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you're pretty much right on the same track. i realized after i sent it
the email only had the main question buried in the middle and i have a
side question to go with it. <br>
<br>
main question: what is the f-factor of a 4" concrete slab?<br>
reason for question: most architects in southern arizona specify, and
contractors build, an unheatd 4" concrete slab for standard
office/retail. 6" concrete slab for warehouses and other spaces where
heavier loads are common. <br>
<br>
secondary question: does a building with a 4" concrete slab meet the
f-factor requirements of 90.1 per table A6.3? (unheated or heated,
unheated in my case though).<br>
reason for question: need to demonstrate 90.1-2004/2007 compliance for
floor f-factor. unclear as to answer.<br>
<br>
1. all of the research/other references to f-factors that i've found
also reference the 6" slab, the same research, and 90.1, and from what
i've seen/can tell they only tested at a 6" slab with 8" and 4" walls
and varying insulations. <br>
2. the problem with calculating an f-factor, even if using ashrae
fundamentals derived constructions, per 90.1, is that calculations are
prohibited by Section A9 Determination of Alternate Assembly U-Factors,
C-Factors, or F-Factors, or Heat Capacities, SubSection A9.2(e),
"Slab-on-Grade Floors: no testing or calculations allowed."<br>
3. which leads me back to section a6.3.2, which states in reference to
Table A6.3, "These <i>F-factors</i> are acceptable for all <i>slab-on-grade
floors</i>." - but is it really? how does one defend a building
official or leed review comment for a 4" slab f-factor? if section
a.6.3.2 is literally correct then the f-factor for an unheated 4" slab
is the same 0.73 as an unheated 6" slab. since the f-factor is based
on linear feet and not square feet this could make sense if the thermal
capacity of the thickness of the slab does not matter for f-factor.
note though that 4", 6", and 8" lightweight concrete all have the same
conductivity (3.7), density (80), and specific heat (0.22) (per the
2009 fundamentals). knowing the thickness of the slab may be
insignificant to the f-factor calculation is one thing,
proving/demonstrating it to a code official/leed reviewer is another.
i have asked my local code officials (who are pe's also) and they don't
know the the answer(s) either ... <br>
<br>
<br>
<br>
<br>
On 3/28/11 2:41 AM, Nick Caton wrote:
<blockquote
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<div class="Section1">
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Hm…<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">The
heart of your query isn’t really crystal clear to me, but I’ll
take a stab:<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Section
A1.2 says if a building official feels sections A2 through
A8 do not “adequately represent” the proposed construction, Section A9
is to be
used, but A.9.2.e. curtly says no alternate procedures are permitted to
find
alternative F-factors for SOG floors. At first glance, it would appear
the
90.1 committee might be giving any extremely meticulous building
officials/reviewers/designers the run-around.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">The
way I see it, Section A6 in its entirety is suggesting concrete
slab thickness varying from 6 inches “doesn’t matter much.” <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">More
precisely: “Real-world” SOG design within the confines of any
90.1 calculations shall be restricted to the following variables:<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">1.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">The
R-value of any insulation, if present<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">2.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">The
configuration of said insulation, if present,<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">3.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Whether
the slab is heated<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Note
there are a series of variables are not brought up or either
explicitly held constant, beyond slab thickness, and I understand these
all can
have a decent effect on perimeter conductivity:<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">1.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">What’s
on top of the slab<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">2.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Slab
height relative to grade / footing exposure<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">3.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Soil
conductivity/moisture properties<o:p></o:p></span></p>
<p class="MsoListParagraph"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">For
further reading, I know there are multiple white papers out
there going well into depth if that’s what you’re seeking – LBNL comes
to mind
as being part of some research… I personally haven’t charged myself
with
crunching the numbers up to this point, rather letting my software of
choice do
the legwork.<o:p></o:p></span></p>
<p class="MsoListParagraph"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">The
reasons I would speculate that section A6.1 specifies a 6”
thickness would include<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">1.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">It
helps ground/quantify from what the numbers in the table are
derived<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">2.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">It
gives a reference to the base construction’s thermal mass –
necessary should you wish to model something different for your
proposed
constructions within the context of, say, an Appendix G performance
rating.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><!--[if !supportLists]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><span
style="">3.<span
style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none;">
</span></span></span><!--[endif]--><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">While
a strict reading of appendix A might lead one to believe
all constructions used in all calculations must follow the prescribed
values, I’ve
only ever run into one reviewer who called into question the use of
custom
constructions and ASHRAE Fundamentals-derived materials/properties
which do not
appear within the (relatively abbreviated) Appendix A. I think the
real intent
is to provide a description of those constructions as defined earlier
in the
code – namely envelope constructions in the context of describing
either a “prescriptive
minimum” or in the context of energy modeling as the “baseline
constructions.”
I do not believe the intent of Appendix A is to restrict/limit the
design
decisions that may be made outside of the presented materials/tables.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">I’m
on a bit of a limb here, but I’m speculating at what may
have prompted your question… does this miss the mark?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">~Nick<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><img
id="Picture_x0020_1" src="cid:part1.03060801.05040707@gmail.com"
alt="cid:489575314@22072009-0ABB" height="37" width="119"></span><b><span
style="font-size: 11pt; font-family: "Stylus BT","sans-serif"; color: rgb(45, 77, 94);"><o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size: 11pt; font-family: "Stylus BT","sans-serif"; color: rgb(45, 77, 94);"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size: 11pt; font-family: "Stylus BT","sans-serif"; color: rgb(45, 77, 94);">NICK
CATON, E.I.T.</span></b><b><span
style="font-family: "Stylus BT","sans-serif"; color: rgb(45, 77, 94);"><o:p></o:p></span></b></p>
<p class="MsoNormal"><span
style="font-size: 7.5pt; font-family: "Calibri","sans-serif"; color: rgb(204, 153, 0);">PROJECT
ENGINEER<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Calibri","sans-serif"; color: rgb(45, 77, 94);">Smith
& Boucher Engineers</span><span
style="font-size: 7.5pt; color: rgb(204, 153, 0);"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Calibri","sans-serif"; color: rgb(45, 77, 94);">25501
west valley parkway<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Calibri","sans-serif"; color: rgb(45, 77, 94);">olathe
ks 66061<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Calibri","sans-serif"; color: rgb(45, 77, 94);">direct
913 344.0036<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Calibri","sans-serif"; color: rgb(45, 77, 94);">fax
913 345.0617<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><a
moz-do-not-send="true" href="www.smithboucher.com"
title="blocked::www.smithboucher.com"><span style="font-size: 10pt;">www.smithboucher.com</span></a></span><u><span
style="font-size: 10pt; font-family: "Calibri","sans-serif"; color: blue;">
</span></u><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p></o:p></span></p>
</div>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<div>
<div
style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">
<a class="moz-txt-link-abbreviated" href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a>
[<a class="moz-txt-link-freetext" href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>] <b>On Behalf Of </b>Patrick
J.
O'Leary, Jr.<br>
<b>Sent:</b> Thursday, March 24, 2011 7:12 AM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> [Bldg-sim] f-factor & table a6.3 (90.1-2004 &
2007)<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">knowing that <br>
<br>
1) appendix a, section 6.1, references that "For the purpose of Section
A1.2, the base assembly is a slab floor of 6 in. concrete poured
directly on to
the earth ..." meets the requirement for an unheated slab f-factor of
0.73, and<br>
2) section a6.3, f-factors for slab-on-grade floors, a.6.3.1 states:
"<i>F-factors</i> for slab-on-grade floors shall be taken from Table
A6.3", and<br>
3) section a6.3.2 states: "These <i>F-factors</i> are acceptable for
all <i>slab-on-grade
floors</i>."<br>
<br>
does the "all slab-on-grade floors" really mean any thickness of
slab-on-grade? i.e. section 6.1 references a 6-inch uninsulated slab
meeting the 0.73 f-factor requirement, but per sections a6.3.2 and
table a6.3 a
4-inch uninsulated slab (or an 8-inch uninsulated slab) would also meet
the
0.73 f-factor requirement. so why would section a6.1 specify a 6-inch
slab when any slab thickness will suffice? the user's manuals (both
years) just refer to table a6.3 for f-factor values.<br>
<br>
the state of washington has a similar section in its energy code (see
link
below), page 41, table 4-2. section 1003.2 (also page 41) lists "All
on-grade slab floors as assumed to be 6 inch concrete poured directly
onto the
earth." note that on page 40, table 10.1, the f-factors
decrease the deeper the below grade the slab-on-grade floor is.<br>
<a moz-do-not-send="true"
href="http://ftp.resource.org/codes.gov/wa_energy.pdf">http://ftp.resource.org/codes.gov/wa_energy.pdf</a><o:p></o:p></p>
</div>
</div>
</blockquote>
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