How to Avoid Getting Stuck with Contractors Who are All Thumbs

Rule of thumb sizing for home heating and air conditioning is outdated, but contractors are slow to adopt “right size” HVAC procedures, even though required by Alabama building codes. Here’s why the AlabamaWISE program is connecting homeowners to contractors committed to doing the job right.

Would you consider hiring a builder who doesn’t believe in accurate measurements? “I’ve been building this way all my life”, they might say, pointing to a historic log cabin down the road, which has stood the test of time for over 100 years. Heck the Egyptians built the pyramids without modern tools and those are still standing too, right?

The fact is nobody would even consider building a home without the basic tools. Even do-it-yourself weekend warriors apply basic tools to the project – a tape measure, square and level are essential if you want doors and windows to open and close smoothly, floors that are flat and level, walls and rooms plumb and square.

Proper sizing for heating and air conditioning requires careful assessment of the building thermal enclosure.

What tools should your contractor be using to ensure the home is comfortable during every season of the year? What tool is required is you want low utility bills and healthy indoor air? Many building contractors aren’t familiar with these tools and most don’t use them because they still use the “Rule of Thumb” approach to home comfort, heating and air conditioning.

Heating and air conditioning contractors have traditionally based system design on a rule of thumb to size equipment based on home size. The primary strategy with rule of thumb is to aim high. Better to have too much heating or air conditioning than not enough. The down side with this strategy is wasted energy and less than optimal comfort during the cooling season because oversized air conditioning systems don’t remove humidity very well.

It wasn’t until the first energy crisis in the 1970s that researchers started investigating home energy use. They soon learned which characteristics had the biggest impact on home energy use and developed tools to measure whole-house air leakage and duct system leakage. They also developed computer software to analyze heat loss through the windows, walls, attic and floor.

The good news is, we now know how to analyze homes and calculate optimal size for residential heating and air conditioning systems using a computer software known as Manual J. The bad news is very few contractors are using Manual J to correctly size heating and cooling systems, even though Manual J calculations are now required by the latest Alabama residential building code.

An incorrectly sized heating and air conditioning system can cost more in wasted energy over the life of the equipment that the original purchase price. Why aren’t more contractors doing the job correctly? One reason is consumers don’t know how to tell which contractors are correctly sizing heating and cooling equipment. This circumstance leads many homeowners to make purchase decisions based on best price, not best value.

A properly sized and installed heating and cooling system requires a Manual J calculation and is required for all new homes in Alabama, but many builders are not in full compliance.

The problem with paying more still doesn’t guarantee contractor performance. If you ask a heating and air conditioning contractor to size equipment with Manual J, what assurance do you have the calculations were done correctly? AlabamaWISE contractors are trained and certified to correctly apply Manual J for heating and air conditioning system sizing. The program also performs random quality assurance to verify contractor performance so homeowners are confident in the work performed by participating contractors.

The benefit of correctly sized air conditioning systems are most noticeable during late spring and early fall when air conditioners are run to dehumidify indoor air in homes across the southeast. Indoor humidity can be effectively managed running the system to reduce air temperature by only one or two degrees. A correctly sized central air conditioner will operate long enough to remove humidity without making the room too cold. An oversized air conditioner lowers temperature too quickly and short cycles before lowering indoor humidity to a comfortable level.

Be sure to ask your contractor whether he’s using Manual J or another approved thermal load calculation when sizing HVAC systems. Otherwise, you may hire one that is all thumbs and you may be stuck with high utility bills and low satisfaction for years to come.