Home Tips & Advice

Saving Money with Insulation

Here are tips and instructions on how to insulate your home. Take a few minutes to read them thoroughly. Following these instructions can save you time and effort.

In this document you will find information about:

  • How Insulating Your Home Saves Money
  • Types of Insulation
  • How Much Insulation You Will Need
  • Spreading Loose-fill Insulating Materials
  • Applying Insulation in Blanket Form
  • Insulating Walls

HOW INSULATING YOUR HOME SAVES MONEY

  • Heating and cooling your home accounts for about 50 percent to 70 percent of the energy used in your home. Unless your home was built as an energy-efficient home, adding insulation will probably reduce your utility bills. Even a small amount of insulation-if properly installed-can reduce energy costs dramatically.
  • You should insulate all areas of your home. Insulation priorities include your attic, including the attic access door, under floors above unheated basements or crawl spaces, and on the edges of concrete slabs. Your options for insulating existing walls are somewhat limited. However, if you are remodeling or residing your home, use the amounts of insulation recommended for new construction. This image shows you where to insulate and also contains the range of recommended R-values for each of those areas in your house. The R-value changes because of the type of heat you use and where you live. It also changes between new and existing homes. To find the recommended R-value for the area of the country you live in, contact your local electric company or gas company. You can also find the recommended R-value by zip code and heat source at the Department of Energy Web site, www.eren.doe.gov.
  • It's interesting to note that the greatest energy savings come from the first inch of insulation installed. You can add more insulation to increase your savings, but a small amount of insulation is almost a must for your home to be comfortable. Keep in mind that for insulation to work properly the air spaces in the insulation must be maintained. Packing too much insulation into an area will reduce the effectiveness of the insulation.
  • Savings from wall insulation are almost equal to those you'll get from ceiling insulation.
  • You can further increase your energy savings, up to 10 percent, by plugging any air leaks prior to insulating. Obvious air leaks can be found around doors, windows, fireplaces and chimneys. Some not-so-obvious air leaks can be found around electrical switches and outlets, pull-down attic stairs, pipes, and behind bathtub and shower stall units. These leaks are often much greater than the obvious ones. However, taking care of these leaks alone cannot do the job-you must also have insulation.
  

TYPES OF INSULATION MATERIAL AVAILABLE

  • Most insulating materials are available in several common forms-loose-fill or spray-applied materials, blanket rolls, batts, boards and foil-faced paper, foam, film and cardboard. Each form is ideal for specific insulating jobs.
  • The type of insulation material you select for any job depends on how you intend to use it, how much you want to spend, and how easy it is to install.
  • The chart below provides a summary of the qualities and suggested uses for the basic types of insulation.
  • Study the chart carefully. Consider the advantages, disadvantages and instructions for using each type of material as outlined in the chart. This table should help you select the correct material for any insulation job.
  • Blanket and batt insulation is usually made from fiber glass or rock wool. It is sized to fit between studs, floor joists and ceiling joists. It comes both faced and unfaced. Faced means the batt or blanket has a cover such as paper or foil on one side. Unfaced means there is no cover. Some batts and blankets now come with a protective covering that reduces the "itchy feeling" you get when you work with insulation.
  • Rigid foam insulation is widely used on basement walls and on exterior walls. If rigid foam is used inside, it must be covered with gypsum board or other building code-approved material for fire safety reasons. When it is applied on the outside, it must be covered with a weatherproof facing. When using a foil-covered rigid foam, the foil must be away from the heated side of the wall to avoid a condensation problem.
TYPES OF INSULATION
FormMethod of InstallationWhere ApplicableAdvantages
Blankets: Batts or Rolls; Fiber glass Rock woolFitted between studs, joists, and beamsAll unfinished walls, floors and ceilingsDo-it-yourself; Suited for standard stud and joist spacing, which is relatively free from obstructions
Loose-fill (blown-in) or Spray-applied; Rock wool; Fiberglass; Cellulose; Polyurethane foamBlown into place or spray applied by special equipmentEnclosed existing wall cavities or open new wall cavities; Unfinished attic floors and hard-to-reach places Commonly used insulation for retrofits (adding insulation to existing finished areas); Good for irregularly shaped areas and around obstructions
Rigid Insulation; Extruded polystyrene foam (XPS); Expanded polystyrene foam (EPS or beadboard); Polyurethane foam; Polyisocyanurate foamInterior applications: Must be covered with 1/2"gypsum board or other building-code approved material for fire safety; Exterior applications: Must be covered with weather-proof facingBasement walls; Exterior walls under finishing (Some foam boards include a foil facing which will act as a vapor retarder. Please read the discussion about where to place, or not to place, a vapor retarder); Unvented low slope roofsHigh insulation value for relatively little thickness; Can block thermal short circuits when installed continuously over frames or joists
Reflective Systems; Foil-faced paper; Foil-faced polyethylene bubbles; Foil-faced plastic film; Foil-faced cardboardFoils, films or papers: Fitted between wood-frame studs, joists and beamsUnfinished ceilings, walls, and floorsDo-it-yourself; All suitable for framing at standard spacing. Bubble-form suitable if framing is irregular or if obstructions are presentt; effectiveness depends on spacing and heat flow direction
  

HOW MUCH INSULATION YOU WILL NEED

  • On a new home, find out what the recommended R-value is for the type of heat you are planning to use for the location of your new home. Again, local electric and gas companies can provide this information to you or you can contact the Department of Energy.
  • On an existing home it is a little more complicated, but not hard. First, you need to identify what type of insulation is currently in your home. It may differ by the various locations in your home. In your attic for example, you may find batt or blanket fiber glass over the top of loose-fill cellulose. You may also find multiple layers of batt or blanket insulation. Next, you need to measure the thickness of each of these different types of insulation at the different locations. To help you with this process, take a regular sheet of notebook paper and make four columns. Label the first column "Location," the second column "Type Of Insulation," the third column "Inches Thick" and the fourth column "R-value per Inch."
  • The table below shows you the approximate R-value each inch of the various types of insulating materials provides. Use this chart to fill in the last column of your worksheet. One inch of fiber glass batts or blankets, for example, provides an approximate R-value of 3.2. To find the R-value of 4" of fiberglass, multiply 4 x 3.2 to get an R-value of 12.8. Repeat this process of multiplying the number of inches thick and the R-value per inch of insulation for each area in your home. If you have two different types of insulation together, like our earlier example, find the R-value for each and then add them together.
R-VALUE
Insulation TypeR-Value per inch thickness
Fiberglass blanket or batt3.2
High-performance fiber glass blanket or batt3.8
Loose-fill fiber glass2.5
Loose-fill rock wool2.8
Loose-fill cellulose3.5
Perlite or vermilculite2.7
Expanded polystyrene board3.8
Extruded polystyrene board4.8
Polyisocyanurate board, unfaced5.8
Polyisocyanurate board, foil-faced7.0
Spray polyurethane foam5.9
  • Let's use an example where we have 6" of cellulose covered by 6" of fiber glass batts in the attic. We take the R-value of cellulose, which is 3.5 and multiply it by 6 to get 21.0. We then take the R-value of fiberglass batts, which is 3.2 and multiply that by 6 to get 19.2. Since the insulation is layered one on top of the other, we add them together 21.0 + 19.2 to get 40.2.
  • If we live in a region where the recommended R-value is 38, we already have 40.2, so we do not need to add insulation. What happens though, if we live in a region that recommends 49-we need to add some insulation, but how much? That's easy too! Take the recommended R-value, which is 49, and subtract what we have already, which is 40.2 (49 - 40.2 to get 8.8). We need to add an R-value of 8.8. The R-value of an inch of fiber glass batts is 3.2. Divide the amount we need to add, 8.8, by the R-value per inch, 3.2, to get 2.75. Batt and blanket insulation comes in several thicknesses. One of these is 3-1/2". So one layer of 3-1/2" fiber glass batt insulation added to what we have will give us a little more than what we need. It is always ok to add more insulation than is recommended. Just remember not to pack it too tightly because packing it can reduce its effectiveness.
  

SPREADING LOOSE-FILL INSULATING MATERIALS

  • Loose-fill insulating materials of rock wool, fiber glass or cellulose are commonly used for insulating attics. Vermiculite is not currently used for homes, but it may be found in older homes. It is best to install these materials with a plywood rake attached to a rake handle, making spreading much easier.
  • To make this type of rake, cut a scrap piece of plywood to the length of the space between the joists plus 4" (see image below). The extra 4" allows for an overhang on the joists.
  • Next decide how deep you plan to install the loose-fill material. For example, suppose you are planning to lay the loose-fill material to a depth of 3" between the attic joists (see image above). Measure the depth in the space you plan to fill then saw the plywood rake as illustrated in this image. The rake should ride on the joist on either side and level the material off evenly to a depth of 3". Attach a handle, making a handy tool that will save you hours of backbreaking labor and enable you to rake the material easily and evenly into otherwise unreachable corners (see image).
  

APPLYING INSULATION IN BLANKET FORM

  • Always apply blanket-type insulation with the vapor barrier facing the interior of your home. The vapor barrier should always be toward the source of heat in the winter (see image). Never place a vapor barrier between two layers of insulation. This can lead to a condensation problem and reduce the effectiveness of the insulation. Lay the blanket as close to the joists and floor as possible. Fill any gaps with loose-fill insulation or place another layer of blanket insulation across the previous layer.
  • Always place insulation on the outside of pipes or ducts (see image). This means the insulation should be between the outside wall and the pipes.
  • When using blanket insulation, always place the vapor barrier toward the heat source and insulation outside of any pipes.
  • Staple blanket insulation when laid between joists in the attic (see image). Most rolls of blanket insulation materials have flanges that can be stapled or tacked to the ceiling joists, as illustrated. Always keep the blanket as close to the joists and floor area as possible-fill any gaps with strips of insulation or loose-fill insulation.
  • Never allow blanket-type insulation to cut off the flow of air and stop proper ventilation in an attic (see image below). Blanket insulation should never block the air movement from the eave vents into the attic.
  
  • Proper ventilation in the attic is very important in any insulation job. Make provision for air to flow in and around the eave vents and to flow out through a ridge vent roof ventilator or through a ventilator on the end of the house (see first image below).
  • Blanket insulation without a vapor barrier can be wedged between existing ceiling joists (see second image below). Make sure the insulation comes to the top of the plate to avoid heat loss from the penetration of wind under the insulation. Failure to pay close attention to this detail can lead to a frost line forming on cold, windy days. It will form on the inside wall where the ceiling and walls come together.
  • There are special formed inserts made of foam or plastic designed to go up next to the roof between the rafters. They help with both the airflow and the frost line. Many of them are designed to be installed during new construction. But they can be installed in an existing roof with very little extra effort.
  • In some cases, it may be easier to apply the blanket between the rafters on the roof (see third image below). In this case, staple the blanket insulation directly to the rafters.
  • Repair any major tears or rips in the vapor barrier and insulation by adding additional vapor barrier and insulation to build up to the level on the normal insulation run.
  • Whether you apply the insulation to the attic roof or the floor, always double it back at the end for maximum efficiency (see fourth image below). Illustration A shows how the blanket of insulation material can be rolled at the end between the attic joists. Illustration B shows how the same material can be doubled back between the rafters of the roof.
  
 
  
  

INSULATING WALLS

  • If possible, lay blanket-type insulating material between the studs in the wall. If you're using insulation blankets without a vapor barrier, they should be forced into the area between the studs. Then, place a polyethylene vapor barrier on the inside face of the wall. Staple the vapor barrier into place.
  • When building a new structure, insulate the full wall, including around the openings for doors and windows.
  • Use drywall with a foil back as a vapor barrier instead of polyethylene if it is more practical.
  • Blanket insulation material with a vapor barrier attached can be stapled into position.
  • When the blanket has a vapor barrier, take the time to staple or tack all sides, bottoms and tops. This increases the efficiency of the insulation.
  • Use scraps of insulation material to insulate all the cracks and crevices around doors and windows (see image). Then use scraps of vapor barrier to seal these areas. Staple the barrier in place.
  
TOOL AND MATERIAL CHECKLIST
Insulation Materials (Proper Type)Heavy-Duty Shears
StaplesTacks
Furring StripsHand Cleaner
WeatherstrippingSharp Knife
StaplerHammer
HandsawVapor Barrier
Face Mask (if handling specific types of insulation materials) 

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Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.

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