Careful consideration of the elements that will affect the ongoing costs associated with the new structure is necessary when designing a new house or commercial building. The choices made during the pre-construction phase will have a big impact on the building's comfort level as well as its monthly costs in terms of plumbing, indoor air quality, and energy efficiency. The proper heating of a new structure is one of the more crucial aspects of new construction. Your construction or HVAC contractor must perform a heat load calculation to determine how much heating is needed for a new home, warehouse, office building or retail store.
A heat load calculation is what?
A heat load calculation is an advanced mathematical technique for calculating the precise amount of heating required to maintain a home or other structure at the preferred indoor temperature level for its occupants. All buildings have a heat load (and a corresponding cooling load) that depends on the building's structural features, the measures taken to make the building more energy efficient, and the level of comfort that the occupants prefer.
What goes into calculating a heat load?
Your HVAC professional will perform a thorough on-site inspection of an existing building or assessment of construction plans when performing a heat load calculation. The technician will be able to generate a precise quantitative measure of the structure's heating requirements using the information from these processes. When calculating a building's heat load, the following thermal, structural, geographic, and climate factors are considered:
- Climate data for the area, including seasonal trends and variations
- Dimensions, form, and direction of the structure
- the building's airtightness or seal
- Existing air leaks in the seal or ductwork, as well as potential energy-loss-causing ductwork design elements
- Location and effectiveness of registers, supply and return ductwork, and vents
- Insulation type, quantity, and location
- Windows' number, location, and type
- number of heat-producing appliances, lights, and other equipment
- Building's construction materials of choice
- Trees, shrubs, earthen barriers, and other landscaping elements that may change how much sunlight, wind, and other elements of nature affect the building
- Energy efficiency and steps taken to improve it, such as adding insulation, caulking air leaks, and installing energy-efficient windows
- The number of people and their preferred temperatures
Why calculate a heat load?
Your HVAC contractor and you will need the information from a heat load calculation to choose the appropriate size and capacity of heating equipment for the new structure. In order to properly size HVAC equipment, heating systems must be chosen and installed that are large and powerful enough to handle the structure's heat load without being oversized or too large, which would result in inefficient energy and heat use. You and your HVAC contractor will be able to select equipment that will produce the required level of heat once you are aware of the building's precise heating load.
Where does a heat load calculation come from?
The methods outlined in Manual J, “Residential Load Calculator,” published by the Air Conditioning Contractors of America (ACCA), should be followed when performing heat load calculations. This manual provides instructions, technical information, and guidelines for performing a precise heat load calculation.
Additional things to think about
- Use Manual J's most recent iteration.
- Accept and use only professional analyses of the heating load data.
- Installing heating systems that are more than 15% oversized is not advised.
- Use Manual S, “Residential Heating and Cooling Equipment Selection,” of the ACCA guidebook for reliable advice on selecting a heating system.
