It used to be that just keeping cool was the goal of air conditioning. This domestic device found its initial development as a means to allow year-round manufacturing in the US while maintaining worker productivity. The first commercial air conditioner was built by Willis Carrier (see right) to cool and dehumidify a printing plant in the early 1900s. Soon other businesses were installing these units as a way to draw customers and improve product quality.
Today’s energy costs and concerns about greenhouse gases have dramatically affected the development of domestic air conditioning systems that not only cool and remove humidity from the air but filter the air to provide a healthier indoor air quality. It is important to understand how your HVAC contractor skills may influence how efficient and effective your air conditioning system is.
We spoke with Michael Strong, president of GreenHaus Builders, Houston, Texas, about what to look for when talking to prospective HVAC contractors. He not only designs energy efficient systems for homes in the Houston area, but also conducts workshops for builders’ groups nationwide about how to design efficient HVAC systems. Strong suggested that you interview several HVAC contractors and pose the specific questions below. If the contractor responds with lukewarm enthusiasm or replies that it is too difficult or complicated to explain, you may want to continue to look for a contractor who has enthusiasm and a passion for designing an effective, efficient system. Here are Strong’s five HVAC contractor questions:
1. Will you review and explain the Manual J report with me? The Manual J report is prepared by the HVAC contractor to determine the “residential load,” or the sizing and design of the air conditioning system to be installed in your home. The Manual J was once calculated manually but is now available as a software program. The Manual J analyzes the home and calculates the requirements for air conditioning (in BTUs per hour) based on the insulation, the number and type of windows and the cubic volume of the interior of the home to be conditioned. Different factors, such as ceiling height, increased insulation and the home’s solar orientation can affect the design and the Manual J Report.
“The biggest problem with the Manual J report,” Strong said, “is that no one ever reads them.” Some contractors will run the report to satisfy local code requirements and once signed off, they will build the system the way they always have. By reviewing the Manual J with the contractor, you can ensure that the details that you know about your new home, such as solar orientation, ceiling height, insulation and fenestration, are included correctly in the design plan. Errors in these early stages can result in unnecessary and costly adjustments and poor system design.
2. Will your Manual D report include a duct blaster test? The Manual D report is used to specify the sizing and placement of ductwork for the HVAC system. It tells the contractor the allowable dimensions for metal and flexible duct work, where a bend or turn is permissible, the sizing of vents and other duct related information. The ductwork is the means for delivering and exhausting the conditioned air from the home’s living areas. An efficient system must provide the appropriate pressurization and return duct work to move air efficiently around the house. The duct blaster test is administered after the ductwork is installed. Click here for additional Energy Star information for new homes. Many duct systems from older installations leak as much as 15-20% resulting in lost energy resources. Properly sealed ductwork can reduce energy costs dramatically and increase comfort and air quality. The Energy Star website states that an airtight duct system can save as much as 20% in heating and cooling costs annually.
3. What SEER rating is best for my needs? The SEER rating is a Seasonal Energy Efficiency Rating and is the air conditioning equivalent to the furnace rating system “annual fuel utilization efficiency” or AFUE. The higher the SEER number is, the more efficient the system is. Since 2009, the minimum SEER rating for homes is 14.5 for a split system or 14 for a package system. Most homes use a split air conditioning system consisting of three components:
• outdoor metal cabinet that contains the condenser and compressor
• indoor cabinet that contains the evaporator coil
• air handler, usually incorporated into furnace or heat pump, that sends the cool air through the duct system
A packaged central air conditioner has the evaporator coil, condenser, and compressor all located in one cabinet, which usually is placed on a roof or on a concrete slab next to the house’s foundation. These packaged units are more often used in commercial settings.
Currently there is a Federal tax credit available for installing a high-efficiency air conditioning system. Efficiencies can range as high as 22 for some systems, but their initial costs can rise dramatically with higher efficiencies. Your HVAC contractor should be able to review the options so you can make an informed decision based on the payback and budget.
4. What kind of air filtration and purification should I have? With one in 20 Americans suffering from asthma or other lung-related conditions, indoor air quality becomes an important consideration for many more people. Today, with decreasing outdoor air quality and tightly constructed homes, airflow and filtration are increasingly important for health and comfort. Your HVAC contractor also should advise you on mechanical ventilation that is essential when your home is tightly insulated.
Air conditioning systems typically come with particulate matter filters, originally designed to keep the mechanical components functioning properly. Some manufacturers now offer separate air cleaner components to be installed with the heating and cooling system. Air cleaners employ “high efficiency particulate air” or HEPA filters, which are designed to capture minute particulates from the circulating air that cause allergic reactions. Some of these particulates might include pet dander, pollen, dust, dust mites or mold. Filters have their own rating system. According to Strong, any air conditioning filter must have a minimum 8 MERV rating, with ratings as high as 13 MERV for a “superior” domestic filtration system. Operating rooms and computer manufacturing “clean rooms” require MERV ratings of 16 to 20 MERV. Air purifiers can employ electrostatic and/or ultraviolet light (UV) to trap bacteria and other “bugs” as well as volatile organic compounds (VOCs).
5. Will you conduct a post-construction inspection and review of our system? A post-construction inspection is standard procedure for commercial systems. Home owners can maximize their efficiency and comfort by having the HVAC contractor test the functioning system after a period of 6-12 months. At that time, your HVAC contractor should return to review how well pressures, comfort and effectiveness of your system in cooling your home. Make note of rooms that seem too cool for occupants and those that might need more airflow. The contractor can use various measuring equipment to adjust the vents for proper pressurization in each area of the home.
Strong advises to keep looking if the response to these questions is a shrug, or advice that “You don’t need that…” To get a properly designed and executed system, it’s important to find the contractor who is eager to explain and design a system that not only keeps you comfortable and healthy but is energy wise as well. “Find a contractor who is passionate about indoor air quality,” Strong said, “and avoid the ones who are still using the same techniques they learned at the tailgate of a pickup truck.”