Environmental Building NewsThe Leading Newsletter on Environmentally Responsible Design & Construction

A Publication of BuildingGreen, LLC www.8uildingGreen.com Volume 19, Number 6 . June 2010

Avoiding the Global Warming Impact of InsulationInsulation is key to reducing carbon emissions from buildings. But the blowingagents in extruded polystyrene and spray polyurethane foam offset much ofthat benefit.by Alex Wilson

EoCOMMON FOAMINSULATIONmaterials are produced withhydrofluorocarbon (HFC) blowing

agents that are potent greenhouse gases-extruded polystyrene (XPS)such as DowStyrofoamofOwens Corning Foamular,andstandard closed-cell spray polyurethanefoam (SPF).While all insulation materialsreduce greenhouse gasemissions (bysavingenergy), insulating with thick layers ofeither of these two particular foams resultsin very long "payback periods" for theglobal warming potential of the insulation,thwarting even the best attempts to createcarbon-neutral buildings. The bottom lineis that designers and builders aiming to

minimize the global warming impactsof their buildings should choose fiberinsulation (cellulose, fiberglass, or mineralwool) or non-HFC foam insulation.

"The more insulation the better" is a com-mon refrain in the green building industry.EBN has long advocated very high levels ofinsulation, particularly in residential andsmall commercial buildings, which areskin-dominated. At the furthest end of thespectrum is the Passive House movement(see EBN Apr. 2010),where it is not uncom-mon to provide R-50under a floor slab,R-60in the walls, and as much as R-100in theattic. High levels of insulation are seen as

a key strategy for achiev-ing net-zero-energy andcarbon-neutral perfor-mance-the latter mean-ing that the building willhave no net contributionto climate change.

How we achieve high lev-els of insulation is a verysignificant issue, howev-er. We rarely pay atten-tion to the fact that insula-tion materials themselvescontribute to greenhousegas emissions and globalwarming. This happensin two ways: through theembodied energy of theinsulation (the energyuse and greenhouse gasemissions that resultfrom manufacturing

(continued on p. 9)

Photo: Bensonwood

Unaware of the recently reported GWP implications of certain foam in-sulation materials, builder Tedd Benson specified four inches of extrudedpolystyrene over 2x6 studs insulated with dense-pack cellulose in thisnet-zero-energy home.

printed on 100% post-consumer recycled paper

In This Issue

Feature Article ••.... 1• Avoiding the Global

Warming Impact of Insulation

mail@BuildingGreen ..• 2• Chemicals Article Lacked

Balance

What's Happening ....•• 3• Cradle to Cradle Certification

System Being Transferred toNew Organization

• USGBC Launches LEED·ND

• Chinese Drywall Manufac·turers Liable for Millions inDamages

• Energy Star Beefs Up Require·ments and Enforcement

• EPA Proposes Disposal Rulesfor Coal Ash

• Newsbriefs

Product News& Reviews ...•••••..••7

• Certain Teed Introduces aFormaldehyde·Free BattInsulation

• Bamboo DimensionalLumber? "Lumboo" Is Here

BackPage Primer ...••• 16• Power·Flushing with

Pressure-Assist Toilets

Quote of the month:

"Specifying a high-GWPinsulation completelydefeats the point of

using it."

- Scott Shell, FAIA of EHDDArchitecture commenting

on new information on theglobal warming potential

of insulation materials(page 12)

Feature Article: Avoiding the Global Warming Impact of Insulation

->;

Avoiding the Global Warming Impact of Insulation (from page 1)

partment ofMechanical Engineeringat the University of Bath in the U'K,for values of embodied energy andembodied carbon for different insu-lation materials. Although its figuresare based on European (rather thanNorth American) data on the energyused to produce and transport build-ing materials, ICE offers the mostaccessible,current information avail-able on embodied energy. Using thisdata and information about insula-tion performance, we can calculatethe embodied GWP of these insulation

materials. Currently, ICE does notaddress blowing agents.

Blowing agentsWhen insulation materials are madewith halocarbon blowing agents(compounds containing halogens,such as chlorine or fluorine), theGWP of those gases far outweighsthe embodied GWPthat results fromthe embodied energy of the insula-tion materials.

Blowing agents create tiny bubblesof low-conductivity gas in closed-cellfoam insulation materials. Chloro-fluorocarbons (CFCs)were originally

used as blowing agents forpolyisocyanurate (poly-iso), extruded polysty-rene (XPS), and closed-cell spray polyurethanefoam (SPF). After it wasdiscovered in the 1970sand '80s how damagingCFCs are to the Earth'sprotective ozone layer,they were replaced with"second-generation" hy-drochlorofluorocarbon(HCFC) blowing agents,which had lower ozonedepletion potential (ODP),as required by provisionsof the Montreal Protocol onSubstances That Deplete theOzone Layer.

and transporting the material); and,with some foam insulation materi-als, through the leakage of blowingagents that are highly potent green-house gases.

Understanding EmbodiedEnergy and GWPResearcher Danny Harvey, Ph.D., ofthe University of Toronto, soundedthe alarm about the climatic im-pacts of blowing agents used in cer-tain foam insulation materials in atechnical paper in theAugust 2007 issue ofthe journal Building andEnvironment. Daniel Ber-gey of Building ScienceCorporation presenteda synopsis of Harvey'sresearch at the North-east Sustainable EnergyAssociation (NESEA)Building Energy Con-ference in March 2010.

.Tablel. OOP and GWP Values of BlowingAgents Used in Foam Insulation

With the help of Ber-gey and John Straube,Ph.D., P.Eng., of Build-ing Science Corpora-tion, EBN reexaminedthe assumptions Har-vey used, included newinformation about theblowing agents in usetoday (which differfrom what Harvey as-sumed), and calculatedthe payback on the life-time global warmingpotential (GWP) of in-sulation materials.

All insulation materialstake energy to manu-facture and transport-something we refer toas embodied energy. Weconsulted the Inventoryof Carbon and Energy(ICE), developed byGeoff Hammond andCraig Jones of the De-

0.065

o 1,430

These second-generationHCFC blowing agentswere required by theMontreal Protocol to bephased out at the begin-ning of 2010; some havebeen replaced with "third-generation" HFC blowingagents. While these HFCshave zero ozone deple-tion potential, they' arequite potent greenhousegases. Initially, there waslittle focus on this prop-erty of halocarbon blow-ing agents, but concernabout GWP of foams is

.growing. Blowing agents

Original CFC-ll

2nd Generation HCFC-141b

3rd Generation HFC-245fa

3rd Generation CO2

Original CFC-12

2nd Generation HCFC-142b

3rd Generation HFC-134a4

45

9.3 0.11

7.2 0

variable 0

4,750

725

1,030

100 10,900

179

13.8

2,310

1. Ozone-depletion potential (ODPI values from U.S. EPA usingMontreal Protocol sources. ODP values are relative to CFC-11, whichis defined as having a value of 1.0.

2. Global warming potential (GWPI values from EPA using IPCCFourth Assessment Report values; lOO-year time horizon assumed.GWP values are relative to CO2, which is defined as having a valueof 1.0.

3. From L.D. Danny Harvey, "Net climatic impact of solid foaminsulation produced with halocarbon and non-halocarbon blowingagents" in Building and Environment, August 2007 (Vol. 42, Issue 8).

4. Despite repeated inquiries, XPS manufacturers declined to saywhat their post-HCFC blowing agent is, and MSDS information hasnot been updated; the blowing agent is assumed here to be HFC-134a, though it may be a mix of HFC and hydrocarbon.

Volume 19, Number 6 . Environmental Building News 9

Feature Article: Avoiding the Global Warming Impact of Insulation

used in common foam insulationmaterials-both historically andtoday-are shown in Table 1 on pre-vious page.

Lifetime GWP of insulationmaterialsBycombining information about theGWP of the blowing agent in foaminsulation (the quantity used in thefoam and assumptions about howmuch leaks out over time) with theembodied GWP based on the em-bodied energy, we can calculate thelifetime GWP of an insulation mate-rial. Lifetime GWP is presented inTable 2 below. The data in this tablehas been normalized by square-footR-value (far right column) to providea common basis for comparison.Note that the values are highly de-pendent on assumptions; we choseconservative assumptions-keyamong them the assumption that50% of the HFC blowing agent infoam will never leak out over the

lifetime of the insulation. (Harveyassumed more rapid loss of blow-ing agents in his analysis.) In ouranalysis, we don't address the rate ofloss, per se, only that 50% of the gas

. will leak out over its lifetime-whichcould be 50 years or 500 years; whathappens to the foam during disposalhas a significant effect on whetherthe blowing agent is released into theatmosphere. There is currently verylittle information on the lifetime ofblowing agents in foam insulation;we hope that the u.s. EnvironmentalProtection Agency or manufacturerswill conduct research on this issue,which has tremendous bearing onthe lifetime GWP of insulation ma-terials.

Calculating GWP paybackThe next step is calculating the "pay-back" of the lifetime GWP in insu-lation materials. By reducing heatloss and unwanted heat gain, anyinsulation material reduces the use

of fossil fuels or electricity requiredfor heating and cooling buildings. Inso doing, these insulation materialsreduce emissions of carbon dioxide(C02), a greenhouse gas that con-tributes to global climate change .We want to know how many yearsof energy savings it will take to payback the lifetime GWP of the insula-tion to figure out whether it's a goodidea to use that insulation materialin our low-energy buildings. An-other way to think about this is howmany years of energy savings willbe required to "break even" on theGWP of the insulation.

In the graphs on page 11, we haveplotted this GWP payback of vari-ous insulation materials: These cal-culations are climate-specific andbased on computer modeling. Thegraphs show the payback of thelifetime GWP of different insulationmaterials plotted as a function offinal R-value in the moderately coldclimate of Boston. We assume that

Table 2. Embodied GWP of Common Insulation Materials

I I !

E b I E b I Emb. i BI. I Blowing I rf t'Insulation R-value Density ~ . C mb . Carbon Blowing Agent Agent ~~~eMaterial R/inch Ib/ffl MJ/k k ~~ /k kgC02/ Agent (GWP) kg/kg GWP/ ft2.R

g g 2 g ft2.R foam I bd-ft

Cellulose 3.7 3.0 2.1 0.106 0.0033 None 0 N/A 0.0033(dense-pack)

Fiberglass batt 3.3 1.0 28 1.44 0.0165 None 0 N/A. 0.0165

Rigid mineral 4.0 4.0 17 1.2 0.0455 None 0 N/A ·0.0455wool

Polyisocyanurate 6.0 1.5 72 3.0 0.0284 Pentane 0.05 0.02 0.0317(GWP=7)

Spray polyure-thane foam 6.0 2.0 72 3.0 0.0379

HFC-245fa0.11 8.68 1.48

(SPF)- closed-cell (GWP=1,030)(HFC-blown)

SPF - closed-cell 5.0 2.0 72 3.0 0.0455 Water (CO2) 0 0 0.0455(water-blown) (GWP=l)

SPF - open-cell 3.7 0.5 72 3.0 0.0154 Water (CO2) 0 0 0,0154(water-blown) (GWP=l)

Expanded 3.9 1.0 89 2.5 0.0307 Pentane 0.06 0.Q2 0.036polystyrene (EPS) (GWP=7)

Extruded 5.0 2.0 89 2.5 0.0379HFC-134d

0.08 8.67 1.77polystyrene (XPS) (GWP= 1,430)

1. XPS manufacturers have not divulged their post-HCFC blowing agent, and MSDS data have not been updated. The blowing agentis assumed here to be HFC-134a.

10 Environmental Buildinq News· June 2010

Feature Article: Avoiding the Global Warming Impact of Insulation

Figure 1. Lifetime GWP Payback XPS & SPF

With XPS and standard closed-cellSPF (produced with HFC-245fa),theGWP payback is much longer. Withone added inch ofXPS(R-5)the GWPpayback is about 36 years; with twoinches, the payback is 46 years; andwith four inches the payback jumpsto 65years. Adding the same R-valueincrements of standard closed-cellSPF yields GWP paybacks of 30, 38,and 54 years respectively. (Becausethe R-value per inch of this SPF issomewhat higher than R-5/inch,those GWP paybacks result from

f-----------~-----~--------------'. somewhat thinner layers.)

Assumptions are key in this analy-sis. In a climate colder than Boston's,the energy savings from the insula-tion will be greater, so the time re-quired to pay back the lifetime GWPof the insulation will be shorter. Ina warmer climate, the payback willbe longer. If we were to assume that100%of the HFCblowing agent leaksout over the life of the insulation, thepayback periods of XPS and stan-dard SPFwould nearly double.

·120.00

20.00

ccSPF50%

XPF 50%

~ 100.00VI•..~ 80.00~~~ 60.00.!l

~ 40.00Q..

Other-l--_,-_-l!f!!!!!!2!!!!!!!!ili!!\lj_I!lII!!i!il!!li!!ijiiiiiiiii!iiii!iiii!!iiiiil~~ Insulation

10 20 30 40

Final R-Valueso 60o

The lifetime GWP payback of extruded polystyrene (XPS) and standard closed-cell spraypolyurethane foam (SPF), both of which are produced with HFC blowing agents, comparedwith other insulation materials, The analysis assumes that 50% of the blowing agent is lostover the life of the material.

Figure 2. Lifetime GWP Payback - Other Insulation

8.00

7.00

r=>; Vi' 6.00•..I'llQ)

5.00~~ 4.00vI'll.!l

3.00>-I'llQ..

2.00

1.00

-/ = Water-blown SPFand Mineral Wool

EPS-I-------------:'7""""--~,..r:::.c::;;;;II"- Polyisocyanurate

Fiberglasst=====~~::::;~~~::==:1/2 lb. SPF

-I-__ ,-_--=::;::==::;::==::;:==::;:==~ Cellulose

10 ·20 30 40 so 60oFinal R-Value

The lifetime GWP payback of various non- HFC insulation materials shown at a scale allowingcomparison. In this analysis, closed-cell, water-blown SPF and rigid mineral wool are nearlyidentical, so those graphs cannot be distinguished.

The results show, first of all, that theGWP payback is very rapid for all in-sulation materials that are producedwithout HFC blowing agents. In add-ing R-25of polyiso (about 4 inches) toan insulated 2x6 wall, for example,the payback of the lifetime GWP ofthe polyiso is about 2.7 years; goingall the way to R-60 with 7.5 inchesof polyiso would increase that GWPpayback to only slightly over 4 years.With cellulose, the GWP payback is

heat is provided by a 90%-efficientgas furnace, and we do not accountfor any change to airtightness as aresult of adding insulation. To pro-vide a consistent basis of compari-son, we assume that the insulationin question is added to a 2x6 wallinsulated with fiberglass insulation(whole-wall R-value of R-14).Thisis a common application for foaminsulation materials, though not forfiber insulation materials, such asfiberglass and cellulose.

Assessment of the IncrementalGWP Payback from AddedInsulationIn his original' [oumol article in Build-ing and Environment, Harvey examinednot only the global warming paybackof insulation materials on a total basis(examining the payback from the lifetimeGWP of the entire amount of insulation inthe system] but also the incremental GWPpayback from adding insulation. In the lat-ter analysis, he models the energy savingsfor lifetime GWP of the last increment ofinsulation-and the results are far moredramatic: paybacks in the hundreds ofyears for high-R-valueincrements. Buildingscience experts John Straube and TerryBrennan argued that this is a flawed ap-proach. "You need to look at the overallpackage, not the marginal," Brennan toldEBN, Life-cycle assessment (LeA) expertGreg Norris agreed that the focus on totalinsulation was more appropriate than onmarginal additions of insulation. For thisreason, we are presenting only resultsthatshow the payback on the total insulation.

always less than one year, even atR-60.

Volume 19, Number 6 . Environmental Building News 11

Feature Article: Avoiding the Global Warming Impact of Insulation

What ThisMeans for theWay We BuilclEBN spoke with several environ-mentally concerned designers andbuilders about the issue ofGWP pay-back of insulation materials. Eventhough it's a complex and confusingissue, we found that interest is strong(at least among this subset of thebuilding industry), and the infor-mation could significantly changebuilding practices.

According to Scott Shell, FAIA, aprincipal at EHDD Architecture inSan Francisco, "combating globalwarming is the most critical issue,and specifying a high-GWP insula-tion completely defeats the point ofusing it." Shell told EBN that he hadbecome aware of this issue and hiscompany is "moving aggressively toeliminate these [HFC-blown foams]on all of our projects."

"This information will influenceour product selection profoundly,"says David Foley, of Holland andFoley Architecture in Northport,Maine. "We do what we do for manyreasons, but anthropogenic climatechange is among the most impor-

tant," he told EBN. "Talk about aninconvenient truth!"

Larry Strain, FAIA,of Siegel& StrainArchitects in Emeryville, California,told EBN that this information "willdefinitely influence our product se-lection." His company has alreadystarted eliminating foam insulationfrom its projects because of concernsabout halogenated flame retardants."If it takes up to 60 years to recoverthe GWP from manufacturing thefoams," he said, "it gives us another,even stronger, reason to find alterna-tives."

Nico Kienzl, of the environmentaldesign consulting and lighting de-sign firm Atelier Ten in New YorkCity, told EBN that his firm haslooked qualitatively at embodied en-ergy and GWP in the past, and thathas influenced what the companyrecommends ("our preferred choicebeing mineral wool"). "More quan-titative information will be valuablein informing a discussion that oftenseems to be too single-mindedlyfocused on more insulation beingalways better," Kienzl said.

Shell says that "there are reasonablereplacements in the vast majority

Photo: John Straube

John Straube used a tongue-and-groove EPS instead ofXPS for insulating beneath the concreteslab in a deep-energy retrofit of his home.

of cases: polyiso for roof insulation,dense-pack cellulose or low-den-sity spray foam (such as Icynene)instead of high-density, and rigidmineral fiber for walls above andbelow grade." There remain somechallenges, according to Shell. "Westill need to look into finding suitableproducts for plaza deck insulation,where paver pedestals need goodstructural bearing capacity; and sim-ilar for below slabs-on-grade."

EHDD just vetoed closed-cell sprayfoam for a Passive House the com-pany is desigriing. "We're usingIeynene in the framed floor over acrawl space, and dense-pack cel-lulose in walls and ceilings," saidShell.Rather than relying on SPFforair sealing on walls, Shell is sealingthe joints ofexterior sheathing with aself-adhered flashing, such as Vycor(from Grace Construction Products)."This is a better and cheaper ap-proach than trying to use spray foamas an all-in-one solution," he said.

EHDD also recently eliminated XPSfrom the Packard Foundation net-zero-energy officebuilding the com-pany is designing," due to high GWPand toxies."In its place, the companyis specifying Roxul mineral wool(see EBN Oct. 2009)both above andbelow grade.

On its Yosemite Institute project,Siegel & Strain Architects has elimi-nated almost all foam, except underslab and slab edge. "We may takeanother look at that now as well,"says Strain.

Tedd Benson, president of Benson-wood in Walpole, New Hampshire,and a well-known leader in the tim-ber-frame construction field, hasbeen refining insulation systemsfor decades. "We have been tryingto make our production more ef-ficient and simultaneously improvethe performance and environmen-tal characteristics of our wall androof systems," Benson told EBN. Thecompany's current wall system-the OBPlus Wall-is the latest in

12 Environmental Building News· June 2010

Feature Article: Avoiding the Global Warming Impact of Insulation

that evolutionary process, relyingentirely on cellulose insulation be-tween wood l-studs, "Wedidn't havethe benefit of your research when wedeveloped the OBPlus Wall," saysBenson, "but I was happy to see thatwe look even wiser now than wethought we were." The company'sfoam insulation decisions are fo-cused on the use of SIPs on some ofits roof assemblies and below-graderequirements. "Your article will defi-nitely guide us toward better deci-sions in these areas."

Paul Eldrenkamp, of the residentialremodeling company Byggmeister,in Newton, Massachusetts, and aPassive House consultant, had al-ready been moving away from SPFwhen he heard Daniel Bergey's pre-sentation at the NESEA BuildingEnergy conference. He had done thisfor three reasons:

First, spray foam (open-cell cer-tainly, but also closed-cell)is muchharder to install well than mostpeople realize. We only began tounderstand this after we startedtesting every insulation job with ablower door. Second, installers donot protect themselves anywherenear well enough from the sideeffects of frequent exposure to thematerial before it's fully cured.And third, the high fossil fuel

. content probably means the priceof spray foam will track the priceof petroleum, whereas cellulose,for instance, will likely alwaysbe a fraction of the cost of sprayfoam for a given Rvalue-e-so weshouldn't forget how to insulatewith cellulose.

Eldrenkamp notes that his com-pany still does use a small amount ofclosed-cell SPF for strategic air seal-ing. "We believe that CCSF [closed-cell SPF] is uniquely effective andappropriate in old basements," hetold EBN. "We have done one deep-energy retrofit in which we sprayedCCSFon the exterior cladding beforeadding new cladding; we've de-cided that, going forward, we'll stripthe cladding and apply rigid PIR[polyiso] instead."

Avoiding High-GWP Insulation Materials

Wall sheathing

Polyisocyanurate

Foamglas (significant cost increase)

APPLICATION I ALTERNATIVE't""4l~~'"':¥~ ,} ~';?C::<'--;"r.~" ~J*%r7 '" :;;*A "'~<!fl1.tl" S • '" YB eess

,~i~~"(.i'.'-,~:fvy0~~i;,'~-Alternativesl;o'extruCleCipolystyrene (XPS) -~.. (... ,'t tJ::~iE;""J:...ct;"\... /":% -~;,::H"::"':."'~J~~•• ';,.."'"t"'''' -~~~ "~~l:t .•..: :''MTt-,~ ~ ~~ ~~ ~ ~

Polyisocyanurate installed on exterior or interior

Expanded polystyrene (EPS) - higher-density recommended for greatercompressive strength

Below-gradefoundation walls'

Avoid insulative sheathing; use cavity.fill insulation with control of ther·mol bridging (offset studs, etc.) and a separate air barrier

High-density EPS on exterior

High-density rigid mineral wool or rigid fiberglass on exterior

Below·grade sub-slob

Interior insulation (polyiso, rigid mineral wool, other fiber insulation)

Rigid mineral wool if compressive strength is adequate (confirm withstructural engineer)

Foamglas (significant cost increase)

Roof sheafhing(below membrane)

EPS - some suggest a minimum 1.5 IblfP density for compressivestrength and moisture resistance (may be difficult to find)

Roof - inverted membrane

Open-cell SPF (increased thickness to achieve comparable R-value)Wall and roof cavity

Covity-hll fiber insulation (increased thickness to achieve comparableR·value)

Envelope oir-seolinq layerWater-blown open-cell SPF or thin layer of closed-cell SPF with cavity-fill insulation

Provide air barrier with separate layer, such as exterior panel sheathingwith self-adhered flashing or tope over joints

Interior insulation overrough foundation wall

Water-blown closed-cell SPF (installation problems have been reportedwith water-blown formulations; obtain performance guarantee andinspect carefully for shrinkage or adherence problems) .

sulation materials with fiber insula-tion alternatives, such as dense-packcellulose installed in double-wallor Larsen-truss (curtain-truss) wall .system, we can avoid the use ofhalogenated flame retardants. Wecan also continue pushing for foaminsulation manufacturing to shiftto safer, phosphorous-based flameretardants and composite manufac-turing with layers that are fire-proof.While the foam insulation industryis transitioning to blowing agentsthat do not contribute significantly toglobal warming, it should also focuson addressing this other concern.

Other issues with SPF are qualitycontrol during installation and po-

Other Concerns With XPSand SPFAlong with the global warming po-tential of the HFC blowing agents inXPS and standard closed-cell SPF,there is also the issue of flame retar-dants. All foam insulation materialstoday are made with halogenated(chlorine- or bromine-based) flameretardants, and there is increasingconcern about the health and en-vironmental impacts of these com-pounds (see "Polystyrene Insulation:Does it Belong in a Green Building?"in EBN Aug. 2009and "Flame Retar-dants Under Fire" in EBN June 2004).

If we replace HFC-blown foam in-

Volume 19, Number 6 . Environmental Building News 13

Feature Article: Avoiding the Global Warming Impact of Insulation

tential performance problems, par-ticularly with the relatively newwater-blown alternatives to HFC-blown SPF.With SPF insulation, theinstaller is essentially manufacturingthe insulation in place. The processinvolves precisely mixing two com-ponents at the right temperaturesand allowing the material to expandand cure (a process that uses watervapor from the air). Because curingSPF is an exothermic (heat-generat-ing) reaction, manufacturers recom-mend installing no more than twoinches (50mm) at one time-and thisis very hard to control, particularlyin a cavity between framing mem-bers that are close together. If thefoam builds up significantly thickerthan two inches, there is potentialfor problems, such as offgassingof harmful chemicals or improperadherence or shrinkage. In short,proper installation of SPF requiresa highly skilled installer and, eventhen, there are risks of performanceand offgassing problems that are notwell understood.

TheFuture ofFoam InsulationManufacturers are working to de-velop and deploy fourth-generationblowing agents that have zero orvery low GWP while still provid-ing the various performance andsafety properties that are required.Such developments would alter theconclusions of this article. Both Du-pont and Honeywell are workingon hydrofluoroalefin (HFO)blowingagents. At the 2010NESEA BuildingEnergy Conference, Gary Loh of-Duf'ont described a zero-Ofzl; low-GWP (less than 10),nonflammable,low-conductivity blowing agent, forSPF, FEA-llOO,that is currently un-dergoing toxicity testing and shouldbe introduced (if toxicity testingcontinues to demonstrate safety)sometime between 2013 and 2015.Honeywell already has a similarproduct on the market in Europefor one-component polyurethanefoams (HFO-1234ze) and expects tobroaden its family of HFO blowing,agents.

When these new products replacethe Hf'Cblown insulations in thecoming years, the argument foravoiding SPF and XPS on the basisof lifetime GWP should largely dis-appear. By then, manufacturers mayalso have replaced the halogenatedflame retardants with safer com-pounds. Until that time, however,there are good reasons to limit useof XPS and closed-cell SPF. .

Final ThoughtsIf our goal is to create buildings thathave little or no net contribution toglobal warming, then the lifetimeGWP of insulation materials is akey consideration. When designinghighly insulated buildings or carry-ing out deep-energy retrofits (a toppriority of green building and reno-vating), we should avoid insulationmaterials with high GWP-extrudedpolystyrene and spray polyurethanefoam that is made with HFC-245fa-so that we aren't sacrificing the veryenvironmental benefits we're tryingto achieve. The table on page 13 listssome of these options.

.Furthermore, the GWP of foam in-sulation materials is high enough(especially earlier-generationmaterials made with CFCs andHCFCs) that it may even make senseto consider the capture and thermaldegradation of these blowing agentsduring building demolition. In theearly 1990s, Northeast Utilities inConnecticut had a program to re-cover and thermally destroy the CFCblowing agents in the polyurethaneinsulation recovered from refrigera-tors that were turned in through anappliance rebate program. That pro-gram was implemented to preventozone depletion, but such a programcould apply as well to greenhousegas emissions. Most of the XPS,SPF,and even polyiso currently in place,was produced with CFC or HCFCblowing agents with significantlyhigher GWP values than today'sblowing agents, so there are con-siderable quantities of high-GWPfoam "banked" in existing build-

ings, even accounting for leakageover the years.As we consider alternatives to XPSand standard SPF,we should try toavoid options that reduce overall in-sulation levels. Achieving very highR-values in our building envelopesshould remain a top priority of greendesign. In most applications, highR-values can be achieved withoutusing high-GWP foams throughthoughtful product specification orchanges to construction details withlittle or no increase in constructioncost. There remain challenging ap-plications, however, such as sub-slabinsulation, where affordable alterna-tives to XPSsimply may not exist orwhere building officials balk at thealternatives.

In making these product substi-tutions or altering our construc-tion details to avoid XPS or SPF,weshould also pay careful attention tolong-term durability. XPS and SPFhave some very attractive proper-ties relative to permeability and airbarrier performance. In some cases,adding more complex framing sys-tems, such as double-stud framingin residential construction, can cre-ate durability problems. If unsureabout proper moisture managementwith new wall systems, seek ad-vice from a knowledgeable buildingscience expert.

For more information:"Net climatic impact of solid foaminsulation produced with halocarbonand non-halocarbon blowing agents"by LD. Danny Harvey in Building andEnvironment, August 2007 (Vol.42,Issue 8)

Inventory of Carbon & Energy (ICE)Sustainable Energy Research TeamDept. of Mechanical Engineering,Univ. of BathBath, UK.+44-0-1225-38-4550www.bath.ac.uk/mech-eng/sert/embodied/

Building Science CorporationWestford, Massachusetts978-589-5100www.buildingscience.com

14 Environmental Building News· June 2010