#AskEnergySaver: Home Cooling

on July 28, 2014 at 5:00 PM

Home cooling accounts for 6 percent of the average household’s energy use. To help you save money by saving energy, our experts are answering your home cooling questions. | Photo courtesy of ©iStockphoto/JaniceRichard


To help you save money by saving energy, DOE launched #AskEnergySaver — an online series that gives you access to some of the Energy Department’s home energy efficiency experts. During 2014, experts from the Department and our National Labs will be answering your energy-saving questions and sharing their advice on ways to improve your home’s comfort.

Summer’s sultry weather can take a toll on more than just your hair. For many households that rely on air conditioning to keep cool, summer’s heat and humidity can lead to higher energy bills. That’s why this month, we asked you to share your home cooling questions.

To answer them, we turned to Dr. Max Sherman, a senior scientist at the Energy Department’s Lawrence Berkeley National Lab. With more than 30 years of experience in building efficiency, Sherman’s research focuses on the connection between heating and cooling equipment, air leakage and indoor air quality.

What is the key to lowering cooling costs? Does a fan use more energy in certain circumstances?
— from PurpleLivesOn via email

Max Sherman: A fan consumes very little energy compared to actual air conditioning. If running a fan provides the comfort you need, then it is going to be more economical.

If you need to use your cooling system, you can cut costs in several ways:

  • Lower the cooling load: Reducing the amount of heat that gets in your house will keep your air conditioner from working as hard, and that means lower energy bills for you. A few ways to lower your home’s cooling load include shading your windows and roof, incorporating high-albedo (or white) surfaces, such as a cool roof, and increasing your home’s insulation. In humid climates, it is important to decrease excess air leakage. Also keep in mind that internal heat sources, such as your oven, can add to your cooling load.
  • Improve the efficiency of your equipment: At the simplest, improving the efficiency means keeping equipment in tune — ensuring your system has proper airflow, is fully charged and has clean air filters. It also means reducing any duct leakage and insulating ducts if possible. For longer-term investments, consider replacing your air conditioner. New high efficiency cooling equipment uses substantially less energy to provide the same cooling services as old equipment.
  • Don’t cool more than you need: Why waste money cooling spaces you aren’t using? Instead, raise your thermostat when you are at work or shut off your air conditioner when on vacation. If you aren’t using some rooms, close the registers. You can also use ventilative cooling, such as whole-house cooling fans, economizers (a technology that pulls in outside air when it is cooler than the air in the house) and evaporative cooling, when conditions permit.

For more on air conditioners, explore ASHRAE’s top ten things about air conditioning.

What are other options for cooling your house without using air conditioning?
— from Demola Livingthedreamplan Eff on Facebook

MS: There are a few techniques that are useful for staying cool without turning on your air conditioner:

  • When the outside conditions are cooler than inside, open your house up to mechanical ventilation — such as whole-house fans — or natural ventilation. This will remove the heat generated inside your house.
  • Keep your house cool by reducing the sources of heat. These can either be internal, such as the appliances in your kitchen, or external, such as sunlight.
  • Air motion of any kind makes the body feel cooler — at least until the air gets above body temperature. A ceiling or portable fan can make you feel cooler by creating a wind chill.
  • If there are big day-night temperature differences, ventilate by opening windows at night to pre-cool the house and minimize temperature rise during the day.

We have a forced air system that is used for cooling and heating. Is it less costly to close the door of a room that is used very little? Or is it generally more beneficial to leave that door open so the air is circulated to the rest of the house?
— from Darneson12 via email

MS: If there is a room in your house that you don’t use, you’ll save costs by isolating it from the rest of the house. To do so, you could shut the door and also shut the supply register to that room. But don’t do this to too many rooms at once because it could cause problems for your central system. If too many registers are blocked off, the pressure in the duct system will build up and reduce the airflow in the system. Not only can this result in new duct leakage and lower efficiency, it could also cause the system’s cooling coils to freeze up.

For more ways to save energy at home, check out Energy Saver.