December 27, 2010
Mary, Mary How Did Your Roof Atop One South Van Ness Grow?
Completed this past October, the new living roof atop One South Van Ness "percolates storm water, reduces peak runoff, reduces cooling loads and energy use within the building, provides a suitable habitat for butterflies & honey bees, and a...park-like view from neighboring buildings."
The living roof is 9,500 square foot and captures, stores, and delivers rainwater for irrigation via a 6,500 gallon tank and pump system; which will help reduce the use of potable water during the summer or dry months.
The plants on the living roof include a variety of California native and adopted plants including Buckwheat, Stonecrop, Tufted Hair Grass and San Bruno Mountain Manzanita.
In addition to the greenery and environmental benefits, the project team prioritized the reuse of roofing and insulation materials. River rock ballasts were reused around the edges of the living roof, provided by the Park and Recreation Department, and the pathways were made out of existing concrete roof pavers.
Cost of construction: $3 million over 10 months, compressed to under 3 minutes below:
∙ One South Van Ness Roof Replacement/Living Roof Project [sfdpw.org]
First Published: December 27, 2010 12:00 PM
Comments from "Plugged In" Readers
Looks swell but a $3 million tag makes it unrealistic for any private building owner.
Posted by: the unnamed at December 27, 2010 12:11 PM
$3 Million! Hmmmm, nice idea, but a bit steep... What is the big expense in this type of project?
Posted by: marco at December 27, 2010 12:16 PM
Three million bucks for a simple roof garden. Was this taxpayer money spent by a nearly bankrupt city? Sounds like it. Drudge likes to link to these frauds, I'll send it to them.
The list of things that could be bought for 3 million is mighty long. Could have bought 3,000 acres of a nice Douglas Fir forest up on the north coast, there's one for sale at that price right now. Imagine what one could do for the environment with 3000 acres. More than can be done with a .2 acre roof garden, that's for sure.
Posted by: unwarrantedinlaw at December 27, 2010 12:42 PM
I love the idea of a green rooftop.
I'd love it even more if there was access so people could go up there and increase their green living!
I'm somewhat surprised about the cost, but then again I don't know the cost of a normal roof of this size.
our local garden store sells a kit that's just a few hundred bucks to make a green roof, so not sure where all the money went.
I'd like more information about costs of this project.
1) how much did this cost compared to a "normal" rooftop
2) how much will this cost to maintain compared to a "normal" rooftop.
in sum, I'd like to see the full long term costs instead of the upfront costs.
how many of us have paid more upfront to reduce the long term costs? (like buying a Honda Civic vs a cheaper Chevy Cavalier).
Posted by: ex SF-er at December 27, 2010 2:31 PM
What were the energy savings? Can we compare copies of the PG+E bills from before and after the remodel? If the savings are on the order of $20K/month then the project made financial sense, but with Green Projects and taxpayer money that's never really the goal.
Posted by: GreenCynic at December 27, 2010 2:32 PM
Green roofs done well are still expensive, but the benefits pay for themselves relatively quickly. Storm water surges are a big problem, and this is one of the few ways to effectively deal with them. Such things that used to be considered externalities are becoming very problematic with continued growth.
Linking this building roof to acres of virgin forest somewhere else might not actually work out over the long term.
Posted by: Mole Man at December 27, 2010 2:34 PM
Environmentally responsible? Check.
Fiscally responsible? Hmmm...
Posted by: WH at December 27, 2010 9:01 PM
3mm, absolutely crazy, it costs 300 a square foot to build a building. Would love the city to show the costs and who got paid. This is why we have a 400mm plus budget shortfall..
Chaos, need to learn to pay reasonable prices and have people do good work, not overpay for ok work that takes too long and does not last. Although I am sure lots of city agencies were involved, full employment.....
Posted by: Chris at December 27, 2010 9:20 PM
What would be the cost to green roof the entire city based on the cost and size of this building? $10 googillion?
Posted by: the unnamed at December 27, 2010 10:01 PM
$3 million for one roof? The payback on this project must be anywhere 10,000 years to never. Seriously.
Posted by: anon at December 28, 2010 8:53 AM
A Green roof can take several decades to pay off according to this 2005 study. But when you consider the average lifespan of a building is +70 years the higher upfront costs are more than justified by the long term economics. This also ignores the savings to reduced sewer usage, cleaner air, cleaner water, and the healthcare and environmental cost savings.
From the study.
"A green roof ignoring the benefit of air pollution uptake generally would break even between 39 and 40 years based upon investment of the energy savings from such a roof. The incorporation of air credits into the system reduces the time for return on investment to 36 years with sedum planted on the roof. Energy savings has the largest contribution to closing the cost gap. The air credits generated from a sedum roof meet 25% of the cost gap at 36 years. If the annual savings were invested at a higher risk with earning eight percent interest instead of 4, the payback period is reduced to 29 years.
If a plant with higher NOx uptake capacity such as tobacco were placed on top of the roof, the contribution from air credits would be increased and break-even period reduced to 15 years."
Posted by: badlydrawnbear at December 29, 2010 4:57 AM
More analysis on the benefits of green roofs.
"A study completed by three researchers at the University of Michigan found that greening 10 percent of Chicago roofs would result in public health benefits of between $29.2 and $111 million, due to cleaner air. For Detroit, having 10 percent green roofs would result in a public health benefit of between $24.2 and $91.9 million."
"A recent study by The Lady Bird Johnson Wildflower Center at the University of Texas showed that a green roof could reduce a building’s air conditioning bill by about 21 percent compared with a traditional, tar-based black roof. Single-story buildings with a high roof-to-wall ratio will experience the biggest energy saving benefit from a cool roof."
"... many experts suggest that green roofs help lengthen the life of the roof membrane underneath the green roof and the facility’s waterproofing. Because of the layers of planting medium and the plants themselves, the membrane is protected from temperature differentials, and the resulting expansion and contraction that normally shorten a roof’s life."
Posted by: badlydrawnbear at December 29, 2010 5:09 AM
Why stop at just sedum? Put up light (plastic) greenhouses and lease out the roof growing space. Get your energy conservation benefits and a side income too. Locavores would get off on veggies that were biked to market. Hell, grow medical marijuana and the roof would pay for itself in a few years.
Posted by: Delancey at December 29, 2010 6:37 PM
"If a plant with higher NOx uptake capacity such as tobacco were placed on top of the roof, the contribution from air credits would be increased and break-even period reduced to 15 years."
Green roofs, brought to you by Marlboro. That'd be great.
Posted by: sfrenegade at January 3, 2011 3:57 PM
The 9,500 sf Green Roof portion of this cost approx. $400,000. The balance of the $3M project cost went to re-roof the entire 65,000 sf rooftop, repairs to window washing equipment tracks, penthouse walls and mechanical systems and included design, permits, construction management and inspection.
Posted by: fact checker at June 14, 2011 6:35 PM