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47
T
ABLE
3.17
Cooling
Load
T
emperatur
e
Dif
fer
ences
for
Calculating
Cooling
Load
fr
om
Flat
Roofs
S
O
URCE
:
Copyright
1985,
American
Society
of
Heating,
Refrigerating
and
Air
Conditioning
Engineers,
Inc.,
www
.ashrae.org.
Abstracted
by
permission
from
ASHRAE
Handbook,
1985
Fundamentals
Chap.
26,
T
able
5.
F
o
r
limitations
and
adjustments
see
notes
in
the
Handbook
table.
(Subsequent
editions
provide
more
extensive
data.)
Design Procedures: Part 1
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Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
48
T
ABLE
3.18
W
all
Construction
Gr
oup
Description
Design Procedures: Part 1
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
49
S
O
URCE
:
Copyright
1989,
American
Society
of
Heating,
Refrigerating
and
Air
Conditioning
Engineers,
Inc.,
www
.ashrae.org.
Abstracted
by
permission
from
ASHRAE
Handbook,
1989
Fundamentals,
Chap.
26,
T
able
30.
(Subsequent
editions
provide
more
extensive
data.)
Design Procedures: Part 1
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
50
T
ABLE
3.19
Cooling
Load
T
emperatur
e
Dif
fer
ences
for
Calculating
Cooling
Load
fr
om
Sunlit
W
alls
Design Procedures: Part 1
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
51
1.
Direct
application
of
the
table
without
adjustments:
V
alues
in
the
table
were
calculated
using
the
same
conditions
for
w
alls
as
outlined
for
the
roof
CL
TD
table,
T
able
3.17.
These
values
ma
y
b
e
used
for
all
normal
air
-conditioning
estimates,
usually
without
correction
(except
as
noted
below)
when
the
load
is
calculated
for
the
hottest
weather
.
F
or
totally
shaded
w
alls,
use
the
north
orien-
tation
values.
2.
Adjustments
to
table
values:
The
following
equation
makes
adjustments
for
conditions
other
than
those
listed
in
note
1.
CLTD
⫽
(CLTD
⫹
LM)
K
⫹
(78
⫺
T
)
⫹
(
T
⫺
85)
co
rr
Ro
where
CL
TD
is
from
T
able
3.19
at
the
w
all
orientation.
LM
is
the
latitude-month
correction
from
T
able
3.20.
K
is
a
color
adjustment
factor
applied
after
first
making
month-latitude
adjustment
K
⫽
1.0
if
dark
colored
or
light
in
an
industrial
area
K
⫽
0.83
if
permanently
medium-colored
(rural
area)
K
⫽
0.65
if
permanently
light-colored
(rural
area)
Credit
should
not
be
taken
for
w
all
color
other
than
dark
except
where
permanence
of
color
is
established
by
experience,
as
in
rural
areas
or
where
there
is
little
smoke.
S
O
URCE
:
Copyright
1989,
American
Society
of
Heating,
Refrigerating
and
Air
Conditioning
Engineers,
Inc.,
www
.ashrae.org.
Abstracted
by
permission
from
ASHRAE
Handbook,
1989
Fundamentals,
Chap.
26,
T
able
31.
(Subsequent
editions
provide
more
extensive
data.)
Design Procedures: Part 1
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
52
Chapter Three
TABLE
3.20 CLTD Correction for Latitude and Month Applied to Walls and
Roofs, North Latitudes
(1) Corrections in this table are in
⬚
F. The correction is applied directly to the CLTD for a
wall or roof as given in Tables 3.17 and 3.19.
(2) The CLTD correction given in this table is not applicable to Table 3.31, Cooling Load
Temperature Differences for Conduction through Glass.
(3) For south latitudes, replace Jan. through Dec. by July through June.
SOURCE
: Copyright 1989, American Society of Heating, Refrigerating and Air Conditioning
Engineers, Inc., www.ashrae.org. Abstracted by permission from ASHRAE Handbook,
1989
Fundamentals,
Chap. 26, Table 32.
Design Procedures: Part 1
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
Design Procedures: Part 1
53
Figure 3.6
Heat gain through fenestration.
exposing a marginal HVAC design to criticism. Sealed glass units
manufactured at low altitudes and installed at high altitudes may not
perform as desired. Care must be taken in specifying and installing
these materials.
It is helpful for the HVAC designer to acquire a sense of the maxi-
mum solar heat gain factors for various orientations, time of day, and
season. Real data must be used for final calculations, but approxi-
mations are useful for quick response in early design coordination
architect / engineer meetings and also for checking calculations. A few
key numbers from Table 3.26 are:
䡲
Noon—direct normal radiation:
Summer: 250–300 Btu / h / ft
2
Winter: varies with latitude
䡲
North wall—varies with latitude, mostly diffuse:
Summer: 45–75 Btu / h / ft
2
Winter: 10–30 Btu / h / ft
2
䡲
East and west walls—all north latitudes fall in a range of 215–245
Btu / h / ft
2
Design Procedures: Part 1
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Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
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54
Chapter Three
TABLE
3.21 Shading Coefficients for Single Glass and Insulating Glass*
1 8
1 4
1 4
1 2
3 8
1 4
1 8
1 2
3 8
1 4
1 8
* Refers to factory-fabricated units with
3
⁄
16
,
1
⁄
4
, or
1
⁄
2
-in airspace or to prime windows plus
storm sash.
†
Refer to manufacturer’s literature for values.
‡
Thickness of each pane of glass, not thickness of assembled unit.
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