Talk:Green roof

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Corrected photo caption[edit]

I changed the caption on the third photo as it's definitely Chicago City Hall. Is the second photo Sao Paulo City Hall? I don't know. Kevin Hayes (talk) 10:12, 8 August 2009 (UTC)

Information request[edit]

Hi I am looking for some specifics on elements for a sod roof to span a ring 15' radius (lower roof for a 60' circle). The posts are 11'6" apart. What do I have to use for rafters and purlins to support such a roof? One can reply directly to

The 'Green Roof Regulations' section contains large amounts of assertions and broad generalizations that are not cited and obviously author opinion, e.g.

"The building industry in the United States tends to look for instant pay-offs rather than long-term investments."

and the author of this section has an obvious agenda to encourage readers to promote the use of green roofs (not that I disagree, I think green roofs are great, I just think that a wikipedia article isn't the place to espouse one's beliefs). Perhaps a section such as 'Promoting the use of green roofs' should be added, and facts, not author suggestions, regarding other's efforts to promote green roofs could be included.

  • I've eliminated some of the essay-style writing and conclusions - more work is needed. BD2412 T 00:16, 16 May 2006 (UTC)
This is a complex issue related to the rise of Green building. In the US price to performance ratios and return on investment (ROI) are considered to be among the most important characteristics of any building. It is only recently that improved techniques have proven to save substantial costs over the lifetime of a building. Now green certified construction is becoming common and corporate centers are increasingly targeting LEED certification at platinum level compliance. So there is a fragment of truth to the remarks, historically, but the issue is more complex and important than the current article states. -- M0llusk 00:31, 14 October 2006 (UTC)


Hi, I just went through and added a lot of documented and fact-based information about green roofs, as well as further editing out the many judgmental statements about why people (particularly builders) do and don't use green roofs. I renamed several sections to simply focus on history, uses and benefits (again, rather than making assumptions about motives), and added a short section on disadvantages. If there's any other data or information I can provide, please let me know. July 7, 2006 - KatherineKatherineN 16:14, 7 July 2006 (UTC)

Realized I probably should have removed the NPOV tag following my edits, and did so now. KatherineN 21:11, 8 July 2006 (UTC)Katherine.



Looking for an instant pay-off vs. long-term investment... What is a building all about, an instant pay-off? Anyway, talking about green roofs and modern green roof technology sometimes leads to judgmental statements because it is a very emotional topic. There is the 'green' group vs. the conservative group. All things are emotional related to nature, flowers and/or gardens . Let's merge everything down to a generalized level: Since nature doesn't need us, do we need nature at all? If so, how much, and who tells us the quantity of nature we are allowed to have? 25 years and many millions of square foot green roof converted me to a 'green' guy. Jorg Breuning--Jörg Breuning 13:54, 29 August 2006 (UTC)

I have removed a link to an external website from the contribution above. It has been pointed out to Jörg Breuning on his talk page that self-promotion and links to commercial websites are against the principles of Wikipedia. Please, Jörg, do not add any more links to your own website. SiGarb | Talk 16:52, 29 August 2006 (UTC)

green building[edit]

Hi! My name is TIP, and I am building a big circular place in Lanark County, Ontario. Right now I am looking for info on roofs to support an 8"layer of soil. I am using reclaimed 12" diameter posts and 10" beams from my property for the frame of a 60' diameter circular building wit a central tower. The tower roof is conventional, the lower roof is a ring 15' in diameter surrounding the central tower. The pitch is 4/6 and the span between posts is 11'6" on center. What sizes and kind of rafters ,purlins,kneewalls (for lookouts)etc do I need to use??? Where can I find this kind of info??? Reply here or to tipmusic AT yahoo DOT com Thanks

green roofs aka living roofs[edit]

Hello, I've never edited an entry, but I thought that the intro paragraph should mention the fact that green roofs are also commonly called living roofs -- which would be good for cross referencing. And for some reason the intro paragraph doesn't have one of those [edit] boxes next to it. The other paragraphs did not seem as appropriate for the cross reference.

Does anyone know the distinctions between green vs living roofs? I was recently told that a living roof might be more accurate, since a "cool roof" (a roof which is painted a light color to reflect heat) may also qualify as a "green" roof, in the sense that green simply means environmentally friendly. CindyBlain 05:46, 8 January 2007 (UTC)

What is a green roof[edit]

In the introduction it is suggested that container gardens are not green roofs. however this is not always the case. I am not editing this remark as it is too lengthy to explain the qualities that makes a container garden a green roof or not, however if you consider the fact tha all a green roof is essentially is a (or number of) giant container(s) it becomes clear that the statement referred to is erroneous.

Secondly it should be noted that the term "green roof" can also be applied to roofs that are designed with an environmentally friendly concept in mind, such as solar panels for electricity production or heating. (----) —The preceding unsigned comment was added by MarcusHawksley (talkcontribs) 22:20, 1 February 2007 (UTC).

temperature differential[edit]

The article currently states "On Chicago's City Hall, by contrast, which features a green roof, roof temperatures on a hot day are typically 25–80 degrees Fahrenheit (14–44 degrees Celsius) cooler than they are on traditionally roofed buildings nearby." I admit that the reference supports this, but it is clearly wrong. For example, the National Weather Service supplies historical statistics that contradict the upper end of this range. The hottest temperature ever observed in Chicago during July was 105 Fahrenheit, in 1934; the coldest July temperature was 45 F, in 1983, a different of only 60 degrees. Admittedly, these figures are from a limited set of measuring stations, but it is clear that an 80 degree separation between adjacent roofs is impossible. Note that if one roof was at 105 F, the highest temperature ever recorded in Chicago, then the roof of City Hall would be (with an 80 degree difference) at 25 F, below freezing. It is beyond unlikely that the roof of City Hall is covered in snow and ice during the hottest heat waves in history.

If we can't find an accurate reference, I'll remove this claim from the article. Tesseran 20:55, 5 August 2007 (UTC)

You are confusing ambient air temperature with roof temperature. I've cooked eggs on a black tile roof, and I have melted polystyrene insulating foam pressed against galvanised steel roofing (polystyrene has a melting point above boiling - it is commonly used for insulated coffee cups!). A 40C difference seems quite plausible. Read Selective surface.--Jaded-view 17:36, 15 September 2007 (UTC)

WP:EL Hanging Gardens[edit]

There's a link to a Wordpress blog that is being edit-warred at present. Do we want this link, or do we not want it?


  • Content is good.
  • Content is largely relevant. Not all green roof, but it's pretty tightly focussed on "greening the city".
  • Content doesn't appear to have commercial, CoI or Spam issues.
  • Content adds some "current news" content from the field that isn't otherwise going to be linked from the article, i.e. WP:EL's "a unique resource beyond what the article would contain if it became a Featured article." is being met to some useful extent.


  • Blog. Is WP:EL a blanket ban on all such links, with no exceptions?
  • Content isn't entirely green roof related.
  • As with any blog link, today's content isn't tomorrow's content and they've always got to be subject to review and recall if things change.

Comments please? Andy Dingley (talk) 13:13, 7 August 2008 (UTC)

Link Consideration[edit]

Hello everyone! My name is Antonino and I'm running an informative/educational blog mainly focussed on Green Roofs, Rooftop Gardens, Urban Farming (especially on green roofs) and more. I wish to ask you to consider whether a link to my blog should be inserted in this cathegory of Green Roof. My site is at Thank you very much!Agiglio (talk) 07:01, 28 October 2008 (UTC)

Ballard Library[edit]

Someone was a little overenthusiastic about the Ballard Library - which, amusingly, happens to be my local library. I took out the details that are totally unrelated to green roofs, as I think it's pretty clear that recycled carpet and waterless urinals are not relevant to this article. Anyone have an opinion on whether the long species list should stay or go? Jadine (talk) 01:35, 17 January 2009 (UTC)

Green roof - Ekopedia[edit]

I suggest adding the following external link.

-- Wavelength (talk) 05:59, 6 February 2009 (UTC)

Wot no disadvantages?[edit]

I am surprised the "disadvantages" or "controversy" sections are so weak in this article. To be blunt, a lot of the positive claims being made strike me as pure wishful thinking; "oh, we have a garden on our roof so that's good for the environment, man!" (insert peace sign.) Real ecology and environmentalism is far more complex. Some specific examples:

  • "Grow fruits, vegetables, and flowers". It may well make do for growing vegetables if you are unfortunate enough to not have a more suitable area. (In a typical multi-storey apartment building averaging less than 10 m² of roof space per resident, unless one resident gets a monopoly on most of the space the vegetable production will make only a token contribution to food; you need at least a suburban sized garden to grow enough to feed someone.) However I would be surprised if it is much good for fruit growing except some of the smaller berries, unless it is actually done hydroponically. The soil depth required to support most fruit trees is simply too great for construction on a roof.
  • "Reduce heating (by adding mass and thermal resistance value) " I'll agree it should do that, although the mass efficiency (and hence, consumption of poorly-recyclable building materials) will be very poor compared to other environmentally friendly insulants such as de-lanolinised wool waste. However, "and cooling (by evaporative cooling)" is bull. If it has a sufficient R value to act as a useful insulator, then the effect of evaporative cooling above that layer will be negligible within the building. I think the author is confusing the cooling effect within the building (purely insulative, keeping out the hot sun) with the potential to cool the entire area through transpiration (true, if you have a lot of area and it will not harm your local environment to use so much water irrigating highly trans-vaporative species.) Bear in mind, the total cooling effect that plants can provide to an area comes from two factors: reflection of incident sunlight, and evaporative cooling through transpiration (some energy is also removed through carbon fixation, but this is a very small effect.) Now the reflective properties of plants may be a lot better than black asphalt, but they are not particularly good. A coat of white paint would do much, much better. And evaporative cooling can be done to exactly the same total amount of BTU, with exactly the same water consumption by retaining the water in a rain catchment tank and using it in an evaporative chiller unit. The difference is that in the latter case we can apply the cooling where and when we want: for example, cooling the inside of the building, and subsequently the outside by heat transfer, rather than just the outside as transpiration does; and avoiding evaporative cooling on humid days (when each litre of water evaporated still removes the same amount of heat, but the increased humidity actually reduces comfort levels.) So while it may be true that transpirative cooling by green roofs can reduce urban heat islands, it is a very poor argument for having them as we can do even better without.
  • "Increase roof life span" What on earth is the source for this improbable claim? (I note a link to the Penn university site **NOTE - THE LINK IS NO LONGER ACTIVE AND THE CLAIM IS NO LONGER ON THE PENN STATE WEBSITE** , but unlike the other claims which they have actually tested experimentally, there is no source or other evidence for this one.) It seems far more likely that roof life span will be considerably reduced, due to a) greatly increased loads, which make large engineering margins uneconomic; b) higher water retention and higher mineral and organic acid content in water, which will increase rates of geochemical and biological degradation of timber, steel and mortar (especially as no practical waterproofing scheme is perfect, and least of all those which avoid the potentially toxic chemicals which are most effective); and c) reduced access to roof fabric for inspection and maintenance. In practice the main type of roof that is strong enough for this to be practical -- ferroconcrete roofs -- have structural lifespans much greater than the typical usage lifespans of urban buildings. So the main issue is not structural life but waterproofing failure, which is made much worse by the difficulty of regular inspection and maintenance, and also by the next issue:
  • "Reduce stormwater run off " slowing storm water run-off from your property as a whole, is a good thing. Slowing storm water run-off from your roof is not. Firstly it would add a considerable dynamic load to a roof which could be very bad unless it was designed for it (by "bad", I mean "killing many people", and yes this is a real problem that has on many occasions caused mass casualties when heavy squalls dumped water on roofs not designed to shed it fast enough.) On a retrofitted roof such a load could be reduced by using only a very thin layer of soil, but in that case the stormwater retention will be small. And while a roof can be designed to support much larger than normal loads, this will require more energy and non-recyclable materials in construction -- which is bad for the environment. Secondly, the more the water builds up, and the slower it runs off, the worse are the effects of minor imperfections in water proofing. Holding all that muddy, humic water on the roof for hours after a storm will turn the smallest leak into a major nuisance that can damage electrical systems, stain or even destroy plasterboard ceilings, or even eventually cause the failure of timber or steel structural members.
  • "Filter pollutants and carbon dioxide out of the air ..." I get tired of pointing this out, but plants are only nett removers of carbon dioxide when their biomass is increasing, and being sequestered to a long-term stable form. In established ecologies operating in equilibrium, carbon is released through catabolic processes (mainly as carbon dioxide, but also to some degree as methane) at the same rate that it is absorbed by anabolic ones. There only two nett savings to atmospheric carbon dioxide production: a) one-off retention of the total carbon fraction of the biomass in the garden, only for so long as you keep it alive (unlikely to be as much as a single tonne unless you have an enormous roof area or a massive soil layer able to support trees); and b) the reduction in transportation fuel costs through growing food on your roof instead of at a farm hundreds of miles away (however, as few roofs will be able to support more than a tiny fraction of your total food requirements, this effect will, once again, be negligible.) As for filtering out pollutants: this seems somewhat incompatible with the view that we might want to eat the produce. If green roofs are actually effective at removing atmospheric pollutants, and we eat from roof gardens, then either the garden bioremediates these pollutants (unlikely, see below) or we have devised an ingenious scheme to maximise the rate at which pollutants can be concentrated in our own bodies.
  • "The soil and plants on green roofs help to insulate a building for sound; the soil helps to block lower frequencies and the plants block higher frequencies" this may well be true, but roofs are a minor conduit for the admission of noise pollution. Most low frequency exterior noise pollution enters via the foundations, and high frequencies mainly via the windows. And that is just the exterior noise pollution: most noise pollution in apartments originates inside the building. (I speak from painful experience, having once lived in an apartment under a flight path. Roof insulation -> useless. Double glazed windows -> very effective. All sound insulation put together -> exacerbated the problem of the religious fanatics who insisted on playing loud folk music early on Saturday mornings to "punish" those residents who liked to have a drink after work on Fridays.)
  • "Filter pollutants and heavy metals out of rainwater" So you can eat them in your home grown veggies? Hmm. I have recently been studying principles of bioremediation of pollutants and it's really a lot more complex than most people think. If you don't do it right, it just plain doesn't work -- and in a few cases, can actually make things worse! If you look at the linked Penn State University site, they found: nett removal of nitrates (because they had very high levels of nitrate pollution in local rain; they expected no nett removal in areas with lower nitrate content in rain, and in some areas the garden might be a nett nitrate adder); metal ion run-off was less than that from a bare metal roof, but *more* than that from a painted roof; excellent remover of acidity, but only by consuming alkaline lime present in their soil, which would need to be periodically topped up. More serious pollutants like chlorocarbons and polynuclear aromatics were simply not studied at all, but in general effective bioremediation of such materials requires a combination of aerobic and anaerobic processing in different layers, and a green roof will not be deep enough to have an anaerobic processing layer.

A few others:

  • "perhaps a once-yearly weeding"? If your green roof is supposed to restore local native species, you will need to weed it a great deal more often than that. In fact in my local area, where all gardeners are battling several nasty species of officially proscribed "noxious and invasive weeds", if you don't weed at least once a week you can expect your rooftop garden to turn into a reservoir of invasive weeds. Quite apart from being bad for the environment and making you a bad neighbour, you will also be subject to stiff fines unless you remove the whole lot within 7 days of receiving your abatement notice.
  • What about rainwater collection? Australia -- where I live -- is subject to periodic droughts and is currently going through a pretty bad one, with resulting restrictions on usage of the municipal reticulated water supply. This is considered an important environmental issue. Consequently there is at the moment intense interest in urban rainwater collection. This water is generally not considered suitable for human consumption when collected in urban or suburban areas but is used for purposes like laundry, flushing toilets, washing cars, evaporative cooling systems and garden irrigation (drip or mist systems.) This roofing system completely opposes that since it reduces total run-off (through transpirative losses) and contaminates the water that does run-off, so it is not usable for any purposes but drip irrigation of gardens (it could not be used for mist irrigation since the microbial content would be too high.)
  • Contamination of run-off: environmental monitors around here regulate the levels of various contaminants in storm water run-off from larger facilities, including total dissolved solids, organic acid levels and turbidity. The run-off from the Penn State experiment violated the maximum permitted levels in all these categories and would have resulted in stiff fines as an environmental polluter. I can only assume that they were able to get away with it in the US because your environmental water quality control standards are a few years behind Australia and Europe. -- (talk) 02:36, 8 September 2009 (UTC)
All good points. I would suggest deleting or diluting claims in the article that you refute and the are not supported by supposedly credible references. On other ones, unfortunately, we'll need to look for credible sources refuting them before we can change the article. Another quick option is to put the [dubious ] tag on stuff that is dubious. --Ccrrccrr (talk) 23:51, 8 September 2009 (UTC)
Followign renewed concerns, I've moved the 'Disadvantages' section to a prominent position in the article (it was hidden at the very bottom of the page). I agree it urgently needs expanding and referencing. I have a number of books on the subject and I'll see if I can find sources. Sionk (talk) 05:43, 6 November 2012 (UTC)

Australian Parliament House[edit]

The Australian Parliament House is the first building that came to mind when I found the "green roof" article, and I would say it is particularly notable, even if green roofs are not very common in Australia.

But wikipedia describes the building as being mostly buried within a natural hill, so does it count as a green roof or not?? (talk) 01:06, 3 October 2009 (UTC)

Examples by Country - Sweden[edit]

This section has a lot of weasel words "it is believed" so I added some weasel tags here. It is also irrelevant to this article what the area of "Västra Hamnen" was built upon, linking to a "Västra Hamnen/Bo01" article should be enough. AadaamS (talk) 06:53, 27 November 2009 (UTC)

External Link Inquiry[edit]

Greetings; my name is Christopher James Botham, and I would like to inquire about posting a link to my website on your 'Green Roof' page; the site is called The World Architecture Map (WAM), and the link follows:

Architecture tagged with ‘Green Roof’ at The World Architecture Map (WAM) database

I am aware that as the site owner, I am unable to add links on Wikipedia myself; the site is free to use and there is no sign-in or membership needed, it's just a great resource for architectural information, so I think it would make a good addition to the page. Christopher Botham (talk) 02:17, 4 August 2010 (UTC)

Examples by Country List[edit]

Is there any reason for the order of the countries, starting with Switzerland and ending with Australia? Would it be better to list them alphabetically (it would save argument about which country's green roofs are most important)? Sionk (talk) 23:18, 21 August 2011 (UTC)

Okay, no suggestions? I'm going to reorder the countries into alphabetical sequence. Here goes... Sionk (talk) 21:51, 2 October 2011 (UTC)

Research Section[edit]

Not sure why research into 'Vegetated Complex Walls' is described here - walls are not roofs! Is this simply some problem in translation? The link refers to French research into vegetated walls. Sionk (talk) 23:18, 21 August 2011 (UTC)

Environmental consequences[edit]

I have created a new section titled environmental consequences. Admittedly, a lot of this is not cited from publications but from my collection of experience in design including the requirements of the ASCE 7 code for building loads. Green roofs are great in the proper application. The problem is that often times they are not the most appropriate use of funds in a limited budget (or for that matter the environment). On a single story building located on a large site, I can use my clients money more effectively to treat stormwater on the groundlevel after it has run off of the roof. Also with the new roof coatings, they reflect a lot of the solar energy to avoid the heat island effect. Switchbackforfun (talk) 01:28, 6 November 2012 (UTC)

I can understand why you did this, because the existing 'Disadvantages' section of the article was hidden at the bottom of the page. I've moved it to a more prominent position. However, I've removed your addition because it seems to give undue weight to your point. Okay, I get the point that building materials use energy to produce and transport, but this could be covered in a single sentence if at all (the environmental cost of building materials is a general factor in all building decisions). Secondly, Wikipedia isn't the place to document your personal experience or knowledge (see WP:OR). Major points should normally be cited to an authoritative published source. Sionk (talk) 05:15, 6 November 2012 (UTC)

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Hi! I feel that the American Society of Landscape Architects (ASLA) Green Roofs section of this article seems like an ad for ASLA. Should this section be removed as per WP:Promo? I think that it should be taken out. What do you think? Regards, Jith12 (talk) 23:59, 10 April 2017 (UTC)