Green Building Forum - Green Roofs - onto existing pitched roof???? Mon, 04 May 2026 20:21:08 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=7956#Comment_7956 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=7956#Comment_7956 Mon, 15 Oct 2007 15:50:53 +0100 James_sc
Anyone seen this done before????

Thanks J]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=7960#Comment_7960 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=7960#Comment_7960 Mon, 15 Oct 2007 16:57:10 +0100 nigel You would also need to consider the structural integrity of the roof as a green roof will be heavier than a traditional roof.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=7964#Comment_7964 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=7964#Comment_7964 Mon, 15 Oct 2007 17:20:56 +0100 tony Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=8043#Comment_8043 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=8043#Comment_8043 Tue, 16 Oct 2007 22:22:30 +0100 fostertom http://i30.photobucket.com/albums/c301/fostertom/ReNatur_Norwegian_House.jpg
http://i30.photobucket.com/albums/c301/fostertom/Optigrun_Meadow_House.jpg
http://i30.photobucket.com/albums/c301/fostertom/norway040s.jpg]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=8049#Comment_8049 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=8049#Comment_8049 Wed, 17 Oct 2007 03:48:44 +0100 Terry Have seen one where they used a series of small terraces to deal with the slope.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=8279#Comment_8279 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=8279#Comment_8279 Sun, 21 Oct 2007 21:31:11 +0100 ken davis try ROCKWOOL themselves, they may know if it worked.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9181#Comment_9181 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9181#Comment_9181 Fri, 09 Nov 2007 20:47:55 +0000 ally.gill Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9183#Comment_9183 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9183#Comment_9183 Fri, 09 Nov 2007 20:56:08 +0000 ally.gill These firms do the waterproofing element.
http://www.safeguardeurope.com/applications/green_roofs_pitched.php
http://www.triton-chemicals.co.uk/prode1.php

Also as it says on the triton site there are such things as vertical green walls so pay no attention to the 'sliding off' comment the growing medium is in little cases stuck on with gripfill.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9184#Comment_9184 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9184#Comment_9184 Fri, 09 Nov 2007 21:11:50 +0000 ally.gill do you have a copy of 'green roofs and facades' by gary grant, bre,2006.
also remember reading somewhere that because the chosen plants only need shallow beds the weight is negligible, even when saturated, compared to tiles or slates which are bloody heavy, will try to reference that comment if i get a chance.
toms photos are great but appear to be a turf roof. an extensive sedum roof is quite different.
greenfix.co.uk has an illustration of a solution for >25 degree pitch.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9187#Comment_9187 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9187#Comment_9187 Fri, 09 Nov 2007 21:41:50 +0000 nigel A good green roof is one that manages to maintain viable growing conditions and that means staying damp.
The safeguard and platon systems both depend on there being a reasonably low pitch to work effectively.

The vertical walls referred to on the triton site refers to a totally different system and there is no mention of how it works.

The rockwool ken refers to is a product called grodan which is mainly used in horticulture but can be used on roofs as a growing medium.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9192#Comment_9192 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9192#Comment_9192 Fri, 09 Nov 2007 22:51:50 +0000 fostertom http://i30.photobucket.com/albums/c301/fostertom/ReNatur_Norwegian_House.jpg
http://i30.photobucket.com/albums/c301/fostertom/Optigrun_Meadow_House.jpg
http://i30.photobucket.com/albums/c301/fostertom/norway040s.jpg]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9485#Comment_9485 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9485#Comment_9485 Fri, 16 Nov 2007 00:09:47 +0000 J..M
Green roofs are a fad & VERY heavy (Especially when wet)

Heres a good idea folks ......... Welsh Blue slate terracotta ridges & lead flashings ....... Your good to go for 100+ years then (Unless someone lands a 747 on it of course..... Now go & turn the landing light off) ;)]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9536#Comment_9536 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=9536#Comment_9536 Fri, 16 Nov 2007 21:55:01 +0000 Terry ]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11431#Comment_11431 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11431#Comment_11431 Thu, 27 Dec 2007 20:56:20 +0000 chocolatepixie
Terry why do you say green roofs aren't as green as we'd like to think?

Not sure slate quarries are particularly green (especially if they're half way round the world)]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11494#Comment_11494 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11494#Comment_11494 Sun, 30 Dec 2007 10:32:55 +0000 ecoworrier "Green roofs" are not sustainable, the roof element has to hold an amount of water and I don't care how good the materials are or how excellent the workmanship is, it will fail.
Pitched roofs will shed water quickly and effectively (even with tiles missing) ,they work and work very well.
'rant over'

:bigsmile:]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11512#Comment_11512 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11512#Comment_11512 Sun, 30 Dec 2007 18:29:17 +0000 chocolatepixie

Green rooves may be a recent 'fad' in this country but they have a long history of use in Scandinavia as this link, with photos from the Faroe Islands and from a restored Viking settlement, demonstrates:
http://en.wikipedia.org/wiki/Green_roof]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11532#Comment_11532 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11532#Comment_11532 Mon, 31 Dec 2007 09:09:19 +0000 jon
If the introduction of a green idea leads to the least green solution, then we should all be worried by it as a failure of concept could lead to future green ideas being rejected. I worry that some of the construction methods suggested for green roofs (not all) may lead to a relatively high annualised embodied content spend (particularly associated with high maintenance costs) for relatively little gain.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11534#Comment_11534 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=11534#Comment_11534 Mon, 31 Dec 2007 09:42:21 +0000 nigel Posted By: jonIf the introduction of a green idea leads to the least green solution, then we should all be worried by it as a failure of concept could lead to future green ideas being rejected. I worry that some of the construction methods suggested for green roofs (not all) may lead to a relatively high annualised embodied content spend (particularly associated with high maintenance costs) for relatively little gain.

Do you have any evidence whatsoever to support this? I suspect not.

As someone who has been living under a green roof for the last 14 years with nil expense incurred on maintenance I suggest you are quite wrong.
If some methods are likely to have high maintenance perhaps you could tell us which?
One of the benefits of a green roof is that the weatherproofing materials are protected from UV and weather by the growing medium and plants leading to low long term maintenance.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12197#Comment_12197 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12197#Comment_12197 Thu, 10 Jan 2008 15:20:11 +0000 James_sc
thanks for all the input.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12322#Comment_12322 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12322#Comment_12322 Sat, 12 Jan 2008 12:58:35 +0000 greenbyname
jon - i'm intrigued to understand what you mean by a green roof being the least green idea? Please expand your thoughts i'm genuinely interested to hear another opinion on the subject. I do know plenty of people who believe using sedum is a waste of time, as it is normally brought in from foreign countries, increasing it's embodied energy. Do not forget Bauder is now actively harvesting sedum in a specialised farm in the UK. Also, don't forget another option is brown roofing, simply topsoiling or using site soil on your roof and letting it go 'wild' with natural vegetation and wildlife.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12767#Comment_12767 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12767#Comment_12767 Fri, 18 Jan 2008 11:22:38 +0000 fostertom
I heard yesterday that some kinds of single layer flat roofing are vapour permeable. Hard to believe - anyone know?
If so, that's radical, as then the massiveness of the green roof can be in contact with the interior, or at least the top of the insulation, not separated from it by a through-ventilated space above insulation.

Anyone know if, given the above, it's possible to rely for insulation on a good (sufficient) thickness of soil? Or would wetting destroy the soil's insulation? What if good drainage prevented the soil from getting too wet/waterlogged?]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12774#Comment_12774 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12774#Comment_12774 Fri, 18 Jan 2008 12:45:18 +0000 steveleigh RoofKrete is ideal for Green Roofs. Some architects have even specified soil directly on RoofKrete and this is okay because it is immune to all the bad things which can happen to petrochemical membranes. We have a large green roof 2,500 sq metres to start in a few weeks. RoofKrete Limited don’t officially do green roofing as a product but the contractors will do green roofs in conjunction with the green roof sedum mat suppliers etc.

I think the molecular structure of all petrochemical membranes allow water vapour to pass through. Even a PET (special dense plastic for bottle liquids) bottle of water would eventually leach out through the bottle walls whereas the water in a glass bottle would not. I do not think that petrochemical membranes can be classified 100% waterproof and have to be called weatherproof but RoofKrete is 100% waterproof.

Vapour permeable membranes under soggy warm deck green roofs are bound to continually feed water molecules into the insulation. It is the same action as bitumen rotting chipboard decks even though the bitumen is not leaking. This is massive problem which people overlook when costing a flat roof over its life span. The Bitumen industry is recommending marine ply (about £80 for a 8' x 4' board) as a solution to this water molecule problem. This is their sustainable solution so the decks don't need replacing.

Cheers Steve]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12776#Comment_12776 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12776#Comment_12776 Fri, 18 Jan 2008 12:55:26 +0000 fostertom Posted By: fostertomAnyone know if, given the above, it's possible to rely for insulation on a good (sufficient) thickness of soil? Or would wetting destroy the soil's insulation? What if good drainage prevented the soil from getting too wet/waterlogged?Come to think, leave "given the above" out of the above question -

Anyone know if, using no membranes except the one directly under the soil, it's possible to rely for insulation on a good (sufficient) thickness of soil? Or would wetting destroy the soil's insulation? What if good drainage prevented the soil from getting too wet/waterlogged?]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12779#Comment_12779 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=12779#Comment_12779 Fri, 18 Jan 2008 13:42:48 +0000 steveleigh Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13011#Comment_13011 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13011#Comment_13011 Mon, 21 Jan 2008 19:55:27 +0000 c-dub
To address the initial question, sloped green roofs are indeed very possible. Generally speaking, there is a "sweet spot" where the slope is steep enough to allow proper drainage, but not so steep that erosion becomes a significant problem. If your roof is shallow, you will likely need to incorporate a drainage layer, and if it's steep, you'll likely need to add a stabilizing structure of some sort to prevent the assembly from sliding off the roof. In either case, the roof will be more complicated, and more expensive. (In general, once the plants have established themselves, erosion becomes less of a problem, as their roots tend to knit everything together.)

Also, many existing buildings can support the weight of a fully-saturated green roof without structural reinforcement; it largely depends on the thickness of the soil (properly referred to as "growing medium"). The thinnest systems weigh no more than the ballast on a conventional membrane roof. A structural engineer or architect should always be consulted, however, to see if an existing building is capable of supporting the loads of a green roof – and it’s not just the roof structure that matters. The loads have to be carried down through the building structure and into the foundations.

Green roofs can be built up in layers and planted in-place, or delivered to the site in pre-grown mats or trays. Sedums are known performers and the most common species used, but natives are increasingly preferred. Sedums alone provide very little habitat benefit, and are sometimes considered invasive.

Green roofs improve water quality and air quality, decrease cooling loads in the heating season, and can even replace certain habitats for birds and beneficial insects. Slate, which was mentioned earlier, is an excellent roofing material, but has few environmental benefits beyond being a natural, long-lived product. Moreover, a green roof will last several times longer than most roof systems used today because the additional layers of the green roof assembly protect the membrane from UV degradation, as well as expansion and contraction due to freeze-thaw cycles.

The most important thing to consider when specifying a waterproofing membrane is that most roofing products are not suitable. Roofing and waterproofing are two very different concepts: roofing is meant to shed water as quickly as possible, whereas waterproofing is meant to tolerate constant exposure to water. Since most of the environmental benefits of green roofs depend on water being sequestered on the roof for use by the plants, proper waterproofing design is critical.

And finally, a few directed comments to previous posters:

@J..M:
I have a hard time considering green roofs a "fad," since there’s good evidence that they’ve been in use for the past 2,000 years in a wide variety of climates.
@Terry:
In what ways are green roofs "not as green as some would like to believe"? True, some green roofs are “greener” than others, depending on the design and implementation, but I’m curious about this blanket statement.
@ecoworrier:
In what way are green roofs "not sustainable"? And as for failure, any roof will eventually fail if not properly maintained -- but as I mentioned above, green roofs actually fail less often than most roofs.
@jon:
The maintenance costs for green roofs are not appreciably higher than for other roofs. There is a bit more work to be done for the first year or two (during the plant establishment period) but not in the long run.
@fostertom:
I wouldn't rely on saturated growing medium for thermal insulation. Most of the thermal benefit from a green roof is seen during the summer, when the plants shade the building and cool it via transpiration.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13148#Comment_13148 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13148#Comment_13148 Wed, 23 Jan 2008 03:59:36 +0000 fostertom Posted By: c-dubI wouldn't rely on saturated growing medium for thermal insulation. Most of the thermal benefit from a green roof is seen during the summer, when the plants shade the building and cool it via transpiration.So the traditionally promoted benefit, that a green roof keeps you cosy (presumably by insulation) and its massiveness stabilises temps below, don't seem to be true. Don't rely on it for insulation apparently - and as in UK through-ventilation beneath it (over the insulation) is a must (otherwise condensation on the underside of the membrane), its massiveness effects will be vented away and not benefit the interior. So what's the point? Not cold-season thermal, maybe habitat etc,.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13202#Comment_13202 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13202#Comment_13202 Wed, 23 Jan 2008 19:56:55 +0000 c-dub
I actually haven’t ever heard cold-weather insulation being touted as a significant benefit; not of contemporary green roofs, anyway, and not in this part of the world. Maybe that was true historically, before the advent of materials that are cheaper, lighter, and far more efficient insulators than wet dirt. However, if you’re talking about an earth-sheltered home, or an “intensive” green roof with considerably more than the 4-6” of growing medium commonly used, you probably would see a significant wintertime thermal benefit. Most new green roofs are relatively thin, though, so “massive” probably isn’t the most apt adjective.

Whether or not you need to ventilate the roof is completely dependent on the nature of the roof assembly, but it has very little to do with the fact that it’s a green roof: all the same general principles apply as do to conventional roofs. Roofs are often built with rigid insulation on the roof deck, no ventilation required.

As far as what the point is of green roofs, there are many: improved water quality and air quality, decreased cooling loads, mitigation of the urban heat island effect, improved building acoustics, habitat restoration, beautification, urban agriculture, construction waste reduction. I don’t know of any other sustainable building technology with such direct and varied benefits.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13246#Comment_13246 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13246#Comment_13246 Thu, 24 Jan 2008 13:39:42 +0000 fostertom Posted By: c-dubif you’re talking about an earth-sheltered home, you probably would see a significant wintertime thermal benefitBut only if the soil was thick enough above to indeed act a insulation such that there's no danger of condensation on the underside of the membrane, so not needing outside air though-ventilation under the membrane. Because such through-ventilation cuts the interior off from any kind of thermal benefit, whether insulation or massiveness, that whatever lies above the membrane might offer.
Posted By: c-dubWhether or not you need to ventilate the roof is completely dependent on the nature of the roof assembly, but it has very little to do with the fact that it’s a green roof
True, but other kinds of roof assembly e.g. a typical flat roof deck, wouldn't be expected to offer the kind of thermal benefits that are wrongly assumed for green roofs.
Posted By: c-dubRoofs are often built with rigid insulation on the roof deck, no ventilation required
If that means insulation above the (unventilated) membrane, then the massiveness of the green roof above the insulation it is still cut off from the interior.
Posted By: c-dubAs far as what the point is of green roofs, there are many: ..... decreased cooling loads, .... improved building acoustics
Even when the interior can't 'see' the massiveness above the insulation and the ventilated airspace above it? True the massiveness will act as a sunshade. So, unless done as para 1 above with no need for below-membrane through-ventilation, green roofs offer no internal thermal benefits, just (good) benefits to the external environment in a wider sense.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13252#Comment_13252 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=13252#Comment_13252 Thu, 24 Jan 2008 16:22:03 +0000 c-dub
In my mind, it’s just easier to insulate above the membrane and eliminate the ventilation altogether. There’s another benefit to this sort of “inverted” roof, especially in the context of green roofs. If the membrane is applied directly to the roof deck, and the insulation is above that, there is far less chance of an eventual leak migrating horizontally through the roof assembly. Therefore, if you see evidence of a leak on the underside of the deck (which is likely exposed, or easily exposed, since the insulation is above), you can pinpoint the location of the leak with some certainty. That’s a boon with any leaking roof, but particularly with a green roof, considering the amount of overburden that has to be removed to locate a leak and make a repair.]]> Green Roofs - onto existing pitched roof???? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=85351#Comment_85351 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=762&Focus=85351#Comment_85351 Wed, 14 Jul 2010 16:00:45 +0100 raffy
I would do a complementary grey water recycling system to irrigate the roof during dry season (water in Aruba is 4 times the cost as in the netherlands). This is relatively simple to do. Also there's a selection of local shrubs that would do fine in dry season to keep maintenance manageable.

Do you have any pointers on green roofs, manufacturers, etc. concerning green roofs? Also do you think I should consider any form of insulation considering the geographical location of the island? Our biggest problem is the UV-penetration which is a big heat element.

Best regards,

Raffy]]>