[Greenbuilding] epdm vs. tar geen roof

[Jason Holstine]

I think green roofs are an example of ³the sum is greater than the parts².
The variety of benefits may individually be minimal to alternatives. But
when factoring in the intangibles of aesthetics, biodiversity and feel-good,
the combination is their driving force‹and a legitimate factor, at that.


On 8/29/11 11:31 AM, "John Straube" <jfstraube at gmail.com> wrote:

> Practical experience with EPDM roofs is that they do not have great
> durability.  This is one reason they, and TPO, are almost never used in green
> roofs. I would also assume you would be specifying a protected membrane roof
> in any case you care about durability.  Worry about which membrane uses more
> or less oil or energy seems completely misplaced if there is a trade off with
> durability which there will be with roofing products. Pick the most durable,
> or nearly the most durable, roof membrane and save environmental impact on the
> life-cycle. 
> Tar roof is not sufficiently specific to make judgements.  There are many
> types.
> I would always recommend either a two-ply modified bitumen roof, or liquid
> applied glass matt reinforced hot rubberized asphalt if all you cared about
> was durability.
> 
> Speaking of cooking the books, Dr Lui's report, like most you will find, over
> sell the performance benefits of green roofs.  They do this by comparing an
> excellent green roof design with the dumbest low slope roof we know how to
> build (an exposed membrane black roof).   A fair comparison is to compare a
> green roof to a protect membrane roof (PMR) with white balast (pavers or river
> rock).  When this is done the energy savings and durability benefits of a
> green roof essentially vanish.  The benefits of dust removal, stormwater
> retention remain.  There are cheaper ways to retain stormwater than a green
> roof.  The reason for a green roof is mostly because they are beautiful to
> look at relative to the options, and in intensely urban areas they add to
> biodiversity (they don't do much in rural settings).
> 
> 
> 
> On 2011-08-29, at 10:20 AM, RT wrote:
> 
>> > On Sun, 28 Aug 2011 23:13:45 -0400, Gennaro Brooks-Church - Eco Brooklyn
>> <info at ecobrooklyn.com> wrote:
>> > 
>> > 
>>> >> So....over 30 years.
>>> >> Tar roof - $40, more petro chemicals consumed, more waster created.
>>> >> EPDM + green roof - $40,
>> > 
>>> >> Your thoughts? How do my numbers look?
>> > 
>> > 
>> > I'd say that the numbers look like they were "cooked" by someone who might
>> have done creative book-keeping for Tony Soprano et al.
>> > 
>> > But aside from that, all or most of the benefits in the comparison are due
>> to the Green Roof component and a Green Roof can be installed over any
>> waterproof membrane and provide the same benefits.
>> > 
>> > Without actually checking the actual numbers (not my job, eh ?) I have a
>> gut feeling that the embodied-energy of a hot-mopped tar membrane is lower
>> than that of an EPDM.
>> > 
>> > But using Gennaro's numbers for life expectancy -- 30 years -- I'd say that
>> that's pretty ?!$$-poor performance (PPPP or 4P).
>> > 
>> > Any Greenie worth their chlorophyll would shun asphalt shingles as a sloped
>> roofing option largely because of their short service life (30 years max) and
>> their high waste factor (ie not recyclable for the most part) so it's curious
>> that one would consider a 30-year tar or EPDM membrane as viable options for
>> a flat roof.
>> > 
>> > That is to say, perhaps third, fourth or fifth non-petro options might be
>> considered for the membrane (the Green Roof being a "given" if for no other
>> reason, because it extends the life of the membrane, like IRMAs).
>> > 
>> > The other benefits are quantified in Dr. Karen Lui's report (if the IRC at
>> NRC) which I've cited here numerous times in the past.
>> > 
>> > -- 
>> > === * ===
>> > Rob Tom
>> > Kanata, Ontario, Canada
>> > < A r c h i L o g i c  at  Y a h o o  dot  c a >
>> > (manually winnow the chaff from my edress if you hit "reply")
>> > 
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> 
> Dr John Straube, P.Eng.
> Associate Professor
> University of Waterloo
> Dept of Civil Eng. & School of Architecture
> www.buildingscience.com
> 
> 
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