Green roof or metal roof?

Which one is better? Metal roof is good for catching rainwater, but the green roof is good too. . . . Which one would you choose, and why?

Green or some type of earth plaster-crate.... Metal is very expensive so I would want something I could build and maintain myself. 

I'd love to have a green roof but metal because of the snow load in my area.
  9 degrees last night I think the snow is coming soon.

Depending on the construction of the green roof, a metal roof might not be more expensive than a green roof.  I personally would choose a metal roof because my cheap frame house will not support the weight of a green roof, I can't afford a green roof, and it would probably die in my climate anyway.

By the time you add the cost of extra framing to support the weight, metal would be cheaper.  In fact it's hard to find a cheaper roof.  That's why they use them on barns and other cheaply-built buildings.

In my case, I have even less of a choice.  Drilling a well would cost double what my house budget is, so I really need to collect every drop of rain I can.

I do hope to put green roofs on some of my outbuildings, someday.

Green roofs provide a range of benefits that metal roofs do not... I'd choose green over anything else if at all possible

Does anyone know how they USED to build green roofs? People keep sending me photos of old huts in  Iceland and  other places, some now heritage sites and there they are standing cheek by jowl with shingled buildings and everything's still looking sound. For sure THEY were built before EDPM pond liner  or any other sorts of plastic. I have some pretty good idea but would love to hear from someone who knows for sure how it was done.

Thanks Pam !
I'd like to know the construction and materials too.

Old roofs might have leaked quite a bit and the building remain "sound" especially if it is mostly built of stone.  We have different standards of indoor comfort than folks had in the past.  In ye olden days, being indoors meant you were mostly dry and the wind wasn't blowing. 

H Ludi Tyler wrote:
Old roofs might have leaked quite a bit and the building remain "sound" especially if it is mostly built of stone.  We have different standards of indoor comfort than folks had in the past.  In ye olden days, being indoors meant you were mostly dry and the wind wasn't blowing.   

Well, that's true although if a roof is leaking in a climate which has severe winters, even stone buildings will soon show signs of stress if the roof leaks.  And most of us today would indeed be unhappy with the occassional dust shower from the ceiling landing in our dinner.

My thought was that there might be some techniques there which could still be helpful, esp if incorporated into the roof with some materials which weren't available in ye olde dayes   

I'm looking forward to eventually doing a roof over here with a metal roof and a big cistern the south slope will get trellises sturdy enough to climb on for grapes or other vine crops.

Pam,
They used Birch Bark !!

http://en.wikipedia.org/wiki/Sod_roof

Makes sense doesnt it?
Birch Bark is amazing stuff.
It was used to make  canoes.

well!  Never thought to google "sod roofs".  Interesting article  thanks!

There are two general types of metal roofs. Exposed fastener and standing seam. Standing seam is quite expensive up front but has one of the longest lifes of any roof material. Exposed fastener is very affordable, sometimes as cheap as mi-high grade asphalt shingles. Its a great choice for green building on a budget especially if rainwater is involved.

As for living roofs, if the old timers has EPDM they would have used it. Its really the best way to waterproof a living roof. They are very expensive, require maintenance and have are very difficult to implement. They tend to be a better choice for areas that are not directly above living space.

Springtime, What material would be good  for construction
of Living Roof above a living space? EPDM is very expensive.

What is EDPM?

EDPM is commonly called pond liner   it's a very heavy (45 mil I think) plastic  (well, synthetic rubber) that has been UV treated  to last

Springtime is mostly correct in the types of metal roofs, with a minor correction. Panel metal roofs, starting with the plain ol wavy corrugated style, to more elaborate profiles, are the cheapest. And true standing seam is more expensive, but there is a middle ground, one that has a standing seam profile but is closer to the panel roofs in terms of price.

I like the construction using Galvanised Steel with Fiber Cement sheets as in fig. 3 here
http://www.wbdg.org/resources/greenroofs.php

It would be sturdy and spread the load well.
Rot-proof with good waterproofing ability.
But expensive.

IMO a metal roof would be better due to the massive structure needed to support a green roof.

Exposed fastener metal roofs have many profiles. Not sure if Iam missing something there.

Jen, in that diagram a liquid asphalt acts as the waterproofing layer. Definitely something better suited for commercial applications. I would never go without a solid liner personally.

I think  the .60 thickness is the preferred product for EPDM roofs. Its really not that expensive compared to anything else. PVC is the other option but I dont like what Ive heard about it. The real expense and risk is in the waterproofing details at intersections. All these products are best suited to nearly flat roofs, a rare thing in residential.

The expense of extra structure needed to support living roofs is pretty small in comparison to the other details but it is a concern especially when that extra structural support is interrupting the insulation details.

Thanks for the insight Springtime.
A friend iwants to build and underground house
but the roof construction is proving to be prohibitively expensive.
He's looking at Ferrocement too , with fiber added to the cement.

Thanks for the link Jen. Iam interested in eventually doing a mostly earth bermed home very similar to Paul's umbrella house link.

I guess your friend has the same concerns as me in that situation of using Polyethelene sheething. It would be very cheap but just not durable enough in my opinion. EPDM in one uninterrupted piece would have to be the waterproof layer to me. Not too pricey but its the structural support of all that heavy soil thats the problem. I have always thought the best way would be commercial grade steel bar trusses which would indeed get expensive.

"green" roof should say rubber roof since thats what is keeping out the water.My nicer buildings have new metal.No exposed fastenrs is best but expensive.Most of my structures have used or found metal roofing.For shop like structures I stick gutter sealant in the old holes.One I cut into shingles but it was a loud process.Still though the metal was free.I also get high aylkl enamel at used building supply stores or wherever for cheap and mix up my own enamel paint which covers rust and further seals the washers on the fasteners.also metal can be recyled unlike the rubber and I use old sheets to cover firewood and all sorts of other stuff.

Pam Hatfield wrote:Does anyone know how they USED to build green roofs? People keep sending me photos of old huts in  Iceland and  other places, some now heritage sites and there they are standing cheek by jowl with shingled buildings and everything's still looking sound. For sure THEY were built before EDPM pond liner  or any other sorts of plastic. I have some pretty good idea but would love to hear from someone who knows for sure how it was done.

I just registered to answer your question I've written a bachelor report on green roofs as it's an interest of mine as I come from a country which has a lot of turf roofs and because I grew up in a house with a traditional turf roof. Here is an example how modern traditional turf roofs are made in Faroe Islands, as well as some comparisons at the end with how it was done before the advent of plastic http://www.kontrast.fo/tidindi/pdf/18.pdf

Today birch bark is only added at the footing of the roof if it's an old building, to preserve the old look. But most modern houses don't have birch bark at all due to cost. But it's said that each layer of birch bark has a lifetime of approximately 10 years, which is only added for each layer... e.g. 5 layers of birch bark and you can expect 50 years of light repairs and maintenance.

NB! The cost of birch bark paved the way for the dimpled plastic method with a fishing/trawler net underneath the turf and sometimes on top of the turf to ensure it stays put (it's very windy in the Faroe Islands)
And the climate has to be able to support the rather water-demanding turf roof, otherwise it's going to be a costly affair to water. For that case a modern green roof with carefully chosen sedum plants would be more suitable for locations where there are more dry periods.

I've always dreamed of a hobbit home style place and done a bit of research on green roofs, etc. one day I will build a green roof but for now I'd stick with a high quality metal system. For me it's a question of climate and how I expect my home to be when I walk in the door. In the olden days people put up with what we would today consider less then ideal living conditions. Where I live with a hight water table the engineering required to make it work is much more complex then other areas. So as always knowing your climate dictates outcome.