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' a rear
vent installation the
floor protection
must
also
extend
under
the stovepipe
a
minimum of
2" (50mm)
beyond
either
side
of the pipe.
How to determine
if
alternate floor protection
materials
are
acceptable.
All
floor protection
must be
non-combustible
(i.e.,.metals, briclq
stone, mineral
filer
boards,
etc.). Any organic
materials
(i.e.,
Si"i.T,'#i83,'!Xo"?:?'':$lf?;",[:J"ffi
i,?,T,i#i'iJi,11".6tltgni[i{*X.kiru;;;i:"
ip"iineai"ii,,ol'
'J-"
ro,"i
Procedure;
1.
Convert specification to
R-value:
i.
R-value
given
-
no
conversion needed.
ii.
k-factor
is
given
with
a
required
thickness
(T)
in
inches:
n
=f
x
f
iii.
K-factor
is
given
with
a
required thickness
(T)
in
inches:
n
=n,.12
x
f
iv.
r-factor
is
given with
a
required
thickness
(T)
in
inches:
R
=
r x
T
2.
Determine the
R-value
of the
proposed
arternate
floor
protector.
i.
Use
the formula
in
step
(1)
to
convert
values
not
expressed
as
,,R".
ii.
For multiple
layers,
add
R-values
of each layer
to
determine overall
R-value.
If
the overall
R-value
of the
system
is
greater
than
the
R-value
of the specified
floor
protector, the altemate
is
acceptable.
Example;
The specified
fl-oor
protector should
b-e
3/4-inch
thick material
with
a
k-factor of
0.g4.
The
proposed
alternate
is
4" brick
with
an
i-factor
of
0.2bver
1/8"
mineraLb;d;iii,';i$;;;;
or0.29.
Step
(a):
Use
formula
above to convert specification to
R_value.
R=
+"t=*nxo.T5
=0.8e3
Step
(b);
Calculate
R
of proposed
svstem.
4"
brick
otr
=
d.2,fherefor6:
Rbricr=O.Zx4=0.431
1/8" mineral
board
of
k
=
O.Zg,
therefore
Rminerat
board
=
#g "
O.IZS
= 0.43I
Rtotal
=
Rbri.k
+
Rmineral
board
= 0.8 +
0.431
=
l.Z3l
ii";t
l:l;,1:f*:"rfltfsed
system
Rtotd
of 1.231 tospecilied
R
or0.8e3.
Since
proposed
system
&ota
is
greater than required,
Definitions
R
_
(ftz) (hr) ('F)
Btu
,.
(Bru)
(in)
K=
(ftz)
(hr)
fF)
r:
(ftz)
(hr)
fF)
(Btu)
(in)
=t
k
^
_
(Btu)
(ft)
(ft2)
(hr)
("F)
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