What Contractors Should Know About Green Roofs

Rooftop View With Vegetation

A Green Roof Can Refer to Vegetation-Based Roofs Or Simple Coatings

Roofer’s Guild is always on top of the latest trends in the commercial roofing industry. Once limited primarily to European countries, green roofs have emerged as a viable roofing system in the United States. As a community of contractors, it is our mutual responsibility to sort through the pros and cons of green roofs, and discern their most ideal application in the context of the commercial industry. Here’s what we know about green roofing:

“Green Roof” References Multiple Roofing Systems

The phrase “green roof” is used interchangeably in varying contexts. When someone describes a green roof, they are describing:

  1. 1.) A new roof with enhanced drainage, to go along with plants and vegetation


  1. 2.) An existing roof coated with an environmentally-friendly (“green”) topcoat

The first example represents a roof that is both literally and figuratively green. Not only does it help the environment, both locally, and at large, but it’s literally green in color. Onlookers will notice the roof, as it stands out from more traditional commercial roofing systems. The second example denotes a roof that is “green” in the sense that it is environmentally-friendly. The roof itself is not green in color, but only in philosophy.

Pros of Green Roofing

Having established what a green roof is allows us to delve deeper into its advantages and disadvantages. It’s not surprising that a green roof would have several environmental advantages. We detailed how “green” is often used as a term to describe environmentally beneficial items, whether they are roofing systems, or something else. Let’s take a look at some of green roofing’s pros:

1) Green Roofs Improve Drainage

Flat roofs often run into drainage problems which can gradually degrade their surface. Because of their lack of defined slope, stormwater really has nowhere to go. With plant-based green roofs, that problem is not only eliminated as a threat, but it is also converted into a benefit. Here’s how:

  1. 1.) Rainfall is stored in plants and released naturally
  2. 2.) Flooding in urban areas is reduced as a result

But what about “green” roofs that don’t host vegetation but are coated with environmentally-friendly substances? It depends. Some commercial roof coatings absorb standing water, while others to not. As a member of Roofer’s Guild, you’ll have access to a wide range of coatings, some which counteract the dreaded ponding water effect.

2) Green Roofs are Energy Efficient

If there’s one aspect to green roofs that is universal, it is energy efficiency. In fact, “green” is often used to describe materials that are energy efficient and sustainable, not just roofs. Insulation problems often sap a commercial building of its energy through the escape of cold air in the summer and hot air in the winter. Unsurprisingly, this loss of air has a butterfly effect that impacts energy bills, HVAC units, and interior comfort. A roof’s process of conserving energy is as follows:

  1. 1.) Absorb / Deflect Sunlight
  2. 2.) Decrease Roof Temperature
  3. 3.) Contain Air
  4. 4.) Curtail HVAC usage

As you might imagine, the process during the winter months is a little bit different, as its function depends more on curtailing air escape than deflecting sunlight. The impact is similar however, because less usage of HVAC units, whether they happen to be AC’s or furnaces, will lower energy bills considerably.

3) Green Roofs Improve Air Quality

Sustainable Roof Coating to Protect Environment

Coatings Discourage Collective Air Heating

Air pollution is a long-standing problem in urban areas. With so many industrial buildings close to one another, the community that breathes in byproducts, fumes, etc. tends to be exposed to greater health risks. One of the most appealing selling-points of green roofing is its ability to improve local air quality. Let’s take a look at the ways a green roof improves the air:

  • Dust Particles: Can reduce the amount of dust particles released into the air, which is a threat to community members
  • Sulfur Dioxide: Can reduce sulfur dioxide, a known air pollutant
  • Urban Island Heat Effect: Green roofs discourage this phenomenon in which groups of bunched up industrial roofs make the surrounding air hotter

Both kinds of green roofs will improve air quality, but full-scale vegetation-based roofs will have the greatest impact. Their plant-life surface discourages more dust than a commercial roof coating would alone, while redistributing stormwater into the atmosphere after processing. Coatings are still beneficial, especially regarding the Urban Island Heat Effect, which most every coating discourages.

Cons of Green Roofing

The Roofer’s Guild is a community of roofers whom values transparency above all else. We can’t help our fellow contractors if we don’t illustrate the ins and outs of the industry. While green roofs have their share of positive attributes, they are also not without their downside. Running a commercial building with a green roof is no picnic, even if it might look like one from the outside. Let’s take a look at some of green roofing’s primary cons:

1) Requires Vigilant Upkeep

Just like a garden takes work, so does a full-scale green roof with plants and vegetation. The maintenance required to keep the system functioning up to its potential is considerable, and something many consumers are not prepared for. To avoid getting a bad review or reputation, you’ll want to detail this attribute to prospective customers. Not only will you as a roofer be responsible for regular maintenance, but so will the building owners themselves. It includes:

  • Landscaping: Keeping weeds from growing around the vegetation, and preserving general appeal
  • Watering: Keeping the plants hydrated like with a garden

For coating-based green roofs, the types of maintenance will differ. Oftentimes coatings require far less upkeep than full-scale green roofs. You’ll want to review each of the commercial roof coatings options and be prepared to communicate which coatings will be the most or least demanding from a maintenance perspective. Remember, educated consumers make better decisions both for you and for themselves.

2) Costs More Money

That’s right, you guessed it, green roofs are quite expensive. As a roofing contractor you might consider that a bonus, but you’ll soon learn that very few businesses are looking to break the bank. To sell a green roof, you’ll want to highlight the financial reimbursement probabilities. For example, ask customers to consider expenses saved on:

  • Energy Bills
  • HVAC Equipment
  • Leaks / Moisture Repairs

Making sure your consumers understand the financial incentive to a green roof makes them less likely to cringe at the throughout of its upfront cost. They will also of course be cognizant of the maintenance frequency, which in some cases might include outsourcing the upkeep to a 3rd party. The overall expense of green roofing is notable, but it’s important to view it within the context of its overall function.

3) Prompts Structural Distress

The most common cause of early roof failure is structural damage. In fact, the best indicator of whether a roof can still be salvaged through restoration, or must be replaced, is structural damage. So what causes structural roof damage? One major threat is excess weight. Full-scale green roofs add considerable weight to a building while “green” coatings add almost none. Consider the differences below:

  • Green Roof W/ Plants & Vegetation: Adds considerable weight to the roof and requires accommodating structural support
  • Green Roof Coating: Generally applied in liquid form, which adds no discernible weight

A full assessment of the structure should be conducted before proceeding with green roof installation. As for coatings, the surface should be cleaned and cleared of debris prior to application. Most green coatings can actually reduce weight by discouraging standing water which can tip the scale if left unresolved. The last thing a customer wants is a collapsed roofing system.

Final Verdict on Green Roofs

Contractors Guide to Green RoofingAt the end of the day, green roofs are a system most commercial contractors should offer. While you may not get a large percentage of your consumer base jumping on a full-scale green roof project, many more will be intrigued by green roof coatings. Still, businesses with major capitol might invest in a green roof in efforts to be progressive and to help the environment. Educating them about the pros and cons outlined in this article helps keep you in the clear of any misunderstandings, and can lead to more jobs down the road.

If you would like to learn even more about green roofing, or to gain access to green roof supplies, consider becoming a full time member of the Roofer’s Guild. We are national community of roofers with mutual dedication to collective excellence. Our group has access to Conklin roofing supplies, which are renowned throughout the industry. Call (877) 282-8968 to join Roofer’s Guild today.

Final Verdict: Green roofs are an intriguing option, but coatings are simpler and less expensive