Chapter 12 Estimating Fiberglass Ductwork INTRODUCTION Fiberglass ductwork has the following advantages over sheet metal: • It costs less than conventionally fabricated steel ductwork:
Trang 1148 Mechanical Estimating Manual
Low Pressure Spiral Ductwork
Shop Hours Straight Hours Per Foot; Fittings Hours Per Piece
Manual Fabrication
—————————————————————————————————————————————
—————————————————————————————————————————————
4” 0.007 1.29 0.67 1.42 1.51 2.25 2.38 2.55
5” 0.007 1.46 0.78 1.45 1.54 2.30 2.47 2.55
6” 0.007 1.67 0.86 1.47 1.56 2.35 2.55 2.55
7” 0.153 1.81 0.95 1.50 1.59 2.39 2.64 2.55
—————————————————————————————————————————————
8” 0.008 2.05 1.05 1.53 1.62 2.43 2.72 2.55
9” 0.009 2.24 1.12 1.56 1.75 2.47 2.81 2.72
10” 0.009 2.42 1.23 1.59 1.81 2.52 2.89 2.83
12” 0.010 2.81 1.42 1.64 1.99 2.86 3.09 3.15
—————————————————————————————————————————————
14” 0.012 3.18 1.61 1.92 2.17 3.14 3.30 3.45
16” 0.013 3.56 1.79 2.10 2.35 3.41 3.50 3.77
18” 0.014 3.72 2.16 2.28 2.53 3.68 3.72 4.09
20” 0.016 4.75 2.38 2.46 2.71 3.95 3.91 4.39
—————————————————————————————————————————————
22” 0.018 5.80 2.69 2.59 2.97 4.22 4.17 4.75
24” 0.020 6.16 3.06 2.81 3.21 4.49 4.33 5.02
26” 0.020 7.07 3.35 2.95 3.62 5.08 4.52 5.72
28” 0.022 8.04 3.86 3.47 4.14 5.68 4.82 6.39
—————————————————————————————————————————————
30” 0.025 8.16 4.20 3.91 4.31 6.23 4.94 7.02
32” 0.026 8.41 4.45 4.35 4.80 6.94 5.13 7.64
34” 0.028 8.98 4.56 4.79 5.31 7.67 5.33 8.26
36” 0.029 9.52 4.74 5.24 5.78 8.35 5.55 8.89
—————————————————————————————————————————————
38” 0.031 9.92 5.01 5.47 6.08 8.72 5.73 9.51
40” 0.032 10.31 5.20 6.56 6.38 9.10 5.95 10.13
42” 0.034 10.88 5.29 5.96 6.68 9.48 6.16 10.75
44” 0.036 11.39 5.40 6.20 6.98 9.85 6.39 11.27
—————————————————————————————————————————————
46” 0.037 11.73 5.64 6.43 7.28 10.23 6.60 11.79
48” 0.039 12.24 5.84 6.68 7.58 10.61 6.77 12.31
50” 0.041 12.58 5.87 6.92 7.88 10.98 7.01 12.78
52” 0.043 12.75 6.16 7.16 8.18 11.36 7.18 13.24
—————————————————————————————————————————————
54” 0.044 12.92 6.38 7.40 8.48 11.74 7.39 13.71
56” 0.046 13.09 6.52 7.64 8.78 12.11 7.56 14.18
58” 0.048 13.43 6.78 7.88 9.08 12.49 7.86 14.65
60” 0.049 13,60 6.93 8.13 9.38 12.87 8.00 15.11
—————————————————————————————————————————————
Trang 2Spiral and Light Gauge Round Ductwork 149
Low Pressure Spiral Ductwork
Shop Hours Straight Hours Per Foot; Fittings Hours Per Piece
Automated Fabrication
—————————————————————————————————————————————
—————————————————————————————————————————————
4” 0.008 0.91 0.47 1.00 1.07 1.70 1.79 1.92
5” 0.008 1.03 0.55 1.02 1.09 1.73 1.86 1.92
6” 0.008 1.18 0.61 1.04 1.10 1.77 1.92 1.92
7” 0.180 1.28 0.67 1.06 1.12 1.80 1.98 1.92
—————————————————————————————————————————————
8” 0.009 1.45 0.74 1.08 1.14 1.83 2.05 1.92
9” 0.010 1.58 0.79 1.10 1.24 1.86 2.11 2.05
10” 0.011 1.71 0.87 1.12 1.28 1.90 2.18 2.13
12” 0.012 1.98 1.00 1.16 1.40 2.16 2.33 2.37
—————————————————————————————————————————————
14” 0.014 2.24 1.13 1.36 1.53 2.36 2.48 2.60
16” 0.015 2.51 1.27 1.48 1.66 2.57 2.64 2.84
18” 0.017 2.63 1.52 1.61 1.79 2.77 2.80 3.08
20” 0.019 3.35 1.68 1.73 1.91 2.98 2.94 3.31
—————————————————————————————————————————————
22” 0.021 4.09 1.90 1.83 2.09 3.17 3.14 3.58
24” 0.023 4.35 2.16 1.99 2.27 3.38 3.26 3.78
26” 0.024 4.99 2.36 2.08 2.56 3.83 3.40 4.31
28” 0.026 5.68 2.72 2.45 2.92 4.28 3.63 4.81
—————————————————————————————————————————————
30” 0.029 5.76 2.96 2.76 3.04 4.69 3.72 5.29
32” 0.031 5.93 3.14 3.07 3.39 5.22 3.87 5.75
34” 0.033 6.34 3.22 75.00 3.75 5.77 4.01 6.22
36” 0.034 6.72 3.35 3.70 4.08 6.28 4.18 6.69
—————————————————————————————————————————————
38” 0.036 7.00 3.53 3.86 4.29 6.57 4.31 7.16
40” 0.038 7.28 3.67 4.63 4.50 6.85 4.48 7.63
42” 0.040 7.68 3.73 4.21 4.72 7.14 4.64 8.10
44” 0.042 8.04 3.81 4.37 4.93 7.42 4.81 8.49
—————————————————————————————————————————————
46” 0.044 8.28 3.98 4.54 5.14 7.70 4.97 8.88
48” 0.046 8.64 4.12 4.72 5.35 7.99 5.10 9.27
50” 0.048 8.88 4.14 4.88 5.56 8.27 5.28 9.62
52” 0.050 9.00 4.35 5.05 5.77 8.55 5.41 9.97
—————————————————————————————————————————————
54” 0.052 9.12 4.51 5.23 5.99 8.84 5.56 10.32
56” 0.054 9.24 4.60 5.39 6.20 9.12 5.69 10.68
58” 0.056 9.48 4.79 5.56 6.41 9.40 5.92 11.03
60” 0.058 9.60 4.89 5.74 62 9.69 6.02 11.38
—————————————————————————————————————————————
Trang 3150 Mechanical Estimating Manual
Low Pressure Spiral Ductwork
Field Hours Straight Hours Per Foot; Fittings Hours Per Piece
—————————————————————————————————————————————
—————————————————————————————————————————————
4” 0.054 0.32 0.32 0.32 0.32 0.32 0.20 0.060
5” 0.063 0.36 0.36 0.36 0.36 0.36 0.20 0.070
6” 0.072 0.41 0.41 0.41 0.41 0.41 0.20 0.080
7” 0.072 0.45 0.45 0.45 0.45 0.45 0.20 0.090
—————————————————————————————————————————————
8” 0.081 0.50 0.50 0.50 0.50 0.50 0.20 0.100
9” 0.090 0.00 0.00 0.00 0.00 0.00 0.20 0.110
10” 0.099 0.59 0.59 0.59 0.59 0.59 0.20 0.120
12” 0.117 0.59 0.59 0.68 0.68 0.68 0.20 0.140
—————————————————————————————————————————————
14” 0.126 0.76 0.76 0.58 0.58 0.58 0.27 0.160
16” 0.135 0.93 0.93 0.71 0.71 0.71 0.34 0.180
18” 0.153 1.11 1.11 0.85 0.85 0.85 0.41 0.190
20” 0.162 1.28 1.28 0.97 0.97 0.97 0.49 0.200
—————————————————————————————————————————————
22” 0.180 1.45 1.45 1.11 1.11 1.11 0.56 0.230
24” 0.198 1.62 1.62 1.23 1.23 1.23 0.62 0.260
26” 0.216 1.79 1.79 1.37 1.37 1.37 0.69 0.000
28” 0.234 1.96 1.96 1.50 1.50 1.50 0.77 0.000
—————————————————————————————————————————————
30” 0.261 2.14 2.14 1.63 1.63 1.63 0.84 0.000
32” 0.261 2.31 2.31 1.76 1.76 1.76 0.91 0.000
34” 0.288 2.48 2.48 1.90 1.90 1.90 0.98 0.000
36” 0.306 2.66 2.66 2.03 2.03 2.03 1.04 0.000
—————————————————————————————————————————————
38” 0.324 2.83 2.83 2.15 2.15 2.15 1.12 0.000
40” 0.333 3.00 3.00 2.28 2.28 2.28 1.19 0.000
42” 0.342 3.18 3.18 2.41 2.41 2.41 1.25 0.000
44” 0.351 3.35 3.35 2.55 2.55 2.55 1.32 0.000
—————————————————————————————————————————————
46” 0.369 3.52 3.52 2.68 2.68 2.68 1.40 0.000
48” 0.378 3.69 3.69 2.81 2.81 2.81 1.47 0.000
50” 0.396 3.86 3.86 2.93 2.93 2.93 1.54 0.000
52” 0.414 4.03 4.03 3.06 3.06 3.06 1.61 0.000
—————————————————————————————————————————————
54” 0.423 4.21 4.21 3.20 3.20 3.20 1.67 0.000
56” 0.432 4.38 4.38 3.34 3.34 3.34 1.75 0.000
58” 0.441 4.55 4.55 3.47 3.47 3.47 1.82 0.000
60” 0.450 4.73 4.73 3.60 3.60 3.60 1.89 0.000
—————————————————————————————————————————————
Trang 4Spiral and Light Gauge Round Ductwork 151
Medium Pressure Spiral Ductwork
Shop Hours Straight Hours Per Foot; Fittings Hours Per Piece
Manual Fabrication
—————————————————————————————————————————————
—————————————————————————————————————————————
4” 0.008 1.52 0.79 1.67 1.78 2.65 1.80 3.00
5” 0.008 1.72 0.92 1.70 1.81 2.70 2.90 3.00
6” 0.008 1.96 1.01 1.73 1.84 2.76 3.00 3.00
7” 0.080 2.13 1.12 1.77 1.87 2.80 3.10 3.00
—————————————————————————————————————————————
8” 0.009 2.41 1.23 1.80 1.90 2.86 3.20 3.00
9” 0.010 2.63 1.32 1.84 2.06 2.91 3.30 3.20
10” 0.011 2.85 1.45 1.87 2.13 2.97 3.40 3.33
12” 0.012 3.30 1.67 1.93 2.34 3.37 3.64 3.70
—————————————————————————————————————————————
14” 0.014 3.74 1.89 2.26 2.55 3.69 3.88 4.06
16” 0.015 4.19 2.11 2.47 2.76 4.01 4.12 4.43
18” 0.017 4.38 2.54 2.68 2.98 4.33 4.38 4.81
20” 0.019 5.59 2.80 2.89 3.19 4.65 4.60 5.17
—————————————————————————————————————————————
22” 0.021 6.82 3.16 3.05 3.49 4.96 4.91 5.59
24” 0.023 7.25 3.60 3.31 3.78 5.28 5.09 5.91
26” 0.024 8.32 3.94 3.47 4.26 5.98 5.32 6.73
28” 0.026 9.46 4.54 4.08 4.87 6.68 5.67 7.52
—————————————————————————————————————————————
30” 0.029 9.60 4.94 4.60 5.07 7.33 5.81 8.26
32” 0.031 9.89 5.24 5.12 5.65 8.16 6.04 8.99
34” 0.033 10.56 5.36 5.64 6.25 9.02 6.27 9.72
36” 0.034 11.20 5.58 6.16 6.80 9.82 6.53 10.46
—————————————————————————————————————————————
38” 0.036 11.67 5.89 6.44 7.15 10.26 6.74 11.19
40” 0.038 12.13 6.12 7.72 7.50 10.70 7.00 11.92
42” 0.040 12.80 6.22 7.01 7.86 11.15 7.25 12.65
44” 0.042 13.40 6.35 7.29 8.21 11.59 7.52 13.26
—————————————————————————————————————————————
46” 0.044 13.80 6.64 7.57 8.56 12.03 7.76 13.87
48” 0.046 14.40 6.87 7.86 8.92 12.48 7.97 14.48
50” 0.048 14.80 6.90 8.14 9.27 12.92 8.25 15.03
52” 0.050 15.00 7.25 8.42 9.62 13.36 8.45 15.58
—————————————————————————————————————————————
54” 0.052 15.20 7.51 8.71 9.98 13.81 8.69 16.13
56” 0.054 15.40 7.67 8.99 10.33 14.25 8.89 16.68
58” 0.056 15.80 7.98 9.27 10.68 14.69 9.25 17.23
60” 0.058 16.00 8.15 9.56 11.04 15.14 9.41 17.78
—————————————————————————————————————————————
Trang 5152 Mechanical Estimating Manual
Medium Pressure Spiral Ductwork
Shop Hours Straight Hours Per Foot; Fittings Hours Per Piece
Automated Fabrication
—————————————————————————————————————————————
—————————————————————————————————————————————
4” 0.008 1.14 0.59 1.25 1.34 1.99 2.10 2.25
5” 0.008 1.29 0.69 1.28 1.36 2.03 2.18 2.25
6” 0.008 1.47 0.76 1.30 1.38 2.07 2.25 2.25
7” 0.180 1.60 0.84 1.33 1.40 2.11 2.33 2.25
—————————————————————————————————————————————
8” 0.009 1.81 0.92 1.35 1.43 2.15 2.40 2.25
9” 0.010 1.97 0.99 1.38 1.55 2.18 2.48 2.40
10” 0.011 2.14 1.09 1.40 1.60 2.23 2.55 2.50
12” 0.012 2.48 1.25 1.45 1.76 2.53 2.73 2.78
—————————————————————————————————————————————
14” 0.014 2.81 1.42 1.70 1.91 2.77 2.91 3.05
16” 0.015 3.14 1.58 1.85 2.07 3.01 3.09 3.32
18” 0.017 3.29 1.91 2.01 2.24 3.25 3.29 3.61
20” 0.019 4.19 2.10 2.17 2.39 3.49 3.45 3.88
—————————————————————————————————————————————
22” 0.021 5.12 2.37 2.29 2.62 3.72 3.68 4.19
24” 0.023 5.44 2.70 2.48 2.84 3.96 3.82 4.43
26” 0.024 6.24 2.96 2.60 3.20 4.49 3.99 5.05
28” 0.026 7.10 3.41 3.06 3.65 5.01 4.25 5.64
—————————————————————————————————————————————
30” 0.029 7.20 3.71 3.45 3.80 5.50 4.36 6.20
32” 0.031 7.42 3.93 3.84 4.24 6.12 4.53 6.74
34” 0.033 7.92 4.02 4.23 4.69 6.77 4.70 7.29
36” 0.034 8.40 4.19 4.62 5.10 7.37 4.90 7.85
—————————————————————————————————————————————
38” 0.036 8.75 4.42 4.83 5.36 7.70 5.06 8.39
40” 0.038 9.10 4.59 5.79 5.63 8.03 5.25 8.94
42” 0.040 9.60 4.67 5.26 5.90 8.36 5.44 9.49
44” 0.042 10.05 4.76 5.47 6.16 8.69 5.64 9.95
—————————————————————————————————————————————
46” 0.044 10.35 4.98 5.68 6.42 9.02 5.82 10.40
48” 0.046 10.80 5.15 5.90 6.69 9.36 5.98 10.86
50” 0.048 11.10 5.18 6.11 6.95 9.69 6.19 11.27
52” 0.050 11.25 5.44 6.32 7.22 10.02 6.34 11.69
—————————————————————————————————————————————
54” 0.052 11.40 5.63 6.53 7.49 10.36 6.52 12.10
56” 0.054 11.55 5.75 6.74 7.75 10.69 6.67 12.51
58” 0.056 11.85 5.99 6.95 8.01 11.02 6.94 12.92
60” 0.058 12.00 6.11 7.17 8.28 11.36 7.06 13.34
—————————————————————————————————————————————
Trang 6Spiral and Light Gauge Round Ductwork 153
Medium Pressure Spiral Ductwork
Field Hours Straight Hours Per Foot; Fittings Hours Per Piece
—————————————————————————————————————————————
————————————————————————————————————————————— 4” 0.060 0.35 0.35 0.35 0.35 0.35 0.22 0.060
5” 0.070 0.40 0.40 0.40 0.40 0.40 0.22 0.070
6” 0.080 0.45 0.45 0.45 0.45 0.45 0.22 0.080
7” 0.080 0.50 0.50 0.50 0.50 0.50 0.22 0.090
—————————————————————————————————————————————
8” 0.090 0.55 0.55 0.55 0.55 0.55 0.22 0.100
9” 0.100 0.00 0.00 0.00 0.00 0.00 0.22 0.110
10” 0.110 0.65 0.65 0.65 0.65 0.65 0.22 0.120
12” 0.130 0.65 0.65 0.75 0.75 0.75 0.22 0.140
—————————————————————————————————————————————
14” 0.140 0.84 0.84 0.64 0.64 0.64 0.30 0.160,
16” 0.150 1.03 1.03 0.79 0.79 0.79 0.38 0.180
18” 0.170 1.23 1.23 0.94 0.94 0.94 0.46 0.190
20” 0.180 1.42 1.42 1.08 1.08 1.08 0.54 0.200
—————————————————————————————————————————————
22” 0.200 1.61 1.61 1.23 1.23 1.23 0.62 0.230
24” 0.220 1.80 1.80 1.37 1.37 1.37 0.69 0.260
26” 0.240 1.99 1.99 1.52 1.52 1.52 0.77 0.000
28” 0.260 2.18 2.18 1.67 1.67 1.67 0.85 0.000
—————————————————————————————————————————————
30” 0.290 2.38 2.38 1.81 1.81 1.81 0.93 0.000
32” 0.290 2.57 2.57 1.96 1.96 1.96 1.01 0.000
34” 0.320 2.76 2.76 2.11 2.11 2.11 1.09 0.000
36” 0.340 2.95 2.95 2.25 2.25 2.25 1.16 0.000
—————————————————————————————————————————————
38” 0.360 3.14 3.14 2.39 2.39 2.39 1.24 0.000
40” 0.370 3.33 3.33 2.53 2.53 2.53 1.32 0.000
42” 0.380 3.53 3.53 2.68 2.68 2.68 1.39 0.000
44” 0.390 3.72 3.72 2.83 2.83 2.83 1.47 0.000
—————————————————————————————————————————————
46” 0.410 3.91 3.91 2.98 2.98 2.98 1.55 0.000
48” 0.420 4.10 4.10 3.12 3.12 3.12 1.63 0.000
50” 0.440 4.29 4.29 3.25 3.25 3.25 1.71 0.000
52” 0.460 4.48 4.48 3.40 3.40 3.40 1.79 0.000
—————————————————————————————————————————————
54” 0.470 4.68 4.68 3.56 3.56 3.56 1.86 0.000
56” 0.480 4.87 4.87 3.71 3.71 3.71 1.94 0.000
58” 0.490 5.06 5.06 3.86 3.86 3.86 2.02 0.000
60” 0.500 5.26 5.26 4.00 4.00 4.00 2.10 0.000
—————————————————————————————————————————————
Trang 7This page intentionally left blank
Trang 8Chapter 12
Estimating Fiberglass Ductwork
INTRODUCTION
Fiberglass ductwork has the following advantages over
sheet metal:
• It costs less than conventionally fabricated steel
ductwork: 5% less than bare galvanized 30% less
than insulated sheet metal 3 5% less than lined sheet
metal
• It costs less than galvanized ductwork fabricated
on a coil line if insulated or lined: 20% less than
insulated 35% less than fi ned
• However, fi berglass costs 15% more than bare
galvanized off of a coil line.
• It requires very little machinery and tools to
fabricate, minimal fl oor space and consequently
overhead costs are far less than a sheet metal shop.
• It’s more fl exible than sheet metal, easier to revise
and manipulate at the job site in order to fi t into
diverse, unpredictable fi eld conditions and to meet
precise outlet locations.
• It can be fabricated either in the shop or at the job
site.
• It’s lightweight Shipping, material handling and
hoisting are far easier than with sheet metal.
• It has built in thermal insulation and acoustical
absorption.
• It has built in built in a vapor barrier.
• And lastly, it’s an automatic energy saver over bare
steel because it’s self insulating and virtually leak
proof.
Takeoff Procedures
1 Use duct take off sheet and fi ll out heading.
2 List inside dimensions of duct.
3 Write down type of duct Use abbreviation.
4 Measure off pipe in 4 foot lengths and list each length.
5 Put down equivalent lengths for each fi tting.
6 List sheet metal components separately on bottom
of duct take off sheet or on separate sheet, as you go along.
Material Extension
1 Total the linear footage on each line and enter total
in total linear foot column.
2 Enter the sq ft/lin ft from the chart which includes the allowance for the 8” comer overlap and a 5% waste factor.
3 Multiply the length times the sq/lin ft and enter in the square feet column.
4 Add up the total square feet.
Material Costs
Typical current prices: Square Feet Ordered
Type Board 0-2400 2400-10,000 Truckload
475 $0.96 $0.87 $0.79
800 $1.06 $0.10 $0.96
1400 $1.32 $1.28 $1.15
Budget Figures
The budget cost of a 1000 square foot or larger batch
of typical fi berglass duct work, under standard conditions, including a markup of 30% for overhead and profi t, based
on union wages, is about $4.41 per square foot of duct Non union cost is about 33% less, roughly $3.04 per square foot.
Trang 9156 Mechanical Estimating Manual
Calculating Labor
Following labor productivity rates are based on:
1 Volume of 1000 SF and up
2 800 Board
3 Average duct size of 18” x 12”, or equivalent 24 gauge galv.
4 Tie rod reinforcing.
5 Rates based on gross square footage including 8” overlap and 5% waste.
6 Using standard grooving machine.
(See Fabrication Labor at the top of the following page.)
Installation Labor
Neither the duct size nor the percentage of fi ttings affects the installation productivity rate appreciably Consequently the erection rate remains relatively constant at 30 sf/hr.
Correction Factors
1 Shop labor
a Hand grooving machine versus grooving machine 1.50
b Auto grooving machine versus manual machine 90
c Auto closer versus manual 70
d Auto groover and closer 60
e Exhaust and return ducts with tie rods in conduits 1.33
f Fittings versus straight duct 1.50
g “V” groove versus shiplap 1.05
2 Channel or “T” bar reinforcing versus tie rods Shop 1.20 Field 1.10
3 475 Board versus 800, Material costs 90
Shop and Field labor 95
4 1400 Board versus 800, Material costs 1.20
Shop and Field labor 1.05
5 Material quantity discounts 0-2400 SF 1.05 2400-20,000 SF 1.00
Factory, truck load 94 Factory, car load 90
Square Foot Per Linear Foot
of Fiberglass Ductwork
—————————————————————————
Width plus 8” corner overlap Allowance
—————————————————————————
—————————————————————————
—————————————————————————
—————————————————————————
—————————————————————————
—————————————————————————
—————————————————————————
—————————————————————————
—————————————————————————
—————————————————————————
Trang 10Estimating Fiberglass Ductwork 157
FABRICATION LABOR
———————————————————————————————————————
———————————————————————————————————————
Percentage 0.12” 13.30” 31.54” 55.84” 85.96”
Fittings SF/ HR/ SF/ HR/ SF/ HR/ SF/ HR/ SF/ HR/
HR SF HR SF HR SF HR SF HR SF
———————————————————————————————————————
Str Duct Only 59 0169 62 0161 56 0179 53 0189 38 0263 10-20% 55 0183 58 0174 52 0191 49 0202 35 0284 20-30% 52 0191 55 0182 50 0200 47 0211 34 0297 30-40% 50 0200 53 0190 48 0208 45 0220 32 0311 Fittings Only 39 0256 41 0244 38 0263 36 0278 25 0400
———————————————————————————————————————
Example of Fiberglass Ductwork
Takeoff and Extension