Attic Insulation – Do You Have Enough?

July 30, 2011

rockwool1Proper attic insulation can make a drastic impact on your utility bills. Any home over 5 years old should have the attic insulation evaluated as settling insulation and higher summer temperatures  can degrade its ability to protect your home from the summer heat.

7 reasons to be concerned about the condition of your attic insulation.

  1. High utility bills.
  2. Its been more than 5 years since the house was built.
  3. You have lived in the house for more than 10 years and never evaluated it.
  4. Some thermal insulation materials settle more than others.
  5. Increasing summer temperatures require more insulation.
  6. Recent contractor activity in the attic  (i.e. telephone, CATV, Security, HVAC). These workers can matt down the insulation while performing their job.
  7. Rodent infiltration. These buggers will easily pack down the insulation to get to various points of interest.

Acceptable attic insulation 10 years ago is not the same as it is today. In fact, in just 3 years, my region has been increased from an acceptable value of R31 to R38.

The Inspection:

  • Determine how much insulation is required. Use this Insulation Chart to determine how much is enough.
  • Enter the attic with great care. Attic entrances may be through a door or attic stair case or possibly a hatch in the closet. WARNING: You must keep your feet/body on the wood joists (beams) as stepping on the sheet rock will cause damage, and possibly cause you to fall through the ceiling.
  • With a flashlight and yard stick: Randomly check the depth of the material. Ensure the measuring device (yard stick) touches the sheet rock and measure to top edge of the insulation material. Try not to crush the insulation while performing the inspection.
  • Determine the type of insulation.  Different material have different R values.

rockwool3If you can see the ceiling joist as in this picture, you  probably do not have enough insulation.  Typical ceiling joists can range from 2 X4’s, 2X6’s to 2X10’s.  For instances, if you have 2X6 beams with loose fill rock wool, you would have a R value of 16.5 (3.0X5.5″=16.5). Newer houses typically have larger beams. Determine the material type as this will help in figuring out how much insulation to add. Use the chart below to calculate the R value of the existing insulation. TIP: If you find you have enough insulation in areas that have not been disturbed, but you find areas matted down due to activity or construction work. Use a soft plastic rake to fluff it back up.

Insulation Table

Common Types of Insulation in Residential Attics

  • batt insulationFiberglass: Comes in batts, blankets, and loose fill, either pink, white or yellow in color. Fibrous in nature and can leave you with microscopic splinters. TIP: Before working with fiberglass insulation, spread a heavy coat of baby powder over any exposed skin, this will fill your pores briefly while working with the material.
  • rockwool2Rock Wool (or Mineral Wool):Loose fill used aggressively prior to 1970. Usually brown or dark gray in color.
  • Cellulose:Loose fill made of recycled paper. Blue or gray in color. With close inspection you will find small pieces 100_0550of newspapers. The product is treated with a fire-retardant solution for safety.
  • Combination:This is not a type, but you may find a combination of two or all three types. Previous owners may have added insulation over the life of the house. This is not a problem, but you should determine how many inches of each type to calculate the value of the existing insulation.

By now, you should know, how much insulation you have vs. what you need. Assuming you need to add insulation, HomeownerBOB highly recommends hiring a professional for this task even though the home centers will provide you tools to perform the work. Once you determine what type of new insulation you prefer, you can easily bid shop the work over the phone.  The professional will need to know 1) square footage of the house, 2) type of insulation material you would like, 3) how many inches to apply.

So how do you determine what type of insulation to use? Read my article on “The Choices“.

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Radiant Barrier – Things to Consider

April 24, 2010

Radiant Barrier has a long successful history as a way to reduce heat loads, but didn’t really get the deserved credit until NASA  acknowledged its use in the Space Program.  As a construction product; it is basically heavy-duty aluminum foil with at least one shiny side. For a greater understanding of the principles of this product, see  How it works? 

During the summer, an attic radiant barrier, combined with existing R-19 attic insulation, may reduce heat gain through the ceiling from 16%-42%. For single-story houses, typically about 15%-25% of the summer cooling load is due to ceiling heat gain. During the summer, the interior ceiling becomes a radiant heater adding heat to the interior spaces. The heat gain reduction from a radiant barrier installation will usually result in a total cooling load savings of 2%-10%-possibly as high as 15% in attics insulated to R-11 or less. Higher savings occur when retrofitting less efficient buildings. Buildings with little to no attic insulation and a high volume of attic ventilation typically provide the most dramatic energy savings from a radiant barrier. The hotter and sunnier the climate is, the more beneficial the radiant barrier installation becomes.

Types of Radiant Barriers

  • Foil Faced Decking Material: With the trade name of TechShield, this radiant barrier product is applied to the back of roof decking during manufacturing and can be applied when the house is built or during a re-roof. Efficiencies of this product is in the neighborhood of 95-97%
  • Rolls or Sheets: The sheets can be applied in a couple of methods; 1) Tacked up on the rafters or 2)rolled out on the attic floor. The labor makes these choices fairly expensive, but you can reduce the installed cost by making it a  DIY project.
  • Spray on Solution:  This is a fairly new option, and came about because of the installed cost  of rolls or sheets. However, spray on radiant barrier is only about 65% as efficient as the aluminum foil types and lacks the low emissivity factor found in the other products. So it may have a lower installed cost, but your benefits will not compare to previously mentioned type.

Things to consider before purchasing or installing a Radiant Barrier

  1. Climate: If living without air conditioning is not an option for you,  you may live in a temperature zone worthy of installing radiant barrier. Studies have shown, this product works better in very hot climates. If your attic regularly exceeds 130 to 140 degrees F, radiant barrier can reduce the attic heat load allowing your HVAC to work more efficiently , in-turn reducing your electricity consumption. If you live in climates similar to Arizona, Florida, or Texas,  you are probably a candidate for radiant barrier.
  2. New Construction or Re-roofing plans: If you are considering either of these projects, foil faced roof decking can be purchased for a couple of dollars per sheet. This is the most inexpensive method to obtain radiant barrier. 
  3. Attic Insulation: Make sure you have enough attic insulation, radiant barrier is not an insulation replacement product but just part of the equation. Having the proper amount of attic insulation combined with a radiant barrier product will provide the maximum benefit.  Also see Insulation: Do you have enough? and Insulation Choices.
  4. Radiant barrier as a DIY project: Choose a product that has high tensile strength or is embedded with tightly woven fiber mesh; either of these features will reduce the opportunity for the product tear during the installation process. There is also a bubble pack version that appears to be as strong too. The bubble pack version is a great product for re-insulating HVAC ducts. Any radiant barrier product should be UL listed and/or have a NFPA “Class A”  flammability rating.
  5. Location to place the radiant barrier: The following table shows a comparison of the effectiveness of the product applied in 4 different locations. Even though the attic floor application appears to be the most effective, this location may 1) cause moisture to collect under the barrier, 2) collect excessive dust; known to reduce its effectiveness and 3) add to the complexity to performing future work in the attic.  HomeownerBOB recommends avoiding using this product on the attic floor. 
Radiant Barrier Location Whole House Tests Test Cell Tests
Mineral InsulationLab Oak Ridge Lab Solar Energy Cntr Tenn. Valley Auth.
Roof: attached to roof deck —- —- 36 – 42% 16%
Roof: stapled between rafters —- —- 38 – 43% —-
Roof: stapled under rafters 24% 25 – 30% —- 23 – 30%
Attic Floor*** 35% 32 – 35% 38 – 44% 40 -42%

If re-roofing is not in your future, installing the barrier on or under the rafters to gain the most long-term effectiveness is probably your best choice. Most of these products qualify as an energy tax credit so take advantage of the opportunity and get it installed before it gets too hot.

Reference Studys of Effectiveness of Radiant Barriers

  1. TAMU Study
  2. Radiant Barrier Fact Sheet; DOE Oak Ridge National  Laboratory