Environmental Impacts of Insulation Types

This document, written by BuildingGreen, is a handy guide for selecting insulation. It summarizes each major type of insulation for material make-up, R value per inch, construction pros and cons, air and vapor permeability profiles, and impact on human health and the environment. At the end is a summarizing comparison chart, as well as a table of their recommendations for various uses.

The top three recommended cavity insulation types:

1. dense pack cellulose
2. dense pack fiberglass
3. mineral wool batts

1. dense pack fiberglass
2. mineral wool batts
3. dense pack cellulose

Here is a link to a Journal of Light Construction article on installing dense pack cellulose.

Aside from R value per inch, there are several criteria you can use to evaluate the appropriateness of insulation. Some things to consider:

– Embodied energy / rate of emissions (energy used / pollution generated to mine the materials for, manufacture, and transport a product)
– Global warming potential (GWP) (must-read article about how an insulation’s GWP will affect its impact on reducing climate change.  and a good summary here).
– Ozone depletion potential (ODP).  New generations of blowing agents have zero ODP, so this is less of an issue now.
– Do they contain halogenated flame retardants (persistent, bio-accumulative toxins that never break down and are believed to cause reproductive, developmental, and neurological impacts- read more here and here)

Brief summary of different insulation types comparing the above criteria:

Fiber (Loose) & Spray in Place Insulation:

– Cellulose has low embodied energy, no ODP or GWP, and no halogenated flame retardants, so ranks best in all criteria. Fiberglass also has no ODP, but has 14x the embodied energy and 5x more GWP than cellulose.
– When choosing a spray polyurethene foam (SPF), pay attention to the type of blowing agent used, which changes its environmental impacts significantly.  Some use water as a blowing agent, and so have low GWP, but also a lower R value.  Most use HFCs (including the office SPF of choice, Walltite Eco).  Closed cell SPF with high R values (above 6) use HFC, and have 35x the embodied energy and 450x (!) more GWP than cellulose.  The lifetime GWP payback (the length of time it will take for the energy savings from the insulation to pay back the greenhouse gas emissions that will result from the use of that insulation) of 4″ of SPF is 54 years, compared to less than a year for an equal R value of cellulose.  Also, SPF has halogenated flame retardants, and possible other health concerns.  While SPF is irreplaceable in some applications, the environmental impacts of spray foam are far higher than any insulation without HFC blowing agents.

Rigid insulation:

– Of all rigid insulation, rigid mineral wool / rock wool (Roxul) has the lowest embodied energy and GWP.  It is naturally fire resistant so no flame retardants are added. 
– The 3 most common rigid boards, Polyisocyanurate,  XPS (closed cell extruded boardstock) and EPS (open cell expanded boardstock) have embodied energy about 5x that of rock wool.  All three use halogenated flame retardants.
– XPS (the only rigid insulation that uses HFC blowing agents) has the highest GWP of any insulation – 20% more than SPF.  EPS and polyiso have low GWP.
– Polyiso is considered the greenest of foam plastic insulations, due to its significantly lower embodied energy.

 A succinct explanation from the president of US Passive House Institute: “It does not make any sense at all to use [insulation materials whose embodied energy is linked to greenhouse gas emissions] if one of the major overarching goals of energy conservation in buildings is to counteract and decrease global warming and climate change.”

*all data cited from linked articles