Manual J Load Calculation in Austin, TX

What Manual J does

Manual J is the industry-standard method for calculating how much heating and cooling a specific home needs. It was developed by ACCA (Air Conditioning Contractors of America) and is the method building codes and many utility rebate programs commonly reference.

The result is a load, measured in BTUs per hour: the heat your home gains on the hottest day and loses on the coldest. That load is what we match your equipment to. It answers three questions:

• How many tons of cooling and how many BTUs of heating does your home need?
• How much airflow does each room need to stay comfortable? (answered by the room-by-room calculation, when ducts are redesigned)
• How much moisture does the system have to remove in summer?

How it is calculated

Manual J adds up every way heat enters or leaves your home, for the whole house or one room at a time when ducts are being redesigned. For any surface, such as a wall, ceiling or window, the heat moving through it follows one basic relationship:

Manual J applies this to every surface, then adds the loads that don't come through the walls:

• Walls, ceilings and floors: area, construction and insulation level. They're the largest share of winter heat loss.
• Windows and doors: size, orientation, glass type and shading. Sun through glass drives the summer cooling load.
• Air leakage: how tight the building envelope is. Outside air that leaks in must be heated or cooled.
• Ventilation: the fresh air the home requires, which adds heat and moisture to the load.
• Ducts: location, insulation and leakage. Ducts in a hot attic lose capacity.
• People and equipment: occupants, appliances and lighting add heat and moisture inside the home.
• Local climate: design temperatures and humidity for your area set the extremes the system must handle.

The software totals the heat loss in winter and heat gain in summer, for the whole house or for each room, split into sensible heat (temperature) and latent heat (humidity). The sum is the load your equipment has to meet.

What it takes to do it right

A Manual J is only as accurate as the information that goes into it. A real one can't be done from square footage alone. Doing it right takes:

• Accurate measurements. Room dimensions, ceiling heights and window sizes, taken from plans or on site.
• Construction details. Insulation levels in the walls, attic and floors, plus the type of windows and doors.
• Orientation and shading. Which way each wall and window faces, and what shades them.
• Air tightness and ductwork. How leaky the home and ducts are, and where the ducts run.
• Local design conditions. Weather data for your area, matched to the approved ACCA procedure.
• ACCA-approved software and a trained operator. The math is done by software, but a person has to enter the data correctly and check that the results make sense.

The common shortcut is a rule of thumb, such as a set number of square feet per ton. Rules of thumb ignore insulation, windows, sun exposure and ducts, and they usually lead to oversized equipment (see why a bigger system isn't better). The Manual J result also feeds the next steps in ACCA's process: Manual S for choosing equipment and Manual D for designing ducts.

Benefits to you

An oversized or undersized system is one of the most common reasons a new system disappoints. A Manual J helps you avoid that:

• Better comfort. Equipment sized to your home, and with a room-by-room design, the right airflow to every room for fewer hot and cold spots.
• Better humidity control. A system that runs long enough removes moisture. An oversized one shuts off before it does.
• Lower energy bills. Right-sized equipment runs in steady, efficient cycles instead of constantly starting and stopping.
• Longer equipment life. Short cycling puts extra wear on compressors and other parts.
• No paying for capacity you don't need. Bigger is not better, and extra tons cost more up front.
• Quieter operation. Properly sized equipment and ducts run at lower speeds.
• Documentation. You get a written record of your home's load, which can help with permits and rebate programs.

What our customers say

 
 
 
 
  EXCELLENT  
  
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 Bryan Miller 
 
4 days ago
 
 
  
Bogdan had our A/C up and running again within hours.  He was super fast, very knowledgeable and did a perfect job.  Highly recommend!
  
 
 
 
 
 
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 Chris Beihl 
 
4 days ago
 
 
  
Bogdan lives in my neighborhood so when I noticed that my AC wasn't cooling as well as it used to I gave him a call.  He was able to come out and diagnose my issue as a leaking evaporator coil within a day and he recharged to keep it going.  Also he followed up on my Trane warranty to get the coil replaced which was done the following week.  The part was covered under warranty but I did have to cover the cost for the refrigerant and labor.  Overall I'm happy with the service and I'll go with Kassa Kool again if I have any issues in the future !
  
 
 
 
 
 
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 Brad Closson 
 
5 days ago
 
 
  
Super fast!  Did an emergency fix on my company A/C.  Very pleased.
  
 
 
 
 
 
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 Gabriel Carrillo 
 
5 days ago
 
 
  
Bogdan is very sharp and a great communicator.  It was a pleasure working with him!
  
 
 
 
 
 
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 Wendy Funk 
 
8 days ago
 
 
  
Bogdan is professional, punctual, thorough and honest. I highly recommend his services!!!
  
 
 
 
 
 
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 Andy Manchala 
 
9 days ago
 
 
  
It’s great working with Bogdan and you can trust his insights and judgment on the HVAC systems.
  
 
 
 
 
 
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 glenn Nossov 
 
9 days ago
 
 
  
I'm so happy  I found an AC company with personal service, fair pricing, quick response, really good service .I left a response on the website in the evening and he was out  the next day .👍
  
 
 
 
 
 
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 Jim Tolles 
 
11 days ago
 
 
  
Bogdan was very friendly, very knowledgeable, diagnosed the bad condenser immediately, replaced it the next day. All good now!
  
 
 
 
 
 
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 Maralee Schmidt 
 
12 days ago
 
 
  
CAme same day we needed help.  Definitely solved some of the issues we were having.
  
 
 
 
 
 
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 Dean Schulz 
 
12 days ago
 
 
  
Had a noise issue with my newly installed AC (by a different company) which they were not able to fix or even to diagnose and insisted that’s how it’s supposed to sound. There is no way I could live with that , so I reached out to Kassa Kool who was quick to respond and fix the problem. Owner is very knowledgeable and was able to address the problem on my Trane unit in the same visit. Reasonably priced, I will become their maintenance customer from now on.
  
 
 
 
 
 
 
 
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Cost: room-by-room Manual J, $250, yours to keep or credited to your new system

The whole-house load calculation is included in every free replacement estimate. A full room-by-room Manual J, done when your ductwork is being redesigned, has a $250 fee. You can use it either of two ways:

• Keep it. The completed calculation is yours, whether or not you move forward with us.
• Apply it. If you buy a new system from us, the $250 is credited toward the purchase.

Learn more

Manual J is published by ACCA, the Air Conditioning Contractors of America. You can read more about the standard on ACCA's Manual J page. Ready to get started? Call us to schedule your Manual J load calculation.