The Pros and Cons of Different Types of Commercial Green Roofing Systems

Green buildings have gained momentum in an era of environmental concerns. Homeowners and commercial property owners consider installing green roofs a sustainable and appealing option. As our planet faces global warming and increased energy consumption, taking steps toward improving our environment is crucial. This guide explores the advantages of green roofs and how access products optimize functionality and maintenance for commercial construction professionals.

Understanding Green Roofs

Green roofs support plant life and serve as gardens, mini-farms, and research centers. They also help to reduce heat islands. They're complex systems that require maintenance but offer numerous benefits.

This guide provides insights for commercial professionals considering green roofs, weighing the pros and cons of various commercial green roofing systems. It discusses covering types, materials, and costs and delves into structural requirements, irrigation systems, and soil considerations. Additionally, a cost-benefit analysis helps evaluate whether a green roof is a worthy investment.

The Pros and Cons of Different Commercial Green Roofing Systems

Many types of vegetated roofs exist, each with their pros and cons. We will discuss four of them - intensive, brown, semi-intensive, and extensive.

Intensive Green Roof

Common in commercial buildings, they support gardens and entertainment spaces. Safety requires installation on flat roofs with a pitch of less than 9.46°. Trees and shrubs can be accommodated due to their deep roots, adding weight to the structure.

Pros:

• Supports gardens and entertainment spaces, enhancing usable outdoor areas for building occupants.
• Accommodates various plant types, including trees and shrubs, creating a lush and visually appealing landscape.
• Provides excellent stormwater management and insulation benefits due to the deep soil layer.

Cons:

• High weight load due to deep soil and large plants, potentially requiring costly structural reinforcement.
• Requires intensive and ongoing maintenance, including irrigation, pruning, and soil management.
• There is a greater risk of waterproofing issues due to the complexity of the landscaping elements.

Brown Roof

Supports biodiversity or addresses ecosystem issues. Utilizes local materials.

Pros:

• Supports biodiversity and addresses ecosystem issues, contributing to local ecology and habitat enhancement.
• Utilizes local materials, reducing the carbon footprint of sourcing exotic plants or materials.
• Can assist in managing stormwater runoff and air quality improvement.

Cons:

• Limited visual aesthetics, as the focus is primarily on ecological benefits rather than visual appeal.
• Requires careful consideration of local conditions and species selection to establish an autonomous biodiverse environment.
• It may still require some maintenance to encourage desired biodiversity.

Semi-Intensive Green Roof

Semi-intensive green roofs are shallower than intensive roofs, accommodating select bushes and grasses, and most suitable for flat or low-slope roofs with a pitch of less than 18.43°.

Pros:

• Accommodates select bushes and grasses, balancing aesthetics and weight load.
• Suitable for flat or low-slope roofs, providing versatility in building compatibility.
• It offers stormwater management and insulation benefits like intensive systems, though to a lesser extent.

Cons:

• Adds weight to the roof structure, potentially necessitating reinforcement, especially for existing buildings.
• Requires periodic maintenance for watering, pruning, and managing plant health.
• Plant selection is more limited compared to intensive systems.

Extensive Green Roof

An extensive green roof is the shallowest and supports moss or sedums. It’s ideal for roofs with high slopes.

Pros:

• The shallow design makes it suitable for roofs with high slopes, expanding the potential range of compatible buildings.
• Requires minimal maintenance once established, often only requiring occasional weeding and inspection.
• It offers stormwater management benefits and can help mitigate the urban heat island effect.

Cons:

• Limited plant diversity, primarily supporting drought-tolerant species like sedums, which might not provide diverse habitat benefits.
• It might provide a different visual impact than lusher and elaborate green roof types.
• The initial establishment phase may require additional maintenance to ensure plant survival.

These pros and cons provide a comprehensive understanding of the advantages and limitations of each type of commercial green roof system. These points vary based on specific project requirements, local conditions, and design choices.

Layers of a Green Roof

Regardless of the roof type you choose, the layers remain consistent:

1. Sheet Metal Substrate/Decking: A structural base that supports the layers above and provides a foundation for the green roof system.
2. Vapor Control Barrier: Prevents moisture from migrating into the roof structure, protecting it from potential damage.
3. Insulation: Enhances energy efficiency by providing thermal resistance and regulating indoor temperatures.
4. Waterproof Membrane: Ensures the roof remains watertight, preventing leaks and protecting the building underneath.
5. Root Barrier: Prevents plant roots from penetrating and potentially damaging the waterproofing layer.
6. Drainage Layer: Allows excess water to drain away from the growing media, preventing waterlogging.
7. Filter Layer: Filters out fine particles and helps prevent clogs in the drainage system.
8. Substrate/Soil: Provides a growing medium for plants, supplying nutrients and anchoring roots.
9. Plants: The living greenery that adds aesthetic, environmental, and functional benefits to the roof.

Application Systems for Green Roofs

Installation methods for plants and substrates vary, but here are the most common types and the pros and cons of each.

Vegetated Mats

Pros:

• Instant Coverage: Vegetated mats provide immediate green coverage after installation, enhancing the visual appeal.
• Erosion Control: Mats prevent soil erosion during establishment and can offer immediate stormwater benefits.
• Reduced Establishment Period: Mats are pre-grown, leading to faster establishment than seed-based systems.

Cons:

• Limited Plant Choice: Mat systems usually have a predetermined plant mix, limiting customization based on local conditions.
• Transport Challenges: Transporting and handling large mats can be logistically complex.
• Maintenance Complexity: Once established, ongoing maintenance can be more challenging due to the uniform plant cover.

Pre-vegetated Trays

Pros:

• Design Flexibility: Trays allow more plant diversity and design flexibility than vegetated mats.
• Modularity: Trays are modular and easy to transport, facilitating installation and replacement.
• Immediate Impact: Like mats, trays offer instant green coverage and some stormwater benefits upon installation.

Cons:

• Initial Costs: The trays' installation cost can be higher than other methods.
• Maintenance Demands: Maintenance needs are like mats, requiring care for established plants.
• Potential Drying: Trays might have higher drying potential due to exposure, requiring careful watering.

Plug Installation

Pros:

• High Customization: Plug installation offers the highest level of plant species customization based on local conditions.
• Strong Root Integration: Direct planting fosters better root integration with the substrate, enhancing long-term stability.
• Adaptability: This method can work well with various roof shapes and sizes.

Cons:

• Slower Establishment: Plug systems take longer to establish compared to pre-grown systems, leading to slower initial coverage.
• Maintenance Intensity: Early maintenance demands can be high to ensure plug survival and growth.
• Professional Skill Needed: Planting plugs requires expertise to ensure proper spacing and establishment.

Naturalized Green Roofs

Pros:

• Local Ecology: Naturalized roofs promote the establishment of local plant species, benefiting local ecosystems.
• Low Maintenance: Once established, these roofs generally require less maintenance than vegetated systems.
• Simplicity: The natural colonization process can be simpler than installing pre-grown systems.

Cons:

• Long Establishment Period: Naturalized roofs take time to develop and might have an extended period without full coverage.
• Visual Appearance: These roofs might not provide the lush green appearance typical of other systems during establishment.
• Initial Weeds: Weed colonization might occur before desired local plants are established.

Remember that the suitability of each system depends on factors such as local climate, building structure, maintenance resources, and project goals. Choose the method that aligns best with your specific requirements.

Irrigation Systems for Green Roofs

Pros and cons of each irrigation method for green roofs, along with the use of moisture sensors and watering schedules:

Spray Irrigation

Pros:

• Uniform Coverage: Sprinkler heads can distribute water evenly across the entire roof surface.
• Quick Application: Spray irrigation is relatively quick, making it suitable for larger green roof areas.
• Cooling Effect: Water droplets can contribute to cooling the green roof surface and the surrounding air.

Cons:

• Water Waste: Spray irrigation can lead to water wastage due to evaporation and overspray.
• Uneven Penetration: Water might not penetrate deeply into the substrate, potentially leading to shallow root growth.
• Maintenance: Sprinkler heads require maintenance to prevent clogging or uneven distribution.

Drip Irrigation

Pros:

• Water Efficiency: Drip irrigation sends water directly to the root zone, minimizing evaporation and waste.
• Precise Targeting: Allows targeted watering, reducing the risk of water-related issues like fungal diseases.
• Less Foliar Wetting: Reduced foliage wetting can lower the likelihood of certain plant diseases.

Cons:

• Slower Application: Drip irrigation might take longer to provide sufficient moisture than other methods.
• Clogging Risk: Drip emitters can be prone to clogging, requiring regular maintenance and cleaning.
• Uneven Distribution: Poorly designed systems can lead to uneven water distribution across the roof.

Drainage Layer Irrigation

Pros:

• Even Moisture Distribution: Flooding the drainage layer or substrate ensures water reaches different root depths.
• Reduced Evaporation: Watering at the substrate level minimizes surface evaporation.
• Low Maintenance: This method typically has fewer components prone to clogging or malfunctioning.

Cons:

• Potential Over-Saturation: Excessive watering can lead to waterlogging if not appropriately managed.
• Drainage Impact: Excessive flooding might compromise drainage system efficiency, affecting roof performance.
• Limited Precision: It might be challenging to precisely control water application using this method.

Moisture Sensors and Schedules

Pros:

• Water Efficiency: Moisture sensors can help avoid overwatering by only irrigating when necessary.
• Plant Health: Proper moisture levels promote healthier plants and reduce the risk of water-related issues.
• Automation: Sensors and schedules automate irrigation, reducing the need for constant monitoring.

Cons:

• Initial Setup: Installing moisture sensors and programming schedules requires technical knowledge.
• Sensor Accuracy: Sensor accuracy can be affected by sensor placement and maintenance.
• Cost: Implementing a moisture sensor system may involve additional costs for equipment and installation.

Consider the specific needs of your green roof project, including climate, plant types, and available resources, when selecting the most suitable irrigation method and automation strategy.

Pros and Cons of Different Types of Soils for Green Roofs

Substrate materials include mulch, clay, peat moss, and more. Choose based on plant needs and consult experts or ASTM E2777.

When choosing soil for green roofs, also known as substrates, several options are available, each with advantages and disadvantages. The choice of substrate is crucial as it directly impacts plant health, water retention, drainage, and the overall success of the green roof.

Here are the main types of soil used on green roofs and their pros and cons:

Extensive Substrates

Pros:

• Lightweight and shallow, ideal for shallow-rooted plants.
• Good drainage, reduced building weight load, and less maintenance.

Cons:

• Limited water-holding capacity might require more frequent watering.
• Little plant diversity due to low nutrients.

Semi-Intensive Substrates

Pros:

• Balances between extensive and intensive systems.
• Accommodates a broader plant range and better water retention.

Cons:

• Heavier ones might need stronger structures.
• Slightly more maintenance than extensive systems.

Intensive Substrates

Pros:

• Supports diverse plants, even trees.
• Offers better water retention in complex ecosystems.

Cons:

• Heavier requires thorough engineering.
• More maintenance due to diverse plant needs.

Custom Blended Substrates

Pros: Tailored characteristics for specific plant preferences and site conditions. 

Cons: Potentially more expensive due to specialized mixtures.

Plant-Based Substrates

Pros: The sustainable option reduces environmental impact.

Cons: It can decompose and may need replenishment.

Mineral Substrates

Pros: Lightweight drainage can be combined with other materials.

Cons: Limited nutrient capacity, higher initial costs.

Choose a substrate based on intended plant types, climate, building structure, and maintenance capabilities. Consult experts for the best fit.

The Pros and Cons of Different Types of Plants for Green Roofs

Native Plants

Pros:

• Biodiversity Support: Habitat and food for native wildlife.
• Adaptation: Well-suited to local climate, less water needed.
• Resilience: Natural defenses against pests, reduced need for chemicals.

Cons:

• Slow Establishment: Longer time to establish.
• Limited Aesthetics: Some might have a subtle appearance.
• Limited Plant Selection: Specific soil requirements.

Productive Plants

Pros:

• Edible Yield: Local food production.
• Educational: Opportunities for occupants.
• Aesthetic Appeal: Visually appealing landscapes.

Cons:

• Maintenance Intensity: More care is needed.
• Weight Load: Heavy soil, need for structural support.
• Complexity: Requires fertility management.

Landscaping Plants

Pros:

• Low Maintenance: Drought-tolerant, less upkeep.
• Aesthetic Enhancement: Improved visuals.
• Pollinator Attraction: Attracts pollinators.

Cons:

• Limited Ecological Impact: Less ecological benefits.
• Limited Habitat: Additional habitat might be needed.
• Invasiveness: Non-natives can become invasive.

When selecting plants, consider project goals, climate, maintenance, and desired benefits.

Structural Requirements for Living Roofs

Structural preparation is vital, especially for these three major considerations:

• Account for added weight, especially for intensive roofs.
• Retrofitting may be necessary.
• Consult experts for design changes.

Benefits of Commercial Green Roofs

Green roofs offer numerous advantages:

• Beauty and green space.
• Heating and cooling cost reduction.
• Longer membrane life.
• An attraction for occupants and customers.
• Research opportunities.
• Stormwater management.
• Plant and produce production.
• Solar panel integration.
• Increased property value.
• Urban heat island reduction.
• Biodiversity enhancement.

Disadvantages of Commercial Green Roofs

The two disadvantages, if you think of them that way, are: 

• Installation costs.
• Ongoing maintenance expenses.

Cost-Benefit Analysis for Green Roofs

When doing a cost-benefit analysis to estimate costs and compare benefits, be sure to include the following steps: 

1. Consult professionals.
2. Account for structural changes.
3. Consider maintenance expenses.
4. Analyze advantages.

Where to Get Started with Green Roofs

Begin with experienced professionals - architects, engineers, and landscapers. Fakro's DXW walkable skylight offers a unique approach to flat roof design. It features a strengthened frame and non-slip coating, allowing safe movement. Its modern design, high-quality finish, and secure glazing unit enhance aesthetics without compromising safety.

Key Characteristics:

• Safe movement across the surface.
• Strengthened frame.
• Excellent thermal insulation (Uw = 0.12 Btu/h ft² F).
• Anti-slip coating for safety.
• Ensures room illumination.
• Resistant to moisture.
• Energy-efficient glazing units.
• Increased break-in resistance.
• Range of accessories.

Installation and Usage

Before installing Fakro's Walkable Skylight DXW, familiarize yourself with fitting instructions, usage guide, and instructional video, and read the specifications to understand fully.

Green Means Go! 

Now that you thoroughly understand the pros and cons of different types of green roofs, you're in a better position to get started. Remember! Commercial green roofs are an environmentally conscious choice with numerous benefits. Integrating access panels enhances their functionality and maintenance. You can create a harmonious environment that benefits your building and the planet by selecting appropriate green roof types and combining the Fakro DXW Walkable Skylight. Always seek professional advice for your specific project.

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Contact our access door specialists, and we'll help you get started on your next project! Reach us at 1-800-609-2917 or let us know what you need by filling out our quiz!