Why won't HVAC contractors follow my Manual J report?
Contractors routinely dismiss independent load calculations and insist on using old rules of thumb or installing oversized equipment instead. This leaves homeowners unable to find someone willing to install the correct size system for their home.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Searching for small, local companies instead of big-name operationsDid this help you?
- 2Consulting friends who work in the HVAC trade for second opinionsDid this help you?
- 3Bringing up independent testing reports during initial consultationsDid this help you?
- 4Getting multiple quotes from different contractorsDid this help you?
- 5Calculating manual J loads independentlyDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“However - every contractor we bring in for an estimate is arguing the findings in the report.”source ↗
“I have met with six or seven different people - some show absolutely no interest in even reading the report.”source ↗
“so I am kind of pulling my hair out trying to find a contractor who will follow the recommendations in the report and take the job.”source ↗
“Every contractor who has bid on my project bids a 2 ton system. some of them use the old rule of thumb of 1 ton/400 sf which isnt appropriate for a small highly insulated modular house that is pretty tight.”source ↗
“Some of them tell me they cant get anything smaller than 2 tons.”source ↗
Where this came up
People with this problem also raised
- 4Should I ask the contractor to redo work or take a deduction?
- 6Contractor installed a different size unit without asking
- 6What to do when hired contractors stop communicating
- 2How to handle disagreements with coworkers over installation standards
- 5Clients who refuse to fix underlying problems before repairs
- 8Contractors asking for admin access but not knowing basic IT