional” April 29, 2008. Imakenews.com. http://www.alturasolutions.com/JaredGreenRoofsArticle.pdf

Fertilizer is another important part of taking care of green roofs. It is recommended that a

slow release fertilizer should be used at the start of the green roof. It should be applied twice in

the first year of the garden. Applied once in the early spring and once in early fall. After that, it

should be applied yearly for the next four years. The natural cycle and composted plant materials

should be able to take over afterwards. Grade landscape fertilizer should not be used.40

There are special instructions for the other parts of maintenance as well. Herbicides and

pesticides are only to be used if there is damage present on the plants. Weeding will need to be

done manually by hand. This is because tools and machinery have the potential to pierce the

layers underneath the dirt and create leaks. Any sort of plant replacement should be done within

the first two months and plant loss can be mitigated with proper care and planting. Debris can be

brought up to the green roof by wind. Occasional checks should be done for debris and weeds.

These inspections can also be used for checking the green roof system.41

40http://www.greenroofsolutions.com/wpcontent/uploads/2010/08/GREEN+ROOF+MAINTENANCE+PROGRAM.pdf 41 http://www.greenroofs.com/Greenroofs101/faqs.htm

Appendix

Graph A42

42 http://www.energy.ku.edu/data/archive/Electricity%20Reports%20thru%20Dec%2008%20AN%20-%2002%2055.pdf

List of Plant Species:

Sedum

- Sedum acre-biting stonecrop

- Sedum album-white stonecrop

- Sedum cauticola-stonecrop

- Sedum divergens-cascade stonecrop

- Sedum ellacombianum-orange stonecrop

- Sedum floriferum-stonecrop

- Sedum kamtschaticum-orange stonecrop

- Sedum middendorfianum-stonecrop

- Sedum oreganum-oregon stonecrop

- Sedum populifolium-stonecrop

- Sedum-puchellum-birds claw sedum

- Sedum reflexum-crooked stonecrop

- Sedum sexangulare-tasteless stonecrop

- Sedum spathifolium-broadleaf stonecrop

- Sedum spurium-creeping sedum

- Sedum stefco-stonecrop

- Sedum stenopetalum-narrow petaled stonecrop

- Sedum telephium-stonecrop

- Sedum ternatum-woodland stonecrop

Forbs

- Allium cernuum-Nodding wild onion

- Dalea purpurea-purple prairie clover

- Fragaria virginiana-wild strawberry

- Koeleria macrantha-prarie junegrass

- Potentilla anserma-cinquefoil

- Sporobolus heterolepsis- prairie dropseed

Tall Grasses

- Schizachyrium scoparium-little bluestem

- Bouteloua curtipendula- side oats grama

- Sorghastrum nutans-Indian Grass

Short Grasses

- Bouteloua gracilis- blue grama

- Pascopyron smithii- western wheat grass

- Stipa- needlegrass