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Board Insulation Guidelines


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The Eskew+Dumez+Ripple guide to specifying environmentally preferable board insulation.

Published in: Design
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Board Insulation Guidelines

  1. 1. Board insulation BuildingGreen does not recommend extruded and expanded polystyrene (XPS and EPS) due to the number/volume of hazardous chemicals used in their production(s), including benzene, styrene, and halogenated flame retardants (especially HBCD, a persistent, bioaccumulative toxic chemical). XPS also uses the blowing agent HFC-134a, which has a high global warming potential (over 1,400 x more powerful than CO2). If one has to use XPS, Owens Corning has now replaced HBCD with a brominated polymeric flame retardant, developed under the EPA Design for the Environment. It is supposed to be much less of a pbt. They also have Cradle to Cradle Silver v3.1 Material Health Certification Here are some other board insulation options. Most versatile EPS/XPS replacement is mineral wool, because some products can be used below grade—an application typically dominated by XPS. Mineral wool: Made from slag a byproduct of steel production and basalt. Products are available in boards and batts; higher-density boards can be used below grade. Average thermal performance < R-4. Pros  Made with high recycled content slag from steel production (70-90%) and readily available basalt.  Excellent flame resistance without flame retardants.  Moisture resistant.  Pest resistant, ants/termites don’t bore through it  Higher density products can be used below grade, though they may require verification/communication between engineers/manufacturers beforehand. Cons  Board products use urea-extended phenol formaldehyde resins (Batt products from Roxul and Thermafiber are formaldehyde-free but those resins are not appropriate for boards exposed to moisture)  Though phenol formaldehyde resins crosslink into a plastic when heated/cured, resulting in very little to no emissions, urea formaldehyde resins do not crosslink so can break down and release formaldehyde under certain conditions (heat/moisture). So, avoid using them on the building interior when possible  High-embodied energy
  2. 2. Best R-value goes to polyiso, though it absorbs moisture and cannot be used below grade. Polyiso/polyisocyanurate: Found in boards, polyiso (PIR) is a form of polyurethane made from one part polyol and one part isocyanate. Pros  Highest R-value of any insulation, up to R-8/in (from factory) reducing to R-6.5/in (after “aging.”) Foil facings can reduce loss of blowing agent.  Low GWP blowing agent (pentane).  Polyiso is available without the halogenated flame retardant TCPP, from Johns Manville, GAF, and Kingspan (inside metal skinned panels). GAF’s EnergyGuard NH is R-5.7/in  A portion of the polyol component can contain biobased material Cons  Isocyanates, such as MDI and TDI, are toxic, and pose a risk to manufacturer/workers during curing. Polyiso uses more MDI than polyurethane (PUR) used in SIPs (see below) Minimal exposure risk to end user, though possible during cutting.  Again, can lose some performance over time, but the products “settle” into consistent performance.  Absorbs moisture so not for below grade use  Most still use chlorinated flame retardants (TCPP)  Made from fossil fuels  Though pests do not use it as food, they can burrow through foam. Best SIP: Those made with polyurethane cores rather than EPS Polyurethane (PUR): Found in SIPs is similar to SPF. The foams are factory applied, reducing potential exposure to isocyanates on the jobsite. Unlike EPS commonly found in SIPs, PUR SIPs do not contain styrene or its associated hazards. There are a lot of PUR SIPs now on the market, but none that use HFO blowing agents…yet. Pro  SIPs have excellent thermal performance. Murus SIPs, for example, have an R-value of 27 for a 4.5 inch thick OSB/PUR SIP compared to R-15 for a similar EPS SIP and R-17 for Neopor EPS.  Potentially less construction waste  A portion of the polyol component can contain biobased material  Closed cell foams do not absorb moisture  Those made with HFO blowing agents should be available in the future, lowering GWP of the blowing agents from about 1000 to <10. –
  3. 3.  Isocyanates, such as MDI and TDI, are toxic, and pose a risk to manufacturer/workers during curing. Once cured, minimal risk.  Most still use chlorinated flame retardants (TCPP)  Most PURs in SIPs still use HFC-245fa as a blowing agent, with a GWP of around 1000. See above.  Made from fossil fuels  Though pests do not use it as food, they can burrow through foam. Intriguing belowgrade option: durable, water resistant, good compressive strength, holds its R-value Foamglas Cellular Glass: Recently purchased by Owens Corning, Foamglas board insulation is made with sand (60%), limestone (20%), soda (15%), and trace minerals (5%). 18" x 24" dimensions in thicknesses from 2" to 8". A bitumen-faced “Readyboard” is available in 2' x 4' dimensions. A VT company is considering importing cellular glass gravel that can be used in a number of applications. Pros  R-value 3.44 per inch.  Contains no HCFCs or high GWP blowing agents  No flame retardants necessary (of course)  0 VOC, though it can give off hydrogen sulfide when scratched  Extremely durable  Can be used for insulating roofs, walls, and below-grade applications, including beneath slabs.  It is impervious to moisture, inert, resistant to insects and vermin, strong, and has an R-value of R-3.44 per inch.  High compressive strength makes it particularly appropriate for roof decks, green roofs, and parking decks. Cons  Expensive  Trades are probably not used to using it  Takes significant energy to make  Can give off hydrogen sulfide when scratched Kooltherm: phenolic insulation with pentane blowing agent. Highest R-value of any board product equivalent to polyiso. It is phenol formaldehyde, but it is also inherently flame retardant. Interesting tradeoff. Pros  R-8 per inch.  Contains no HCFCs or high GWP blowing agents
  4. 4.  Requires no flame retardants Cons  Is made from formaldehyde, but it is phenol formaldehyde so if they get the manufacturing/crosslinking right, emissions should be very low  Similar to polyiso, it is susceptible to water so not for below grade use. There are also cork and wood (Agepan) board insulation options. Agepan is interesting because it is moisture resistant yet breathes in both directions (it is not a food source for insects (according to the company). Using it would require careful detailing and skinning to make that work.