Load Calculation Data and Procedures
ASHRAE Technical Committee 4.1

Scope of TC 4.1

TC 4.1 is concerned with the identification and compilation of engineering data and the development of procedures for calculating heating, cooling, refrigeration and ventilating loads of structures.


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 2021 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.

Review a Handbook Chapter: To provide your feedback about a specific Handbook chapter, you can answer the brief survey questions on the Handbook Chapter Review Form.


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.

TC 4.1-sponsored programs at the 2018 Winter Meeting:

Seminar 50 - Low Energy Design Impacts on Peak Heating and Cooling Load Calculations

Energy codes like Standard 90.1 and technological change have reduced peak loads significantly. This trend continues in RP 1742, Update to Measurements of Office Heat Gain Data, used in the latest ASHRAE Handbook, Fundamentals volume. This significantly impacts design of HVAC and other building systems and can create a new set of pitfalls. Engineers should recognize these trends and the impact they have on old "rules of thumb." Likewise these trends can have a significant impact on energy modeling and built environment energy use. Tuning existing buildings and systems to take advantage of these trends is a major industry opportunity.
>1. Heating and Cooling Load Trends: Down, Down, Down - Steven Bruning, P.E., Fellow ASHRAE, Newcomb & Boyd, Atlanta, GA .
As energy codes have evolved over the years since ASHRAE 90-75, their requirements have steadily improved building envelopes and reduced allowable lighting loads. While technology exploded with the advent of personal computers in the early 80's, plug loads resulting from that technology at first significantly increased cooling loads. More recently that trend has reversed with improved technology, thin clients and cloud technology. What impact have these trends had on HVAC design, the old one cfm/sf rule of thumb is literally out the window. 
>2. Decreasing Internal Loads: Could This Lead to Problems? -
Christopher K. Wilkins, P.E., Member, CBR USA, Cambridge, MA .
This presentation reviews the downward trend for internal loads over time, with an emphasis on lighting loads and plug loads. The presentation also discusses the most recent research by TC 4.1 on low energy lighting (LED) and plug load measurements. The presentation also introduces the question of determining the point where lower loads can present system or indoor air quality issues. 
3. Low Loads: Reap the Benefits but Read the Fine Print -
Manalee Nabar, P.E., Associate Member, Bright Power Inc., New York, NY .
Low loads, both overall and internal plug/lighting are pivotal factors when achieving energy efficient (Passive House, Net Zero, etc.) building design. This presentation first delves into the basic components of heating and cooling loads and examines how different load calculation methods handle the interdependency and time lag between them. Next, strategies to minimize internal loads is discussed. Lastly, common pitfalls in HVAC system sizing due to low loads is discussed and what factors should be kept in mind when specifying equipment. 

 Programs Sponsored or Co-Sponsored for Past Conferences:
 2017 Summer - SEM19 - Changes to Heat Gain Tables in the Handbook Commercial Load Calculatons 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 1729-RP: Experimental Verification of Cooling Load Calculations for Radiant Systems.
 Research Project 1742-RP:
Update to Measurements of Office Equipment Heat Gain Data

Recently Completed Research Projects:
 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 183-2007 (RA 2014)

Title: Peak Cooling and Heating Load Calculations in Buildings Except Low-Rise Residential Buildings
This standard establishes requirements for performing peak cooling and heating load calculations for buildings except low-rise residential buildings.
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.
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 203-2015

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.

Other Activities

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)