Manual J, S, and D calculations
Green Building Energy Sustainability (GBES) can help you evaluate the heating and cooling loads placed on a building in any given climate and orientation using different types and styles of construction, insulation techniques, and Energy Component Values. Software is used to model the structure, and it then runs hourly simulations of sun movement and exposure on walls, windows, roofs, and other energy components to determine the heat gain and heat loss in each room of the house.
The Manual J heat load calculation was simple when all energy components were standardized years ago. The standard was 1 ton of A/C per 1000 square feet. As tighter structures were built, more efficient windows were installed, and higher R-value wall and ceiling insulation values were used, the tonnage per square foot started to fall. New ACCA (Air Conditioning Contractors Association) 183 Standards On new houses built under the 2015 IECC, we see 1 ton per 450 square feet. That is 1/2 the A/C load in homes just 20 years ago.
Once the Manual J (Heating and Cooling load calculation) is created, you can match different HVAC equipment to create a Manual S (Sizing) for the equipment selection. Not all systems are the same. They have different fan speeds, coil types, and pressure capabilities. To efficiently design an HVAC system, you want it to meet and slightly exceed all designed heat and cooling loads. If the system is too small, people will not be cool in the house during the summer. If the system is too large, mold and high humidity from short cycling become an issue. The Manual S reports establish an excellent middle ground to help correctly size the system.
Once you select the HVAC equipment, you create a Manual D (Ducting) using the specifications of a particular unit to calculate duct sizes that will ensure that an adequate amount of airflow is delivered to each room to meet the Manual J requirements for that room.
Together this package of reports provides information on duct pressure and airflow to help make each room comfortable as the sun moves across the sky and shines into and on the building’s windows, walls, and floor. Commercial buildings have an Air Balancing test that must be performed to ensure adequate heating and cooling are delivered to each room. Residential building codes are not far behind in incorporating those requirements.
Building Code adoptions vary from state to state and even municipality to municipality. The 2021 IECC (International Energy Conservation Code) is the latest Energy Code. A new building code is generated every three years based on previous versions and changes in construction and technology. The code-making process is like making sausage, so the end product is not always the best option. It is usually an improvement by compromise. Different states or municipalities then adopt a version of the code based on their experiences, climate, and construction techniques in their local market. They may skip several code cycles and jump from the 2009 version to the 2015 or 2018 version. Numerous jurisdictions are moving to the 2021 IECC for many reasons and are now becoming commonplaces across the United States.
Regardless of your needs, we have the experience and staff to help meet your needs. If GBES can help you evaluate your existing building or plan for the construction of a new building, please give our team of Engineers a call to start on your project. Our Office number is 940-808-1430.We have a dedicated phone for our Spanish-speaking clients. If we can answer questions or schedule an inspection, please call us at 682-246-8150