Q&A - Apps for Doing Proper Loads - Short #215 · HVAC School - For Techs, By Techs summary

Key takeaways

Load calculations are complex and essential for HVAC system performance, incorporating multiple factors affecting energy transfer.
Using reliable software like Wrightsoft, RedCalc, and ASHRAE resources supports effective load calculations.
Regional knowledge about building practices is critical; it helps contractors better estimate insulation values.
Combining advanced measurement tools with thorough local knowledge leads to more accurate HVAC load calculations.

Summary

Understanding Load Calculations

In this episode, Brian addresses a listener's query regarding reliable methods for performing load calculations without invasive measures like cutting into walls. He emphasizes the complexity of these calculations, which consider how BTUs can enter and leave a home through conduction, convection, and radiation. Notably, the insulation's R-value is highlighted as essential, since it impacts heat transfer. Brian points out the necessity for accurate calculations to optimize HVAC system design.

Valuable Software and Resources

Brian discusses various software applications and resources available to HVAC professionals. He particularly recommends quality HVAC design software like Wrightsoft and Kwik Model, which incorporate features for assessing a home's age and location. He also highlights ASHRAE's handbooks for R-values and U-factors as crucial resources for Manual J load calculations. Notably, RED Calc emerges as a featured app that assists contractors in calculating R-values and U-factors based on real-time measurements.

Regional Knowledge and Specific Tools

Understanding local building practices is essential for effective load calculations. Brian explains that familiarity with common construction types and material properties in a given area can significantly enhance a contractor's precision in estimating insulation values. He provides a selection of other tools and resources, such as REScheck, engineering toolbox utilities, and manufacturer charts, which can help in gathering relevant information.

Achieving Accurate Load Calculations

Brian stresses that while advanced tools are beneficial, having a solid grip on the specific characteristics of local homes—as well as employing techniques like blower door tests—can lead to the most accurate load calculations. He acknowledges that there is often no single solution that fits all cases, but a combination of methodologies and technologies yields the best results for HVAC professionals.

Show notes

In this short Q&A podcast, Bryan answers a listener-submitted question about apps for doing proper loads. Fred specifically asks about apps or charts that can help an HVAC contractor determine the insulation value of a home without assuming numbers or drilling into walls during load calculations.

Load calculations account for all the ways that BTUs can enter or leave a home: conduction, convection, and radiation. Insulation prevents heat transfer via conduction, so it's important to the load calculation process. High-end HVAC design software like Wrightsoft and Kwik Model 3D will have these features built into them (based on the age and location of the home). ASHRAE's handbook also has tables and data with R-values and U-factors to help you out with Manual J load calculations.

RED Calc is an app that allows you to calculate a wall's R-value with measurements, including surface and air temperatures indoors and outdoors. This RED Calc software is available through the U.S. Department of Energy, as is REScheck. The DOE insulation fact sheet is also quite valuable, as are The Engineering Toolbox and materials straight from the insulation manufacturers.

The best way to get a comprehensive load calculation is to have a lot of tribal knowledge about how houses are built in your area, analyze energy bills, and combine tools like RED Calc with building performance tests.

RED Calc is available through the U.S. DOE at https://basc.pnnl.gov/redcalc. REScheck is available at https://www.energycodes.gov/rescheck.

ASHRAE's resources are available at https://ashrae.org/technical-resources.

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Q&A - Apps for Doing Proper Loads - Short #215