Load Calculation Data and Procedures
ASHRAE Technical Committee 4.1

The ASHRAE Handbook is published in a series of four volumes, one of which is revised each year, ensuring that no volume is older than four years.  The Handbook can be purchased at the ASHRAE Bookstore by clicking on this link.

TC 4.1 is responsible for writing and maintaining the following two chapters in the ASHRAE Handbook - Fundamentals Volume

Chapter 17 - Residential Cooling and Heating Load Calculations
This chapter covers cooling and heating load calculation procedures for residential buildings.  It covers detailed heat balance methods that serve as the basis for the cooling load calculation, and simplified cooling load procedures suitable for hand calculations.  Discussion of straightforward heating load calculations are also included.

Chapter 18 - Nonresidential Cooling and Heating Load Calculations
This chapter covers cooling and heating load calculation procedures for non-residential buildings.  The chapter starts by explaining fundamental load calculation principles.  Next the common elements of cooling load calculation are described (e.g., internal heat gain, ventilation, infiltration, moisture migration, fenestration heat gain).  Finally, two methods of heating and cooling load calculation are discussed: the heat balance (HB) method and the radiant time series (RTS) method.  Extensive examples using the ASHRAE HQ buiiilding in Atlanta are used to illustrate application of the principles described in this chapter.

TC 4.1 is working on the revision of these chapters for the 2025 edition of the ASHRAE Handbook - Fundamentals.

Comment on the Handbook: ASHRAE welcomes your comments on the Handbook or a specific Handbook chapter.  To submit a comment about any aspect or part of the Handbook series, you can use the Handbook Comment Form.

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Technical committees develop and sponsor technical sessions at the winter and annual conferences. Information about their future technical program is discussed at each TC meeting and at the TC’s Program Subcommittee meeting.
2024 Annual Conference - Indianapolis
Seminar 29: Infiltration Challenges and Impact to Load Calculation
Monday, June 24, 11:00 AM - 12:00 PM EDT
JW Marriott, Grand Ballroom 7
Infiltration is a difficult parameter to quantify, but also is a parameter with significant impact on heating and cooling load calculations.  This seminar addresses fundamental code requirements regarding infiltration, the multitude of factors that play a part in infiltration uncertainty and the impact of infiltration uncertainty on load calculations.
Presentation 1: Distilling Infiltration Information into Load Inputs
Chris Wilkins, PE, RFS Engineering, Laconia, NH
Codes set maximum quantities for infiltration, but these are represented in terms of what the tested leakage rate would be at 50 Pa (0.2 in.wc.) or 75 pa (0.3 in.wc.).  These pressure values represent the differential pressures that are used for leakage testing but do not represent the expected pressure differentials for a building at the time of peak cooling load. 
This presentation will review fundamental code requirements, the relationship between wind speed and building differential pressures, how to adjust pressure values for actual wind speed, and how to input infiltration into load calculation programs.
Presentation 2: Sensitivity of Load Calculation to Infiltration
Daniel Howard, Oak Ridge National Laboratory, Oak Ridge, TN.
Blower door testing uses differential pressures of 50 Pa (0.2 in.wc.) to determine the air infiltration rate for buildings, but estimate of natural infiltration for a building is challenging given only that data.  In addition to the impact of a building's climate zone, stories, exposure, and air leakage distribution to infiltration, dynamic factors including building temperature gradient, wind, and equipment operation can play a significant role.
This presentation will review multiple sources of uncertaintly associated with infiltration quantification.  It will then estimate the impact of these uncertainties in infiltration to load calculation through a series of case studies.

 Programs Sponsored or Co-Sponsored for Past Conferences:

 2024 Winter - SEM23 - Speed Seminar - Load Calculations in 50 Minutes
 2023 Summer - WRK02 - Decarbonized Heating in Cold Climates: Are Enhanced Heating Load Calculations Required?  
 2022 Summer - SEM09 - Load Calculations for the ASHRAE Headquarters Building: The Transition to the Heat Balance Method  
 2020 Winter - SEM45 - Demystifying Thermal Load Calculations for New HVAC&R Engineers 
 2020 Winter - SEM06 - Updates and Lessons Learned from Recent Load Calculation Research
 2019 Winter - SEM26 - Load Calculation Considerations for Radiant Systems
 2019 Winter - SEM38 - Tall Space Load Calculations
 2019 Winter - WRK03 - Room Loads to Equipment Sizing Missing Link: How Can ASHRAE Help Young Engineers?
 2018 Summer - WRK02 - Load Calculations Missing Link - Taking Load Calculations Through to Equipment Sizing
 2018 Summer - SEM61 - Convective vs Radiant Load Calculations - Are They Different?
 2018 Winter - SEM50 - Low Energy Design Impacts on Peak Heating and Cooling Load Calculations
 2017 Summer - SEM19 - Changes to Heat Gain Tables in the Handbook Commercial Load Calculations Chapter 18
 2017 Winter - SEM11 - Current State of the Art for an Automated Pathway from BIM to Cooling/Heating Load Calculations
 2017 Winter - SEM21 - Low Energy LED Lighting Heat Gain Distribution in Buildings (ASHRAE RP-1681)
 2016 Summer - SEM23 - Parting the Clouds to See the Future of Residential Load Calculations
 2016 Winter - SEM24 - Back to Basics: The Science, Application, and Art of Load Calculation
 2016 Winter - SEM50 - Double Skin Facade Design and Application
 2016 Winter - SEM52 - Peak Envelope Cooling Loads: How Did We Get to Today?  Is This Where We Want to Be?
 2015 Summer - SEM10 - New Weather Data for Design Calculations and Energy Simulations
 2015 Summer - SEM23 - Climate Change: ASHRAE Design Day Weather Data
 2014 Winter - SEM08 - The Latest Trends & Abilities of Mobile Applications for Load Calculations & Building Evaluation
 2014 Winter - SEM42 - Cooling Load Calculations for Radiant & UFAD Systems: Are they the Same as Traditional Methods?
 2013 Winter - SEM25 - When is the Load Not What You Think?  The Radiant Effect of Non-Uniform Surface Temperatures
 2012 Summer - SEM21 - Can I Determine my Loads with my Energy Modeling Program?
 2012 Winter - SEM41 - Loads on the Move: Mobile Applications
 2011 Summer - SEM02 - BIM Load Calculations: Pain or Pleasure?  Phase 2 of the ASHRAE HQ Case Study
 2011 Winter - SEM56 - Low Energy Load Calculations

ASHRAE publishes papers and transactions from presentations at its conference events. In addition, ASHRAE records most of the seminar sessions from its conferences on DVD. These DVDs are ideal for use at chapter meetings, in university courses, or company lunch and learns. Products available from the most recent conference may be found here.

Technical Committees are responsible for identifying research topics, proposing research projects, selecting bidders, and monitoring research projects funded by ASHRAE. Information about their specific research program is discussed at each TC meeting and at the TC’s Research Subcommittee meeting. 

The TC 4.1 research subcommittee identifies research needs related to load estimating.   It then sets priorities, writes work statements, evaluates proposals, manages research projects and approves the final results.

Ongoing Research Projects:
  Research Project 1923-RP: Preparing Climatic Design Conditions for 2025 ASHRAE Handbook (co-sponsor with TC 4.2)
  Work Statement 1857-TRP: Improved Simplified Methodology for Describing and Calculating Heat Conduction between Building and the Ground. (co-sponsor with TC 4.7)
  Research Project 1850-TRP: Evaluation of ASHRAE's Design Day Procedure against Recorded Weather Data (co-sponsor with TC 4.2)
  Research Project 1816-RP: Reporting the Energy Use and Heat Gain from Imaging Equipment (co-sponsor with TC 4.7)

Recently Completed Research Projects:
 Research Project 1847-RP: Updating Climatic Design Information for 2021 Handbook (co-sponsor with TC 4.2)
 Research Project 1778-RP: Heat and Moisture Load from Commercial Dish Room Appliances and Equipment (co-sponsor with TC 5.10)
 Research Project 1742-RP: Update to Measurements of Office Equipment Heat Gain Data
 Research Project 1729-RP: Experimental Verification of Cooling Load Calculations for Radiant Systems. 
 Research Project 1681-RP: Low Energy LED Lighting Heat Gain Distribution in Buildings
 Research Project 1631-RP: Countertop Commercial Appliance Emissions (co-sponsor with TC 5.10)
 Research Project 1616-RP: Revise Load Calculation Applications Manual
 Research Project 1482-RP: Update to Measurements of Office Equipment Heat Gain Data
 Research Project 1453-RP: Updating the ASHRAE Climatic Data for Design and Standards (co-sponsor to TC 4.2)
 Research Project 1416-RP: Development of Internal Surface Convection Correlations for Energy and Load Calculation Methods (co-sponsor to TC 4.7)
 Research Project 1363-RP: Generation of Hourly Design Day Weather Data (co-sponsor to TC 4.2)
 Research Project 1362-RP: Revised Heat Gain and Capture and Containment Exhaust Rates from Typical Commercial Cooling Appliances (co-sponsor to TC 5.10)
 Research Project 1343-RP: Method of Testing and Data Collection for Energy Characteristics of Healthcare Equipment (co-sponsor to TC 9.6)
 Research Project 1326-RP: Application Manual for Non-Residential Load Calculations
 Research Project 1311-RP: Improving Load Calculations for Fenestration with Shading Devices

ASHRAE writes standards for the purpose of establishing consensus for: 1) methods of test for use in commerce and 2) performance criteria for use as facilitators with which to guide the industry. ASHRAE publishes the following three types of voluntary consensus standards: Method of Measurement or Test (MOT), Standard Design and Standard Practice. ASHRAE does not write rating standards unless a suitable rating standard will not otherwise be available. ASHRAE is accredited by the American National Standards Institute (ANSI) and follows ANSI's requirements for due process and standards development. Standards may be purchased at the ASHRAE Bookstore.

TC 4.1 is the cognizant committee for the following standards:

ANSI/ASHRAE/ACCA Standard 183-2024

Title: Peak Cooling and Heating Load Calculations in Buildings Except Low-Rise Residential Buildings
Purpose: This standard establishes requirements for performing peak cooling and heating load calculations for buildings except low-rise residential buildings.
Scope: This standard sets minimum requirements for methods and procedures used to perform peak cooling and heating load calculations for buildings except low-rise residential buildings.
Summary: Standard 183 was created in a collaborative effort between ASHRAE and ACCA (the Air Conditioning Contractors of America).  It establishes minimum requirements for performing peak cooling and heating load calculations for buildings except low-rise residential buildings.  Although there are many methods available to perform peak cooling and heating load calculations, the intent of this standard is to establish a minimum level of requirements that is inclusive of as many methods as possible while still being restrictive enough to mandate an appropriate level of care and accuracy.  An accurate estimate of peak cooling or heating load requires not only that a sound method be used but also that inputs to the method are reasonable and realistic (the execution of the method). 

ANSI/ASHRAE Standard 203-2018 (RA 2021)

Title: Method of Test for Determining Heat Gain of Office Equipment Used in Buildings
Purpose: This standard prescribes methods of test to determine the range and average operating heat gains of electrical equipment for use in cooling load calculations.
Scope: This standard applies to plug load type electrical equipment used in buildings.

TIP: If MTG involvement add here otherwise leave blank.

TC 4.1 participates in the following Multidisciplinary Task Groups

BIM.HCDG: Building Information Modeling
This MTG will coordinate the activities of multiple TC/TG in the area of standards and approaches to support the implementation of BIM within ASHRAE products and within the industry workplace.  MTG-BIM will also represent ASHRAE interests within the BIM marketplace outside of ASHRAE and provide a conduit for funneling information about the BIM industry to ASHRAE members.

MTG.HCDG: Hot Climate Design Guide
This MTG will coordinate TC/TG/TRG technical Activities to help support the development of the technical basis and adoption of the Hot Climate Design Guide. Responsibilities include suggestions for Research, Development and Presentations and special publications detailing aspects of the Hot Climate Design Guide.

ASHRAE Technical FAQs are provided as a service to ASHRAE members, users of ASHRAE publications, and the general public. While every effort has been made to ensure their accuracy and reliability, they are advisory and provided for informational purposes only, and in many cases represent only one person’s view. They are not intended and should not be relied on as an official statement of ASHRAE. Technical questions not addressed may be submitted to the ASHRAE Technical Services department at tse@ashrae.net.

TC 4.1 is responsible for the following Frequently Asked Questions.

Does ASHRAE sell software for residential load calculations? (14)
Does ASHRAE sell software for commercial load calculations? (15)
Does ASHRAE have an easy method for heating and cooling load calculations?  (21)
How can I calculate heating and cooling loads for a commercial building?  (77)
How can I calculate heating and cooling loads for a residential facility?  (78)
Which load calculation methods or software packages are recommended by ASHRAE?  (89)