compare today insulate and save tomorrow - insulation ... · settling is an important...

Introduction

Whether your pocketbookor the planet is your chiefconcern, energy efficiency

can add up to a lot of savings. Reducing energy demand

reduces the amount of fossil fuelcombustion needed to heat andcool homes, which in turndecreases the amount of carbondioxide emitted into the atmos-phere. In terms of your pocket-book, reducing your energy con-sumption means lower utility bills.

While there are many things youcan do to increase your home’senergy efficiency, one of the mostinexpensive ways is to install addi-tional insulation.

Before Choosing Your Insulation

Things to consider when choosing aninsulation product include ease of appli-cation, thermal performance and value.

However, you should also consider theoverall lifetime performance of an insula-tion product as well as its related safetyaspects prior to purchase and installation.

A Side by SideComparison

One way to compare insulation prod-ucts is to do a side by side comparison.Here we compare the two most commontypes of insulation: fiber glass and cellu-lose. The following comparison revealsimportant differences between the twoproducts which you should considerbefore making a final decision.

Comparing Fiber Glassand Cellulose Insulation

Compare TodayInsulate and Save Tomorrow

#35I N S U L AT I O N

F A C T S

Thermal Resistance

Water Vapor Sorption

Convection

Impact of Weight

Fire Safety

Use of RecycledMaterials

Sound Control

Resistance toCorrosion

Air Infiltration

Settling & Loss of R-Value

Safetywww.naima.org

Settling is an important considera-tion in insulation product selection

as it directlyrelates tothe installedthermal per-formanceover time.

Fiber Glass InsulationProperly installed fiber glass batts and

rolls do not settle. Some fiber glassloose-fill insulation may settle over time(usually around 1 percent). This settlingdoes not alter the thermal performanceof fiber glass insulation.

When manufacturers’ installation pro-cedures are employed, fiber glass insula-tion maintains its thermal performancefor the life of the building.

Cellulose InsulationCellulose manufacturers agree that

their products settle over time.2 Most setthe settling rate at about 20%. Therefore,if cellulose is mistakenly installed to itslabeled settled thickness, it may loseabout 20% of its R-value when it settles.When the product is not labeled forinstalled thickness, the Insulation Con-tractors Association of America (ICAA)recommends that an additional 25% ofthickness be added above the labeled set-tled thickness.

SETTLING AND LOSS OF R-VALUE

The thermal resistance of insulationis designated by R-value. R-value is

resistance to heat flow - the higher theR-value, the greater the insulatingpower. Thickness of insulation is onlyone factor that determines its R-value.To ensure that consumers are providedwith accurate information regardingR-values, the Federal Trade Commission(FTC) in 1980 established a rule whichmandates that specific R-value informa-tion for homeinsulationproducts bedisclosed incertain adsand at thepoint of sale.The purpose

of the FTC R-value disclosure require-ment for advertising is to prevent con-sumers from being mislead by certainclaims which have a bearing on insu-lating value. When insulating a home,it’s important that the homeowner getsthe R-value specified and that the ther-mal performance lasts over time.

Fiber Glass InsulationThe R-value per inch of fiber glass

insulation can vary depending on thedensity. Fiber glass batts and rolls, bothfaced and unfaced, have R-values printedon them. Standard fiber glass batt insula-tion has an R-value per inch of approxi-mately 3.0. Most fiber glass manufactur-ers offer high-performance insulationproducts that yield a higher R-value per

inch (4.0+). However, in nearly all appli-cations, the overall R-value specified iswhat counts, not the R-value per inch.It’s also very important that the R-valuedoes not deteriorate. The R-value of fiberglass does not deteriorate over time.

Cellulose InsulationCellulose insulation manufacturers

promote the product’s “higher R-valueper inch” as making it a better value thanfiber glass. Higher R-value per inch is notimportant in selecting insulation material.It is an advantage only in areas with littlespace for insulation. In those particularapplications, fiber glass high density insu-lation (R-13 and R-15 batts) provideshigher R-value per inch than cellulose.1

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THERMAL RESISTANCE R-VALUE

WATER VAPOR SORPTION

In general, insulation will lose R–valuewhen wet. However, there are impor-

tant differences in the water vaporsorption properties of the two insula-tions which can impact their installed

performance.

Fiber GlassInsulation

Insulationmade of fiberglass is notabsorbent.

If exposed to moisture, it will not wickup and hold water, thus it resists any per-manent loss of R-value. If fiber glass insu-lation becomes saturated as the result offlooding or other events not related toactual product use, it should be removedand replaced.

Cellulose Insulation Cellulose insulation is made of shred-

ded newspaper and will absorb moisture.Also, if soaked, cellulose will “mat” downand thermal performance can be perma-

nently reduced. Assuming existing cellu-lose does dry after becoming wet, thereis a concern that the fire retardant chemi-cals may “wash away” leaving insulationmaterials insufficiently protected. Inaddition, studies conducted in Canada,New England and Ohio demonstratedthat wet-spray applications of celluloseinsulation do not achieve their advertisedR-value until dry and may take as long astwo months to dry.3 In many cases, wet-spray applications may need to remainuncovered until completely dry.

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CONVECTION

Convection is a form of heat flow inwhich heat is transmitted by air

currents. When air is heated, itexpands, becomes less dense and movesin an upward direction. Generally,convection hasno effect oninsulation per-formance.

Fiber Glass InsulationFiber glass batts and rolls are not

affected by convection. However, somelighter density loose-fill fiber glass maybe affected slightly in limited applica-tions such as those found in extremelycold weather environments. Laboratoryattic tests have shown that loose-fill prod-ucts experience improved thermal per-formance as the temperature in an atticdrops, but that some light density loose-fill products then may see a reduction inthermal performance as attic tempera-tures drop further.

Cellulose InsulationConvection will not affect the ther-

mal performance of cellulose due to itsheavy density.

THE IMPACT OF WEIGHT

When installing insulation aboveceilings, homeowners should take

into consideration the impact that theinsulation weight can have on the ceil-ing structure of the home. The impactof weight isprimarily anissue in north-ern climateswhere R-valuesof 30 andhigher are com-monplace.

Fiber Glass InsulationFiber glass insulation is extremely

thermally efficient, yet light in weight.Homeowners can install fiber glass insu-lation up to R-70 over 1/2″ ceiling dry-wall with framing spaced 24″ on centerswithout causing drywall sag.

Cellulose InsulationBased on U.S. Gypsum weight limit

recommendations for backloaded standarddrywall* and the installed density of shred-ded newspaper insulations, there is poten-tial for ceiling drywall to sag at R-valuesabove R-30 for regular cellulose insulationwhen installed over 1/2″ ceiling drywallwith framing spaced 24″ on centers.

* Gypsum Construction Handbook, 1992 edition, pages 28 and 102

FIRE SAFETY

Fire resistance is an importantattribute of any insulation material.

It is in ahomeowner’sbest interest toconsider theflame-resis-tance proper-ties of theinsulation inhis or her

home. In terms of fire safety, fiber glassand cellulose perform quite differently.

Fiber Glass InsulationFiber glass insulation is made from

sand and other inorganic materials whichare melted and then spun into fiber glass.Fiber glass is naturally noncombustibleand remains so for the life of the prod-uct. It requires no additional fire-retar-dant chemical treatments. Unfaced fiberglass insulation also is recognized bybuilding code groups as an acceptablefire stop in residential wood frame walls.

Most kraft and foil facings availableon some fiber glass insulation are them-selves combustible. Products with suchfacings are intended for non-exposedapplications and should not be leftexposed. When properly installed, theseproducts do not pose a fire hazard.

Cellulose InsulationCellulose insulation is made of ground-

up or shredded newspaper which is natu-rally combustible. In fact, cellulose insula-tion is regulated as a recognized fire hazardby the Consumer Product Safety Council(CPSC).4 To protect against fire hazards, cel-lulose insulation is heavily treated with fireretardant chemicals prior to installation.

Tests conducted by the CaliforniaBureau of Home Furnishings and ThermalInsulation have demonstrated that some cel-lulose samples failed the standard fire safetytest only six months after installation.5

Additionally, smoldering combustion andre-ignition problems are concerns with cel-lulose insulation should a fire start.6 Evenproperly treated cellulose insulations willburn at about 450°F. That’s the surfacetemperature of a 75 watt light bulb.7

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AIR INFILTRATION

Air infiltration is the uncontrolledleakage of air into and out of a

home. It is driven by wind, tempera-ture differences, or HVAC appliance-induced pressures.

If a wall cavity has been properlyclosed off using drywall, sheathing, andcaulking, very little air will flow through awall cavity regardless of the type of insula-tion used. Openings for wiring runs, lightswitches and electrical outlets where airinfiltration can occur, can be sealed withfoam sealants, caulking or foam gaskets.To control air leakage in a home, a house-wrap or other air infiltration controlstrategies should be considered to limit airinfiltration through cracks and joints.

Recently, there has been somedebate over which insulation productsare better at reducing air infiltration.The fact is, research shows that air infil-tration is dependent on the sealant

package, and not the insulationinstalled in the wall cavity.

A 1997 study conducted by theNational Association of Home Builders(NAHB) Research Center for the U.S.Environmental Protection Agency’sEnergy Star Homes Program9 could findno relationship between the type of insu-lation used and the amount of air infil-tration. The studydetermined thatthe individual airsealing practicesof the insulatorshad a largerimpact on airleakage than theinsulation products themselves. Thesefindings were confirmed by a 1997 studyconducted by a researcher at Penn StateUniversity10 and a 1996 study by a St.Louis, MO utility company.11

Fiber Glass InsulationProperly installed fiber glass insula-

tion in a wall cavity matches cellulose incombating heat loss from air infiltration.Minimizing air infiltration is dependenton the sealant package, not the insula-tion. The purpose of insulation is to pro-vide thermal performance.

Cellulose Insulation Despite claims that wet-spray cellulose

eliminates air infiltration, the researchshows that what’s in the cavity of the wallor attic - fiber glass or cellulose - has little,if any, effect on air infiltration.12

In general, the density of the insulationmaterial in a sidewall assembly has lit-

tle, if any, effect on the Sound Transmis-sion Class (STC) rating of the assembly.STC ratings are a measure of the effec-tiveness of a given partition constructionin reducing airborne sound transmis-sion. Insulation thickness, however, hasa more significant effect on STC ratingsthan does density. In comparison testing,representative 2 x 4 and 2 x 6 wood studand metal stud walls demonstratedequivalent or slightly better performancefor fiber glass over cellulose when thecavities were completely filled.13

Fiber glass InsulationFiber glass insulation significantly

reduces sound transmission in wall, ceil-ing and floor assemblies. The first inch offiber glass insulation can increase the STCvalue by 3 or 4 points in some construc-tions. Each additional inch of fiber glassinsulation increases the STC value fromone to two points. (Refer to NAIMA pub-lication BI405 - Sound Control for Com-mercial and Residential Buildings)

Cellulose InsulationCellulose insulation is also considered

a good insulator against unwanted soundin wall and ceiling assemblies.

SOUND CONTROL

It makes senseto avoid the

use of productsthat may causecorrosion prob-lems in a home.

Fiber Glass InsulationFiber glass insulation is not corrosive

and contains no chemicals that can cor-rode pipes and wires.

Cellulose InsulationCertain chemicals routinely applied

as a fire retardant to most cellulose insu-lation (particularly the sulfates) can causethe corrosion of pipes and wires undersome conditions.8

RESISTANCE TO CORROSION

Increased attention has been given torecycling and recycled products as

concerns about our environment haveheightened. Both fiber glass and cellu-lose manufacturers use a significantamount ofrecycledmaterials inthe manufac-ture and pack-aging of theirproducts.

Fiber Glass InsulationBetween 1992 and 2000, the fiber

glass insulation industry recycled approxi-mately 8,355,848,000 lbs. of pre- andpost-consumer glass containers, eliminat-ing the need for millions of cubic feet oflandfill space.

Many fiber glass insulation manufac-turers have plants that use up to 40% ormore recycled materials in their products.The current industry average is 30% recy-cled content. Manufacturers are cur-rently exploring ways in which their useof recycled materials can be increasedwithout compromising the effectivenessof their insulation products wheninstalled in attics, sidewalls and floors.

In addition, the packaging materialsused by fiber glass manufacturers canbe recycled.

Cellulose InsulationCellulose insulation is generally made

up of about 80% recycled newspapers and20% fire-retardant chemicals. On the sur-face, cellulose insulation may appear to bethe more environmentally acceptableinsulation choice as it is made from shred-ded newspaper. However, it takes threetimes more cellulose material by weightthan fiber glass to insulate a typical home.In addition, an average 1200 square footattic insulated to R-38 with cellulose insu-lation would introduce 300 pounds of fireretardant chemicals into the home.

USE OF RECYCLED MATERIALS

The value of scientific researchregarding the health aspects of insu-

lation materials cannot be overstatedin relation tothe safety ofworkers andthe public.

Fiber Glass InsulationFiber glass insulation is one of the

most thoroughly tested building materi-als in use today. The great amount ofmedical scientific evidence compiledover more than fifty years by industry,government and independent researchorganizations supports the conclusionthat fiber glass insulation is safe to usewhen manufacturers’ recommendedwork practices are followed.

Cellulose InsulationQuestions about the health and safety

aspects of cellulose insulation persist inthe building industry because comprehen-sive medical scientific testing of the prod-ucts has never been conducted. Repeatedrequests by union and contractor groupsthat such testing be undertaken have beenignored.14 Given the high levels of expo-sure measured during cellulose installa-tion, only after long-term experiments areavailable will it be known if cellulose insu-lation is safe to use.

SAFETY

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PUB. NO. BI475 3/02

ABOUT NAIMA

NAIMA is the association for NorthAmerican manufacturers of fiber glass,rock wool, and slag wool insulationproducts. Its role is to promote energyefficiency and environmental preserva-tion through the use of fiber glass, rockwool, and slag wool insulation, and toencourage the safe production and useof these materials.

For more information, contact:

NAIMA44 Canal Center Plaza, Suite 310Alexandria, VA 22314Tel: 703/684-0084 Fax: 703/684-0427E-mail: insulation@naima.orgWebsite: http://www.naima.org

NAIMA BUILDING INSULATIONCOMMITTEE MEMBERS:

CertainTeed CorporationPO Box 860Valley Forge, PA 19482800/233-8990

Johns ManvillePO Box 5108Denver, CO 80217-5108800/654-3103

Knauf Fiber GlassOne Knauf DriveShelbyville, IN 46176800/825-4434

Owens CorningOne Owens Corning ParkwayToledo, OH 43659800/GET-PINK

REFERENCES

1. ASHRAE Fundamentals Handbook, 1997

(pps.24.4-24.5).

2. Arizona ICAA Chapter Request, Insulation

Contractors Monthly (May 1995).

3. “Wet-Spray Cellulose - Questions About

Drying,” Energy Design Update, July 1989

Edition, p.1. “Effect of Wet-spray Cellulose

on Walls,” Energy Design Update, October

1989, p.3.

4. 16 C.F.R. Part 1209.

5. California Bureau of Home Furnishings and

Thermal Insulation, Long-Term Aging Stud-

ies on Loose-fill Cellulose Insulation: Part

IV 7V (1991).

6. Letter to Dale Lewis from Lewis County

(Washington State) Public Utility District,

March 20, 1991.

7. Facts #30, Insulation and Fire Safety,

The North American Insulation Manufactur-

ers Association (NAIMA).

8. Corrosiveness Testing of Thermal Insula-

tion Materials - A Simulated Field Exposure

Study Using a Test Wall, Report ORNL/Sug.

78-7556/4, September 1988.

9. Field Demonstration of Alternative Wall

Insulation Products. Prepared for the U.S.

Environmental Protection Agency by NAHB

Research Center, Inc., November 1997.

10. A Field Study of the Effect of Insulation

Types on the Air Tightness of Houses.

G.K. Yuill, Ph.D, Pennsylvania State

University Department of Architectural

Engineering, 1996.

11. Research and Development Project,

“Maple Acres,” Union Electric, St. Louis,

MO. William Conroy, Division Marketing

Supervisor, 1995.

12. Ibid.

13. National Research Council of Canada

Report, “Gypsum Board Walls: Transmis-

sion Loss Data.” March 1998, #761.

14. Arizona ICAA Chapter Request, Insulation

Contractors Monthly (May 1995), and Let-

ter to TSCA Public Docket Office from the

Laborers’ Health and Safety Fund of North

America (September 23, 1991).