How to Pass Load Calc Requirements for a Permit
By Chris Morin -
HVAC Pro Blog
is nothing more frustrating in the HVAC trade than not
knowing permit fees, expectations, or even code
requirements that seem to be rarely enforced
unilaterally across municipalities.
Based on conversations with Building Code Inspectors in
MA, there is nothing more frustrating to them either!
Sometimes, the perception is that the Code Official is
‘out to get me’, but typically this couldn’t be further
from the truth! What I usually find is the HVAC
Contractor does not know, what they don’t know.
So, let me save you the trouble of failed permit
applications, arguments, and appeals. This is what you
should be providing for information which must be
Print the Property Card (Town Assessor)
This is so simple, and will set you up for success. If
your load calculation software does not provide a
floorplan, this will easily show the code official the
layout. I recommend using a ruler and drawing in the
interior walls, dimensions of the room, locations of
windows, etc. Don’t go overboard, they probably will not
need this to scale!
This is another 'black and white' check in the box. Your
internal design conditions must match recommendation
in International Residential Code (IRC) and the
International Energy Conservation Code (IECC). Your
Outside Design Conditions must match the Manual J
Table 1A/1B for the closest weather data city.
continues below ↓
Walls, Ceilings, & Fenestration
Obviously, we are expecting the exterior walls and
ceilings dimensions to match the floor plan on the
property card. Speaking with code officials, being exact
on the square footage is not necessary, but a range of
+/- 5% is ‘believable’. If you are using a form style
load calculation software, like Elite Software, marking
these dimensions on the floor plan for submission with
the permit will definitely aide in the building
department’s approval process.
Ceiling construction, materials, and insulation
should match the typical material vintage (or what is
actually on site).
Glass surface area, type, frame material, shading,
and direction should be as close to exact as possible to
accurately calculate the cooling gain of the building.
Something so simple, yet easy to confuse, is the
direction each wall and window/door faces. I have a bad
habit of not noting this during the site survey, and
have come to rely on Google Maps to remind me which
direction the front door faces (to orient the rest of
When thinking internal gains, most Contractors
immediately think of number of occupants. This is
simple, as the number of people is the total number of
bedrooms + one (assuming two in the Master Bedroom).
Equipment Loads tend to make up much more of a total for
the building. If you are using any adjustments above the
three scenario options made available, justification for
these additions must be made (i.e. above average
lighting load, unvented stove/dishwasher, ceiling fans,
etc.). Honestly, anything more than Scenario Two: 2,400
but/hr will need justification in most municipals.
sealing, and surface area can significantly impact
the load. The duct condition is one of the major
differences in using Manual J v8 compared to the out of
date v7. A poorly insulated, unsealed, trunk and branch
duct system located within an unvented attic can
contribute as much as 1/2 ton or more to the Cooling
gains. That same duct system in a basement could impact
the latent gains enough to alter the size of the system
as well. Is all of your ductwork within the conditioned
space, or using ductless equipment? Then you will have a
smaller system with zero losses or gains on that metal.
New Duct System? Expect the need for Manual D Friction
Rate Worksheet, Duct Sizing Worksheet, and sketch
showing sizes of trunks runs.
I hope this helps set some basic expectations with your
next permit application. Providing the above details,
and having them be correct, will go a long way for your
successful process and inspection.
P.S. If you don’t know how to identify all of the above
I provide training for this!
About HVAC Pro Blog
In 2012, while working as a Tech Instructor for a
Utility Rebate Program Implementer, I realized I had a
lot more to share about my experience in the HVAC
Industry than just what my classes were providing an
outlet for. Since my first readers were mostly
Technicians, I began writing about the
Cooling service topics I was known for locally. As
my role in the industry changed, and I met with more
Salespeople and Business Owners, I expanded my content
System Design and
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