[Greenbuilding] Insulation fasteners

John Salmen terrain at shaw.ca
Thu Nov 15 12:04:51 CST 2012


What is incorrect and false and impedes what kind of progress?

 

I am not talking about mechanically fastening foam we are talking about
fastening wood against foam through to framing. EIFS screws and washers like
dekfast and windlock are great for attaching foam (if you need to) but you
need the washer so still about .35 per screw and washer – and it is usually
minimum1 screw per square foot for eifs. That is the equivalent cost of 2”
of eps (I pay about .18 per board foot for eps). I am not sure what is
progressive about thousands of screws and plastic washers - I prefer foam
adhesives

 

So for mechanically fastening battens or wood components against foam ONE
large head structural screw at framing intervals at a cost of .30 per screw
is I think a pretty responsible approach  (don’t buy them at home despot).
And yes screw heads snapping or screws bending is a common problem when
embedding a long low strength metal screw 1-1/2” into spf framing. And I am
not sure why there would excuses if there wasn’t a perceived problem.

 

I’ve also borrowed a detail from current sailboat rigging practices where
ropes are once again being used to replace metal fasteners. ¼” carbon or
vectran fibre rope or  webbing can be punched through foam and fastened to
framing – makes a great connector for any component that needs to be
attached to an exterior face.

 

 

 

From: John Straube [mailto:jfstraube at gmail.com] 
Sent: November-15-12 6:36 AM
To: John Salmen
Cc: george at houseisasystem.com; 'Green Building'
Subject: Re: [Greenbuilding] Insulation fasteners

 

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).
You can get long screws that are not "structural screws".  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.
Yes, long structural screws are what you find at Home Depot, but these
expensive and problematic in a number of ways.
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.  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. 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.

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).  

The screws are also NOT the most expensive part of the assembly.  Not even
close.
If you purchase relatively heavy 6" long screws from, say, here 
http://www.bestmaterials.com/detail.aspx?ID=9221
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).
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.



Dr John Straube, P.Eng. 
www.BuildingScience.com

On 12-11-14 11:10 PM, John Salmen wrote:

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 [mailto:greenbuilding-bounces at lists.bioenergylists.org]
On Behalf Of George J. Nesbitt
Sent: November-14-12 6:57 PM
To: jfstraube at gmail.com; 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:

We have tested up to 8" of foam (EPS, XPS is stronger) with #10 screws and

furring strips. Works fine with siding ( safety factor of more than 10).

3/8" lags is crazy: never need it. The foam provides a lot of the

strength.

Check our buildingscience.com website or my book for more detail on how

this works.

 
Sent wirelessly from my BlackBerry device on the Bell network.
 
-----Original Message-----
From: Clarke Olsen  <mailto:colsen at fairpoint.net> <colsen at fairpoint.net>
Sender: "Greenbuilding" 
 <mailto:greenbuilding-bounces at lists.bioenergylists.org>
<greenbuilding-bounces at lists.bioenergylists.org>
Date: Wed, 14 Nov 2012 09:50:23
To: Green Building <mailto:greenbuilding at lists.bioenergylists.org>
<greenbuilding at lists.bioenergylists.org>
Reply-To: Green Building  <mailto:greenbuilding at lists.bioenergylists.org>
<greenbuilding at lists.bioenergylists.org>
Subject: Re: [Greenbuilding] Insulation fasteners
 
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--
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, www.houseisasystem.com, (510)
655-8532 office, (510) 599-5708 mobile
 
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