Green Roofs – A Cautionary Tale; May 2018 SAG Newsletter
Green roofs sound like a good environmental initiative – right? But what happens when it becomes legislative mandate? Let me share a tale of what happened in Denver, Colorado and the economic development standstill that occurred.
It seems that in 2016 a well-intentioned individual started a signature campaign to make green roofs mandatory within the City and County of Denver. It takes about 4,900 signatures to get a voter-driven initiative on the ballot. As this signature campaign occurred about the same time the US withdrew from the Paris Climate Accord, the well-intentioned residents of Denver gladly signed the petition thinking they were protecting the environment.
Having collected the required signatures, the initiative made it on to the 2017 election ballot. At the time, almost no one believed it would pass. Being an off-year election, about 20% of Denver’s registered voters actually cast votes – and 11% of voting population approved an initiative that would have far-reaching economic impact.
So, what did the initiative require?
- All Denver buildings over 25,000 square feet to have percentage of roof dedicated to vegetation and/or solar
- Up to 50,000 square feet – 20%
- Up to 100,000 square feet – 30%
- Up to 150,000 square feet – 40%
- Up to 200,000 square feet – 50%
- Over 200,000 square feet – 60%
While this sounds simple enough, very little of the implementation impacts had been thought through. For example, the building department had virtually no code requirements defined for green roofs. And, there were more than a few complicating factors around structural loads, root repellant systems, wind uplift pressures, water retention mats, leakage testing, mold, annual maintenance, insurance, and the list goes on…
In addition to new construction, the mandate would apply to existing buildings as well when roof replacement would be required. Since the mandate went into effect on January 1st, 2018 – not one new construction building permit had been issued for the City and County of Denver as of July 2018. Major renovation of existing buildings had also ground to a halt. It seems that no studies had been conducted to project the economic impact on building owners. Once the legislation was passed, engineering studies were commissioned using the following four comparative scenarios;
- Apartment building 55,000 square feet, 5 floors, 11,000 square foot roof. Green roof coverage 30% or 3,300 square feet
- Industrial building 150,000 square feet, 1 floor, 150,000 square foot roof 10% green roof 15,000 square feet
- Retail building 150,000 square feet, 1 floor 150,000 square foot roof 50% green or 75,000 square feet
- Office building 300,000 square feet, 15 floors, 6,000 square foot roof 60% green or 3,600 square feet
Below are the roof replacement estimates incorporating the green roof, or combo green roof/solar requirement;
Replacement Cost Normal Green Combo
Apartment $137,700 +$149,636 +$134,634
Industrial $1,539,000 +$490,000 +$533,000
Retail $1,539,000 +$2,224,000 +$2,548,000
Office $101,000 +$132,000 +$140,000
As shown above, the roof replacement cost more than doubled for the sample structure scenarios. These figures did not include annual maintenance, insurance or other potential cost factors.
Facing a business development economic disaster, the City and County of Denver is proposing legislative action to the city council that would alter the green roof directive to be more of a broad energy efficiency mandate with a number of more affordable options available. While not yet up for city council vote at time this article was authored, it is expected to pass in the near future.
This was titled “a cautionary tale”, as not all environmental ordinances are necessarily a good thing. While most of us probably favor stricter benchmarking and energy efficiency requirements – we do need to avoid crossing the line of being economically impractical.
I want to thank John Logan of the law firm Laff Gordon Bennett Logan P.C. for providing the primary content for this article. Click Here for a copy of the PDF presentation containing additional details on the green roof initiative and cost studies.