ACCA Manual J Reports

The Air Conditioning Contractors of America's (ACCA) Manual J 8th Edition

is the ANSI-recognized industry standard for calculating your home's heating and cooling needs.

Comfort Geeks is Southern Arizona’s source for accurate, comprehensive ACCA Manual J heat gain/loss calculation reports. Leverage our industry expertise and attention to detail to elevate your home’s comfort and energy efficiency.

What is a Manual J Heat Load Calculation?

The ACCA Manual J standard is a scientific process used to calculate your home’s heating and cooling capacity needs (HVAC system size). Some inputs include local climate data, building orientation, home age and air sealing quality, construction materials, insulation R-values, and door/window construction.

When is ACCA Manual J required?

In southern Arizona (and most other municipalities across the US), a Manual J load calculation report is always required to obtain an HVAC system installation or replacement project permit.

If your HVAC contractor isn’t using ACCA Manual J to size your new comfort system, they’re gambling with your indoor comfort at stake.

Manual J Report FAQs:

(click/tap the + next to the Q to reveal the A)

Why can't my new HVAC system be sized using square footage per ton?

Sizing a comfort system by square footage is not an industry-approved (or legal) method. If your HVAC contractor isn’t using ACCA Manual J to size your new comfort system, they’re not qualified to install it. Consider two identically sized houses, one built in 1960 and the other in 2010. Is it feasible that these homes, built under drastically different construction codes, require the same cooling and heating capacity?

Why can't I replace my current 3.0-ton system with a new 3.0-ton system?

Contrary to popular belief, the HVAC system “tonnage” is not an actual measurement of system capacity. Cooling capacity is rated in BTUs (British Thermal Units)— specifically Sensible BTU and Latent BTU, which vary drastically from system to system. In short, the cooling capacity of two 3-ton systems can vary by thousands of BTUs.

Is it okay to perform the Manual J calculations post-sale?

That’s what we call putting the cart before the horse. In this case, contractors typically generate Manual J reports to justify the HVAC system sizing they’ve already selected… which may or may not be the correct size for your home. Our rule is that a homeowner should never receive a proposal for an HVAC system installation without an accompanying ACCA Manual J and S report. How can a project be (accurately) priced before the correct HVAC system sizing is known?

Why do the calculation results vary by contractor?

Whether using a software application or the old-school manual calculation method, the load calculation output is only as accurate as the data inputted. While most HVAC contractors are excellent with the hands-on scope of work, few are proficient in building science or component construction identification—both required to ensure your home is comfortable for the next 10-15 years.

Can I use the Manual J Report from one of my neighbors?

No. Each home has unique characteristics that contribute to heat gain and loss and HVAC system sizing requirements. A few examples are building orientation, home improvements, appliances, and personal lifestyles.

What will happen if my new HVAC system is undersized?

– Failure to maintain comfortable indoor temperature and humidity levels.
– Excessive HVAC system runtimes and high energy bills.
– Premature HVAC system failure and costly repair bills.

What will happen if my new HVAC system is oversized?

– Hot/cold spots in your home with poor humidity control.
– System short cycling (rapidly turning on and off).
– Premature HVAC system failure and costly repair bills.
– Reduction in expected operation life (by years).

More questions about ACCA Manual J Reports? Drop us a line!