Q&A: SEER rating and energy efficiency tips.
A: SEER stands for Seasonal Energy Efficiency Ratio. SEER is determined in a laboratory setting to rate the efficiency of the equipment only. It is also important to remember that SEER is only speaking to the efficiency of the cooling capacity of the HVAC equipment. The heating efficiency is taken into account within the HSPF (heating season performance factor) rating The main point I'd like for you to understand is that both of these efficiency related numbers refer only to the piece of mechanical equipment. There are other components of an HVAC system that also affect the efficiency of the system. Think of it this way: You could buy a Toyota Prius that is rated to get 55mpg, but if you load it down with 5 people, poke a few holes in the gas tank, and never change the fuel filter, you'll be fortunate to get 25mpg.
The SEER or HSPF ratings on HVAC equipment represent the absolute best efficiency that you could ever hope to achieve, assuming the other components are all designed and installed to work in conjunction with this piece of equipment.
Since I don't have room to discuss all of the components in detail, I'll focus on two that typically decrease the efficiency of the system the most: ductwork and charge.
The first thing to understand about an HVAC system is that every unit is designed to have a different amount of airflow across the coils (through the unit itself). The standard system requires approximately 400cfm (cubic feet per minute) per ton to flow across the coils. So, if you have a two-ton system, the manufacturer expects it to be installed to move around 800cfm across the coil. This means that the return should suck 800cfm from your house and the supplies should provide 800cfm back to your house. Most systems have ductwork that is undersized, therefore reducing the amount of air that the fan can pull across the coils. If the system mentioned above is only able to pull 600cfm from the house (due to undersized ductwork), then it is not performing at its rated efficiency. Low air-flow not only decreases the efficiency of your system, but also creates comfort problems within the home.
Duct leakage also results in a large decrease in your system's overall efficiency. What would happen to the system's efficiency if it was pulling thirty percent of its return air from the attic, instead of the riving space? Do you think it would cause the efficiency to go down? You bet! What if your supply ductwork was losing 25 percent of its air into the attic or crawlspace? What would this do to the efficiency of your system? This equates to having a hole in the gas tank of your Toyota Prius--not a good idea. Duct leakage also decreases IAQ considerably by pulling in air from unhealthy places.
The last element is the "charge" of the heat pump. The charge relates to the amount of refrigerant in the system. This fluid is the vehicle for transporting BTU's of heat from inside to outside, or vise-versa. If you have too much or too little. the efficiency of your system decreases (not to mention its lifespan). If you decide to replace your ductwork, because you want to increase the amount of airflow across the coils (raises efficiency), and you also seal all of the holes in the ductwork (also raises efficiency), then you must have your unit's "charge" adjusted to work in conjunction with the increased air flow across the coils. All of these elements are tied together. Ignore one of them and your system's efficiency WILL go down.
Studies show that less than two percent of residential HVAC systems have been properly air-balanced. The average residential HVAC system performs at 50 to 65 percent of its rated efficiency, due to the imbalance of airflow, excessive duct leakage, lack of insulation, and improper charge. This means that your brand new 19 SEER unit that is installed onto your old ductwork will most likely be performing at a SEER rating of 9.5 to 12.5!
For the same investment as a new 19 SEER unit, you could probably purchase a 14 SEER unit AND have your ductwork balanced/retrofitted, resulting in a more comfortable (proper air flow) and healthier (no duct leakage) living environment.
Search for a contractor in your area that understands airbalancing, preferably with a certification (National Comfort Institute is one of the most trusted in the industry). They will be able to look at all of these elements with reference to each other and provide you with an HVAC system that actually performs efficiently as a system.
Isaac Savage is the president of Home Energy Partners, Inc., Asheville, NC. For more information, call 877-511-0117.
Q: "What are the most cost effective things I can do to make my existing house more energy efficient?"
A: Many of us live in older homes that are not very energy efficient. Older wood windows, while beautiful, are extremely energy inefficient by today's standards. And general construction practices until the 1970's or so were also not built to maximize energy efficiency. Trying to retrofit an old house with modern windows and modern insulation is expensive. So here are some things you can do that are pretty inexpensive, most of which you can do yourself. All of these have to do with either your heating, ventilating, or A/C systems (HVAC) or your water systems.
HVAC: If you have forced hot air or A/C, seal all the ductwork in your basement, attic and wherever else you can get at it, with water based air duct sealant, which is a gooey paint-on gray sealant. If there is old duct tape. remove it, scrape off as much residue with a wire brush as you can, and brush on the new mastic sealant at all duct joints, sealing up all holes.
Lift up all your heating/A/C grilles from the living side of the space, whether it's wall, floor, or ceiling, or supply/return. Check to see if any of your conditioned air could be leaking into the joist spaces, basement, or attic. If so, use mastic sealant paint and/or foil duct tape to seal those connections between the duct and the surrounding area it is attached to.
Wrap all accessible duct work with foil bubble wrap after applying the proper sealants, using foil duct tape, not the old fashioned gray kind.
Install a whole house fan at the highest common space of your home. These are relatively inexpensive to buy and install: one-tenth the cost of air conditioning. If used properly, they can exhaust the warm air build-up during the day in your home with cool fresh evening air. You may need to install an attic exhaust fan as well it you have minimal ventilation in your attic. In the morning, you should close your windows to keep in as much of the cool air as possible for as long as possible. This concept works for climates with hot humid days but cool and dryer nights.
In addition to, or instead of, a whole house fan, you could install an attic exhaust fan to exhaust heat build-up in your attic. These are installed on your roof. Again, the provision of a fresh air source from the attic eave vents or gable vents is important, or else you could be sucking out conditioned air from inside the house.
Water Issues: When it's the cold water dripping, you are using the water authorities' resources, but when you have paid to heat water that is wasted, it's a double whammy. Both are costing you money on your water/sewer bills.
For efficiency, fix leaky faucets and toilets. Also, purchase a water-saver shower head and install a water-saver aerating faucet head at all your bathroom and kitchen faucets. Then install a new water-saver toilet to replace any toilet installed prior to 1992 when water saving toilets became a requirement for new construction.
Insulation issues for both HVAC and water lines: Insulate your attic with blown insulation to a depth of twelve inches or so. You can rent a machine and buy the materials to do it yourself or hire someone to do it for you. Any type is fine, although recycled/recyclable cellulose is best.
Lay a radiant barrier on top of your new blown insulation. (Google "radiant barrier" for many options.) This is a reinforced perforated mylar/foil type product. This keeps winter heat in and summer heat out. It also provides an air-transfer barrier between the insulation and the unconditioned area of your attic. This barrier is important to really maximize the insulation you have installed. Without it, the insulation cannot do as good a job as it otherwise could because the cold winter air or hot summer air is penetrating the attic insulation and eventually making its way through your ceiling. The radiant barrier reflects the heat before it is transferred to the side where you don't want it.
Insulate between the basement and the living area above, and beside it in the case of a semi-finished basement, with the thickest batt insulation that will fit in the joist or stud cavity. Use kraft-faced batt insulation with the facing towards the warm side of the cavity. Make sure to cover all areas, and cut and fit carefully around pipes, wires, and ducts. Don't mash it into place-it needs to stay puffy to do its job.
Spray expanding foam insulation at all penetrations for pipes, ducts and wires between the basement and the next floor and/or the attic and the floor below. This comes in a spray can like spray paint. Be aware it will expand, so allow it the time and the room to do so.
Wrap your water heater with a water heater insulator available from most do-it-yourself home centers.
Wrap any of your hot water pipes that you can get to with black foam plastic pipe insulation and tape them up tight. Same for any refrigerant lines from your A/C outside unit to the air handler. The thicker the better, and take note of the size of the pipes you are insulating to get the right size.
Spray expanding foam insulation between the wood frame sill plate and the foundation, especially wherever you feel a draft or you can see daylight.
These are the cheapest, most easily accomplished and effective solutions for making an older house more energy efficient with minimal cost to you. We hope this helps you get on your way!
Camille Victour, AIA is principal of Camille Victour Architect, PLLC and owner of Vesta Design+Build, LLC. She has been a student, advocate, and practitioner for sustainable design for over 25 years. Visit her at www.camillevictourarchitect.com or www.vesta-designbuild.com.