The days when rough calculations were enough to determine the energy efficiency and code compliance of new residential buildings are over now. It is a good sign that the assistance comes at a time when homes and additions are facing even greater scrutiny about how much energy they use.

In many states, the International Energy Conservations Code (IECC) has been adopted. This adoption means there is standardized ways to prove whether your project meets certain codes or not. That’s where REScheck and Manual J come in.

Manual J Created by the Air Conditioning Contractors of America (ACCA), “Manual J8 Residential Load Calculation” or “Manual J” for short, is a tool that provides detailed requirements for producing residential load calculations for single family residential homes. Those load calculations are then used to get the correct size heating and cooling equipment into the home.

Window measurements, insulation, roof design, local climate, and many more factors are used to determine the HVAC equipment needed to condition interior spaces without wasting energy.

When You Need Each

REScheck is fast becoming an industry standard across America to meet energy code requirements. Many states as well as local governments insist on being furnished with proofs of meeting this requirement. The fact that it was developed under federal sponsorship makes it a widely popular product today; nonetheless, it will be more prudent if you check with your county building office since this could not be enough proof of compliance with code. Here is a list from https://www.energycodes.gov/states-can-use-rescheck-show-compliance of states currently allowing the use of REScheck to show compliance with energy codes.

Since this voluntary guideline was made law by various states within their territories following its introduction at federal level through Energy Star Version 3 Residential Program. Before long all 50 states will demand IECC AND Energy Star compliance.


Because Version 3 requires broader HVAC measures, Manual J is gaining wide acceptance among local building authorities as the gold standard for Energy Star compliance. It will take much more than the installation of appliances that are energy efficient. They must now help choose the right sized systems for each home and its environment now. This can be done through Rescheck HVAC sizing techniques.

Click here to see which states require Energy Star ratings (https://www.energystar.gov/partner_resources/residential_new/homes_prog_reqs/national_page).

More than just codes

Even if not building a new structure, and only replacing an old HVAC system, it is still necessary to have a Manual J calculation done. Older HVAC systems (10 years or older) can be unreliable and less efficient than newer ones. There may be some indications that you need a Manual J calculation in order to know whether it is time to replace your old/outdated HVAC system:

- Clients who are complaining about hot weather discomfort
- Clients who are complaining of inability to regulate indoor  
- Short cycling of equipment 
- Capacitors and compressors failing repeatedly

It acts as initial tool for identifying possible comfort and system performance issues. According to the national surveys, well over half of the HVAC contractors size heating and cooling systems incorrectly.

Efficiency improvement, comfort and lower maintenance/operating costs over the lifespan of the new system – these are some most common benefits from changing an old HVAC system into a newer one.

HVAC companies almost always install oversized systems primarily because they think that “bigger is better.” However, large sized systems can come with many other problems. These include:

- Higher installation costs
- Low performance causing high utility charges
- Frequent breakdowns leading to a higher maintenance cost
- Generation of moisture resulting in mold growth or humidity levels

REScheck, Manual J, or Both

The future direction for code compliance has placed more responsibility on homeowners, architects, and builders to prove that minimum standards have been met. The number as well as complexity of regulations make it difficult to know where one should start from. As such REScheck and Manual J options are increasingly becoming standard practices in both private sector and government circles.

Contact us today for you energy code compliance tool that best suits you.