HVAC system duct design 4e 2006

HVAC SYSTEMS DUCT DESIGN SHEET METAL AND AIR CONDITIONING CONTRACTORS’ NATIONAL ASSOCIATION, INC www.smacna.org HVAC SYSTEMS DUCT DESIGN FOURTH EDITION − MAY 2006 SHEET METAL AND AIR CONDITIONING CONTRACTORS’ NATIONAL ASSOCIATION, INC 4201 Lafayette Center Drive Chantilly, VA 20151−1209 www.smacna.org HVAC SYSTEMS DUCT DESIGN COPYRIGHT E SMACNA 2006 All Rights Reserved by SHEET METAL AND AIR CONDITIONING CONTRACTORS’ NATIONAL ASSOCIATION, INC 4201 Lafayette Center Drive Chantilly, VA 20151−1209 Printed in the U.S.A FIRST EDITION – JULY 1977 SECOND EDITION – JULY 1981 THIRD EDITION – JUNE 1990 FOURTH EDITION – MAY 2006 Except as allowed in the Notice to Users and in certain licensing contracts, no part of this book may be reproduced, stored in a retrievable system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher FOREWORD In keeping with its policy of disseminating information and providing standards of design and construction, the Sheet Metal and Air Conditioning Contractors’ National Association, Inc (SMACNA), offers this comprehensive fundamental HVAC Systems−Duct Design manual as part of our continuing effort to upgrade the quality of work produced by the heating, ventilating and air conditioning (HVAC) industry This manual presents the basic methods and procedures required to design HVAC air distribution systems It does not deal with the calculation of air conditioning loads or room air ventilation quantities This manual is part one of a three set HVAC Systems Library The second manual is the SMACNA HVAC Systems−Applications manual that contains information and data needed by designers and installers of more specialized air and hydronic HVAC systems The third manual is the HVAC Systems−Testing, Adjusting and Balancing manual, a recently− updated publication on air and hydronic system testing and balancing The HVAC duct system designer is faced with many considerations after the load calculations are completed and the type of distribution system is determined This manual provides not only the basic engineering guidelines for the sizing of HVAC ductwork systems, but also related information in the areas of: a b c d e f g h i j Materials Methods of Construction Economics of Duct Systems Duct System Layout Pressure Losses Fan Selection Duct Leakage Acoustic Considerations Duct Heat Transfer Testing, Adjusting and Balancing With emphasis on energy conservation, the designer must balance duct size with the space allocated and duct system pressure loss Duct pressure loss increases fan power and associated operating costs Materials, equipment, and construction methods must be carefully chosen to achieve the most advantageous balance between both initial and life cycle costing considerations This manual is designed to offer both the HVAC system designer and installer detailed information on duct design, materials and construction methods Both U S and metric units have been provided in examples, calculations, and tables The SMACNA HVAC Systems−Duct Design manual is intended to be used in conjunction with the American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc (ASHRAE) Fundamentals Handbook The basic fluid flow equations are not included here, but may be found in the ASHRAE handbook Practical applications of these equations are included through use of reference tables and examples Some sections of this manual have been reprinted with permission from various ASHRAE publications Another important source of HVAC systems information is the Air Movement and Control Association International, Inc (AMCA) SMACNA and the entire HVAC industry owe these two organizations a debt of gratitude for continued investments testing and development of HVAC standards Although most HVAC systems are constructed to pressure classifications between minus inches water gage (wg) to 10 inches wg, (−750 to 2,500 Pascals (Pa), the design methods, tables, charts, and equations provided in this text may be used to design other duct systems operating at higher pressures and temperatures Air density correction factors for both higher altitudes and temperatures are included SMACNA recognizes that this manual will be expanded and updated as new material becomes available We will continue to provide the HVAC industry with the latest construction methods and engineering data from recognized sources including SMACNA research programs and the services of local SMACNA Chapters and SMACNA Contractors SHEET METAL AND AIR CONDITIONING CONTRACTORS’ NATIONAL ASSOCIATION, INC HVAC Systems Duct Design • Fourth Edition iii SMACNA DUCT DESIGN COMMITTEE Ken Groeschel, Jr., Chair Groeschel Company Malone, Wisconsin Dwight D Silvia D D S Industries Inc Somerset, Massachusetts Michael F Mamayek Illingworth Corporation Milwaukee, Wisconsin Eli Howard, III, Staff SMACNA, Inc Chantilly, Virginia Roy Ricci McCusker – Gill, Inc Hingham, Massachusetts Peyton Collie, Staff Liaison SMACNA, Inc Chantilly, Virginia TECHNICAL CONSULTANTS Jeffrey R Yago, P.E., CEM J R YAGO & ASSOCIATES Gum Spring, Virginia iv HVAC Systems Duct Design • Fourth Edition NOTICE TO USERS OF THIS PUBLICATION DISCLAIMER OF WARRANTIES a) The Sheet Metal and Air Conditioning Contractors’ National Association ( SMACNA") provides its product for informational purposes b) The product contains Data" which is believed by SMACNA to be accurate and correct but the data, including all information, ideas and expressions therein, is provided strictly AS IS," with all faults SMACNA makes no warranty either express or implied regarding the Data and SMACNA EXPRESSLY DISCLAIMS ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR PARTICULAR PURPOSE c) By using the data contained in the product user accepts the Data AS IS" and assumes all risk of loss, harm or injury that may result from its use User acknowledges that the Data is complex, subject to faults and requires verification by competent professionals, and that modification of parts of the Data by user may impact the results or other parts of the Data d) IN NO EVENT SHALL SMACNA BE LIABLE TO USER, OR ANY OTHER PERSON, FOR ANY INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES ARISING, DIRECTLY OR INDIRECTLY, OUT OF OR RELATED TO USER’S USE OF SMACNA’S PRODUCT OR MODIFICATION OF DATA THEREIN This limitation of liability applies even if SMACNA has been advised of the possibility of such damages IN NO EVENT SHALL SMACNA’S LIABILITY EXCEED THE AMOUNT PAID BY USER FOR ACCESS TO SMACNA’S PRODUCT OR $1,000.00, WHICHEVER IS GREATER, REGARDLESS OF LEGAL THEORY e) User by its use of SMACNA’s product acknowledges and accepts the foregoing limitation of liability and disclaimer of warranty and agrees to indemnify and hold harmless SMACNA from and against all injuries, claims, loss or damage arising, directly or indirectly, out of user’s access to or use of SMACNA’s product or the Data contained therein ACCEPTANCE This document or publication is prepared for voluntary acceptance and use within the limitations of application defined herein, and otherwise as those adopting it or applying it deem appropriate It is not a safety standard Its application for a specific project is contingent on a designer or other authority defining a specific use SMACNA has no power or authority to police or enforce compliance with the contents of this document or publication and it has no role in any representations by other parties that specific components are, in fact, in compliance with it AMENDMENTS The Association may, from time to time, issue formal interpretations or interim amendments, which can be of significance between successive editions PROPRIETARY PRODUCTS SMACNA encourages technological development in the interest of improving the industry for the public benefit SMACNA does not, however, endorse individual manufacturers or products FORMAL INTERPRETATION a) A formal interpretation of the literal text herein or the intent of the technical committee or task force associated with the document or publication is obtainable only on the basis of written petition, addressed to the Technical Resources Department and sent to the Association’s national office in Chantilly, Virginia In the event that the petitioner has a substantive disagreement with the interpretation, an appeal may be filed with the Technical Resources Committee, which has technical oversight responsibility The request must pertain to a specifically identified portion of the document that does not involve published text which provides the requested information In considering such requests, the Association will not review or judge products or components as being in compliance with the document or publication Oral and written interpretations otherwise obtained from anyone affiliated with the Association are unofficial This procedure does not prevent any committee or task force chairman, member of the committee or task force, or staff liaison from expressing an opinion on a provision within the document, provided that such person clearly states that the opinion is personal and does not represent an official act of the Association in any way, and it should not be relied on as such The Board of Directors of SMACNA shall have final authority for interpretation of this standard with such rules or procedures as they may adopt for processing same b) SMACNA disclaims any liability for any personal injury, property damage, or other damage of any nature whatsoever, whether special, indirect, consequential or compensatory, direct or indirectly resulting from the publication, use of, or reliance upon this document SMACNA makes no guaranty or warranty as to the accuracy or completeness of any information published herein APPLICATION a) Any standards contained in this publication were developed using reliable engineering principles and research plus consultation with, and information obtained from, manufacturers, users, testing laboratories, and others having specialized experience They are HVAC Systems Duct Design • Fourth Edition v subject to revision as further experience and investigation may show is necessary or desirable Construction and products which comply with these Standards will not necessarily be acceptable if, when examined and tested, they are found to have other features which impair the result contemplated by these requirements The Sheet Metal and Air Conditioning Contractors’ National Association and other contributors assume no responsibility and accept no liability for the application of the principles or techniques contained in this publication Authorities considering adoption of any standards contained herein should review all federal, state, local, and contract regulations applicable to specific installations b) In issuing and making this document available, SMACNA is not undertaking to render professional or other services for or on behalf of any person or entity SMACNA is not undertaking to perform any duty owed to any person or entity to someone else Any person or organization using this document should rely on his, her or its own judgement or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstance REPRINT PERMISSION Non−exclusive, royalty−free permission is granted to government and private sector specifying authorities to reproduce only any construction details found herein in their specifications and contract drawings prepared for receipt of bids on new construction and renovation work within the United States and its territories, provided that the material copied is unaltered in substance and that the reproducer assumes all liability for the specific application, including errors in reproduction THE SMACNA LOGO The SMACNA logo is registered as a membership identification mark The Association prescribes acceptable use of the logo and expressly forbids the use of it to represent anything other than possession of membership Possession of membership and use of the logo in no way constitutes or reflects SMACNA approval of any product, method, or component Furthermore, compliance of any such item with standards published or recognized by SMACNA is not indicated by presence of the logo vi HVAC Systems Duct Design • Fourth Edition TABLE OF CONTENTS Duct Size (in y in.) Gage 12 x 24 x 24 x 12 48 x 12 48 x 24 96 x 24 96 x 48 24 24 24 22 22 2O 18 63 31 24 28 23 27 22 28 125 34 27 31 26 30 25 31 1/1 Octave Band Center FrequencyĊHz 250 500 1000 2000 37 40 43 Ċ 30 33 36 Ċ 34 37 Ċ Ċ 29 32 Ċ Ċ 33 Ċ Ċ Ċ 28 Ċ Ċ Ċ Ċ Ċ Ċ Ċ 4000 Ċ Ċ Ċ Ċ Ċ Ċ Ċ 8000 Ċ Ċ Ċ Ċ Ċ Ċ Table A−32 TLout vs Frequency For Various Flat−Oval Ducts Duct Size (in y in.) Gage 12 x 24 x 24 x 12 48 x 12 48 x 24 96 x 24 96 x 48 24 24 24 22 22 2O 18 63 18 17 15 14 12 11 19 125 18 17 16 14 21 22 28 1/1 Octave Band Center FrequencyĊHz 250 500 1000 2000 22 31 40 Ċ 18 30 33 Ċ 25 34 Ċ Ċ 26 29 Ċ Ċ 30 Ċ Ċ Ċ 25 Ċ Ċ Ċ Ċ Ċ Ċ Ċ 4000 Ċ Ċ Ċ Ċ Ċ Ċ Ċ 8000 Ċ Ċ Ċ Ċ Ċ Ċ Table A−33 TLin vs Frequency For Various Flat−Oval Ducts 1/1 Octave Band Center FrequencyĊHz 125 250 500 1000 2000 4000 0.01 0.04 0.01 0.04 0.01 0.04 0.02 0.05 0.02 0.05 0.02 0.05 0.03 0.07 0.02 0.03 0.22 0.69 0.91 0.96 0.99 0.18 0.22 0.82 1.00 1.00 1.00 1.00 0.48 0.53 1.00 1.00 1.00 1.00 1.00 0.76 0.84 1.00 1.00 1.00 1.00 0.97 63 Non−Sound Absorbing Materials Concrete Bare Sheet Metal Sound Absorbing Materials in 3.0 lb/ft3 Fiberglass Insulation Board in 3.0 lb/ft3 Fiberglass Insulation Board in 3.0 lb/ft3 Fiberglass Insulation Board in 3.0 lb/ft3 Fiberglass Insulation Board Table A−34 Absorption Coefficients For Selected Plenum Materials Duct Size in y in P/A 1/ft 6×6 12 × 12 12 × 24 24 × 24 48 × 48 72 × 72 8.0 4.0 3.0 2.0 1.0 0.7 63 0.30 0.35 0.40 0.25 0.15 0.10 Attenuation − dB/ft 1/1 Octave Band Center Freq.ĊHz 125 250 0.20 0.10 0.20 0.10 0.20 0.10 0.20 0.10 0.10 0.07 0.10 0.05 Above 250 0.10 0.06 0.05 0.03 0.02 0.02 Table A−35 Sound Attenuation In Unlined Rectangular Sheet Metal Ducts If duct is externally lined, multiply results associated with 63 Hz, 125 Hz and 250 Hz by A.66 HVAC Systems Duct Design • Fourth Edition Dimensions in y in 4×4 10 6×6 10 12 18 8×8 12 18 24 10 × 10 16 20 30 12 × 12 18 24 36 15 × 15 22 30 45 18 × 18 28 36 54 24 × 24 36 48 72 30 × 30 45 60 36 × 36 54 72 42 × 42 64 84 48 × 48 72 Insertion Loss − dB/ft 1/1 Octave Band Center Freq.ĊHz 63 2.00 1.49 1.28 1.16 1.08 0.82 0.77 0.69 0.77 0.65 0.60 0.56 0.63 0.55 0.53 0.51 0.56 0.51 0.50 0.40 0.51 0.40 0.36 0.32 0.40 0.33 0.30 0.27 0.30 0.25 0.23 0.21 0.24 0.21 0.19 0.21 0.18 0.16 0.18 0.16 0.14 0.16 0.14 125 2.06 1.63 1.43 1.32 1.24 0.96 0.90 0.79 0.90 0.74 0.67 0.60 0.71 0.59 0.55 0.51 0.60 0.52 0.48 0.43 0.51 0.44 0.39 0.34 0.43 0.35 0.32 0.28 0.32 0.26 0.24 0.21 0.25 0.21 0.19 0.21 0.17 0.16 0.18 0.15 0.14 0.16 0.13 250 2.18 1.89 1.75 1.66 1.60 1.35 1.29 1.18 1.29 1.12 1.04 0.96 1.09 0.94 0.89 0.82 0.96 0.85 0.79 0.74 0.82 0.75 0.68 0.62 0.74 0.64 0.59 0.54 0.59 0.51 0.47 0.43 0.49 0.43 0.39 0.43 0.37 0.34 0.38 0.32 0.30 0.34 0.29 500 3.66 3.33 3.16 3.05 2.98 2.66 2.57 2.42 2.57 2.34 2.22 2.09 2.29 2.06 1.98 1.87 2.09 1.90 1.81 1.70 1.87 1.71 1.61 1.52 1.70 1.54 1.47 1.38 1.47 1.34 1.27 1.20 1.31 1.20 1.13 1.20 1.09 1.03 1.11 1.01 0.96 1.03 0.94 1000 10.10 8.90 8.27 7.80 7.62 6.52 6.23 5.74 6.23 5.49 5.10 4.70 5.34 4.62 4.37 4.02 4.70 4.14 3.85 3.54 4.02 3.57 3.29 3.03 3.54 3.09 2.90 2.67 2.90 2.55 2.37 2.19 2.48 2.19 2.03 2.19 1.93 1.79 1.96 1.72 1.61 1.79 1.58 2000 10.36 8.95 8.22 7.78 7.48 6.26 5.94 5.41 5.94 5.13 4.72 4.29 4.97 4.21 3.94 3.59 4.29 3.71 3.41 3.10 3.59 3.12 2.85 2.59 3.10 2.65 2.46 2.24 2.46 2.13 1.95 1.78 2.06 1.78 1.63 1.78 1.54 1.41 1.57 1.35 1.25 1.41 1.22 4000 4.80 4.41 4.21 4.07 3.98 3.59 3.49 3.31 3.49 3.21 3.06 2.90 3.15 2.86 2.76 2.62 2.90 2.67 2.54 2.41 2.62 2.42 2.29 2.17 2.41 2.20 2.11 2.00 2.11 1.94 1.85 1.75 1.91 1.75 1.67 1.75 1.61 1.54 1.63 1.50 1.43 1.54 1.42 8000 2.87 2.74 2.67 2.63 2.60 2.46 2.42 2.36 2.42 2.32 2.26 2.20 2.30 2.19 2.15 2.09 2.20 2.11 2.06 2.00 2.09 2.01 1.96 1.90 2.00 1.91 1.87 1.82 1.87 1.80 1.76 1.71 1.78 1.71 1.67 1.71 1.64 1.60 1.65 1.58 1.55 1.60 1.54 Table A−36 Insertion Loss For Rectangular Ducts With in Of Fiberglass Lining HVAC Systems Duct Design • Fourth Edition A.67 Dimensions in y in Insertion Loss − dB/ft 1/1 Octave Band Center Freq.ĊHz 63 125 250 500 1000 2000 4000 8000 4×4 10 3.54 2.57 2.15 1.92 3.81 2.99 2.60 2.38 4.52 3.91 3.59 3.40 7.61 6.94 6.58 6.36 10.10 8.90 8.27 7.88 10.36 8.95 8.22 7.78 4.80 4.41 4.21 4.07 2.87 2.74 2.67 2.63 6×6 10 12 18 1.78 1.27 1.16 1.00 2.23 1.69 1.56 1.35 3.27 2.74 2.61 2.38 6.20 5.54 5.55 5.05 7.62 6.52 5.36 5.74 7.48 6.26 5.94 5.41 3.98 3.59 3.49 3.31 2.60 2.46 2.42 2.36 8×8 12 18 24 1.16 0.93 0.83 0.74 1.56 1.25 1.11 0.98 2.61 2.26 2.08 1.90 5.36 4.89 4.64 4.37 6.23 5.49 5.10 4.70 5.94 5.13 4.72 4.29 3.49 3.21 3.06 2.90 2.42 2.32 2.26 2.20 10 × 10 16 20 30 12 × 12 18 24 36 15 × 15 22 30 45 18 × 18 28 36 54 24 × 24 36 48 72 30 × 30 45 60 36 × 36 54 72 42 x 42 64 84 48 × 48 72 0.88 0.72 0.68 0.62 0.74 0.64 0.60 0.48 0.62 0.48 0.42 0.37 0.48 0.38 0.34 0.30 0.34 0.28 0.26 0.23 0.27 0.23 0.21 0.23 0.19 0.17 0.20 0.17 0.15 0.17 0.15 1.20 0.95 0.87 0.78 0.98 0.81 0.73 0.64 0.78 0.65 0.57 0.49 0.64 0.51 0.46 0.40 0.46 0.37 0.33 0.29 0.35 0.29 0.26 0.29 0.24 0.21 0.24 0.20 0.17 0.21 0.17 2.19 1.87 1.76 1.61 1.90 1.66 1.53 1.42 1.61 1.43 1.30 1.18 1.42 1.21 1.12 1.02 1.12 0.97 0.89 0.81 0.94 0.81 0.74 0.81 0.70 0.64 0.71 0.61 0.54 0.64 0.55 4.79 4.32 4.15 3.91 4.37 3.99 3.78 3.56 3.91 3.58 3.38 3.19 3.56 3.23 3.08 2.91 3.08 2.81 2.67 2.51 2.76 2.51 2.38 2.51 2.29 2.18 2.33 2.12 1.97 2.18 1.99 5.34 4.62 4.37 4.02 4.70 4.14 3.85 3.54 4.02 3.57 3.29 3.03 3.54 3.09 2.90 2.67 2.90 2.55 2.37 2.19 2.48 2.19 2.03 2.19 1.93 1.79 1.96 1.72 1.56 1.79 1.58 4.97 4.21 3.94 3.59 4.29 3.71 3.41 3.10 3.59 3.12 2.85 2.59 3.10 2.65 2.46 2.24 2.46 2.13 1.95 1.78 2.06 1.78 1.63 1.78 1.54 1.41 1.57 1.35 1.21 1.41 1.22 3.15 2.86 2.76 2.62 2.90 2.67 2.54 2.41 2.62 2.42 2.29 2.17 2.41 2.20 2.11 2.00 2.11 1.94 1.85 1.75 1.91 1.75 1.67 1.75 1.61 1.54 1.63 1.50 1.41 1.54 1.42 2.30 2.19 2.15 2.09 2.20 2.11 2.06 2.00 2.09 2.01 2.96 1.90 2.00 1.91 1.87 1.82 1.87 1.80 1.76 1.71 1.78 1.71 1.67 1.71 1.64 1.60 1.65 1.58 1.53 1.60 1.54 Table A−37 Insertion Loss For Rectangular Ducts With in Of Fiberglass Lining A.68 HVAC Systems Duct Design • Fourth Edition Dimensions in Dv7 < D v 15 15 < v 30 30 < D v 60 63 0.03 0.03 0.02 0.01 Attenuation − dB/ft 1/1 Octave Band Center Freq.ĊHz 125 250 500 1000 2000 0.03 0.05 0.05 0.10 0.10 0.03 0.03 0.05 0.07 0.07 0.02 0.02 0.03 0.05 0.05 0.01 0.01 0.02 0.02 0.02 4000 0.10 0.07 0.05 0.02 Table A−38 Sound Attenuation In Straight Round Ducts Diameter in 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 63 0.38 0.32 0.27 0.23 0.19 0.16 0.13 0.1.1 0.08 0.07 0.05 0.03 0.02 0.01 0 0 0 0 0 0 0 Insertion Loss − dB/ft 1/1 Octave Band Center Freq.ĊHz 125 250 500 1000 2000 4000 0.59 0.93 1.53 2.17 2.31 2.04 0.54 0.89 1.50 2.19 2.17 1.83 0.50 0.85 1.48 2.20 2.04 1.64 0.46 0.81 1.45 2.18 1.91 1.48 0.42 0.77 1.43 2.14 1.79 1.34 0.38 0.73 1.40 2.08 1.67 1.21 0.35 0.69 1.37 2.01 1.56 1.10 0.31 0.65 1.34 1.92 1.45 1.00 0.28 0.61 1.31 1.82 1.34 0.92 0.25 0.57 1.28 1.71 1.24 0.85 0.22 0.53 1.24 1.59 1.14 0.79 0.19 0.49 1.20 1.46 1.04 0.74 0.16 0.45 1.16 1.33 0.95 0.69 0.14 0.42 1.12 1.20 0.87 0.66 0.11 0.38 1.07 1.07 0.79 0.63 0.08 0.35 1.02 0.93 0.71 0.60 0.06 0.31 0.96 0.80 0.64 0.58 0.03 0.28 0.91 0.68 0.57 0.55 0.01 0.25 0.84 0.56 0.50 0.53 0.23 0.78 0.45 0.44 0.51 0.20 0.71 0.35 0.39 0.48 0.18 0.63 0.26 0.34 0.45 0.15 0.55 0.19 0.29 0.41 0.14 0.46 0.13 0.25 0.37 0.12 0.37 0.09 0.22 0.31 0.10 0.28 0.08 0.18 0.25 0.09 0.17 0.08 0.16 0.18 0.08 0.06 0.10 0.14 0.09 8000 1.26 1.18 1.12 1.05 1.00 0.95 0.90 0.87 0.83 0.80 0.77 0.74 0.71 0.69 0.66 0.64 0.61 0.58 0.55 0.52 0.48 0.44 0.40 0.34 0.29 0.22 0.15 0.07 Table A−39 Insertion Loss For Acoustically Lined Round Ducts − in Lining HVAC Systems Duct Design • Fourth Edition A.69 Diameter in 63 Insertion Loss − dB/ft 1/1 Octave Band Center Freq.ĊHz 125 250 500 1000 2000 4000 8000 0.56 0.80 1.37 2.25 2.17 2.31 2.04 1.26 0.51 0.75 1.33 2.23 2.19 2.17 1.83 1.18 10 0.46 0.71 1.29 2.20 2.20 2.04 1.64 1.12 12 0.42 0.67 1.25 2.18 2.18 1.91 1.48 1.05 14 0.38 0.63 1.21 2.15 2.14 1.79 1.34 1.00 16 0.35 0.59 1.17 2.12 2.08 1.67 1.21 0.95 18 0.32 0.56 1.13 2.10 2.01 1.56 1.10 0.90 20 0.29 0.52 1.09 2.07 1.92 1.45 1.00 0.87 22 0.27 0.49 1.05 2.03 1.82 1.34 0.92 0.83 24 0.25 0.46 1.01 2.00 1.71 1.24 0.85 0.80 26 0.24 0.43 0.97 1.96 1.59 1.14 0.79 0.77 28 0.22 0.40 0.93 1.93 1.46 1.04 0.74 0.74 30 0.21 0.37 0.90 1.88 1.33 0.95 0.69 0.71 32 0.20 0.34 0.86 1.84 1.20 0.87 0.66 0.69 34 0.19 0.32 0.82 1.79 1.07 0.79 0.63 0.66 36 0.18 0.29 0.79 1.74 0.93 0.71 0.60 0.64 38 0.17 0.27 0.76 1.69 0.80 0.64 0.58 0.61 40 0.16 0.24 0.73 1.63 0.68 0.57 0.55 0.58 42 0.15 0.22 0.70 1.57 0.56 0.50 0.53 0.55 44 0.13 0.20 0.67 1.50 0.45 0.44 0.51 0.52 46 0.12 0.17 0.64 1.43 0.35 0.39 0.48 0.48 48 0.11 0.15 0.62 1.36 0.26 0.34 0.45 0.44 50 0.09 0.12 0.60 1.28 0.19 0.29 0.41 0.40 52 0.07 0.10 0.58 1.19 0.13 0.25 0.37 0.34 54 0.05 0.08 0.56 1.10 0.09 0.22 0.31 0.29 56 0.02 0.05 0.55 1.00 0.08 0.18 0.25 0.22 58 0.03 0.53 0.90 0.08 0.16 0.18 0.15 60 0 0.53 0.79 0.10 0.14 0.09 0.07 Table A−40 Insertion Loss For Acoustically Lined Round Ducts—2 in Lining A.70 HVAC Systems Duct Design • Fourth Edition Diameter in 63 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 0.64 0.59 0.54 0.50 0.46 0.43 0.40 0.38 0.35 0.33 0.32 0.30 0.29 0.28 0.27 0.26 0.25 0.24 0.23 0.22 0.20 0.19 0.17 0.15 0.13 0.10 0.07 0.04 Insertion Loss − dB/ft 1/1 Octave Band Center Freq.ĊHz 125 250 500 1000 2000 4000 8000 1.00 0.95 0.91 0.87 0.83 0.79 0.75 0.72 0.69 0.66 0.63 0.60 0.57 0.54 0.52 0.49 0.47 0.44 0.42 0.39 0.37 0.35 0.32 0.30 0.27 0.25 0.22 0.20 1.26 1.18 1.12 1.05 1.00 0.95 0.90 0.87 0.83 0.80 0.77 0.74 0.71 0.69 0.66 0.64 0.61 0.58 0.55 0.52 0.48 0.44 0.40 0.34 0.29 0.22 0.15 0.07 1.58 1.54 1.50 1.46 1.42 1.38 1.34 1.30 1.26 1.22 1.18 1.14 1.11 1.07 1.04 1.00 0.97 0.94 0.91 0.88 0.85 0.83 0.81 0.79 0.77 0.76 0.75 0.74 2.25 2.21 2.18 2.16 2.13 2.10 2.07 2.04 2.01 1.98 1.94 1.90 1.86 1.82 1.77 1.72 1.67 1.61 1.55 1.48 1.41 1.33 1.25 1.17 1.07 0.98 0.87 0.76 2.17 2.19 2.20 2.18 2.14 2.08 2.01 1.92 1.82 1.71 1.59 1.46 1.33 1.20 1.07 0.93 0.80 0.68 0.56 0.45 0.35 0.26 0.19 0.13 0.09 0.08 0.08 0.10 2.31 2.17 2.04 1.91 1.79 1.67 1.56 1.45 1.34 1.24 1.14 1.04 0.95 0.87 0.79 0.71 0.64 0.57 0.50 0.44 0.39 0.34 0.29 0.25 0.22 0.18 0.16 0.14 2.04 1.83 1.64 1.48 1.34 1.21 1.10 1.00 0.92 0.85 0.79 0.74 0.69 0.66 0.63 0.60 0.58 0.55 0.53 0.51 0.48 0.45 0.41 0.37 0.31 0.25 0.18 0.09 Table A−41 Insertion Loss For Acoustically Lined Round Ducts—3 in Lining Fw Insertion lossĊdB unlined elbows lined elbows fw < 1.9 0 1.9 < fw < 3.8 1 3.8 < fw < 7.5 7.5 < fw < 15 11 15 < fw < 30 10 fw > 30 10 Table A−42 Insertion Loss Of Unlined And Lined Square Elbows Without Turning Vanes fw = f x w where f is the VI octave center frequency (kHz) and w is the width of the elbow (inches) HVAC Systems Duct Design • Fourth Edition A.71 Fw Insertion IossĊdB fw < 1.9 1.9 < fw < 3.8 3.8 < fw < 7.5 fw > 7.5 Table A−43 Insertion Loss Of Round Elbows fw = f x w where f is the VI octave center frequency (kHz) and w is the width of the elbow (inches) Insertion IossĊdB Fw unlined elbows line elbows fw < 1.9 0 1.9 < fw < 3.8 1 3.8 < fw < 7.5 4 7.5 < fw < 15 fw > 15 Table A−44 Insertion Loss Of Unlined And Lined Square Elbows With Turning Vanes fw = f × w where f is the VI octave center frequency (kHz) and w is the width of the elbow (inches) Face Velocity fpm 63 125 1/1 Octave Band Center Freq.ĊHz 250 500 1000 2000 4000 8000 Insertion LossĊdB + 1000 14 31 45 51 53 51 33 + 2000 12 26 43 47 48 47 30 − 1000 19 36 44 48 50 48 29 − 2000 19 34 42 46 48 46 28 Regenerated Sound Power LevelsĊdB + 1000 58 52 42 36 37 35 30 30 + 1500 64 57 58 49 45 49 48 46 + 2000 72 65 64 63 55 56 57 56 − 1000 55 52 54 55 55 64 64 55 − 1500 61 58 59 61 61 66 75 66 − 2000 69 66 65 75 71 73 79 76 Table A−45 ft, Rectangular, Standard Pressure Drop Duct Silencers A.72 HVAC Systems Duct Design • Fourth Edition Face Velocity fpm 63 125 1/1 Octave Band Center Freq.ĊHz 250 500 1000 2000 4000 8000 Insertion LossĊdB +1000 18 33 41 47 24 15 +2000 17 32 39 44 24 16 +2500 17 30 37 42 24 15 −1000 11 21 35 41 45 22 12 −2000 11 21 36 40 43 21 11 −3000 21 34 38 40 20 10 Regenerated Sound Power LevelsĊdB +1000 58 51 40 34 35 28 27 19 +2000 67 61 58 53 51 54 52 45 +2500 74 68 65 62 56 59 60 55 −1000 58 49 46 44 49 45 34 25 −2000 70 61 59 56 57 62 58 50 −2500 74 67 64 62 61 65 65 57 Table A−46 ft, Rectangular, Low Pressure Drop Duct Silencers Face Velocity fpm 63 125 1/1 Octave Band Center Freq.ĊHz 250 500 1000 2000 4000 8000 Insertion LossĊdB +1000 21 32 38 38 26 20 +2000 20 32 38 38 27 21 +3000 19 31 38 38 27 21 −1000 23 33 39 37 25 19 −2000 23 34 37 36 24 16 −3000 10 24 34 37 36 24 16 Regenerated Sound Power LevelsĊdB +1000 62 43 38 39 36 25 22 28 +2000 62 58 53 54 53 51 45 35 +3000 72 66 62 64 63 64 61 54 −1000 56 43 41 38 37 31 23 28 −2000 66 56 54 54 57 54 49 41 −3000 76 64 63 64 67 67 65 60 Table A−47 Round, High Pressure Drop Duct Silencers HVAC Systems Duct Design • Fourth Edition A.73 Face Velocity fpm 63 1/1 Octave Band Center Freq.ĊHz 250 500 1000 2000 125 4000 8000 Insertion LossĊdB +1000 13 26 32 24 16 14 +2000 13 25 32 24 16 13 +3000 13 23 31 24 16 13 −1000 16 28 35 25 24 30 −2000 16 28 35 25 17 15 −3000 16 29 35 25 16 15 Regenerated Sound Power LevelsĊdB +1000 60 44 39 34 29 25 24 30 +2000 62 58 48 47 49 45 38 31 +3000 69 63 55 55 57 58 54 47 −1000 58 46 43 38 33 30 24 30 −2000 65 52 50 49 48 44 36 33 −3000 72 57 57 57 56 57 52 49 Table A−48 Round, Low Pressure Drop Duct Silencers Rectangular C1 C2 C3 C4 High Pressure Drop 0.6464 0.3971 2.637 × 10−7 2.012 Low Pressure Drop 0.6015 0.4627 9.802 × 10−8 2.011 High Pressure Drop 5.108 × 10−3 1.999 4.007 × 10−8 2.002 Low Pressure Drop 5.097 × 2.000 1.104 × 2.022 Circular 10−3 10−8 Table A−49 Coefficients For Determining Static Pressure Drop Across Duct Silencers Distance between silencer and closest edge of system component (fan, elbow, branch TO, etc C(up) Upstream from entering edge of silencer C(down) Downstream from leaving edge of silencer Deq × or greater 1.0 1.0 Deq × 1.4 1.4 Deq × 1.9 1.9 Deq × 0.5 3.0 3.0 Directly Connected 4.0 Not recommended Table A−50 Coefficient For System Component Effect On Duct Silencers A.74 HVAC Systems Duct Design • Fourth Edition Thickness (in.) Surface Weight (lb/ft2) Transmission LossĊdB 1/1 Octave Band Center Freq.ĊHz 63 125 250 500 1000 2000 4000 Gypsum Board 3_i 1.6 11 17 22 28 32 24 1_w 2.1 14 20 24 30 31 27 5_i 2.7 10 15 22 26 31 28 30 4.6 13 18 26 30 30 29 37 Dimensions (ft y ft y in.) Surface Weight (lb/ft2) Transmission LossĊdB 1/1 Octave Band Center Freq.ĊHz 63 125 250 500 1000 2000 4000 14 19 24 26 Acoustical Ceiling Tile − Exposed T−Bar Grid Suspended Lay−in−Ceilings × × 5_i × × 1−1_w 0.6 – 0.7 9 0.9 10 11 15 20 25 × × 5_i 0.95 – 1.1 11 13 15 21 24 28 × × 5_i 1.2 – 1.3 10 11 15 19 22 24 14 18 22 27 30 Acoustical Ceiling Tile − Concealed Spline Suspended Ceiling × × 5_i 1.2 14 Table A−51 Transmission Loss Values For Ceiling Materials t Ceiling Configuration Gypboard: Gypboard: No Ceiling Diffusers or Penetrations 0.0001 Gypboard: Few Ceiling Diffusers and Penetrations Well Sealed 0.001 Lay−in−Suspended Tile: No Integrated Lighting of Diffuser System 0.001 Lay−in−Suspended Tile: Integrated Lighting and Diffuser System 0.03 Table A−52 Correction Coefficient “t” For Different Types Of Ceilings Room Absorption Coefficient 1/1 Octave Band Center FrequencyĊHz Type of Room 63 125 250 500 1000 2000 4000 Dead Acoustical ceiling, plush carpet, soft furnishings, people 0.26 0.30 0.35 0.4 0.43 0.46 0.52 Medium Dead Acoustical ceiling, commercial carpet, people 0.24 0.22 0.18 0.25 0.30 0.36 0.42 Average Acoustical ceiling or commercial carpet, people 0.25 0.23 0.17 0.20 0.24 0.29 0.34 Medium Live Some acoustical material, people 0.25 0.23 0.15 0.15 0.17 0.20 0.23 Live People only 0.26 0.24 0.12 0.10 0.09 0.11 0.13 Table A−53 Average Sound Absorption Coefficients, a, For Typical Receiving Rooms HVAC Systems Duct Design • Fourth Edition A.75 Air Absorption Coefficient 1/1 Octave Band Center FrequencyĊHz M (1/ft) 63 125 250 500 1000 2000 4000 0 0 0.0009 0.0029 Table A−54 Air Absorption Coefficients N 10 Log N (dB) 20 Log N (dB) N 10 Log N (dB) 20 Log N (dB) −10 −20 100 20 40 12 −9 −18 125 21 42 16 −16 160 22 44 −7 −14 200 23 46 25 −6 −12 250 24 48 32 −5 −10 320 25 50 −4 −8 400 26 52 −3 −6 500 27 54 63 −2 −4 630 28 56 −1 −2 800 29 58 1.0 0 1,000 30 60 1.25 1,250 31 62 1.6 1.600 32 64 2.0 2.000 33 66 2.5 2.500 34 68 3.2 10 3,200 35 70 4.0 4.000 36 72 5.0 14 5.000 37 74 6.3 16 6.300 38 76 18 8.000 39 78 10 10 20 10.000 40 80 12 11 22 12.500 41 82 16 12 24 16.000 42 84 20 13 26 20.000 43 86 25 14 28 25.000 44 88 32 15 30 32.000 45 90 40 16 32 40.000 46 92 50 17 34 50,000 47 94 63 18 36 63.000 48 96 80 19 38 80.000 49 98 100 20 40 100,000 50 100 Table A−55 Decibel Equivalents Of Numbers (N) A.76 HVAC Systems Duct Design • Fourth Edition No .01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 Logarithm −2.00000 −2.30103 −2.47712 −2.60206 −2.69897 −2.77815 −2.84510 −2.90309 −2.95424 −1.00000 −1.04139 −1.07918 −1.11394 −1.14613 −1.17609 −1.20412 −1.23045 −1.25527 −1.27875 −1.30103 −1.32222 −1.34242 −1.36173 −1.38021 −1.39794 −1.41497 −1.43136 −1.44716 −1.46240 −1.47712 −1.49136 −1.50515 −1.51851 −1.53148 −1.54407 −1.55630 −1.56820 −1.57978 −1.59106 −1.60206 −1.61278 −1.62325 −1.63347 −1.64345 −1.65321 −1.66276 −1.67210 −1.68124 −1.69020 No 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 Logarithm −1.69897 −1.70757 −1.71600 −1.72428 −1.73239 −1.74036 −1.74819 −1.75587 −1.76343 −1.77085 −1.77815 −1.78533 −1.79239 −1.79934 −1.80618 −1.81291 −1.81954 −1.82607 −1.83251 −1.83885 −1.84510 −1.85126 −1.85733 −1.86332 −1.86923 −1.87506 −1.88081 −1.88649 −1.89209 −1.89763 −1.90309 −1.90849 −1.91381 −1.91908 −1.92428 −1.92942 −1.93450 −1.93952 −1.94448 −1.94939 −1.95424 −1.94904 −1.96379 −1.96848 −1.97313 −1.97772 −1.98227 −1.98677 −1.99123 −1.99564 No 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 Logarithm 0.00000 0.30103 0.47712 0.60206 0.69897 0.77815 0.84510 0.90309 0.95424 1.00000 1.04139 1.07918 1.11394 1.14613 1.17609 1.20412 1.23045 1.25527 1.27875 1.30103 1.32222 1.34242 1.36173 1.38021 1.39794 1.41497 1.43136 1.44716 1.46240 1.47712 1.49136 1.50515 1.51851 1.53148 1.54407 1.55630 1.56820 1.57978 1.59106 1.60206 1.61278 1.62325 1.63347 1.64345 1.65321 1.66276 1.67210 1.68124 1.69020 No 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 Logarithm 1.69897 1.70757 1.71600 1.72428 1.73239 1.74036 1.74819 1.75587 1.76343 1.77085 1.77815 1.78533 1.79239 1.79934 1.80618 1.81291 1.81954 1.82607 1.83251 1.83885 1.84510 1.85126 1.85733 1.86332 186923 1.87506 1.88081 1.88649 1.89209 1.89763 1.90309 1.90849 1.91381 1.91908 1.92428 1.92942 1.93450 1.93952 1.94448 1.94939 1.95424 1.95904 1.96379 1.96848 1.97313 1.97772 1.98227 1.98677 1.99123 1.99564 No 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 575 600 625 650 675 700 725 750 800 850 900 950 1000 2000 3000 4000 5000 6000 7000 8000 9000 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 100,000 Logarithm 2.00000 2.09691 2.17609 2.24304 2.30103 2.35218 2.39794 2.43933 2.47712 2.51188 2.54407 2.57403 2.60206 2.62839 2.65321 2.67669 2.69897 2.72016 2.74036 2.75967 2.77815 2.79588 2.81291 2.82930 2.84510 2.86034 2.87506 2.90309 2.92942 2.95424 2.97772 3.00000 3.30103 3.47712 3.60206 3.69897 3.77815 3.84510 3.90309 3.95424 4.00000 4.30103 4.47712 4.60206 4.69897 4.77815 4.84510 4.90309 4.95424 5.00000 Table A−56 Five Place Logarithms HVAC Systems Duct Design • Fourth Edition A.77 THIS PAGE INTENTIONALLY LEFT BLANK A.78 HVAC Systems Duct Design • Fourth Edition SHEET METAL AND AIR CONDITIONING CONTRACTORS’ NATIONAL ASSOCIATION, INC ... air conditioning (HVAC) duct system is to provide: GENERAL APPROACH TO DUCT DESIGN Basics of duct system design, including pressure losses, duct and diffuser noise, and basic system balancing... these listed codes 1.8 HVAC DUCT SYSTEM TYPES 1.8.1 Commercial Duct Systems ASHRAE divides the application of commercial HVAC systems into single−path systems and dual−path systems, and single−zone... supply fan HVAC Systems Duct Design • Fourth Edition 1.5 1.9 Dual−Path Systems: Dual duct, constant volume Multi−zone In recent years, most commercial HVAC supply air ductwork has been designed