HVAC heat load
HVAC heat load

The Major Importance of Accurate Heat Load Calculation in HVAC


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Heat Load Calculation is one of many fundamental skills any HVAC professionals should possess. During the building process, an HVAC designer has to be regularly present. He will directly collaborate with the construction engineer to look for the ideal areas in which different air systems are to be installed. HVAC professionals work closely with the architect, too. The latter focuses more on designing the buildings step by step, considering the many given suggestions and specifications from the HVAC expert. Real-time collaboration between parties involved is best achieved using advanced software tools like construction project management software. Thus, a software tool like this is worth investing.

In buildings, space cooling is undoubtedly considered one of the highest energy expenses, particularly during the summer season. However, to appropriately size a cooling system, HVAC professionals must first know the exact amount of heat that should necessarily be removed – this is precisely where the critical purpose of heat load calculation will unfold. Additionally, the best construction management software like Pro Crew Schedule is also an essential tool to have apart from acquiring knowledge about the specifics.

In this blog, heat load calculation will be outlined alongside the four significant sources of heat and lastly, the five tips to achieve accurate HVAC heat load calculations efficiently.

What is Heat Load Calculation?


The heat load calculation is directly referring to a particular process of determining the heat load for a quantity of matter or individual spaces. Heat load refers to the amount of heat energy that should directly be added to maintain a desired temperature set point. This might also be referred to as either thermal load or heating load. Cooling load referred to the opposite process, yet noting the significant distinction between the two types of loads is necessary. In the HVAC industry, the method of heat load calculation should be prioritized first because it determines the amount of heat energy that must either be removed or added to obtain the desired set point. Apart from it, other priorities include the utilization of construction scheduling software that contributes to the overall development of any projects and best used for scheduling purposes.

While there are several ways wherein heat can either be directly or indirectly heated, the following cited below are the four major sources of heat.

1. Outdoor Air Heat

Outdoor air is the term used to describe the warm air that lies outside of any air-conditioned spaces. It is also at times called atmospheric air. Due to the very high temperature at times, outdoor air tends to increase the average room temperature during indoor entries. While some air exchange sounds so typical when both windows and doors are open, outdoor air is very capable of entering air-conditioned spaces through emerging leaks around the windows, doors and other building envelope elements. The heat seized by the outdoor air usually comes in from prime areas where there is sunlight, yet it could also originate from nearby buildings or vehicles. Details as important as this should be kept securely. That is why a builder trend software must be used to save all important notes and listings. Sorting, updating, organizing all saved files and records anytime and anywhere can be efficiently done using the cloud-based software tool.

2. Solar Heat Gain

There are numerous ways where the heat coming from the sun can immediately reach interior spaces – convection, conduction and radiation. Convection refers to the transfer of the heat due to the bulk movement of indoor air movement or hot outdoor air between any surfaces at different temperatures. Next, conduction often occurs across roofs and walls since these are more exposed to a specific temperature difference between the warmer outdoor environment and the surrounding buildings. Lastly, radiation is defined as a direct form of a heat transfer that typically occurs when sunlight is entering premises through the windows or perhaps other transparent surfaces. As proven, both convection and radiation can immediately interact with conduction any surfaces of roofs and walls. For project management for construction, what is proven to be also beneficial is the use of advanced tools like software applications.

In most buildings, the sun is certainly the largest sole source of heat. For specific indoor areas like rooms, solar heat gain varies on its alignment or direction. Take a look below.

· East-facing windows and walls are exposed to position sunlight during mornings

· South-facing surfaces are exposed to direct sunlight during every noon

· West-facing surfaces exposed to direct sunshine during the afternoons

· Only the walls facing the north often experience meager solar heat gain

HVAC contractors, when starting off any projects, which certainly helps them to collaborate in real-time with other co-workers and to have consistent communication, is a crew schedule software. A software application such as this allows any contractor to monitor and supervise every dedicated crew and subs efficiently. Work is much better using this application and productivity gets higher. Additionally, a construction crew management also needs to be implemented and good thing that the software itself makes it easier to achieve and implement.

3. Heat from Humans

People also have a contribution to gained heat. Any occupants living in buildings are considered as a significant source of heat. Finding a person who consumes hundreds of calories every day by consuming a lot of foods, this part of the energy will be released as heat during metabolic processes. Apparently, the heat directly released by people is found to be higher during extreme physical activities through sweating or perspiration.

Furthermore, the occupants’ density is also one factor that the heating effect tends to increase progressively. With that being said, the human contribution towards the total heat load could be notably higher in spacious air-conditioned areas like auditoriums, halls, etc.

4. Heat from Electronic Appliances

Noticeably, indoor spaces are often filled with electronic and electrical appliances like television sets, lighting fixtures, water heaters, coffee machines, etc. The list goes on for these appliances and each of them has consumed electricity that releases moderate heat in conditioned spaces. That is why to use highly energy-efficient appliances is often being suggested by HVAC experts. HVAC professionals not only inform or give in-depth technical explanations to clients but also are to consider other necessary things. A builder schedule software, for example, is one of the topmost essential tools they used as of now. The tool is for scheduling and project management purposes that help them manage any projects as well as the involved working team members. It makes the work immensely easier to control which is very crucial.

5 Tips for Accurate HVAC Load Calculations


Here are some useful tips for HVAC design professionals to guarantee reliable load calculation numbers.

1. Get the right info upfront

It is essential to have all the plans and specifications for the house that HVAC professionals will have to design. The list goes on and on for the needed information. However, if there are holes or lacking in all details and numbers they need, ensuring to track it all down and obtain it all is extremely necessary. With that being said, doing walkthroughs of all homes and properties with similar construction will help HVAC designers understand further when dealing with load calculations.

Performing precise load calculations on several existing properties and homes for energy upgrade proven to have conflicts along the way. However, the accuracy of the partial estimate varies from the information gathered from the field.

2. Make good use of the tools

Make sure to have manuals and obtain a hard copy of it when you are tasked to do load calculations. Keep in mind that while commercial software packages could help an HVAC expert like you in the designing process and in working through the iterations required, it must be operated with a firm understanding of all design procedures. Once again, accuracy is the key to this area. In the iterative HVAC design process, load calculations are known as the very first step. Hence, you cannot afford to have these all wrong.

3. When in confusion or hesitation, test

For instance, an experienced HVAC designer like don’t have all of the information and on top of that, unsure of the exactness of the infiltration value and estimated R-value of the enclosure, one practical option to get passed on this is to test the same house under construction to get the accurate data. In the same way, if you are going to perform an energy upgrade on any existing properties and currently missing essential details about the infiltration values and insulation, it’s the time to test. Proven already, blower-door tests are capable of providing information about air-infiltration rates. When it comes to insulation, drilling a hole and a quick dropping of a camera probe are two most common ways in order to have a better look on the inside.

4. Beware of the Short-Cycle

So what will happen if the heating and cooling system of the house is over-sized? Do a little extra horsepower could serve as insurance? The answer to that question is no. To reach highest operational efficiency, HVAC system needs to run for as long as possible for it to meet loads. If an HVAC system is over-sized, it has tendencies to short-cycle leading to many possible risks.

· Air in the ducts will fail in maintaining a constant temperature where it causes discomfort to occupants and it possibly leads to frequent thermostat adjustments

· Increasing operational costs causes by wear and tear from the equipment and insufficient use of energy potentially causing failure.

· Insufficient removal of moisture on the air, leaving the space uncomfortably damp and possibly breeding ground for mold. Perhaps, one of many essential things about HVAC system designs is that it isn’t necessarily intuitive – a system that performs better when it runs longer.

5. Don’t lose sight of the three major keys

HVAC design professionals have to consider three major factors during heat load calculation and they have to ensure in addressing them all.

· Design Considerations – these refer to the size of the property, location, indoor and outdoor design conditions. Usually, other variables are considered, like latitude, relative humidity, directional orientation and elevation.

· Internal Loads – this usually includes the exact number of occupants in the property, all electronics used, appliances, lighting, and system ductwork. An HVAC system where ducts are passing through an uninsulated attic is found to have different loads compared to others.

· Thermal enclosure – the window’s U-values are included in this area, the property’s air tightness and insulation values, as well as internal and external shading, are also included. The better the house’s enclosure, the more those windows have a significant effect on the loads.

Key Takeaways


The heat load calculation is a tedious and highly specialized task known to be complicated by nature. Thus, only those who have the expertise like the qualified HVAC professionals are permitted to handle complex tasks like this. Furthermore, this type of calculation has always been considered as a crucial step in reaching optimal cooling performance by giving on the basis for selecting an HVAC system that is suitable for the application.

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