Green Roof Design: 3 Must-Haves for Your Next Commercial Project

roof terrace

Green roofs are a versatile solution for commercial architects, as they not only look beautiful, but provide a host of benefits for building occupants and owners alike.

Green roofs support the performance of a building in a multitude of ways. They reduce the amount of water that would otherwise run off a roof surface and can aid in building insulation, which can reduce energy costs. They also provide ample green space for both human and wildlife use.

Planning a green roof in your commercial building design is a great way to take your building’s performance and design further, especially when you take the following strategies to heart.

1. Insulation to Further Reduce Energy Costs

The combination of soil and plants offers some insulation on its own, but a green roof itself doesn’t offer measurable insulation for your building.

“Since most of the green roof heat management happens right at the surface — in the vegetation and the planting media — any additional energy conservation measures that go underneath the drain layer should supplement the vegetation/media heat management, not the other way around,” advises Chris Wark, Energy Editor for

He notes that designers and architects should plan for the amount of insulation carefully, keeping in mind it “should be calculated for your specific building and location before assuming how much is necessary.”


Green roof insulation solutions like XPS board function as a membrane barrier between the soil and the roof itself. It’s similar to how you'd place house wrap between the sheathing and the siding of a house.

Insulation products like Kingspan’s GreenGuard XPS boards come in a range of available solutions for roofing, wall and foundation applications. The GreenGuard XPS products are available in square edge boards or drainage channel boards, providing an extra barrier to green roofs against moisture infiltration.

2. Drainage to Prevent Stagnation

Proper drainage for green roofs is required for two reasons: to protect your structure from moisture damage and to ensure the health of the plants on your green roof.

Excessive moisture can destroy a roof, so imagine adding moisture-loving plants to your roof. This increases your risk of damage unless you have proper drainage for your roof landscaping.

Vegetative Roof Render

Standing water can wreak havoc on a roof, but this is easily managed by including a proper drainage system. Your drainage system should account for your region’s precipitation levels to ensure water is collected for maintaining healthy growth. But it should also drain off excess water when too much moisture is present.

Having a proper system to divert water away from plants that aren’t thirsty (like more native plants) will keep them healthy and your roof looking beautiful.

Solutions like GreenGuard XPS are available in drainage channel boards for vegetative roof systems, allowing easy drainage and air movement between layers of insulation.

3. Irrigation to Encourage Healthy Growth

Unirum Planta

Irrigation control is equally as important as drainage in a well-designed green roof. And it’s essential if you’re designing with plants and other vegetation native to your region.

A drip irrigation system is a great solution for green roofs. This system slowly distributes water directly to the plants’ roots, instead of spraying widely over the leaves. This uses much less water than traditional sprinkler systems.

You can also use this type of system to deliver nutrients to the plants. Drip irrigation systems are highly recommended for green roofs, as they conserve the most amount of water and are installed to work seamlessly with your design.


The Future of Building is Green

“Although green roofs are not simple or cheap, many cities recognize that long-term benefits outweigh the initial cost concerns,” says Carla Davis with NC State University.

“New York City, for example, has a pilot program encouraging the installation of green roofs by offering tax abatements. Provided that other cities follow suit, you might be seeing more and more roof gardens.”

Green roofs require time and care when it comes to planning, construction and initial upkeep, but your effort will be rewarded with a beautiful vegetative roof system that requires less maintenance over the years. When designing your green roof, remember these must-haves to better insulate and protect your roof, provide drainage, and have adequate irrigation for your plants.

Want more information about insulation solutions for your green roof? Check out some of our products and design ideas here.

Solutions like GreenGuard XPS are available in drainage channel boards for vegetative roof systems, allowing easy drainage and air movement between layers of insulation.

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