Green Lancaster header displaying a picture of an Amish buggy, and corn field, horses in a field, cows being milked, and windmills.

Educate>Green roofs

Green Roofs

What is a Green Roof?

Green roofs are vegetated roof covers, consisting of different types of plants growing on top of a roof. Green roofs resemble the natural environment and replace the vegetative footprint removed by buildings and other structures.

Green roofs can also be referred to as living roofs or vegetative roofs. These roofs are much more complex than potted plants on top of a conventional roof. A living roof becomes part of a structure, allowing that building to reap the various benefits of nature.

Lancaster's plan for green roofs

Green infrastructure v. gray infrastructure

Intensive green roofs v. extensive green roofs

Why green roofs?



Modular systems v. built-in-place systems

Layers of a green roof

Types of plants

Sloped roofs v. flat roofs

Researching green roofs?

Cost analysis

Who should I talk to about installing a green roof?

Groff's case study

Roof Gardens



Future of green roofs in Lancaster


Lancaster’s Plan for Green Roofs

According to Mary Gattis-Schell, Senior Planner of the Lancaster County Planning Commission, Lancaster County’s goal is to replace gray infrastructure with green infrastructure. By doing this, Lancaster will welcome back a better sense of natural environment within the community.

Lancaster County has seven different buildings that are equipped with vegetative roofs.

The first building in Lancaster to receive a green roof was National Novelty Brush Company. This organization received its green roof in May of 2009.

The Groff’s Family Funeral Home received the most recent green roof in May of 2010.


Photograph of Groff's green roof, in late Fall.

By Parker McCaffrey


Green Infrastructure vs. Gray Infrastructure

There are two types of infrastructure:

    • green infrastructure

    • gray infrastructure

Green infrastructure consists of trees, plants and open areas of grass.

The most common green infrastructures are parks and forests. A simple way to put it is that green infrastructure is everything in the natural environment.

Gray infrastructure is everything that is not part of the natural world. This ranges from roads and sewers to buildings and houses. The general infrastructure of a city is commonly gray.

Green roofs are a great way to place greener infrastructure into Lancaster city. By building green roofs, the physical framework of Lancaster city will no longer be gray. An even balance of green and gray infrastructure will benefit the city greatly.

Mary Gattis believes that living roofs will help support the Lancaster community, giving Lancaster more plant life.


Intensive Green Roofs v. Extensive Green Roofs

There are two types of green roofs:

    • intensive

    • extensive

Both have the same benefits, but factors such as roof space, slope, and capacity dictate what type to use. The cost willing to be spent can also dictate what type to go with.

Intensive green roofs are more expensive and are generally designed for human interaction. These roofs are generally more complex in structure, adding additional weight to a roof. They also allow for a more diverse selection of plants.

Plant sizes for intensive roofs can range from 8 inches to 15 feet. These roofs can also house gardens, ponds, walkways and benches. Due to these factors, most intensive roofs must be on flat or slightly slanted roofs.

Extensive green roofs are lightweight and less expensive. The vegetation is low growing and requires little maintenance.

Extensive green roofs can grow on up to 30% slopes. For roofs that are steeper, grids can be put in place to support the plants.


Why Green Roofs?

Green roofs can transform the outer layer of a city into living landscapes. Green roofs provide ecological, economical and aesthetical benefits.


Lancaster city has an opportunity to correct the loss of the natural environment due to construction trends by using green roofs. Living roofs provide many ecological advantages, more so in urban settings like Lancaster city. The more buildings covered with green roofs, the greater the benefits.


Greens roofs offer great economical benefits through energy conservation and capital savings. Living roofs can lower maintenance and building costs. The economical advantages of living roofs are argued to be the reason for cities and home owners to consider using one.


Living roofs make building visually appealing. Communities of plants living within a city can create an enthusiastic environment for its inhabitants.

Concrete roofs and warehouses can become beautiful, welcoming works of art. The possibilities green roofs present can offer to Lancaster city will enable the community to show its culture and tradition.



Green roofs offer a large array of benefits. There are private and public benefits living roofs provide. With the installation of a green roof, many problems encountering society today can be stopped.

Green roofs provide an aesthetical benefit too. The landscapes they form can change the quality of life for residents of an area.

Private Benefits

Energy Conservation

The largest benefit a green roof offers is energy conservation. Reducing the price of energy costs can be very helpful to your budget.

A vegetative roof gives a house or building an extra layer of insulation. Thus, reducing the amount of energy used to heat and cool a house. The less energy used to heat and cool a house means homeowners will save money!

A conventional roof becomes very hot during the summer and very cold during the winter. Green roofs avoid this from happening to roofs so there is no extra cost from that effect. Transpiration, a natural process of a plant, will result in the cooling of roof during the summer.

Roof Life

Green roofs have a longer life span than standard roofs. Conventional roofs last an average of 20 years. Vegetation can extend a roof’s life up to three times longer, or 20 years.

There is a rapid change in temperature yearly, even every day. Plants can shield a roof from such temperature fluxes, increasing its longevity.

Green roofs also protect a roof from ultraviolet radiation and other natural factors. Roofs are prone to ware and tare from the environment, but green roofs protect the roof from such stresses. In turn, the service life of the roof is longer.

Since green roofs react so well with the environment, maintenance is reduced. Less maintenance is needed for a green roof compared to a conventional one.

The lifespan of a green roof is a cost saving investment by itself.

Noise Pollution

Green roofs reduce sound reflection and increase sound insulation. They are good sound insulators which keep noises outside of a building out of the building and keep noises inside the building in the building.

Cities are busy, noisy places. The use of green roofs will comfort the lives of people living within the city and provide more peace to the community. Loud sounds will not bounce up and down buildings, and airplanes will scare the people they fly above.

Utilization of Space

Green roofs can be used for insect and animal life or human interaction. Gardens, walkways and picnic areas can be incorporated into most green roofs.

This can save building owners from buying additional space or give them more space to use. Green spaces in city setting can be a great place for social interaction and relaxation. It provides a new, natural environment for everything to benefit from.


Public Benefits

Storm Water Management

The greatest public benefit green roofs provide is storm water management. They can greatly reduce flooding in cities and local areas.

Green roofs reduce storm water runoff into drains. Green roofs can reduce flooding by up to 90%. The type of plant and amount of cover depict how much runoff will occur.

Sewer systems can become backed up and have added stress from flooding. Other forms of storm water management can lead to flooding. Green roofs are a perfect way to absorb excessive rain.

Urban areas cannot always build storm water runoff devices, but green roofs can always be placed on top of existing building. Living roofs are the most practical source for storm water management.

Metals commonly found in rainwater can disperse in the soil of green roofs instead of into water supplies. The amounts of copper, lead, and zinc can greatly be reduced by the use of green roofs.

Urban Heat Islands

The temperature of a city is warmer than that of surrounding areas. This is known as the urban heat island effect.

Cities are warmer than rural areas because buildings, roads and roofs reflect energy and absorb little. This makes the quality of life in cities lower.

Green roofs can reduce the urban heat island effect greatly. Green infrastructures absorb much of the sun’s energy. But, green infrastructure is hard to place in a city because the lack of space. Green roofs can lay on existing roofs and absorb a lot more energy. Also, living roofs will not reflect energy off other buildings.

Mary Gattis trusts that vegetative roofs will help cool Lancaster city’s ambient temperatures during the summer time.


Green roofs provide favorable habitats for insects, birds and native plants. A large section of cities are sealed by concrete and payment.  Green roofs create a valuable space for wildlife which was removed when a building is constructed.

Robert Kornman, Registered Landscape Architect, at Derck and Edson Associates, believes insect life is good for every environment.

Insects balance nature by producing pollen and are crucial components of the food chain.

Green roofs provide food and shelter for birds and insects such as butterflies and bees. Living roofs are mini-habitats which can bring wildlife back into a city. Even densely populated cities can have a range of wildlife to benefit from. 

Air Quality

Green roofs filter pollutants and toxins found in the air. Plants also reduce the amount of carbon dioxide and replace it with oxygen.

High temperatures can make breathing difficult in cities. Air pollutants can cause negative health effects to residents of a city.

The tight nit design of cities often leaves pollutants trapped in between buildings. Traffic and industrial technology create air borne toxins which loiter at every corner. City air can be cleaned through the use of vegetative roofs.


A change in environment can reduce stress levels. Green roofs provide relief and increase the quality of life for others around. The visual appeal associated with living roofs is calming and welcoming.

Vegetation has many spectacular smells and visuals on a large spectrum. Many of which cannot be found in urban areas. This adds health and beauty to a community.

Green roofs offer visuals that are uncommon and new to inhabitants to cities. In turn, this boosts human interaction with nature. The more interested a person is about green roofs, the more he or she will learn.

Living roofs offer a place for rest and relaxation that is not found in urban settings. Plant life will allow for buildings and structures to blend in more with the natural environment.

Many buildings and warehouses are unappealing. Green roofs will turn structures into wonderful works of art that welcome people.

Robert Kornman thinks is it a good idea to place green roofs on and inside of parking garages. These will make for great congregate areas no commonly found in cities.

Emotional and mental health are greatest in natural spaces. Green roofs provide a link between one’s mood and nature. Therefore, they are therapeutic in a sense.

Green roofs are more welcoming than concrete structures and black roads. They give urban areas more color and diversity.

Green Roofs give a greater richness to a community, allowing them to show culture and tradition.



Many existing structures may not be able to support a green roof. Green roofs are heavy and need a lot of structural support.

Always be aware of the structural capacity the building in question. Mary Gattis thinks it is important to find out if your building or home can handle the additional weight.

Most green roofs weigh 15-50 pound per square foot. This is more weight than a normal roof is used to. Be cautious of the weight of a green and the structural capacity of the building.

Owners should always be watchful of roof leaks. Incorrect installation practices can lead to leaking roofs.

The waterproofing will not always be installed correctly. Make sure the builder is knowledgeable about how this procedure is done correctly.

Base your contractor on past experience not price. Green roofs are relatively new idea in Lancaster County. Make sure your contractor is knowledgeable of the subject.

Ask to see previous green roofs your contractor has built. Call that place of business or residence and find out some information about how the roof is holding up.

The initial costs of building a green roof are high. The cost of materials and labor can reach outside of your budget.

Capital costs are high, but the life span of your green roof is more important than initial costs. Also, using the cheapest contractor may not save you money in the long run.

Robert Kornman understands that the costs of green roofs are more competitive than normal roofs. But, the life cycle costs make a great return on investment.


Modular Systems vs. Built-in-Place Systems

Both systems serve different purposes. Modular systems are typically used for extensive green roofs. Build-in-place systems are usually used for intensive green roof structures.

Modular Systems

A modular green roof uses individual, interlocking containers. Modular systems are commonly referred to as tray systems. This system can normally be placed on a existing roof. Modular systems are easy to maintain because they can be removed and replaced regularly.

Plants in tray systems are not disturbed by being removed. Each module has pre-planted vegetation grown by a nursery. This allows for installation of tray systems anytime of the year.

Modular systems are easy to modify since each plant or group of plants is in its own container. This allows for future add-ons and variations.

Maintenance of trays requires weeding and watering for the first year. After that point, the containers are self sustainable to a degree.

Built-in-place Systems

Built-in-place systems are commonly used for human interaction. Plants are more diverse in this system, allowing beautiful gardens to be created. 

Built-in-place systems are more expensive to install. This system must be built in place of an existing roof.

Built-in-place systems require more components and installation time. These systems need detailed design plans because of the complexity of layers that need to be incorporated.

The added components add extra weight to the roof. The soil must be at least 8 inches deep.  A roof must be able to support 40-200 pounds per square foot.


Layers of a Green Roof

The type of green roof dictates the number of layers needed. Intensive green roofs require more layers, while extensive green roofs require less. There are six central layers every green roof should have.

The first component is plants. Obviously, every green roof will have a visible layer of vegetation. The type of vegetation will vary depending on preferences.

Plants must be able to withstand year-round climate. Plant types should be able to withstand droughts while being able to absorb large amounts of water.

The growing medium is the next component. Different types of soil can be used for different plants and roof capacities.

A soil should be able to absorb water while retaining it. The amount of water soil can hold plays an influential role in water management.

Soils are usually organic and lightweight. The lighter the soil, the easier the stress is on a roof. Natural soils are heavier on roofs. Though they are organic, they are usually engineered by professionals.

Next, a filter membrane sits underneath the soil. This membrane blocks soil, debris and other particles from clogging the drainage layer. The filter also holds the soil above in place.

Filter membranes should allow for a good flow of water to the drainage layer while blocking other particles. If particles clog the drainage layer, flooding will occur.

The fourth component is the drainage layer. This layer carries away excess water which passes through the filter membrane.

When building a green roof, the drainage system must consider fluid transportation to water underneath the roof. Water on the surface needs to be drained using semi-conventional gutters and drains.  

The fifth component of a green roof is insulation. This insulation prevents water within the green roof from changing the temperature inside a house or building.

The weight of a green roof will not compact the insulation. This allows for it to be used fully and correctly.

The last component of a green roof is the water proofing layer. This is an important layer because it prevents the roof from leaking.

In certain cases, a root barrier may need to be applied so plants' roots will not penetrate the waterproofing.

Many green roof malfunctions are from leaks in the roof. Waterproofing plays an important role in the overall success of a green roof.



Photograph of a variety of sedums with pebbles as the growing medium.

By Parker McCaffrey


Types of Plants

The types of plants used for a green roof depend on the type of green roof. The depth of the soil plays a role in plant choice as well. Both intensive and extensive roofs use different plants.

Choosing plants that are native to the area will ensure they can handle the climate.

The best types of plants to use in Lancaster County span from sedums to perennials and grasses.

Intensive Green Roof Plants

Intensive green roofs allow for a more diverse selection of plants and shrubs. Small trees can even be used in intensive green roofs. The soil in intensive green roofs is deeper than that of extensive green roofs.

Plants include: grasses, perennials, shrubs and trees.

Each type of plant offers different degrees of benefits. Human interaction and visual appeal are important when choosing plants for intensive green roofs.

Extensive Green Roof Plants

Extensive green roofs limit the types of plants that can be used. Plants are low to the ground with smaller roots.

    Plants include:

    • many types of sedums

    • mosses

    • herbs

    • grasses

These plants can tolerate most weather conditions, decreasing the need to choose native plants.

Modular systems are grown before a green roof is constructed. This allows for the trays and plants to be installed any time of the year.

These plants require much less maintenance than ones on intensive roofs. These plants are more self-sustaining and do not need to be cared for regularly after the first year.



Photograph of two sedums on the Groff's green roof.

By Parker McCaffrey


Sloped Roofs vs. Flat Roofs

Green roofs do not only grow on flat roofs. Sloped and rounded roofs can also support living roofs. The slope of the roof decides if necessary precautions need to be made.

Flat Roofs

Flats roofs are roofs with a slope under 2 degrees. Slopes under 2 degrees can form puddles on the surface. This is because they cannot remove water as easily because they are not sloped.

Flat roofs offer a endless arrangement of plants and patterns. They can hold intensive and extensive green roofs.

Flat roofs make for easy interaction with vegetation. This allows for human interaction to be typical.

Sloped Roofs

There are many precautions when building a green roof on a slope.

Soil can slide off a sloped roof. Large plants will not grow upright on sloped roofs, causing unnecessary damage and loss of benefits.

A slope that is greater than 10 degrees can cause soil to slide down a roof.

With slopes greater than 15 degrees, stabilizers must be put in place to ensure the stability of a living roof.
Slopes that are more than 50 degrees generally cannot support green roofs.

Extensive green roofs work better for sloped roofs. The low-grounded plants and low soil depth allow the green roof to pleasantly rest on the roof.

Researching Green Roofs?

If you are interested in getting a green roof of your own, there are many things that need to be addressed, for instance:

1. Take into consideration your budget. Initial costs of green roofs are high and it would be a shame if you had to stop half way through the project. 

2. Research the structural capacity of your roof and its slope. Can a green roof be built on your slope? Can your house support the additional weight?

3. Choose plants that are native to the area and visually appealing to you. Native plants will respond to the climate better than other forms. This will give you the maximum benefits possible attained from a green roof.

4. Since the green roof will be part of your home, choose plants that you enjoy and colors that appeal to you.

5. Take into account your local surroundings. If you live by a railroad or airport, green roofs will help reduce the noise pollution entering your home. 

6. Decide what other benefits green roofs can offer you. Are you interested in energy conservation or storm water management?

7. Talk to variety of experts and consultants. Find out what is best for you and your home. Find out who is the most knowledgeable and can tend best to your needs.


Cost Analysis

Initial costs of vegetative roofs are much greater than conventional roofs. This is due to the complex steps and processes needed to successfully construct a green roof.

Long term benefits will outweigh these initial costs because green roofs offer longer life spans of roofs and energy conservation.

The type of green roof you choose (intensive or extensive) and the plant types will play a leading role in costs. 

Depending on the technologies used, an intensive green roof can cost on average anywhere from $15- $25+ per square foot.


  • Similarly, extensive green roofs cost an average of $8- $20+ per square foot.

  • There are several other factors which will increase the cost of a green roof.

  • A structural analysis will cite recommendations for repairs before a green roof is installed.

  • Consultant fees will be necessary for contractors, designers and builders.

  • The irrigation system for drainage and sprinklers will had additional costs.

  • Garden materials such as soil, trays and fertilizer will tack on more fees.

  • Building permits and codes may apply, these change depending on municipalities.

  • Short and long term maintenance will add more costs.

  • Costs vary for every job. Depending on location, extra costs might apply for transportation of materials.

Who Should I Talk to about Installing a Green Roof?

There are many areas of expertise which should be consulted before installing a green roof. Each professional examines different aspects of a house and potential green roofs. Material suppliers should also be contacted to see if they can accommodate your needs.

Green roofs are relatively new to Lancaster. Always make sure to consult a professional who knows the subject well. Ask for information from previous jobs. Don’t be scared to ask a lot of questions!


Seek advice from engineers to make sure your house can handle the weight of a green roof. They can also point out potential dangers a house possesses if a green roof is installed.

Landscape Architects

Architects can create a green roof for your house. They follow certain specifications and regulations which they are very knowledgeable about. Landscape architects can choose appropriate plants and craft special features, making your green roof different than the rest.

Roofing Contractors & Sub-Contractors

Roofing contractors can build the foundation of green roof. Most roofers have not gotten into green roof trends yet, so they may need to hire landscape companies to finish the job.

Be wary of who you hire to complete a job. Not all roofing or landscape companies know the proper procedures for constructing green roofs.

Suppliers & Nurseries

Material suppliers can provide the components needed to build a green roof. Suppliers have fabrics, drains and other materials.

Nurseries provide the plants and soils used for green roofs. Most nurseries have a large variety of plants. Plants grow in the nurseries so you can get plants in different stages of maturity.


Groff’s Family Funeral Home Case Study

The Groff’s Family Funeral Home is located on Orange Street in Lancaster city. In May, 2010, the Groff’s had a green roof constructed.

The green roof was only the 7th green roof installed in Lancaster. The first living roof was installed only one year prior to the Groff’s.

The Groff’s have an extensive green roof. The plant selection they chose was a variety of sedums.

The roof is not yet mature, but by next summer the plants will have grown greatly.

There is little maintenance necessary with the green roof, only the clipping of plants for propagation purposes. By next summer the funeral home’s roof will have even more plants than now.

Lisa Groff, President of The Groff’s Family Funeral Home, believed passing up the opportunity to get a green roof was a bad idea.

The energy conservation and extended roof life will be a good return on investment.

Lancaster city is beginning to regulate storm water management. The Groff’s now have a manageable way to control storm water. The funeral home is now one step ahead of city ordinances.

The Groff’s did not get a green roof to create business, but they do plan to make the roof interactive for clients in the future.

Although the roof uses extensive materials, it has the capacity to hold additional weight. The funeral home was once Lancaster’s Western Market. The roof docked cars for a local car dealership.

The Groff’s Family Funeral Home is taking steps to better Lancaster city. With their inspiration, other businesses in Lancaster will begin to take similar steps.



Photograph of the Groff's green roof in November.

By Parker McCaffrey


Roof Gardens

Roof gardens are gardens which reside on the top of a roof.

Vegetable gardens on roof tops do not provide the same degree of benefits as green roofs. This is because roof gardens do not cover the entire roof.
There are many arguments whether a roof garden is a green roof.

Roofs gardens provide similar benefits as green roofs but to a lesser degree.

Roof gardens produce a different assortment a herbs, beans, and vegetables. This is an excellent way for city dwellers with no lawn to grow fresh produce.

The different types of produce a roof garden can yield include: lettuces, herbs, pole beans, bush beans, snow peas, cherry tomatoes, spinach and zucchini.

Residents in Lancaster City can conserve energy while producing their own fresh produce. Trends in our economy make this idea a no-brainer.


Frequently Asked Questions

Why are they called green roofs?

  • Green roofs did not get their name because they are green in color. Green is term than means environmentally friendly or sustainable.

  • These vegetative roofs are considered green roofs because they help and become part of the environment.

What type of plants should I use?

  • The best types of plant to use are plants that are native to your area. These plants have the best chance of surviving climate changes. Native plants adapted to environment already, assuring they can handle different types of weather in the area.

  • Choose plants from which you enjoy the colors and patterns. Visually appealing plants are great for your mentality.

What is the return on investment of a green roof?

  • The return of investment of green roofs changes for every structure.

  • The amount of energy used and the surrounding environment play a role, too.

  • The addition lifespan of a green roof provides a return on investment, but this is over the course of many decades.

  • The social interaction and spirited mentality green roofs offer can also be considered a return on investment.

  • The new vigorous environment a living roof provides lets people escape from a city’s environment.

What country does the most green roof research?

  • Germany has performed intense research on green roofs for over 35 years. Germany has tested for many industry standards.

  • Many of the green roof guidelines in Germany involve: types of green roofs and vegetation, building technique requirements and procedures.

  • Berlin has the most green roofs of any city in Germany and one of many research centers is located there.

  • Germany not only does the most research on living roofs, but has the buildings with green roofs.

Should I use an intensive or extensive green roof?

  • There are many decisions involved when deciding this question.

  • The first thing you should look at is your budget. Intensive green roofs are more expensive than extensive green roofs.

  • Find out how your house will support both structures. Be sure to check for costs before installation of your green roof.

  • Think of the uses you want to receive from your green roof. Homeowners generally use green roofs because it is cost saving. Businesses can use living roofs for the same reason, but allowing human interaction will create more business and positive vibes.


Green roofs are hard to install. Consult with professionals when considering a green roof. Attempting to build a green roof yourself can lead to serious problems. You may find yourself spending more time and money choosing the do-it-yourself direction.

Green roofs will become a permanent part of your home. They should be aesthetically pleasing and welcoming to you. Choose a design that defines you as a person and brings out your favorite parts of nature.

Robert Kornman considers two ways to look at green roofs:

    • Green roofs are a good investment

    • Green roofs can actually be used

Begin to research green roofs soon. It is never too late to consider using a green roof. This is a great way of sustainability!


Future of Green Roofs in Lancaster

Green roofs are new to Lancaster County. The knowledge of vegetative roofs is growing rapidly.

Lancaster is already taking steps to build more green roofs in Lancaster. Every year Lancaster city will begin to see more and more green roofs.

The Lancaster County Planning Commission sponsors the Lancaster County Roof Greening Project.

The Planning Commission received a grant in 2008 from the Department of Environmental Protection Energy Harvest Fund.

With the money granted, they plan to reveal the numerous benefits green roofs offer. The commission also plans to encourage local businesses to consider green roof technologies.

Lancaster has a wonderful opportunity to build upon all the tradition already bestowed upon the city.

Lancaster must begin to accept green roofs as living, breathing, sustainable beings, which are beneficial to the environment. In order for this to be done, people must experience green roofs first hand.

Lancaster’s inhabitants need to experience green roofs, in turn creating the acceptance of green roofs.

Lancaster plans to eventually replace the vegetative footprint the city removed when it was being constructed. Lancaster can become a city running off positive, environmentally friendly energy.



Top of page



This site was created by Parker McCaffrey at Millersville University of Pennsylvania

© 2010 Millersville University. All Rights Reserved.