Choosing the Right Insulation

Lots of remodelers still think green building is an exotic animal of some kind. Or a hippie thing, where resulting projects are geo-domes made of ugly gray foam.

Of course, that’s not true. But the 1970s projects that celebrated function over beauty didn’t exactly advance the green building movement, because people thought you had to compromise comfort and beauty to save energy and trees.

Today, baffled remodelers (even the ones without the gray ponytails) still pull me aside to ask, “What is this green thing really about?” My answer: The green building movement largely asks that you use greener versions of your traditional building products. It does not ask that you radically change your approach to building. In fact, if you are reading this magazine, you are probably already a green builder, in terms of the high-integrity thermal envelopes you design and build. So, your next steps are to use: a) low-toxicity/non-toxic building products and b) sustainably harvested/recyclable materials. That’s getting easier, as manufacturers and regulations move in to make these products more widely available.

Green alternatives

One area where you have some great green alternatives now is insulation. Sure, insulation has always been green in the sense that it resists the movement of heat, a.k.a. R-value. But there are degrees of green even among insulation products, depending on what’s inside the product or what propels it into place. Let’s take a look at the categories.

Insulation generally breaks down into SIPS, batts, foams and loose fills.


In terms of performance and toxicity, SIPS are a very green solution. OSB sandwiches EPS foam to make a SIP, and SIP walls can give you R-30 and great sound attenuation, while reducing the amount of framing required. SIPs are very green, indeed. With the attention to formaldehyde, a known carcinogen contained in many OSBs, you have a VOC (volatile organic compound) situation, but it is largely minor. Plus, there are formaldehyde-free OSBs available, and if you don’t want to use EPS foam (which uses pentane, a hydrocarbon propellant), you can get a straw core. Wow, now that’s really green.


With fiberglass batts, you have choices that focus not on the fiberglass — which is inert — but on the binder that holds it together. Johns Manville has loudly broadcast their formaldehyde-free status, but others, like Owens Corning, have countered that the formaldehyde in their binder doesn’t emit at harmful levels, and they have lined up third-parties to confirm the claim, like Greenguard, SCS and now NAHB’s “Green Approved Products” seal of approval.

Since the California Air Resources Board (CARB) sets broad-reaching indoor-air quality standards, which are widely viewed as the toughest in the nation, look for more batt manufacturers to meet those CA standards and advertise the fact, even if they aren’t selling into California markets.


You get great performance from foams, but the top-rated products for R-value (high-density, closed-cell polyurethanes, delivering R-7 per inch) use the most hazardous chemicals (like HCFCs). Open-cell foams don’t perform as well by comparison but use fewer hydrocarbons and can even use bio-based (e.g. soy) components and CO2 as a blowing agent, as you see in BioBased 501.

Loose fills

JM’s Spider is a formaldehyde-free blow-in fiberglass product, and it achieves R-23 in a 2x6 wall, with a Sound Transmission Class (STC) of 43. (By comparison, a single 16-in. o.c. wood-stud wall with 1/2-in. type X gypsum board on each side, and 3 to 4 in. of fiber batt will give you an STC of around 45. Every 10 STC points reduces noise by 50 percent). But loose fill made of recycled paper and cardboard is cheaper and can be equally effective in resisting heat flow, though it is substantially heavier than all the other alternatives. No matter what you use, it should be treated with an EPA-approved fungicide. And it can be treated for resistance to fire and insects.