HVAC Design: The Importance of Accurate Heat Load Calculation

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HVAC Design

The term HVAC stands for Heat, Ventilation and Air Conditioning. HVAC is an engineering field that requires multiple disciplines. If you are making a new building or making major modifications to an already built house, then you definitely need an HVAC Firm or at least an HVAC designer in order to help you with:

• Choosing the proper Air conditioning system.
• Making the plans for the pipelines.
• Making the necessary calculations such as heat load calculations.
• Making sure that the indoor air quality will meet the necessary standards.

Main Heat Sources

Heat can be generated in many ways whether directly or indirectly. Below are some of the main heat sources:

• Solar Heat: Solar energy can be one of the main sources of heat that a house or building can experience. However, while Sun can be a great source of energy and power generation, it could also cause major cooling and heating issues. There are three different types of solar heat that can significantly affect the heat load calculation of a building:
  • Convection: It refers to the heat transfer due to the movement of large pockets of warmer outdoor air or indoor air from rooms that are at a warmer temperature.
  • Radiation: It is the direct heat transfer that occurs when unfiltered sunlight penetrates buildings through clear surfaces such as windows.
  • Conduction: refers to the heat transfer when the outdoor barriers of a building, such as walls or the roof, are exposed to a difference of temperature between interiors and the warmer outdoor environment.
• Heat from People: Another major source of heat could be human beings especially when they are engaged in activities such as working out, doing housework or any other strenuous activity.
• Atmospheric Air Heat: Atmospheric air is simply the outside air or outdoor. Since typically outside air is warmer than inside, it raises the indoor temperature when it enters interior corridors and spaces.
• Heat from Electrical and Electronic Appliances: The interior space of buildings such as houses is filled with electrical appliances, such as lights, A/V equipment, coffee machines, water heaters, and of course computers. These devices consume electricity and warm-up and expel their generated heat. This heat affects the heat load calculation more than one might realize.

What is Load Calculation?

The load calculation is a mathematical process that is used in order to determine the best size, the best application as well as the best style of the HVAC System for a building. Below are the main objectives and goals of doing the necessary HVAC Load calculations:

• Verifying the total square footage.
• Counting the entryways such as doors and windows.
• Checking the insulations.
• Counting the floors.
• Checking the landscapes.
• Checking the windows treatment as well as the condition of the ductwork.

Despite the importance of load calculation, many people don’t even bother to ask their HVAC engineering firm or company to perform the necessary calculations without which there is the possibility of fatal design mistakes especially if a building is complicated or brand new.

Importance of Heat Load Calculation

During the building design process, the presence of the HVAC designer is essential as he works directly with the construction engineer to find the ideal places to install different air systems with appropriate sizes. So before embarking on the construction, the architect should design the building step by step with the HVAC designer considering his recommendations. the importance of the heat load calculations are the followings:

• Air-conditioning system of the right tonnage: The HVAC designer selects the appropriate air conditioning system to meet the temperature requirements of all rooms in the desired building based on thermal load calculations. The failure to calculate the thermal load leads to the wrong choice of the size of the air conditioning system. Choosing a system with a larger size than needed will lead to a rise in the operating cost, while the choice of a smaller size will lead to a decrease in room temperature which will make the air conditioning system become worthless. Therefore, accurate calculations of the heat load are vital, as it enables the HVAC designer to know which systems will be most effective to provide adequate cooling at the lowest possible cost.
• Air conditioning system of the right type: After doing the necessary heat load calculations, the HVAC designer will recommend the proper air conditioning system with the proper size for the proper application.
• Avoid the breakages in the room: since heat load calculations will most likely be carried out prior to the actual construction of the room, the HVAC designer will make sure that the proper air conditioning system will fit the room so preventing any breakages in the room.

Heat Load Calculation Procedure

The first step for doing a heat load calculation is to conduct a survey of all the rooms in the building aimed at identifying all the existing heat sources. Then based on the survey and the calculated heat load, the HVAC designer will recommend the type of air conditioning system that is suitable for the application as well as the required capacity. The heat load calculation is highly specialized, time-consuming, and complex; however, it is essential in order to provide optimal and efficient results. There are two possible methods for carrying out a heat load calculation, these two methods are manually calculation or software calculation.

In the first method which is the manual process, the data gathered from the survey done on the building, and the complementary documents are analyzed using predefined equations and parameters. Based on the results of the calculations, the HVAC designer recommends a suitable air conditioning system for the building.

The second method, i.e., software calculation, is more commonly used due to advances in computer technology and software engineering. Most HVAC designers use such software as Trace 700 and HAP (Hourly Analysis Program) in order to do the heat load calculations. Software calculation makes the entire process easier and much faster.

Conclusion

Performing necessary heat load calculations is an important process and must not be ignored. In order to have the best and optimal results in a building without wasting a significant amount of energy and potentially money, it is an indispensable part of any HVAC design.