Green Roof

weight is a key issue. a 50 year old wood structure... I would guess the weight of dirt, plants, grass, etc would weigh more than rolled roof, membrane, or tar and gravel. I am sure you could accurately figure out the weight. I am sure an engineer could tell you if it could work.

One question, though, how are you going to get the lawn mower up there? :wink:

I agree with joe b. Check out the epa's website: http://www.epa.gov/hiri/strategies/greenroofs.html
According to their website, a "light" version of a living roof will add as little as 12 to 50 lbs per square foot. I've seen a lot of Eichler roofs sag in areas with large spans (i.e. the garage) under normal conditions due to weight of gravel and rain water. Having an educational background in structural engineering, I would be concerned about some of the following areas of the structure:
1. Too much sag from the 1.5" tongue and groove deck boards (especially at overhangs)
2. Too much added weight on the 4x supporting beams (especially at long spans, i.e. garage)
3. Problems with lateral earthquake loads due to additional roof weight
4. Other areas of structure not meeting current structural standards

I'd be interested in seeing a new Eichler style home designed and built to today's standards with a living roof. I don't have much experience in living roof design, but I'd be interested in seeing a detail on edge drainage which maintains the thin Eichler roof profile (i.e. 2x8 fascia boards). An Eichler built similar to the X-100 might do the trick because structural steel can be strong and fairly low-profile at the same time.

Another option for putting a "green" roof on an existing Eichler is to install foam roofing topped with solar panels. Foam roofing saves energy, eliminates problems with roof sag, and reduces "heat island effect" with its Cool Roof coatings. Next, install an array of photovoltaic solar electric panels and you have the complete package!

Thanks for the responses. We've already got a Dura-Foam roof, but I'm looking to go even further to avoid heat gain in order to avoid having to get A/C. I figured the extra weight would be too much so it's back to the mini-split drawing board. Anyone install a high velocity system like Unico AFTER already having a foam roof?

I asked my contractor about it. He also had concerns about the weight. You have to carry the soil, plants, and whatever rainfall stays during the rainy season.

We did get a preview of the Cal Academy roof a few weeks, missing the mile long crowd yesterday. I could see how that roof gets REALLY heavy. Cool idea though.

We have an Eichler and are redoing our roof, hence my living roof question to my contractor. I thought about a steel roof but our architect/contractor came up the idea of using a cool roof. My contractor has done a few in the SF Bay Area and has seen definitely temperature during the summer, around 30 degrees or more. Our plans were submitted to the city last week so we'll see how long the process takes.

Btw, we still have tar/gravel roof. The previous owner put in a roof top AC which has caused the roof to sag. Not a good idea...

I have seen BIG planter boxes full of dirt (and plants) on an Eichler in Palo Alto. The house was on a curved street and had a separate carport. We installed the foam roof in l982, and the carport ( with the planter boxes ) was still standing after the '89 earthquake....much to our surprise. The house belonged to an architect (no surprise??). Carports are especially flimsy, lacking the plywood covered walls that give the structure the sheer wall strength.
Since everybody is talking about putting soil on Eichler roofs, we should mention a 'singularly unique' characteristic of sprayed foam. The 'sprayed foam' (unlike Board Foam) is the ONLY insulating material that can be used in roofing, or filling low spots, that does NOT soak up water.

Presentation Center (a conference and retreat center located off of Bear Creek Road in the Los Gatos Mtn area) has a green roof on its welcoming center. It works very well and they don't need air conditioning (according to one of the siters who lives there year round). I am sure that the hay bale walls help with this as well...Of course the whole building is green and worth visiting, as it was the first truly green building in the Silicon Valley.

The fire department was pretty doubtful about the roof and made them install a sprinkling system on the roof, which they did. The roof is composed of native grasses, I believe.

tom, you're a smart person, I am sure you have already thought of these, but here are some additional ideas for naturally cooling your house:

1. skylights that open. they will allow heat to escape.
2. cross ventilation. create air flow with open doors and open windows.
3. strategic landscaping. trees in the right spot can do wonders. Quaking Aspens grow 5 ft/year
4. tile or concrete floor. I think you have that one covered. nothing like a cool slab with bare feet in August!
5. sale shade(s) in the right spot.

If all has failed and you must have AC, I would try a portable for the extreme areas before committing to a large system