What Is A Green Roof? 23 Things (2024) You Have To Know

As the focus on sustainability continues to take center stage, more people are seeking ways to decrease their carbon footprint – and one unique method is a green roof.

This sustainability feature also has many other added benefits that homeowners can appreciate.

Let’s take a closer look at why this building system is becoming more popular in the United States so you can decide if it is a good choice for you.

1. What Is A Green Roof?

A green roof, also known as a living roof, is a roof that is either partially or entirely covered with plants and vegetation.

It consists of a waterproof membrane base, a growing medium (generally soil), and vegetation, which can be a wide variety of plants.

2. What Is The Purpose Of A Green Roof?

These roofs have many different purposes, benefiting both the homeowner and the environment.

They dramatically reduce electric costs by providing insulation, thermal mass, and shade to the building.

When it comes to the environment, green roofs provide a much-welcomed urban habitat for animals and plants, increasing local biodiversity.

3. How Does A Green Roof Work?

Green roofs provide exceptional insulation by moderating the urban heat island effect, which causes temperatures to skyrocket during the day.

They regulate internal building temperature by providing shade from the sun and removing heat from the surrounding atmosphere and the roof’s surface.

4. What Are The four Main Benefits?

Living roofs have many ecological and economic benefits, making them one of the most effective and impactful sustainability options available.

Let’s take a look at the top four benefits.

bulletRainwater Buffering

When rainwater hits the roof, its vegetation absorbs and purifies the water before discharging the excess into the sewage system.

This process ensures cleaner water enters the sewer systems, reducing the load on the sewage purification system.

It also reduces the chance of flooding and helps stabilize groundwater levels.

bulletAir Purification

It’s no secrete that plants are powerful air purifiers by removing contaminates and CO2 from the atmosphere and converting them into clean oxygen.

Green roofs effectively help purify the air, reducing emissions and providing clean, fresh air.

bulletAmbient Temperature Reduction

One relatively unknown specialty of plants is their ability to cool the surrounding area.

In fact, plants absorb a whopping 50% of sunlight and reflect another 30% drastically reducing the ambient temperature in the direct vicinity.

The result is a cooler internal building temperature which can lead to substantial air conditioning savings and an overall temperature reduction in the city of up to 3 degrees!

bulletIncreases The Roofs Life Span

Since a green roof offers protection against the elements, it can expand your conventional roof’s lifespan to as much as forty years or longer!

That means in as little as eight to twenty years; you could recoup your investment while enjoying the cool comfort your new roof provides.

5. What Are The three Types Of Green Roofs?

It is important to note that different regions may have a slight variation in the kind of roof offered.

However, the most widely accepted types are intensive, semi-intensive, and extensive, each with its own benefits and uses.

bulletIntensive Green Roofs

As the name suggests, intensive green roofs are the most labor-intensive model.

They often contain gardens or even parks and need constant maintenance to thrive.

The vegetation used can vary greatly, from simple turf to shrubs, trees, vegetables, and flowers.

bulletSemi-Intensive Green Roofs

Semi-intensive green roofs also require routine maintenance, but they may be smaller and less demanding than their intensive cousin.

While still requiring daily care, a semi-intensive roof may be a better option for those with limited gardening experience.

bulletExtensive Green Roofs

Extensive roofs are easier to maintain, are lighter in weight, and cost less than the other two roof varieties.

They generally thrive on rainwater, do not require regular irrigation, and can contain a variety of different types of vegetation.

6. What are The Main Disadvantages?

Green roofs have many advantages and very few disadvantages, making them one of the best environmentally-friendly building materials to use.

However, while the benefits far outweigh the drawbacks, there are a few disadvantages to note.

bulletInstallation Cost

The installation cost of a green roof is its main disadvantage since it is more expensive than other roof choices.

This cost increase is due to the need to reinforce the underlying roof structure to support the additional weight caused by the vegetation.

bulletMaintenance

Depending on the type of roof you choose, it may require additional maintenance throughout the year.

However, if you select a low- to no-maintenance option, you will not have to worry about daily upkeep.

7. Do You Need To Water Green Roofs?

Green roofs are generally low maintenance and require minimal upkeep – including watering – once established.

However, following installation, you should irrigate the vegetation as instructed by your roofer to ensure they develop a substantial root base.

Depending on your region, you will want to use native vegetation that thrives on local weather conditions, especially in dry, hot climates.

Using drought-resistant plants in these areas will ensure irrigation is rarely needed following the necessary two-year establishment time period.

8. Can You Walk On A Green Roof?

Yes, you can!

In fact, it’s actually necessary since they require once-yearly fertilization for proper upkeep.

The plants used on green roofs are generally hardy and will not suffer from the occasion trek.

If you live in a region that freezes, it’s not advisable to walk on your roof while the vegetation is frozen since this can cause damage.

It is important to note that depending on the slope of the roof, walking along it can be dangerous, so always use proper safety precautions.

9. Do You Mow A Green Roof?

One of the best parts about using a green roof is how low maintenance it is, ensuring you never have to worry about mowing!

While you can prune the vegetation blanket that develops, it isn’t necessary and will not affect the growth rate or structure stability.

10. Do they Attract Bugs?

Green roofs are a biodiverse habitat, so they will naturally attract bugs.

Bees, butterflies, yellow jackets, and wasps are some of the most popular insects that are drawn to living roofs, using the vegetation to build nests and for pollination.

While the attraction of insects may seem like a deterrent for some, they should not affect your daily routine, and the benefits of having these flying neighbors far outweigh any disadvantages they may present.

11. Can You Use Any Roof?

Yes, any existing traditionally roofed structure can be turned into a living roof!

Depending on whether you have a flat or sloped rooftop, you may be able to install the green roof yourself, but it is highly recommended to use a professional who is well-versed in the structural demands of the extra vegetation weight.

Additionally, sloped roofs require specialized soil and water retainment systems, so the roof stays put even when fully saturated.

12. Can Green Roofs Survive Winter?

Yes! They are incredibly hardy and can survive even the coldest weather.

During winter, the plants become dormant, allowing them to resist the damage freezing temperatures may cause.

When it snows, the snow acts as a protectant to the plants, shielding them from the wind’s desiccating effects and convective heat transfer.

Snow also offers protection from sudden temperature changes, which can have devastating effects on even hardy plant species, which is another reason why green roofs love winter!

13. Are Green Roofs Flammable?

While you may be concerned about their flammability, green roofs are surprisingly ignition resistant.

Ensuring your roof stays well irrigated is the key to preventing a devastating fire.

14. Can You Grow Food On A Green Roof?

Yes! They are excellent for growing food and are used extensively for this purpose in urban settings.

These unique roofs provide much-needed space for gardening a variety of delicious fruits and vegetables, and in some cases, even fruit trees!

Although, in theory, all green roofs can grow food, it’s best practice to try this intensive form of gardening on a flat roofed surface.

15. Do You Need A Slope?

Green roofs grow well on any roof pitch, making them one of the most flexible, sustainable growing materials.

Still, you will need to add a retainment structure for pitches greater than 9.5 degrees.

16. How Deep Does A Green Roof Need To Be?

They require a depth of between four to six-inches to adequately manage rainwater and root growth.

For blanket vegetation, which includes sod and shallow-rooted plants, this depth is sufficient for long-lasting growth and protection from a variety of weather conditions.

However, if you’re planting edible vegetation, you may need as much as twelve inches of soil to ensure the plants thrive.

Some vegetation may even require up to four feet.

17. Do Green Roofs Increase Property Value?

Adding a living roof to your home or property is one of the best ways to increase not only your property value but the value of the surrounding properties as well.

In fact, properties with green roofs are valued around 16% higher than those using regular roofing material!

18. How Often Do They Need To Be Replaced?

Green roofs can last an astonishingly long time.

The typical lifespan is between 40 and 55 years, but it’s not uncommon for them to last much longer in the right climate.

19. Do You Need Planning Permission?

In some cases, installing a green roof onto your home or property doesn’t require planning permission or permits.

However, it’s always a good idea to check your local regulations and ordinances to ensure you don’t need to receive prior authorization.

20. How Much Water Does A Green Roof Need?

Once your roof has become established, it will only require watering every twenty-eight days or so.

The time span between waterings depends greatly on the type of vegetation used and the depth of the soil with shallow substrates requiring more frequent watering for continued growth.

Drought-resistant plant species have been known to go up to eighty-eight days without water, but this length of time should be avoided if at all possible.

21. Do Green Roofs Reduce Flooding?

Since green roofs contain living plant life, they readily absorb rainwater on impact.

The soil and vegetation act like a sponge, soaking up the rain before it runs off onto the ground.

Since they capture such a large concentration of water, these roofs significantly reduce the amount of rain that accumulates on the ground, reducing the chance of flooding in the nearby surrounding area.

22. What Layers Are Needed On A Green Roof?

There are four to six layers that make up a green roof, which is why hiring a professional contractor proficient to install one is so important.

The layers include:

bulletWaterproof membrane

bulletRoot barrier

bulletDrainage

bulletAn optional additional water retention layer

bulletA filter fabric

bulletA growing medium like soil

bulletPlants and vegetation

23. How Does A Green Roof Drain?

Once the soil on your green roof is sufficiently saturated, the water will drain through the roof’s drainage layer.

The excess water will simply flow off the roof onto the ground below, just like with regular roofing material.

The drainage layer also provides aeration to the vegetation’s roots, which keeps them healthy and helps prevent rot.

Final Thoughts

A green roof has many environmental and economic advantages, making them one of the best investments you can add to your home or property.

It is an excellent option if you’re looking to lower your carbon footprint, reduce your heating and cooling costs, and increase sustainability.

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Erika Gokce Capital

Disclaimer: we are not lawyers, accountants, or financial advisors and the information in this article is for informational purposes only. This article is based on our own research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.

Erika

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