Heating, Ventilation, and Air Conditioning
Environmental Energy Technologies Divn., Lawrence Berkeley National Laboratory

• Air-to-air heat pumps are basically air conditioners with the capability of running backwards in the wintertime. During the summer, air conditioners remove heat from your house, and shunt it outside. Air source heat pumps have a switching system that allows them to operate in reverse in the winter, removing heat from the outside air, bringing it into your house. Since air source heat pumps are not actually creating heat, but moving it from one place to another, they are less expensive to operate than electric resistance heaters, and depending on the costs of both natural gas and electricity, possibly gas furnaces as well.

• Gas is sufficiently cheaper than electricity that an air source heat pump is generally more expensive to operate than gas furnaces. For those who are unable to receive gas services, the air source heat pump is probably the best bet.

• One drawback to air source heat pumps is that they get less efficient when the outside air temperature gets colder. It is harder to extract the residual heat from colder air. Electric resistance furnaces become more cost effective when the average winter air temperature is below 30°F.

• Another option is ground- or water-source heat pumps. These units extract heat from the ground by using an underground loop, or from water, through an open or closed loop. Since the average ground temperature hovers around 50°F year round for most of the United States, this is a very good source for heat in the winter, and cooling in the summer. Although putting in a ground loop is expensive and repairs can be costly, ground-source heat pumps are good options for some people.

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• What you're experiencing is a major problem with large appliances that require contractors for installation. Scary as this may seem, there is no price list available in this type of situation. Prices can vary widely by contractor or area. It is even difficult to get wholesale listings from manufacturers, since they may charge different amounts to different contractors. If a local home repair store carries the brand of furnace you are interested, you can get a general idea of the unit cost. Unfortunately this does not cover labor and installation costs.

• The best way to figure out if a contractor presents a reasonable bid is to shop around. Before you sign a contract, get several bids from different contractors. Five to seven would be ideal. For each bid, get all of the details in writing, and make sure the bids are comparable. Be careful if one of the bids is dramatically lower than all of the others. Make sure that the same work is actually being bid on. In addition, check with the local Better Business Bureau and find out if any of the contractors have complaints against them, and get details about complaints if you can.

• There are a lot of good contractors who do quality work for reasonable prices. However there are also a lot of contractors doing shoddy work, and contractors who overcharge consumers because they can.

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• Yes, digital thermostats will normally reduce the energy used for air conditioning or heating by quite a bit. Programmable thermostats, not always digital, save money by turning the air conditioner to a higher setting (or heater to a lower setting) when no one is present in the house, or in the evenings when it is cooler. You can achieve the same savings without the programmable thermostat, but you would have to remember to change your thermostat every day when you leave the house, and turn it off every night when you go to bed. In addition, if you are using the thermostat to regulate your heater, you would wake to a cold house. The programmable thermostat does all of the remembering for you once it is set.

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• The duct systems in most houses leak. Leaks can be as small as pinholes or tiny cracks and as large as completely disconnected ducts. However, any leak is wasteful, since it allows conditioned air to escape into your attic or crawlspace. Duct sealing is a process of stopping leaks by pressurizing the ducts with a tracer substance, such as smoke, and then physically locating and patching leaks. A new aerosol method is under development at Lawrence Berkeley National Laboratory, which would seal ducts without the need for a laborer to manually reach and plug every leak.

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• If you're building a new house from scratch, this can be a real concern. Your architect should be able to design adequate ventilation as part of the plan. But if you have an older house, there are usually so many ways for air to get into your house that tightening up will save you energy but still leave an adequate supply of fresh air.

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• Mechanical ventilation is typically accomplished with a small fan located on a dormer vent. These fans are usually hardwired into a house's electrical system and are controlled by a thermostat. They usually draw electricity in the range of 2 to 70 kWh per year, depending on local weather conditions and your attic temperatures. The cost of this energy of course depends on the local price of electricity.

• Approximately one square foot of ventilation is recommended for every 150 square feet of floor area. You would have to check the specifications of the particular fan you are considering to determine the equivalence to regular vents.

• One alternative to mechanical venting is a combination of ridge vents and eave or soffit vents (see diagram below). Ridge vents run along the ridge of your roof, and eave and soffit vents are located at the base of the roof. With this combination, the natural convection of the hot air in your attic powers the venting. In addition, because of the locations of the inlet and outlet vents, virtually the entire attic space is vented, reducing the likelihood of pockets of hot air.

• Mechanical venting, can provide adequate venting for your house, but is dependent on electricity. Other forms of venting, such as the ridge/soffit combination mentioned above, provide superior venting, but requires modification of your roof to install. If you were already planning on installing a new roof, you should seriously think about a ridge/soffit combination.

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We would like to thank the Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory for the above information. Please visit their website at www.hes.lbl.gov