Monday, July 18, 2011

Green Roofs and Historic Structures

We are involved in a small green roof project now in a historic neighborhood and on an addition to a historic structure.
U.S. Department of Interior's Guidance for Rehabilitation of Historic Structures

What could be moe historic than plants used in the same manner as those in the Hanging gardens of Babylon or any other number of historic structures?  Apparently the U.S. Department of interior has reservations concerning Green Roofs.

And green roofs and rooftop gardens may be an issue for concern to local ro municipal regulators when reviewing a project for compliance to code, typically due to the infrequency of green roof installations on historic structures.

The latest guidance to renovation of historic structures issued by the U.S. Secretary of Interior can be downloaded here.  Interestingly, the cover page to the document has a photo of a green roof planted with sedum.

Sedum certainly is an appropriate historical plant for some areas of the world and history has shown us of her use in portions of Europe.  Because certain species of sedum may now be added to watch lists for aggressive and invasive species lists, I think a green roof depicting native wildflowers would have been more appropriate.

After reviewing the document I offer the following comments;
  • The document recommends against the use of non-natives that may displace native species yet the document has a photo of a roof with, unless I am mistaken, Sedum acre being used.  Sedum acre is listed across Canada and in some U.S. jurisdictions as potentially invasive, including listings by the U.S. National Park Service. Though I do believe Sedum is appropriate for select green roof projects, monoculture type projects with oen or two genus should not grace the cover of our Nation's Park Service stewards (epic fail).  You can read more of my Sedum rantings here from previous posts.
  • Under the guidance round ugly satellite dishes are easier to approve on historic buildings than green roofs.
  • Green roofs are not afforded the same treatment as window boxes.  The guidance recommends a green roof be not visible from the street.
  • and more...
Download the document and keep for future reference!

I'll be doing a post once we complete the historic building review process to share what we learn.

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