How to Prepare Your Home for a Manual J Load Calculation

Garbage In, Garbage Out. This computer science maxim applies perfectly to HVAC. A Load Calculation is only as accurate as the data you feed it.

To prepare for manual j calculation, you shouldn't just wait for the auditor to show up. Having specific documents and access ready will ensure they don't have to guess on critical values.

1. Provide the Plans (If Available)

If you have original blueprints or floor plans, dig them out. This gives the auditor exact room dimensions without needing to manually measure every wall.

2. Know Your Windows

Windows are often the biggest unknown in a manual j home evaluation.

• Find the NFRC stickers (usually on the top inside frame).
• Write down the U-Factor and SHGC.
• If you replaced them recently, find the receipt or invoice.

3. Attic Access

Clear a path to the attic hatch. The auditor NEEDS to see what kind of insulation you have.

"I think it's pink stuff" isn't good enough. They need to measure the depth (inches) to calculate the R-Value.

4. Renovation History

Create a quick list of any work done to the house.

• "We finished the basement in 2018."
• "We added a sunroom."
• "We upgraded the siding to insulated vinyl."

5. Occupancy Habits

A manual j inspection doesn't just measure the house; it measures how you LIVE in it.

Be ready to answer:

• How many people live here?
• Do you have a home office with lots of computers? (Internal heat gain)
• Do you cook big dinners every night? (Kitchen load)
• What temperature do you actually keep the thermostat at?