Architekwiki
  • WIKI
  • Start Here
  • Resources
  • Other
    • Reading List
    • OFFPLAN
    • Details
    • About
    • Sign Up
    • Terms of Use
  • WIKI
  • Start Here
  • Resources
  • Other
    • Reading List
    • OFFPLAN
    • Details
    • About
    • Sign Up
    • Terms of Use

Architekwiki

A Resource For Architects
Subscribe

Are Green Roofs Worth The Extra Cost?

9/29/2014

 
Green Roofs

I admit that my experience is limited. We designed just one green roof as a demonstration project for a storm water authority, circa 2004. The utility especially likes the decrease in rate of run off. In fact we have two spouts side by side to demonstrate the difference between the vegetated roof and an equal area of typical roof. The difference is dramatic.
Lately I've been wondering, "Is it just me or has the din about green roofs died down?" The touted benefits list is fairly long.


Benefits
  • The roofing lasts longer
  • Provides extra insulation  
  • Moderates the temperature differential between inside and outside
  • Slows time of concentration of storm water runoff
  • Absorbs CO2
  • Eliminates the heat island effect of the building
  • Provides habitat
During the course of that project, I learned that the benefits if a green roof isn't the only thing to consider.

Liabilities
  • Requires materials and workmanship that are far above the norm, between two and three times more costly
  • Requires more maintenance of the ’green’ part
  • Roof leaks are hard to find and fix, which tears up the ’green’ part too. (So far I don't have any firsthand experience, thankfully.)
  • Although roofs protected by vegetation last much longer, they have to be replaced eventually. That installation will be expensive, too.
  • You can't inspect the roofing for signs of deterioration, so an alarm system is common to give early warning of water being where it shouldn't be. 
  • Requires a stronger roof structure
  • Design and specs need to be perfect to defend against litigation because if there is a problem it will be larger than the normal roof leak. 

Add your opinion...
Is Green Roof Use Growing or Not?
Personally I am not impressed by some of the benefits.

Questionable Benefits
  • Extra insulation - energy consumption in buildings over 10,000 SF is not driven by envelope.  
  • Moderates the temperature differential between inside and outside - see extra insulation comment
  • Slows time of concentration of storm water - this works, however this isn't an energy issue and there are cheaper and more maintainable ways to achieve this benefit. 
  • Absorbs CO2 - The amount of CO2 sequestered is likely to be measured in hundreds of pounds per year. Compare that to the 10,000 pounds that each auto produces on average per year. This isn't helping much and may barely offset the CO 2 generated in making the stronger roof structure. (Here's a handy resource.)
  • Eliminates the heat island effect - heat islands are not ’natural’ so they must be bad! Unless the structure is in an urban location the benefit is almost immeasurably small. They do seem to keep mild tornadoes away from cities. 
  • Adds habitat - this is another way to say ’Attracts insects and vermin’. 

My vote is that green roofs are not worth it; and my personal opinion is that they will go the way of Pet Rocks. But read up on Wikipedia and make up your own mind.
Rick
###

Image credit: installation plan by Human Nature

Comments are closed.
    Resources

    Start Here

    Picture

    Picture

    Trello-PM

    FeeCalqs

    Picture

    Terms of Use
    Your use of Architekwiki is implicit agreement with the 
    ​
    Terms of Use.

    RSS Feed


    Categories

    All
    Business Development
    Communications
    Concepts
    Design
    Detail
    Estimating
    Finances
    Legal Issues
    Management
    Miscellaneous
    Money
    MyCorbu
    People
    Planning
    Process
    Projects
    Records
    Services
    Specifications
    Standards
    Time
    Tools


    Archives

    March 2021
    February 2021
    January 2021
    December 2020
    November 2020
    October 2020
    September 2020
    August 2020
    June 2020
    April 2020
    March 2020
    February 2020
    January 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    January 2018
    December 2017
    November 2017
    October 2017
    September 2017
    August 2017
    July 2017
    June 2017
    May 2017
    April 2017
    March 2017
    February 2017
    January 2017
    December 2016
    November 2016
    October 2016
    September 2016
    August 2016
    July 2016
    June 2016
    May 2016
    April 2016
    March 2016
    February 2016
    January 2016
    December 2015
    November 2015
    October 2015
    September 2015
    August 2015
    July 2015
    June 2015
    May 2015
    April 2015
    March 2015
    February 2015
    January 2015
    December 2014
    November 2014
    October 2014
    September 2014
    August 2014
    July 2014
    June 2014
    May 2014
    April 2014
    March 2014
    February 2014
    January 2014
    December 2013
    November 2013
    October 2013
    September 2013
    August 2013
    July 2013
    June 2013
    May 2013
    April 2013
    March 2013
    February 2013
    January 2013
    December 2012
    November 2012
    October 2012

    Resources
VISIT ARCHITEKWIKI'S RESOURCES
Picture
Architekwiki | Architect's Resource | Greater Cincinnati | (859) 444-4560
© 2012-2020   Architekwiki​