Insulation Precautions

The Old House Web

Confused about R-values, rolled or blown-ininsulation, vapor barriers and other insulation terms? This series of stories,adapted from the U.S. Department of Energy "InsulationFact Sheet" explains the ins and outs of home insulation -- and may helpyou save significantly on your heating and cooling costs.

Topicscovered in Part 7: Take precautionswhen insulating * Blanketinsulation * Rigid board insulation * Loose-fillinsulation * Reflective systems *

Take precautions when insulating

These do-it-yourself instructions cover installation of batts and blankets,loose-fill or poured-in materials, rigid boards, and reflective insulations. Beforebeginning the work, read and observe the following precautions:

  • Wear clothing adequate to protect against skin contact and irritation. A long-sleeved shirt with collar and cuffs buttoned, gloves, hat, glasses, and disposable dust respirator are advisable in all do-it-yourself insulation projects. Also, read the label and follow all the manufacturer's directions.
  • Do not cover or hand-pack insulation around bare stove pipes, electrical fixtures, motors, or any heat-producing equipment such as recessed lighting fixtures. Electrical fire-safety codes prohibit the installation of thermal insulation within three inches of a recessed fixture enclosure, wiring compartment, or ballast, or above the fixture so that it will trap heat and prevent free circulation of air, unless the fixture is identified by label as suitable for insulation to be in direct contact with the fixture. This is for fire safety!
  • Also, if your home is very old, you may want to have an electrician check tosee if the electrical insulation on your wiring is degraded or if the wires areoverloaded. In either of these two situations, it may be hazardous to addthermal insulation within a closed cavity around the wires because that couldcause the wires to overheat.
  • If your home was wired using a now obsolete methodcalled knob and tube wiring, the National Electric Code forbids the installationof loose, rolled, or foam-in-place insulation if the insulation would surroundthe wires and prevent heat dissipation from the electrical conductors to a freeair space. This is for fire safety!
  • Do not cover attic vents with insulation. Proper ventilation,especially in attics, must be maintained to avoid overheating in summer andmoisture build-up all year long.

Blanket Insulation: Batts and Rolls

Installing batts and rolls in attics is fairly easy, but doing it right isvery important. On unfinished attic floors, work from the perimeter toward theattic door. In new construction, the vapor retarder facing should be installedwith the facing placed down toward the ceiling gypsum board, except in hot humidclimates where unfaced batts should be used.

If re-insulating over existinginsulation, it is recommended that unfaced batts be used. If there is not anyinsulation in your attic, fit the insulation between the joists. If the existinginsulation is near or above the top of the joists, it is a good idea to placethe new batts perpendicular to the old ones because that will help to cover thetops of the joists themselves and reduce heat loss or gain through the frame.Also, be sure to insulate the trap or access door. Although the area of the dooris small, an un-insulated attic door will reduce energy savings substantially.

On walls, begin at the top and work down. Place the vapor retarder towards the lived-in side, except in hot humid climates.

Fit the insulation between the wood frame studs, cut off the excess length where necessary, and secure the insulation by stapling the flanges of the vapor retarder according to the manufacturer's instructions.

Cut the batt carefully to fit around obstructions with no gaps.

Don't compress the insulation to fit behind pipes or wires. Instead cut to the middle of the batt's thickness so you have a flap under the wire and one over the wire.

The kraft paper or standard foil vapor retarder facings on many blanketinsulation products must be covered with gypsum or interior paneling because offire considerations. Some blanket products are available without these facingsor with a special flame resistant facing (labeled FS25 - or flame spread index25) for places where the facing would not be covered. Sometimes, the flameresistant cover can be purchased separately from the insulation. Also, there arespecial fiber glass blanket products available for basement walls that can beleft exposed. These blankets have a flame-resistant facing and are labeled toshow that they comply with ASTM C 665, Type II, Class A.

When a fiber glass blanket is used to insulate the inside of basement walls,it is necessary to attach wood furring strips to the walls by nailing orbonding; or to build an interior stud-wall assembly on which the interior finishcan be attached after the insulation is installed. The cavity created by theadded framing should be thick enough for the desired insulation R-value.

When a fiber glass blanket is used to insulate the walls of an unventilatedcrawlspace, it is sometimes necessary to attach wood furring strips to the wallsby nailing or bonding. The insulation can then be stapled or tacked into place.Alternatively, the insulation can be fastened to the sill plate and draped downthe wall. Because the insulation will be exposed, be sure to use either anun-faced product or one with the appropriate flame spread rating. If you live ina very cold region, you should continue the insulation over the soil for abouttwo feet (on top of the necessary ground vapor retarder discussed previously).

Batts and rolls must be cut and fit around such obstructions as cross-bracingbetween floor joists, and window frames in walls. Strips of insulation may becut off and stuffed into tight spaces by hand. Do not hand-pack insulationaround hot spots such as recessed light fixtures. This could cause heat build-upand may become a fire hazard.

When batts or rolls are used overhead, such as above an unheated crawl spaceor basement, fit the insulation between the beams or joists and push it upagainst the floor overhead as securely as possible without excessive compactionof the insulation. The insulation can be held in place, either by tackingchicken wire (poultry netting) to the edges of the joist, or with snap-in wireholders. Don't forget to place insulation against the perimeter that rests onthe sill plate. If you insulate above an unheated crawl space or basement, you will alsoneed to insulate any ducts or pipes running through this space. Otherwise, pipescould freeze and burst during cold weather.

Rigid Board Insulation

When rigid foam insulation boards are used to insulate the interior ofmasonry walls, they do not require added vapor retarder treatment. If foil-facedboard is used, the foil side is placed toward the room. To install boards, woodfurring strips should be fastened to the wall first. These strips provide anailing base for attaching interior finishes over the insulation. Fire safetycodes require that a gypsum board finish, at least 1/2-inch thick, be placed overplastic foam insulation. The gypsum board must be attached to the wood furringstrips or underlying masonry using nails or screws.

When rigid foam insulation boards are used to insulate the walls of anunventilated crawlspace, they can be bonded to the wall using recommendedadhesives. Because the insulation will be exposed, be sure to check the localfire codes and the flame-spread rating of the insulation product. If you live ina very cold region, you should continue the insulation over the floor of thecrawl space for about two feet (on top of the required ground vapor retarderdiscussed previously). If you live in an area prone to termite damage, checkwith a pest control professional to see if you need to provide for termiteinspections.

Loose-Fill Insulation

This insulation is most efficiently installed by blowing it into place withpneumatic equipment. This method effectively breaks up any lumps andincorporates air so that the insulation has the desired density and thickness.When using loose-fill insulation in new construction, install a vapor retarderon the living side (See Part 4:Controlling moisture.) When loose-fill isused as additional insulation, either placed over existing loose-fill or overbatts or blankets, do not install an additional vapor retarder.

Loose-fill insulation must be prevented from shifting into vents, eaves, orfrom contacting heat-producing equipment (such as recessed lighting fixtures).Block off those areas with baffles or retainers to hold the loose-fillinsulation in place.

Reflective Systems

Installing reflective insulation is similar to placing batts and blankets.Proper installation is very important if the insulation is to be effective.Study and follow the manufacturer's instructions. Often, reflective insulationmaterials have flanges that are to be stapled to joists in attics or floors, orto wall studs. Since reflective foil will conduct electricity, avoidmaking contact with any bare electrical wiring.

Radiant barriers may be installed in attics in several configurations. Theradiant barrier is most often attached near the roof, to the bottom surface ofthe attic truss chords or rafter framing.

The potential benefit of attic radiant barriers isprimarily in reducing air-conditioning cooling loads in warm or hot climates.Radiant barriers usually consist of a thin sheet or coating of a highlyreflective material, usually aluminum, applied to one or both sides of a numberof substrate materials. These substrates include kraft paper, plastic films,cardboard, plywood sheathing, and air infiltration barrier material. Someproducts are fiber reinforced to increase the durability and ease of handling.

<-Back to introduction

To Part 8 ->
If you have insulation done professionally

About the Author
The Old House Web

Search Improvement Project