The History of the Denver Green Building Law

The new Denver Green Building Law has a significant focus on cool roofs (in fact, they are mandated for all new and existing buildings in Denver). But it wasn’t always meant to be that way. The original ordinance, which Denver citizens voted for in November of 2017, would have required all new and existing buildings to install a green roof, not a cool roof.

After the Green Roof Initiative passed in November 2017, it quickly became obvious that the language would have some unintended consequences, so a task force was formed to ensure a good compromise was met between private interests and local citizens. It became very clear that requiring green or vegetative roofs on all buildings would be challenging for many local industries. The task force, which had 25 people, consisting of City staff, real estate experts, green roof experts, and roofing industry representatives, spent over 6 months deliberating the original ordinance.

In addition, many channels and opportunities for public comment and feedback were created in order to ensure that whatever law was passed would both allow Denver to mitigate the impact of the Urban Heat Island effect while also allowing it to be as easy to comply with as possible.

The result? The task force provided a proposal to City Council that they felt would meet the environmental goals of Denver while also allowing building owners and development companies a myriad of options to comply in easy and affordable ways with the ordinance. The City Council approved the proposal and voted the new ordinance into law on October 29th, 2018, almost a whole year after the initial mandate made headlines. The new law went into effect on November 2, 2018.

Now there are several compliance pathways that focus on much more than green roofs but instead focus on the overall impact of the building. For example, many building owners can opt for renewable energy programs with Xcel, or install solar energy on their building in order to comply. But regardless, all buildings must have a cool roof. That is how a law that focused on green roofs became a cool roof ordinance that focused more on green building in general. This mitigates any unintended consequences of the original language and gives building owners more options that are environmentally and budget friendly.

Need help with your green building project? Contact Sow Green today for a consultation!

Why did voters pass the Green Roof Initiative in Denver?

In November 2017, voters passed the Green Roof Initiative that requires large buildings to install green roofs or solar. It is important to understand the motivation behind this passing. Although, we do not know that exact reason everyone voted for this, we know the main ideas behind the messaging of the Green Roof campaign.  

Reduce Urban Heat Island and improve Air quality

The Urban Heat Island effect is when urban areas become hotter than the surrounding rural areas due to the large amount of impermeable surfaces, such as concrete parking lots and black rooftops.  According to the EPA, during the summer months pavement and roofs can be 50–90°F warmer than shaded or moist surfaces (1). It is estimated that anywhere from 5%-10% of energy used by a community in the summertime is compensation for the Urban Heat Island effect (2). Denver is the 3rd highest Urban Heat Island in the US.

More green spaces reduce the Urban Heat Island and the overall ambient temperature in our community. Increasing vegetation in urban areas can also improve storm water management and air quality. More green spaces in Denver could mean more vegetation to filter pollutants from the air. A study in Toronto found that 58 metric tones of air pollutants could be removed if all the roofs in the city were converted to green roofs (1). The level of reduction in pollution depends on the type of vegetation and roof design, with extensive green roofs having a lower impact than intensive ones.

Why is this important? First off, almost 50% of Denver residents do not have any kind of air conditioning unit or system in their home. As summers in Denver reach record high temperatures each year, so does the risk of heat-related illness and deaths. Large areas of Denver contain what are known as “vulnerable populations,” such as the elderly or those with pre-existing conditions that affect the bodies ability to regulate temperature, such as diabetes. Keeping our city cool protects those most vulnerable in our community while improving the quality of life for everyone else.

Storm water management

Urban development in major cities has created more surfaces laden with concrete and steel instead of soil and trees. This not only increases the Urban Heat Island but also causes stormwater issues. Green roofs reduce the amount of stormwater a building has to treat because the soil and vegetation soak it all up (and in many cases can reduce pollution runoff). So not only are you reducing the impact your building has on the natural environment, but you’re saving money in the long term on stormwater fees. Many cities even have programs that give a reduced rate to buildings with vegetative roofs or permeable surfaces like brick parking lots.

In many cities, developments often require a retention pond for stormwater runoff, requiring the purchase of additional land. With a green roof, such purchases can be reduced or mitigated entirely. For example, a 4″ extensive sedum roof could potentially capture 60-75% of annual rainfall. A deeper growing medium could retain even more water, reducing stress on sewage systems and instances of flooding. If the runoff from large storm events is delayed, our sewer systems and bodies of water do not overflow.

This was the main messaging that resulted in Denver voters passing this by 8.5%. There was also messaging around energy efficiency and reducing greenhouse gases and resonated with voters. These became important criteria in creating the revised Green Building Initiative, which we will discuss more next week.


1.     CURRIE, B.A. & BASS, B. (2008) Estimates of air pollution mitigation with green plants and green roofs using the UFORE model. Urban Ecosystems 11: 409 - 422.

2.     YANG, J., YU, Q. & GONG, P. (2008) Quantifying air pollution removal by green roofs in Chicago. Atmospheric Environment 42: 7266 -7273.

What You Need to Know Before Building a Roof in Denver

As of November 2nd, 2018, the City of Denver has enacted a Green Building Ordinance. This requires any roof over a 25,000 square foot building to have a cool roof and another eco-friendly option. If you’re building a new building, your roof will have to comply, and existing building will have to comply when replacing their current roof (unless the roof being replaced was damaged in an emergency). So what do you need to know in order to be compliant in the Mile High City?

Step 1: Understand Your Options

There are two compliance pathways you can take, one for existing buildings and one for new construction. All roofs must be cool roofs, and in addition to that, you must choose at least one of several compliance options. New buildings have eight compliance options, and existing buildings have five. The options range from green roofs (otherwise known as vegetative roofs), solar panels, green energy programs with Xcel, green building certifications, or a cash-in-lieu fee of $50 per square foot that goes into a City Green Fund. Some options are expensive and some are quite affordable, but almost all of them will actually save you a lot of money in the long run.

Step 2: Establish Your Goals

Whether you are building a new roof or replacing one, your goals for meeting these compliance options are important for determining with pathway is best for you. You may, in fact, want to choose the most difficult, but the most sustainable option simply because you know that a sustainable building with a green roof will last longer, save you money, and have a positive impact on the community in which your building resides. Or you may be on a very small budget and want to choose the least expensive option. Maybe there is a way you can do a little bit of both. But knowing what your values are will help you determine the right options within your budget and timeline.

Step 3: Hire the Right People

So how do you align your goals with the right compliance pathway and make sure everything goes to plan? You hire the right people. From green roof consultants to green building contractors, you want to make sure you hire someone who understands local laws and can make sure you are compliant. In addition, you want to hire someone who will choose the best option for your budget. There are a lot of financing options for green roofs and alternative energy projects that have low interest rates and terms, as well as tax or saving incentives for green building projects. And depending on the compliance pathway you want to choose, you may need additional help such as structural engineers or landscape architects.

It may seem daunting at first, but the Green Building Ordinance is actually a great document that gives building owners and contractors a lot of options to be compliant, no matter what your situation is. If you think you’ll need help with replacing or building a roof, contact Sow Green today. We can help you understand your options and hire the right people to make sure your project goes as smoothly as possible!

Green Roof Myths Debunked: They Are Not Covered by Insurance

Fires. Natural disasters. Acts of violence. We don’t want to think about them, but they do happen, and when disaster strikes we need to be ready. That is why despite its confusion and unpopularity, insurance coverage is necessary. One of the common myths surrounding green roofs is that they are not covered under insurance. If you don’t already have a green building, it is possible that the vegetation and irrigation system is not covered by your current property or roof insurance plan. But we're here to bust another myth because they can be!  

One way to make sure your green roof is covered is by purchasing landscape insurance to cover the loss of plants, growing medium, and the water source (irrigation). This might not be included in your property insurance plan if you don’t already have landscaping, but it can easily be added by a lot of insurance providers. If you don’t feel like the landscaping insurance is going to cover the cost of your green roof, you can write up specific endorsements to ensure you’re covered in the event of a loss. If you do this, you’ll want to properly determine the value of your roof so that you aren’t paying too high a premium. High insurance premiums will simply cut into the cost savings and benefits of having a green roof.

This option is great if you simply placed a green roof on a not-so-green building. But if your building is sustainable or green certified, you might want to consider purchasing green building insurance from a provider that understands and values the losses associated with rebuilding.

Many insurance companies are now offering green building insurance to the U.S. commercial marketplace. Their offerings can include special green infrastructure endorsements, alternative energy production protection, and vegetative roofs. They also often have coverage to protect green building owners investments such as tax incentives, utilities, loans, and more. Even though the plans vary from company to company, you can be sure to find a plan that fits your needs and budget. The green building market is one of the fastest growing in the world, and insurance companies are more than willing to offer services to help. In fact, there were over 65,000 LEED certified projects in 2017 in the US alone (1)!

A lot of hard work goes into the design and construction of a sustainable building, so it's important to realize that when bad things happen, you don’t just have to rebuild, you’re missing out on all the cost savings and health benefits your building gives you!




David and Goliath, Compromise and Government: The Tale of the Green Roof Initiative

Monday night, October 27th, was a monumental night for sustainability. In Denver, City Council passed a revised Green Building Initiative. After almost a year of hard conversations and compromise, this is now one of the strongest pieces of local green building legislation in the country. As President of City Council, Jolon Clark said: “thank you all for setting a great example, not just as leaders in our city but in our country.” He continued, “The entire nation should look to this room to see how government can and should work. Take note that it is messy and it’s hard work and took a lot of time and hours. But it is totally worth it...”

It all started with Brandon Rietheimer, a manager at a local Red Robin. The divisive political climate inspired him to improve the environment. He came across Toronto’s Green Roof Bylaw and wanted to enact something similar in Denver to mitigate climate change. City Council said no, so he took it to the ballot. He had never run a campaign before, but he single-handedly got 4,000 signatures and assembled volunteers. Even though he was outspent 12 times over, with his team’s hard work and dedication, they convinced voters and won by 8.5%!

After the law passed in November 2017, the City formed a task force of various stakeholders, mostly from industry opposition. It took over 6 months of deliberation and in the beginning, conversations were tense. But the group eventually came to a consensus, with a newly revised Green Building Initiative. Kathie Barstnar, who spearheaded opposition to the ordinance stated Monday night: “the proponent and opposition are in complete agreement with the revised ordinance. This day and age, coming to a complete consensus is a unique thing.”

This newly drafted ordinance requires all new buildings over 25,000 sq. ft. and roof replacements to have a cool roof. They also must choose another eco-friendly option, such as a green roof, solar energy, or energy upgrades.

It was powerful to hear from the biggest opponent, Kathie Barstnar head of  NAIOP Colorado. NAIOP represents owners, developers, and investors in commercial real estate. Kathie states “this ordinance is a delicate balance of ideas and solutions that will not only result in eager compliance but ultimately result in even more environmental benefits than original ordinance would have.”

In a day and age of political dispute and often feeling powerless as citizens, this is proof that a single person can make a difference. When one individual can work towards a better city, great things can happen. Opposite viewpoints can come together and reach a compromise. This is how our city passed legislation that will make Denver a leader in protecting our environment. As elections near, remember your vote, and your voice, matter more than you think!

Green Roofs Myths Debunked: Expensive to Irrigate

In a drought-prone area such as Denver, you might think that green roofs are costly and difficult to irrigate. We already use more water than we should, and as our summers get hotter the need for water will increase. Shouldn’t we be conserving as much water as possible? It’s time to debunk another green roof myth.

It is true that in the few first years of development, many green roofs need irrigation to help plants establish roots and mature. If you are installing an extensive roof, you can avoid costs and reduce the development period considerably by using pre-grown mats made offsite. If not, you will need some sort of drip irrigation or manual method (like a good old-fashioned water hose).

Luckily there is a myriad of ways to reduce the amount of water needed for irrigation. You can design thicker layers of growing medium that can absorb and retain more water, and install a water retention layer that can catch drainage. Using native plants, and plants that are drought resistant such as sedums can also help reduce water use. In addition, you can use water recycling methods such as grey water irrigation or collecting HVAC condensation. But even if a small amount of water is used for irrigation, it is just a drop in the bucket compared to how much water green roofs can save.

Denver Water did a study on Denver’s Green Roof Initiative and decided that there will there is no negative water impact. Most buildings are expected to have extensive green roofs that don’t need much irrigation. Also, the amount of water retained on green roofs helps the city prevent overflow during storm events.

Remember how we’ve mentioned that cities are getting hotter each year? Living architecture such as green roofs and green walls help mitigate urban heat islands, reducing the average temperature of our neighborhoods and our overall consumption of energy. It can also insulate buildings, further reducing the energy needed for heating and cooling. And energy production requires an astonishing amount of fresh water.

In fact, a study at Virginia Tech found that the amount of water needed to burn an incandescent light bulb for one year could be anywhere from 3,000 to 6,000 gallons (1). The natural gas extraction method most commonly known as “fracking” can use anywhere from 1.5 to 16 millions gallons of water per well depending on how they are managed (2). In addition to using an enormous amount of water, the fossil fuel industry is also responsible for negatively impacting the quality of water. Either from oils spills, extraction processes, wastewater from refineries, or groundwater contamination, the fossil fuel industry is a major water polluter (3). Decreasing our dependence on fossil fuels and reducing our energy consumption are great ways to conserve water and keep it clean, and living architecture is one of many ways to do just that.

That’s another green roof myth debunked! Stay tuned for more myth-busting in the future. Need help with your green roof project? Contact Sow Green today and let us give you a hand.





Green Roofs Myths Debunked: Too Expensive

As the Green Roof industry grows, we are finding more instances where people reject the idea of a green roof on their building due to a lack of information (or misinformation). So here at Sow Green, we are setting out to combat some misconceptions about green roofs with a series of articles debunking the most common myths.

Myth #2: Green Roofs are Too Expensive

Although green roofs do cost anywhere from $10-25 per square foot, they are not more expensive than traditional roofs overall, and there are several reasons why.

Green roofs last longer than traditional roofs. In fact, they often last two times as long, if not more. This is because the layers of soil, root barriers, and vegetation protect the waterproofing membrane of a roof from UV, hail, wind, and other damage. Therefore, you don’t have to replace or retrofit your roof as soon (which can save you a lot of money in the long run).

You also save money on heating and cooling costs. Black roofs often get hot in the summer by absorbing the sun’s rays, which often makes buildings hot too. Thanks to a nifty natural process called evapotranspiration, the vegetation on a green roof can make the ambient temperature above the roof at least 6 degrees cooler. It also insulates the roof, keeping cool air from your A/C or heater inside. This is especially true in winter since warm air rises, many buildings often lose heat through their roofs. But with a green roof, you don’t have to use as much energy to climate control the building, so you save money. How much money varies depending on the type of green roof and the insulation of the rest of the building. And finally, with an increasing amount of volatile weather and many cities experiencing extreme flooding, stormwater management costs are at an all-time high. This is because urban development in major cities is created more surfaces laden with concrete and steel instead of soil and trees. But green roofs reduce the amount of stormwater a building has to treat because the soil and vegetation soak it all up (and in many cases can reduce pollution runoff). So not only are you reducing the impact your building has on the natural environment, but you’re saving money in the long term on stormwater fees. Many cities even have programs that give a reduced rate to buildings with vegetative roofs or permeable surfaces like brick parking lots.

Although it is important to do a cost-benefit analysis before embarking on any large scale project, many green roofs offer long-term advantages. Like with many other sustainable projects, green roofs are a little more expensive upfront but can give you big savings in the long run, and therefore should be treated as a sound investment instead of a financial burden.

Green Roofs Myths Debunked: Leaks

As the Green Roof industry grows, we are finding more instances where people reject the idea of a green roof on their building due to a lack of information (or misinformation). So here at Sow Green, we are setting out to combat some misconceptions about green roofs with a series of articles debunking the most common myths.

Myth #1: Green Roofs Leak, and Often

Because many green roofs require irrigation and drainage, one of the most common misconceptions is that they can leak, and when they do they leak a lot. Although there are cases where vegetative roofs have leaked, especially shortly after installation, whether or not a roof will leak has nothing to do with it being a green roof. In other words, traditional roofs are just as susceptible to leaking, and there is no evidence that green roofs have more of these issues. In fact, more evidence supports just the opposite.

Because the additional layers of vegetation and soil cover the waterproofing membrane of a green roof, it is protected from UV light and therefore receives less UV damage over time. Those additional layers also protect the membrane from hail, wind, and storm damage. This is why green roofs often last up to, if not more than, twice the lifespan of a traditional roof. Also, many green roofs have an additional protective barrier that keeps roots from digging too deep.

One of the reasons why some green roofs do leak is that the membrane was damaged during construction or that the seal between the membrane and the drains are not adequate. Green roofs DO require irrigation and drainage, so it’s important to make sure that during installation, the membrane is installed correctly. Many cities with green roof legislation like Denver, require leakage tests to prove the membrane is waterproof.

When performing maintenance, it is also crucial to make sure that any digging or tilling of soil does not damage the waterproofing membrane. Often when getting a green roof installed, the first few years of maintenance (what we in the industry call the establishment period) is included in the budget and done by a professional contractor or landscaping team that is familiar with the system and won’t damage it.

So there you are! Leaking is not a problem specific to green roofs. As with any project, correct installation and maintenance are key in keeping any issues at bay. That’s one myth debunked, stay tuned for our next article in this series!

The Latest Green Roof Trends in North America

Last week, Sow Green attended CitiesAlive in New York City, hosted by Green Roofs for Healthy Cities. CitiesAlive is the largest Green Roof conference in North America, and we walked away with a plethora of information and soaked up the latest in vegetative roof installation. From that, we gleaned some of the latest trends and the future of the green roof industry. We thought we’d share some of our favorite insights from CitiesAlive here:

Be bold and innovative

We heard from world-class designers across North America, some of which created incredibly innovative green spaces. Their experience allowed them to incorporate nature and aesthetics while still reducing environmental impact.

Fernando Ortiz Monasterio of Mexico City decided he needed to help transform the concrete jungles of the Mexican capital to a lush landscape. So he wrote a petition to citizens in Mexico City, asking how they would feel about covering Mexico City highways in green walls, as well as suggestions on how they should fund it. The response was overwhelming, with over 80,000 signatures! Countless meeting with government officials and city representative later, they were able to fund over 1,000 highway pillars with ad space above the green walls, with felt made from recycled plastic bottles. Talk about greening a city and building community!


We also heard a great talk from Ken Yeang, who initiated and inspired nature-based architecture into modern buildings. Yeang uses a process called bioclimatic design, which uses design to build structures that will naturally heat, cool and light themselves. He creates interactive and functional projects and eco-cities by incorporating natural features, the interaction of people, buildings and the local habitat. Ken has been named one of the Top 50 people who can save the planet.

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Education and client expectation

Managing client expectations is always important, but it can be especially stressful in the case of sustainability projects. The sustainable way is often the natural way, and nature takes time. For clients who expect fast and cheap, this can be a struggle. For example, there are only certain times of the year one can plant vegetation on a green roof. There is a lot of preparation needed in order to select and grow the right plants, and the local climate and habitat often play a part. Green roofs also need to be able to hold more weight and need the correct waterproofing membranes. This is especially necessary for clients who are in need of a retrofit to understand. Green roofs also need irrigation (at least for the first few years) and regular maintenance. This needs to be planned for early and included in the budget. Communicating the process, budget, savings, and work involved in installing a green roof is critical not only for your clients' peace of mind but also to help the industry grow with a solid reputation.

Education is also going to be increasingly important in our industry. There are still a lot of myths (which we will debunk in our next few blog posts) associated with green roofs. It is imperative that everyone in the industry is working to educate the public and their clients about the realities of green roofs.

More cities are requiring green roof laws

We attended a great talk from Rafael Espinal, the City Council member of New York City that proposed a green roof rule for new buildings, and he is not alone. Many cities across North America are creating green roof requirements or mandates. As the conditions caused by climate change become increasingly challenging, cities are in need of solutions that reduce the heat island and increase the number of natural habitats. We talked with Brandon Rietheimer, a young Denverite who started and ran Denver’s Green Roof Initiative, pushing for a local green roof mandate via public election. The initiative won, despite opposition from development (Fun fact: He is 31 years old, and this was his first campaign, but he managed to get 4,000 signatures all on his own!). Experts Andy Creath and Jennifer Bousselot also gave a presentation on their contributions to Denver's Green Roof Law. A group from Portland also attended, discussing their new Green Roof requirement, which took over 8 years to enact! Seeing so many people working together to make their cities a little greener has inspired us, and it makes government support and encouragement one of our favorite trends from this year!

The large crowds and excitement surrounding the CitiesAlive conference got us really fired up for the future! We met a lot of inspiring people and got to witness firsthand how the industry is growing (pun intended). We can't wait to see where things will go from here!

Green Roof Failures and How to Prevent Them

We talk a lot about how great green roofs are. They have amazing benefits to both property owners and the local community. When done correctly, they can offer cost savings and add a great amenity to a residential or commercial building. But what happens when they don't work? They don't happen very often, but green roof failures do exist and they can be costly to a maintenance budget. In this article, we discuss the most common green roof failures and how to prevent them.


A flat roof isn't always truly flat. There are typically a lot of highs and lows in traditional concrete slabbed roofs. And since you'll need irrigation to help plants develop well, good drainage is key in order to prevent a very common issue with vegetative roofs: puddles of water and wetness that perpetuate throughout the year. Before installing planting medium and the plants themselves, proper testing to see where the water goes is crucial to properly place your drains. And in addition to good placement, you also need to ensure you have enough drainage. Many people assume that since the soil and plants will absorb a lot of water that not much drainage is needed, but you probably want to be conservative in your estimate. Too much standing water can lower your plant's survival rate and attract pests. The best way to prevent ponding is to create a 1:60 slope on flat roofs.  

Soil and Plant Selection

Correct plant and soil selection are crucial for your green roof to survive. Sedums (similar to succulents) are often selected because they can survive in a variety of climates and require a growing medium that is dry and has low amounts of organic matter. But depending on the needs of your specific project, you may require shrubs or flowers to make the roof more ornamental. If this is the case, make sure you work closely with your contractor to make sure they are knowledgeable of what does best in your local climate. That means using native plants and native soil (although soil left over from the construction site may not necessarily be the best choice). If the architect or contractors are not familiar with soil and plant selection for the local region, hire a horticulturist. In Denver, many successful green roofs already exist, so we have the luxury of having a lot of examples to work from.

A Different Microclimate

A roof that sits several stories above floor level has a different microclimate than your backyard garden. Temperature and wind vary at that height, and if your green roof sits atop a skyscraper even the barometric pressure can fluctuate. You also get higher UV levels the taller you go. So plants are often exposed to very different elements and they need to be taken into account.


Assuming you have proper drainage, erosion can be another issue especially at the edges or corners of the roof. Making sure that vegetation is sectioned and contained by edges of pebbles or gravel paving will allow good drainage of water without taking soil and plants with it. Often these "pathways" double as access for the maintenance staff, so they may already be included in the design.

Green roofs are becoming more popular every year, so the amount of knowledge surrounding their success is growing. But even contractors with good intentions can struggle with good green roof design and installation. Looking for contractors with experience will help prevent failures up front. The moral? When in doubt, hire an expert.