Contractors and builders are walking into permit offices and being told they have to size their heating and cooling equipment and their duct work according to something called ACCA Manual J and Manual D. Okay, what the heck is that and how do you get them done, never mind done accurately???
The truth is, it is very difficult to find trained HVAC designers who can properly navigate not only Manual J and Manual D theory, but also the ACCA certified software, ASHRAE & ACCA rules, each different programs rules (LEED, EnergyStar, CALGreen, HERSRaters), unusual wall or ceiling construction components, unusual shaped buildings, multiple zones, and so on. We see reports on a regular basis where someone paid for a Manual J and it gets rejected by their permit office because it was done improperly.
You cannot just pop the software into your computer and be off to the races. It takes easily a 100 simple projects to develop an intermediate skill level, never mind complex projects. For example, we saw a report from upstate New York with an 84 F outdoor summer design temperature and 75 F indoor summer design temperature, about 2,500 sq feet and the calculated cooling load was 12.5 tons! The fact that the designer didn’t intuitively know that doesn’t even make sense is scary…
All the green websites preach how critical it is to properly size your HVAC equipment because
oversized heating and cooling equipment waste money and energy. That is why they (LEED, HERSRaters, CALGreeen, permit offices) always require a Manual J, S & D report as one of the line items in their certification process.
Most likely your contractor does not provide Manual J services. If they do, make sure they are following ASHRAE & ACCA design rules and using ACCA Certified software. You should expect to pay for the service. No contractor can just provide designs during the quote stage or they would be out of business quickly. Nor can they absorb the cost of providing these services so you can obtain a permit. If your permit office requires a Manual J & S (and some require a Manual d also), it is just a cost you will have to absorb.
The Manual J heat gain and heat loss must be calculated on a room by room basis using ASHRAE recommended peak design conditions. From there your contractor can select HVAC equipment based on EnergyStar guidelines and Manual J load calculation report. The selection of properly sized equipment is called Manual S HVAC equipment sizing. Once the Manual J is completed, and the Manual S equipment is selected, your HVAC designer can then provide a Manual D duct design where your supply and return registers and duct work are properly sized based on ASHRAE and ACCA design rules.
We have been providing accurate, affordable ACCA compliant Manual J load calculations, Manual S HVAC equipment sizing and Manual D duct layouts since 2005. Not only have we completed thousands of HVAC designs, making us the #1 Provider in the United States, we also have a 100% PASS Rate with all our projects!