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Home Building Articles

Frequently Asked Questions

May 2016

AC Unit

What does SEER mean?

Seasonal Energy Efficient Ratio. It is the energy efficiency of the condensing unit. The higher the SEER rating, the more energy efficient the system will be.

I got bids from several A/C contractors and the prices are very different. How should I choose to be sure that I'm getting the best deal?

First, make sure that you are comparing apples to apples. Look at tonnages brands of equipment warranties. As your HVAC consultant, Parr Associates is available to answer any of questions.

There are so many potions to upgrade my HVAC system. Do I really need all of that?

If you are not sure about something, please ask. We can always provide you with more information. If you have special issues, such as allergies, frequently entertaining large crowds, an area of the house that will hardly ever be used, etc. . .we can help you find a solution to fit your needs.

What is a Manual J and why do I need one?

The manual J is a calculated heat load analysis used to determine proper tonnage needed for the home and CFMS needed per room. Square footage, windows, doors, insulation, porch overhangs, and several other factors go into the calculation of the Manual J. It is very important that your HVAC system is properly sized to function correctly. Over sizing and under sizing can lead to problems.

What information is needed to do a Manual J?

To do the Manual J as accurate as possible, we need a set of floor plans with dimensions and window sized, a plot plan or the address of the home to determine front facing ( for facing direction of windows) and type and R-value of insulation in walls and ceilings. We need to know if the house is on a slab or pier and beam. Where you are building is important because for example Galveston has different design conditions than Houston.

Are you sure this will be enough tonnage for my house? Shouldn't it be 500 sq. ft. per ton?

This is a common "rule of thumb". Not all houses are built the same. A smaller house with a lot of windows and poor insulation my actually be more tonnage than a larger house with less windows, porch coverings the windows and better insulation, This is why we never play guessing games. We always run a manual J to determine proper sizing. (According to a study done by CenterPoint Energy. 47% of HVAC systems are oversized.) Over sizing can lead to short cycling of the system causing humidity problems. Bigger is not always better.

Why do I need an HVAC Ductwork Design Layout?

The Ductwork Design Layout is a preliminary design of your HVAC system designed personally for you home. It can be useful when meeting with your framer to determine return air placement and where chases or fur downs need to be built to accommodate ductwork. It can be used for HVAC Contractors to bid equally on the size and number of supply and return air grilles. More city jurisdictions are starting to require the Manual J and HVAC layout for the building permit. We draw our designs in AutoCAD so changes can be made easily.