Many homeowners know very little about their heating and cooling equipment-until something goes wrong. If you're lucky, you can fix it yourself. But it's just as likely that you'll be looking at new equipment to solve the problem. How can you get the best service for your needs and not spend unnecessarily? Blue Egg spoke to Max Sherman, a senior scientist at the Lawrence Berkeley National Laboratory, who filled us in on what you should know when talking to an HVAC contractor.

• Every HVAC contractor sets prices according what he thinks he can get. Knowing this, shop around and take bids. If you're about to spend thousands of dollars, it's worth your while to consider at least three bids. Don't be afraid of doing this - Sherman says contractors expect it.
• Some HVAC contractors deal with only one or two manufacturers' equipment. Since each manufacturer approaches its market differently, you should do your research. Consider what is important to you. Is it more flexibility, higher performance from your equipment, or lower cost? Shop around for new brands, but also evaluate what you're currently using. If you've been pleased with its performance, you might just want a newer version of what you already have.
• Check with your town's housing bureau to see if they offer a list of local contractors in your area with key HVAC certification. Ones to look for include: the Air Conditioner Contractors Association (ACCA), or the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE).
• If your neighbors have had HVAC work done on their homes, ask them how they liked their contractor and the job he or she did.
• An HVAC contractor should have a calculator tool that will show you how long it will take for you to recoup the money you spend on more efficient systems. Consider where your money is best spent: If you can save $500 on equipment, that cash could be put into insulation, which will further increase energy efficiency and lower your operating costs.

Cooling

• Whether you're facing a heating or cooling issue, it's a fact of HVAC life - ducts leak. If your AC isn't working properly, this is the first thing you'll want to check. Often, leaky ducts can be fixed as a DIY project. Even if you have a professional seal the ducts, you'll be saving money when compared with buying new equipment. Sherman says that having a duct inspection is important. If you have an older house, for instance, your home might be leaking 20 to 40 percent of the cool air being pumped into it.
• Your location also factors into the equation: According to Sherman, if you've got a conditioned basement in the Midwest, and your ducts are inside the conditioned space, leakage won't be such a big concern. But if you live in the Sunbelt, and your ducts are in an unconditioned attic, it's a big deal, because you're losing the cool air to the outside.
• If your AC isn't cooling you down as quickly as you'd like, you might want to look at bulking up your insulation. Before you plunk down a hefty chunk of change for a new cooling system, consider adding insulation to your home to maximize the efficiency of your current AC. Or, if you're buying a new AC system, you might be able to stick with the same size as the one you have now by adding insulation. Sherman says, unfortunately, these procedures are often not integrated: "Insulation guys want to sell you more insulation, HVAC guys want to sell you a bigger system. HVAC contractors want to sell you a box, a new heating or cooling system to replace the one you have now. They don't have the whole-house mindset, because it wouldn't be a very good business model for them." You'll have to talk to both an HVAC and insulation professional to weigh costs and benefits. If you find a pro who is familiar with green building practices, you're more likely to benefit from a whole-house approach.
• While the equipment HVAC contractors sell is the same all over the country, the needs of the customers are not identical, says Sherman. In the southeast, moisture is a big problem, so you'd want to look at humidity control features. In the southwest, you have big temperature swings, so you'll want to know how quickly it can cool at peak conditions. An AC system that works well in Atlanta is probably not appropriate for a home in Phoenix. Sherman says HVAC contractors should be familiar with regional conditions, because the equipment brochures won't address these local issues. If the contractor doesn't know your special weather requirements, you'd better be familiar with the topic. Or better yet, find someone who knows the area well.
• The current major standard for cooling systems is the Seasonal Energy Efficiency Ratio (SEER). Years ago, it was the Energy Efficiency Ratio (EER), which indicates how well a system will work at peak conditions. Companies will advertise a machine's SEER, but the EER should still be included in brochure information. ASHRAE says SEER 13 is the minimum efficiency you should consider. Sherman gives an example of knowing the importance of both numbers. "I was looking at two different AC models. One had a SEER 14, and one had a SEER 13. The EER was the same for both machines. The SEER 14 was $700 more expensive. I live in California, where seasonal differences aren't extreme, so EER is what I really care about. I saved that $700 and put it toward insulation." Knowing what is important for your region will maximize the way your dollars are spent.
• All HVAC systems will have some sort of filter on them. They prevent particles from entering the air you breathe, but their most important function is to keep the equipment clean, since dust and moisture can build up and damage parts. Sherman says always go with paper filters (he refers to the fuzzy filters as "boulder catchers" and says they don't do much). Filter effectiveness is measured in MERVE. Sherman recommends at least a MERVE 6, which, he says, is the low end of the pleated paper filters, which go way up to very effective HEPA filters, and he says a range of MERVE 6 to 10 is a good one. MERVE 6 is the minimum because, Sherman says, the cooling coil is essentially a MERVE 5 filter. "It makes a lot more sense for the dirt to get caught in the MERVE 6 paper filter that you can throw away, rather than the MERVE 5 permanent filter that you just spent a ton of money on." Know that paper filters offer more resistance to air flow, so that has to be taken into consideration.
• Of course, keeping the filters clean or replacing them according to manufacturers' directions should be a routine part of your DIY maintenance. Sherman suggests that you request a 4-inch slot for the filter, instead of the usual 1-inch-wide filter slot. The advantage of the 4-inch is that it has to be changed only once or twice a year instead of every month. Sherman says, "I recommend that people order replacements on the Internet. You can order them to automatically be sent to your home when it's time to replace your filter, which is a good reminder that it's time to change."
• If you're in the southwest, you should be familiar with a residential economizer. In drier climates, the temperature drops at night, and rather than running your AC, you can run cool outdoor air inside, if it's cooler outside than inside. This is a function you can add to your AC system. An older version of this is a whole-house fan, which is also effective. The key difference? A whole-house fan requires that someone manually turn it on and off while a residential economizer automatically engages when the outdoor temperature drops.

Heating

• The same filter and duct issues that apply to your cooling system should be considered in your heating system.
• An old furnace that needs to be replaced is probably running at 60 percent efficiency, says Sherman. With new furnaces, 80 percent is standard, and there are some models with 95 percent efficiency. If you are replacing a furnace, be aware that you'll have many more options this time around: one- or two-speed furnaces, for instance. The two-speed is going to cost more because it requires a different fan, but it actually tends to be more efficient than a simple or one-speed because it runs at a steady rate, instead of turning on and off.
• Know that an ultra-high efficient furnace, which can run at 90 percent and above efficiency, will be very expensive. Sherman says this type of furnace might not be worth it if you compare the 10 to 15 percent in fuel savings against the high installation costs. You might be better off using that money to increase the insulation or to install new storm windows in your home. "There are no general rules because the costs, especially in a retrofit, can be so variable." Again, your contractor should be able to calculate your cost savings and payback time estimates with each furnace type.

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