[Greenbuilding] SCIPs questions

[Bruce Donelson]

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org]On Behalf Of Leslie
Moyer
Sent: Saturday, December 23, 2006 10:59 PM
To: GREENBUILDING at LISTSERV.REPP.ORG;
organic_architecture at yahoogroups.com
Subject: [Greenbuilding] SCIPs questions


After researching SCIPs (structural concrete insulating panels),
specifically Green Sandwich Technologies (http://greensandwichtech.com),
we think we've settled on this product as a building shell.  I do have a
few concerns/questions, however, and I thought I'd request input here
prior to meeting with the builder next week (at which time I will also
ask these questions).

1. If utilities need to be relocated or serviced in the future, I can't
imagine an easy access to them.  We are planning to build this house to
last 100 years, and if the previous 100 is any indication of the kind of
change that is possible in utilities, I assume that we (or someone else)
*will* need to access, add, or change the utilities inside the wall
cavity--probably even within the next 25 years.  SIPs have a similar
problem, though not quite as difficult.  Ideas?  (If structurally
possible, we would like to use an earthen plaster for the inside, making
access a little more accessible, but not much.)  Interior walls will
likely still be normally accessible--either an agriboard product or a
traditional drywall.

1. Lots of empty conduits would help on the exterior walls. Keeping as much
of the water system as possible on the interior partitions is also a help.

2. Insulation/R-value:  The website says an "R-40 performance".  I
understand this is achieved with a tight building envelope, high thermal
mass, and a thermal break.  But the insulation still seems insufficient
to me.

THIS IS A VERY COMMON SCAM WHEN DEALING WITH THESE PRODUCTS. The "R-40
performance" relies on perfect conditions, where the daily temperature swing
goes above the heating target by the same amount that it goes below it. For
example, say you wish to hold the interior temperature between 68F and 74F.
If the high temperature of the day is 78F and the low is 58F (or
thereabouts) then the thermal mass of the walls will cause the net energy
consumed to hold the house at that temperature to be about the same as a
conventionally built house with R-40 wall insulation. If the daily high is
40F, and the low is 30F, the real R-value would be the operable number. This
is much more likely to be about R-10 for the walls. That is, the house will
require about as much energy to heat as a conventionally framed house with
R-10 walls. This is based on the R-value of their foam being about R-5 per
inch, and it having about 2 inches of foam. Some climates commonly have
daily temperature swings that balance out around a desirable daily
temperature, but they are a bit rare. In temperate zones with warm summers
and cold winters the R-40 performance is not acheivable. To get to that
level, you might consider adding another 6 inches of foam to one side or the
other. It would be more effective to add the extra foam to the outside of
the wall, so that the thermal mass is to the interior.

3. My ignorance about concrete / stucco / plaster is evident when I ask
how one prevents problems like cracking, flaking, etc. from occurring.
(Someone posted a link to some photos last week that detailed the
failure on once house--failure that compromised the integrity of the
wood frame itself....can't find the link at the moment.) Will the steel
reinforcement of the SCIP prevent cracking & keep the structure intact?

3. The steel reinforcement is there to provide some reinforcement for the
stucco. This is analagous the the chicken-wire type of lath used for
traditional 3-coat stucco products. The worst factor for cracks in stucco is
freeze-thaw cycles. Say you have a thin crack, with some moisture in it.
When it freezes, the ice expands the crack. The more cycles that the crack
endures, the faster the cracks develop. Settling foundations, or foundations
built on expansive soils, can also induce cracking. Places that seldom
freeze, or places that stay frozen are the most stable environments for
stucco. Some synthetic stucco coatings (used in EIFS systems), are flexible
and resist cracking. These are generally acrylic-based. They can bridge over
hairline cracks in the substrate. If the building is moving or settling,
nothing can prevent cracking.


Bruce Donelson
A Better Builder

Thanks for any input.  I feel like this is the most important decision
we'll make about our house and I appreciate all of the great minds here
on these two lists!

--Leslie Moyer / Oklahoma




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