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<div class="moz-cite-prefix"><font face="Helvetica, Arial,
sans-serif">John, much of what you say is not correct. This
bothers me because I routinely hear these false claims made, and
this incorrect information impedes progress in making good
energy efficient buildings (something I know you care about).<br>
<b>You can get long screws that are not "structural screws".</b>
I know, because we and many others installing thick layers of
foam insulation and have been doing this for years. There must
be a few dozen case studies alone on our website.<br>
Yes, long structural screws are what you find at Home Depot, but
these expensive and problematic in a number of ways.<br>
It is quite possible to get #10 or #12 screws in lengths of 6"
and up. #10 is typically only available to about 6" length, and
then #12 to about 12 or 14" long, and then you are up to #14 /
1/4" dia for lengths up to 20" or so. We regularily find that a
#12x6" can be cheaper than a #10x6" and thus use them, but #10
is what we have always tested in the lab because they are the
smallest available and hence the most flexible with the lowest
pullout loads. Their heads DO NOT torque off when used to
attach foam. They are NOT intended for screwing through solid
wood but through insulation, which is why they work perfectly
well. </font><font face="Helvetica, Arial, sans-serif"><font
face="Helvetica, Arial, sans-serif">Millions of 6" long or
longer screws are installed every year through foam in the
commercial low-slope roofing and EIFS industry (see for
example Wind-lok for #10x6" long). This is the first stop if
you are looking for long thin screws that have corrosion
resistance, are easy to install and affordable. These
products in these building niches all have a long track record
of being installed by the thousands without problems of
torquing off heads, driver slippage, bending, or whatever
other excuses I have heard. </font>They have been designed
for embedding about 1 to 1.5" in wood after screwing through
4-12" of roof or EIFS insulation. What is not easy for
individuals and small contractors is finding these screws
because they are typically carried by larger supply houses and
commercial sales outlets. If more people start super insulating
their houses, I am pretty sure the fastener industry will
respond by marketing their roof screws as wall screws and the
problem will go away.<br>
<br>
The HeadLok screws are great for many structural applications,
but I think these are used for attaching foam and furring only
because they are available at retail outlets. There are quite
nice, but are usually twice as expensive as the alternatives (40
cents each and up), and often three times the cost retail (eg we
get supply house prices of 12 cents on a #10x6" and the
contractor tells us that HeadLok or GRK cost $150 for a 250
pack). <br>
<br>
<b>The screws are also NOT the most expensive part of the
assembly.</b> Not even close.<br>
If you purchase relatively heavy 6" long screws from, say, here
<br>
<a class="moz-txt-link-freetext" href="http://www.bestmaterials.com/detail.aspx?ID=9221">http://www.bestmaterials.com/detail.aspx?ID=9221</a><br>
They cost maybe 20 cents each (these are #12-14 screws) Not
the cheapest source but not bad. Often available for 15 cents.
If you use one screw every 12" vertically and 24" horizontally
(pretty conservative), that is 1 screw per 2 square feet or
about 10 cents/square foot at 20 cents each. When labour is
added, the screw might be 3 times as expensive (30 cents /square
foot).<br>
4" of polyiso will cost something in the order of $2 to $2.50
per square foot, making the screw less than 5% of the cost of
materials for the exterior insulation (adding the cost of
furring strips changes little). 4" of EPS will be about $1.50.
With labour, the screw is still around 10% or less.<br>
<br>
<br>
</font>
<div class="moz-signature">Dr John Straube, P.Eng. <br>
<a class="moz-txt-link-abbreviated" href="http://www.BuildingScience.com">www.BuildingScience.com</a></div>
On 12-11-14 11:10 PM, John Salmen wrote:<br>
</div>
<blockquote cite="mid:02c701cdc2e7$344df2d0$9ce9d870$@ca"
type="cite">
<pre wrap="">When you get into long screws they are structural screws - equivalent to a
3/8" bolt (actually better). For sure they are overkill but that is where
eng. crosses practicality. When you increase length on anything the design
requirements for actually getting the screw into the material override the
design criteria for loading. The reason being that you cannot screw a long
softmetal screw into an assembly without torqueing off the head. - I don't
even think you can even find a #10 standard soft metal screw in long lengths
anymore - I remember putting an order in from one manuf. a decade ago and
half the screws were thrown away from having heads torqued off. 1/4" and
3/8" lag bolts would also self destruct far too often in application to make
them practical for a load that an 1/8" of metal would carry. We are talking
about crews that have to install a lot of bolts/screws in a day and wasting
their time with defective material is an overriding consideration.
Headlok screws that I mentioned will cost about .30 per for 6" and about .50
per for 8" and each screw will do what is supposed to do. They drive in
quickly and perfectly each time. They have a large wafer head equivalent to
a washer so one screw generally takes the place of at least 2 screws in
design.
Fastening is the overriding cost in assemblies at this point and it is split
between the cost of the fastener and the time taken to fasten. That is why
most buildings are being put together with adhesives.
-----Original Message-----
From: Greenbuilding [<a class="moz-txt-link-freetext" href="mailto:greenbuilding-bounces@lists.bioenergylists.org">mailto:greenbuilding-bounces@lists.bioenergylists.org</a>]
On Behalf Of George J. Nesbitt
Sent: November-14-12 6:57 PM
To: <a class="moz-txt-link-abbreviated" href="mailto:jfstraube@gmail.com">jfstraube@gmail.com</a>; Green Building
Subject: Re: [Greenbuilding] Insulation fasteners
I'm about to screw through 4-1/2" of polyiso, I can only find 6" screws
affordably ($13/100ea), longer screws are $1ea. Sources & prices for 6"+
#10 screws?
On 11/14/2012 7:53 AM, John Straube wrote:
</pre>
<blockquote type="cite">
<pre wrap="">We have tested up to 8" of foam (EPS, XPS is stronger) with #10 screws and
</pre>
</blockquote>
<pre wrap="">furring strips. Works fine with siding ( safety factor of more than 10).
</pre>
<blockquote type="cite">
<pre wrap="">3/8" lags is crazy: never need it. The foam provides a lot of the
</pre>
</blockquote>
<pre wrap="">strength.
</pre>
<blockquote type="cite">
<pre wrap="">Check our buildingscience.com website or my book for more detail on how
</pre>
</blockquote>
<pre wrap="">this works.
</pre>
<blockquote type="cite">
<pre wrap="">
Sent wirelessly from my BlackBerry device on the Bell network.
-----Original Message-----
From: Clarke Olsen <a class="moz-txt-link-rfc2396E" href="mailto:colsen@fairpoint.net"><colsen@fairpoint.net></a>
Sender: "Greenbuilding"
<a class="moz-txt-link-rfc2396E" href="mailto:greenbuilding-bounces@lists.bioenergylists.org"><greenbuilding-bounces@lists.bioenergylists.org></a>
Date: Wed, 14 Nov 2012 09:50:23
To: Green Building<a class="moz-txt-link-rfc2396E" href="mailto:greenbuilding@lists.bioenergylists.org"><greenbuilding@lists.bioenergylists.org></a>
Reply-To: Green Building <a class="moz-txt-link-rfc2396E" href="mailto:greenbuilding@lists.bioenergylists.org"><greenbuilding@lists.bioenergylists.org></a>
Subject: Re: [Greenbuilding] Insulation fasteners
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</pre>
</blockquote>
<pre wrap="">
--
George J. Nesbitt, Environmental Design / Build, Building Performance
Contractor HERS I Verifier & HERS II Rater, GreenPoint Rater new & existing
SF & MF, CABEC CEPE (Certified Energy Plans Examiner), Certified Passive
House Consultant, BPI Multifamily Analyst, <a class="moz-txt-link-abbreviated" href="http://www.houseisasystem.com">www.houseisasystem.com</a>, (510)
655-8532 office, (510) 599-5708 mobile
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</pre>
</blockquote>
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