Green Wiki

Energy Efficient House

There are many ways to make your house more energy efficient and save money in the process.

They include:

  • Upgrading Attic Insulation
  • Energy Efficient Window Film
  • Fixing or Replacing Leaky Air Ducts
  • Fixing Air or Thermal Leaks
  • Energy Efficient Lighting
  • Energy Efficient Furnace or Air Conditioning

This article will explore the options to address energy efficiencies in these areas.

Attic Insulation

Reducing house heat or cooling loss through the attic can we one of the best things to focus on to make your house more energy efficient -- especially if it is an older house. There are a number of options to consider here.

Fiber Insulation

Fiber Insulation

Fiber insulation is typically blown into the attic or laid down in rolled sections called batts. Fiber can be made out of fiberglass, cellulose, mineral wool or sheep's wool. Fiber insulation in the attic is placed between and on top of the rafters. It reduces energy loss by stopping heat or cool from escaping from your living areas into the attic.

Each of these materials have "R" values which represents the materials resistance to heat flow. The higher the R value, the better the insulation of that material and, in general, the more expensive the material is. The amount of insulation or R-value you'll need depends on your climate, type of heating and cooling system, and the section of the house you plan to insulate.

Here's a good link to determine how much insulation to add to a new or existing house: Insulation Calculator

Rolled in insulation can be a fairly easy do-it-yourself project, but blown in insulation is almost often a professional job.

Blown in insulation has an additional advantage over rolled in insulation as it doesn't leave gaps in which heat or cool can escape.

Spray-In Foam Sealing

Spray-In Foam Insulation

Spray-in foam sealing is a different approach to energy loss and is becoming more popular in new home construction. The foam is generally made polyicynene or polyurethane although other variants exist.

Spray in foam is almost always professionally installed and is applied to the underside of your roof and completely seals the attic from any air leaks from the attic.

This approach is very energy efficient and substantially reduces the temperature of your attic in the summer and increases it in the winter as the temperatures more closely represent those that are in your living spaces. An additional benefit of spray in foam is that it is also a noise barrier.

Thermal Shield

Radient Barrier Insulation

A thermal shield is also a reasonably new method of insulation. A thermal shield is a thin layer (looks like tin foil) that reflects radiant heat escaping from your living areas back into them instead of letting it escape into the attic. When installed in the attic, it can be either laid on top of the rafters, or applied to the underside of the attic roof or a combination of both.

Energy Efficient Window Film

Energy Efficient Window Film

The U.S. Dept. of Energy estimates that during the summer up to 60% of a home’s cooling energy is lost through its windows and during the winter up to 25% of a home’s heating energy is lost through its windows.

If you have very old single pane or leaky widows the best option is to replace them. However, if you have window that aren't leaky, their energy performance can be substantially improved by adding energy efficient window film.

This film allows most visible light to pass through (usually around 80%), they blocking almost all (usually close around 98%) of harmful ultraviolet light from entering the house, and they block most infrared solar heat from penetrating the window. This means that in the summer about 70% of solar heat is prevented from entering your house and in the winter, about 40% of heat is prevented from escaping to the outside through your windows. There are many manufacturers of these products and you can dial the performance you'd like to certain level.

Energy efficient window films can be installed professionally or they can be a do-it-yourself project.

Fixing or Replacing Leaky Air Ducts

Duct Testing

This should be a big area of focus for older houses with forced air heating and/or cooling. The problem is, that over time, the duct system that carries the hot or cool air develops leaks and becomes inefficient. Since the ducts typically run through the attic, or in the basement or under-house crawl space, the leaks mean heat or cool is lost to non-living spaces. With an older house or in a house where ducts could have been damaged, leakage could range up to 50% or more which is a huge loss of energy efficiency and money waste.

Unfortunately, it is not easy to determine your self if you have leaky ducts. The only way to be sure is to hire a professional heating/cooling expert that is setup with the equipment to do a thorough duct test. To do this, all of the vents where heating or cooling enters your living spaces are blocked (with tape or temporarily installed coverings) and then a blower is applied to the ducts to pressurize the duct system and then leakage is measured with a professional tool.

If it is determined that your ducts are leaky, they can either be fixed by replacing sections or sealing them with tape or spray-on sealant or the duct system could be completely replaced.

In addition to sealing leaks, the energy efficiency of your ducts can be improved by adding insulation to the ducts if they do not have them. This insulation surrounds the ducts and further reduces heating or cooling loss.

Fixing Air or Thermal Leaks

Air Leaks

In a house, there could be problem areas where there are air is allowed to leak from or into the house. This means heating or cooling is lost to the outside making your house less efficient than it should be.

Air leaks can come from many sources:

  • Door and window frames
  • Mail chutes
  • Electrical and gas service entrances
  • Cable TV and phone lines
  • Outdoor water faucets
  • Where dryer vents pass through walls
  • Bricks, siding, stucco, and foundation
  • Air conditioners
  • Vents and fans.

Blower Door Test

A heating / cooling professional that is capable of doing a house leakage test will find leaks by executing a blower door test. For this test, a door is removed from the house and a blower door is temporarily installed that blocks the opening except for the section that icludes a blower or fan. When installed and turned on, air pressure will build in the house and special instruments will measure how air-tight your house is.

If the house is determined to be leaky, the professional will typcially walk around the house use a smoke pencil to emit a safe smoke that in areas that may be leaking that can then be seen emerging from the ouside of the house or into the attic or crawl space if an actual leak is present. The areas that are identified as leaky can then be fixed.

Thermal Leaks

Image From a Normal Camera

Thermal Image

Thermal leaks are areas that could come from air leaks, but may also be areas where heating or cooling is escaping without any air leakage. These leaks are often hidden. An example of this type of leak is an area in a walls or ceilings that don't have adequate insulation or where the insulation was improperly installed or damaged. These types of leaks cannot be detected with a blower test (see above) so require another method to identify called thermal imaging.

Thermal imaging uses a special camera to identify which makes areas of heat or cold easily that are different from the surrounding areas easily identifiable.

The images to the left show a an area around a window usig a normal camera and using a thermal camera . With the thermal image, you can clearly see that there is a an area around the window that has a thermal leak that is not visiable from either the inside or outside that needs to be addressed.

Thermal imaging is typically done by a professional because the best thermal cameras can be very expensive, but if you have one or want to buy one, using it to find hidden leaks in your house can be relatively easy. However, some hidden leaks can be very subtle so it may be easy for a an inexperienced person to miss the leak when looking at a thernal image.

Energy Efficient Lighting

The three best options for improving the lighting energy efficiency over standard incandescent lights are:

  • Compact Florescent Lighting (CFL)
  • Light Emitting Diode Lighting (LED)
  • Energy Efficient incandescent lighting

Compact Florescent Lighting (CFL)

CFL Light

Compact Fluorescent Lights (CFL) are four times as efficient as incandescent lights, they last up to ten times longer and they use 50-80% less energy. While they are initially more expensive, they will be cheaper over the medium and long term.

Early CFLs had very cold, bright light that was not as "warm" and liked as much as incandescent lighting but more recent products offer have now closely matched the preferred incandescents light.

Another are of dislike for CFLs is that unlike incandescent or LED lighting they take time to warm up to full lighting.

One environmental concern about CFLs is that they contain mercury. While the quantities included in a bulb are so low to not be of concern to a household that breaks one, the amount of mercury that could potentially be exposed to the environment as they fail and are thrown away is a long term concern for these bulbs.

Light Emitting Diode Lighting (LED)

LED Light

Light Emitting Diode (LED) lighting are superior to both incandescents and CFLs. They last up to five to ten times as long as CFLs and are generally over twice as efficient as CFLs. They use no mercury, so are better for the environment, and they are more durable as their construction is more solid so they better withstand jarring or bumping.

Similar to CFLs, early generation of LEDs had a cold, bright light, but recent versions can produce light almost identical to incandescents in warmth.

The only downside of LEDs is the cost which is quite a bit more expensive than CFLs but over the life of the bulb will be cheaper than CFLs.

Energy Efficient Incandescent Lighting

While more efficient incandescent lights such as halogen lighting have existed for a long time, there is continued research and development of of energy efficient incandescent lighting. THere is a misconception that based on recent laws, incandescent lights bulbs will become illegal, but in fact the law only set standards for lighting efficiency that must be made and any technology can be used.

Some manufactures like Philips already have a newer generation of incandescent bulbs that are around 30% more efficient. While no where near as efficient as CFLs or LEDs, they are lower cost options of improving lighting efficiency and further development could improve this.

Comparison of Incandescent, CFL and LED Lighting

The following table compares some of the key characteristics of LED, CFL and Incandescent bulbs. It shoudl be noted that bulb costs can change rapidly, the cost for power varies widely from region to region and new generations of bulbs further improve performence. However, thie table does provide a good comparison viewpoint.

LED CFL Incandescent
Light bulb projected lifespan 50,000 hours 10,000 hours 1,200 hours
Watts per bulb (equiv. 60 watts) 10 14 60
Cost per bulb $35.95 $3.95 $1.25
KWh of electricity used over
50,000 hours
300 500 700 3000
Cost of electricity (@ 0.10per KWh) $50 $70 $300
Bulbs needed for 50k hours of use 1 5 42
Equivalent 50k hours bulb expense $35.95 $19.75 $52.50
Total cost for 50k hours $85.75 $89.75 $352.50

The following tble compares the total houshold cost for LED, CFL and Incandescent bulbs over 50,000 hours, assuming 25 bulbs per houshold.

Total cost for 25 bulbs $2143.75 $2243.75 $8812.50
Savings to household by switching
from incandescents
$6668.75 $6568.75 0

This clearly illustrates the long term cost savings of both LED and CFL over incandescent and even though LED lights are ore expensive than CFLs, they still are slightly cheaper over the long term.