[Greenbuilding] epdm vs. tar

[JOHN SALMEN]

Tar and gravel or built up (BUR) roofs are estimates at 20 -25 years
typically (4ply/5ply)
Epdm roofs are rated at 12-25 yrs depending on thickness and backing
(45-80mil)

A BUR roof will use just under a lb (.6-.7) of tar per square foot and an
epdm will
An EPDM roof will use .3 -.4 lbs of material per square foot

An epdm roof is an elastomer with mostly carbon as a filler
A tar roof was traditionally a coal tar but is mostly elastomers as well at
this point

So an epdm roof will use about 1/2 the base material so I think you could
safely say than an epdm roof used 1/3-1/2 of the material of a BUR roof.
EPDM typically has 0 to maybe 3" recycled content.

Longevity is about the materials degrading (typically uv/weather) with
exposure. A lot has been said about the benefit of green roofs as protecting
the roof from degrading. That is true but most roofs fail at joints and
penetrations and even on a green roof these are often exposed or even if not
exposed the adhesives naturally fail over time. 



-----Original Message-----
From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of RT
Sent: August-29-11 7:20 AM
To: Green Building
Subject: Re: [Greenbuilding] epdm vs. tar

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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