By Danny M. Orlando, Energy Star Regional Program Manager

Understanding the Problem

It’s been ten years since I first began to understand the relationship between energy leaks in my house and the size of my monthly energy bill. Energy leaks cost you money and come in many shapes and sizes. Go exploring in your house and you will find air leaks, energy leaks, duct leaks, and inefficiencies. All of these are directly related to how high your power bill is and many affect the comfort level in your house.

Like many of you, when I purchased my home (circa 1985) in 1991, I was only interested that the air conditioner and furnace were in working order. Energy leaks were not on my mind until the utility bills started growing and comfort issues became evident. During this time period, the cost of power per therm [1] or kilowatt-hour also started to rise. Not coincidentally, as the cost of power grew, so did my knowledge of energy efficiency.

An event that stands out in my mind and that made me realize I had more than a minor problem occurred one cold winter morning. The temperature approached zero degrees Fahrenheit, which for Atlanta is unusual, and the windows in my kitchen had a considerable amount of ice forming on the inside of the aluminum window frames. Even if you don’t know much about energy efficiency, this type of event should get your attention because ice on the inside of your home in the winter is a clear sign that cold air is moving into your house. There were other signs of inefficiencies too: The bedrooms farthest from the heating and air system (HVAC) were hot in the summer and cold in the winter; I would dust one day and have to dust again the next day; the garage was often more comfortable than some of the living areas, and some of my exposed garage and attic insulation was looking like age had turned it black.

As my knowledge grew, so did the realization that something needed to be done to correct these problems. I focused first on the cost and the associated payback for the investments. Some projects had a good payback in dollars and others did not. However, I learned, like those who choose leather seats for their cars, that payback isn’t everything. Comfort can many times be the main reason for initiating an energy efficiency project. Another compelling reason can be your health or that of your family. The air in your home can be more polluted than the air outside even in metropolitan cities. EPA states that we spend approximately 90 percent of our time indoors.[2] In general, indoor air is four to five times more polluted than outdoor air.[3] These are all good reasons for getting a better understanding of building science or asking for help to improve your indoor environment.

Where to Start

The first and most important information I received was from a blower-door test and discussion offered by a local HVAC contractor in 1996. A blower-door test determines how leaky your home is and identifies where leaks are occurring in your house. To understand this test, imagine blowing up a beach ball that has many holes in it.[4] The amount of air it takes to keep the ball inflated is measured as CFM50 (cubic feet per minute at 50 Pascal’s [5] of pressure).[6] The higher CFM50 is, the leakier the house. The results from this test set me on my path to energy efficiency. This analytical test of your house is the most important step most homeowners can take before deciding on what energy upgrades to pursue.[7] If you begin energy efficiency projects without this information, you can make mistakes, some of which can be costly. In some cases, you can even make the situation worse.

So, what did I learn during this initial assessment? I learned that my house was very leaky (3733 CFM50). The amount of leakage was like a hole in the side of my house, three by one foot, open all the time. I felt like I lived in Pandora’s Box. Some of the problems identified could be fixed without hiring a contractor (DIY) and some would require professional assistance (C). The problem areas included:

  • the main bathroom had a very deep skylight. The shaft leading to the roof was at least twelve-feet in length. The skylight was sucking costly conditioned air out of the house into the attic. (DIY)
  • the furnace flue shaft leading from the basement to the attic was another route for conditioned air to escape and needed to be sealed. (DIY and/or C)
  • convective loops, heat transfer caused by air movement, were a problem throughout the house. When hot attic air travels into interior walls it causes energy losses in your house. (DIY)
  • unsealed penetrations were everywhere – under sinks and bathtubs, along the walls, and around the ceiling light fixtures. (DIY)
  • the wall separating the garage from the house also had some electrical penetrations. (DIY)
  • exterior doors were not sealing properly and the attic hatch was not insulated or sealed. (C)
  • the main floor of the home overhangs the basement (the upstairs has a larger area than the downstairs). This difference in area causes and overhang or cantilever which can create cavities that are conditioned space on one side, but are exposed to the elements on the other side. These are trouble and you lose energy in many ways. They need to be air sealed and insulated. (DIY and/or C) we suspected that the ducts were very leaky and needed to be sealed. (DIY)
  • let’s not forget the ice on the window frames in the winter! (DIY and/or C)

These were just a few of the problems found and over the ensuing years, more were discovered. Many of the problems were inexpensive to fix. Indeed one of the things I learned through my leak hunting activities is that air leakage is one area where doing it yourself can make sense, but some work may require professional help.

Leak Hunting

Be warned, leak hunting can be addictive. Once you start it’s hard to stop. Every leak is like finding dollar bills lying on the floor. Twenty-five to forty percent of the energy we pay for is typically wasted because of air leakage in a typical home. [8] Leaky homes are a problem because the leaks can allow humidity, dust and allergens, outdoor air pollution, evaporative emissions from cars and lawn equipment in attached garages, and bugs. All leaky areas can lead to comfort issues and sometimes to health problems. Reduced air infiltration combined with proper ventilation cannot only reduce your energy bill, but it can also improve the quality of the air inside your house. Outdoor air that leaks into your house can make it difficult to maintain comfort and can lead to high energy bills. Remember when I started this process in 1996; my house had an air flow of 3733 CFM50. The most current blower door test results yielded a 1970 CFM50. This infiltration measurement is a 47 percent improvement since the original test. If the house were any tighter, active ventilation to introduce outside air would need to be installed. “Building tightness limits, for single family homes without whole-house ventilation system, vary between 1000 to 3000 CFM50 – depending on height, occupancy, wind and shielding.” [9] Remember from above that a tight house is more comfortable and comfort has a lot to do with stable humidity. Consider a rainy and foggy summer Georgia morning when moisture is sp prevalent it is literally dripping off the outside of the windows. When this occurs, the humidity in my house is about 47 percent. The flip side is the 20 percent humidity winter day when it is thirty degrees Fahrenheit outside. Once again the humidity indoors will be about 42 percent. Humidity is an important indicator of air leakage and of how well your home is performing. You should consider purchasing an inexpensive hygrometer to keep track of the humidity in your home.

Another key area for wasted energy is from your air duct system, particularly those located in crawl spaces and in attics. Ducts typically leak 7-12 percent or more of the conditioned air delivered into them.[10] However, it is not uncommon to find completely disconnected ducts that can be wasting most of the conditioned air sent through them. Conditioned air costs you money and you want it to go where it was intended. Sealing duct leakage and air leakage around the main air handler where pressures are highest can yield great benefits. The leakage test for ductwork is called a ‘duct-blaster’ and is similar to the blower-door test except it is designed just for the duct system. Ducts should be sealed with mastic. Mastic is a fiber-reinforced putty-like compound. You can buy mastic at local home improvement stores. Mastic is a wonderful material for sealing air leaks. Investigate your ducts (peel the insulation away from the duct area you are working on) where they bend and where they connect to the main trunk lines. Don’t use duct tape or any type of tape for air sealing. Tapes do not permanently seal ductwork any better than tape would stop a leak in a water hose.

I sealed the ducts in my house with mastic in 1997-98 and was fortunate that they were easily accessible. The duct blaster test indicated only 4.8 percent leakage and most of my ducts are in the conditioned envelope of the house. Duct sealing is particularly critical when they are located in unconditioned areas such as the attic, garage, or crawlspace. If they are not accessible, your only real choice is to have a contractor use an adhesive sealer that can be blown into the ductwork.[11]

If you want to be a leak hunter, winter is a great time. On a cold and windy winter day, slowly check for leaks all throughout your house. The wind pressure on your house will cause the pressure differences needed to find many leaky areas and the cold air will make them easy to feel. Another way to spot leaks in your attic is to turn on the lights in your house at night and go take a peek in the attic. Many of the leaks will be lit up. Once you find some leaks, it’s time to grab the can of foam, rigid foam board, or mastic and jump into action.

Getting to Work

In 1996, my eyes were opened and I began to fix the problems that were identified. Here is a list of improvements made since 1996; however, they could have been implemented in a more systematic order that could have saved additional energy. The reason I mention the order of installation is that you optimally would want to reduce the lighting load first (install compact fluorescent lamps as a replacement for incandescent and halogen lamps and use dimmers and occupancy controls to turn off lights when not being used), tune up the existing system (programmable thermostats and air sealing), reduce the exterior/interior heat loads (i.e. spectrally selective windows, window tinting, lighting controls, planting trees, Energy Star appliances, and so on), seal the duct work and examine insulation levels, and finally consider replacing the heating and cooling system. One benefit of doing the upgrades in this order is that the heating and cooling system can be sized as small as possible, saving additional money. But, life’s situations do not always allow you to proceed in the perfect order.


Pay Now or Pay Later

Since I began this journey ten years ago, my energy usage has decreased 32 percent. At ten cents per kilowatt-hour that is an annual savings of about $600.00 dollars. With rapidly increasing energy costs, the decision to install the smallest and most efficient gas furnace available is turning out to be a very good decision. One contractor told me that a 96.6 percent efficient furnace would never pay for itself. He was wrong. Most of the upgrades I installed paid for themselves within six years. The window retrofits were the payback exception. As a general rule, retrofitting windows in an existing home in the South does not make economic sense at least in the short to medium term. In my case however, the payback from the new more efficient windows is as much an issue of comfort as it is cost savings. In new construction, upgrading the windows to the best available technology that makes sense in your climate will provide an excellent payback. Most new residential codes in the U.S. now require low-emissivity spectrally-selective windows in new construction.[17]

All the performance data on the home sounds great, but I was curious and daring enough to pay for an energy rating known as the Home Energy Rating System (HERS) to see just how efficient or how successful I had been. [18] If the house could perform as required by HERS, I would have achieved what few have done – qualified an existing home as an ENERGY STAR.[19] Late in 2005, the results were in and the home qualified as ENERGY STAR! Amazingly, ten years of leak hunting had finally scored the trophy.

Final Words

In today and tomorrow’s energy market, you can’t afford not to be energy efficient. Why not have a home that is extremely comfortable, potentially more valuable as an asset, [20] and incur energy costs far lower than in the average home month after month? As Americans, our energy appetite continues to grow to feed our endless array of electronic devices and larger homes. Using energy efficiently and buying renewable power, where it is available, is the path that will lead all of us to a sustainable [21] and affordable future.