What's the Healthiest Insulation?

CC BY 2.0. Cork is the healthiest insulation/ Lloyd Alter

A new report from the NRDC has some surprises.

Insulation is a touchy subject in green building. Many designers just want the best R value and tightest seal, which you can get from plastic foams. They say "solid petrochemicals are a lesser of two evils when compared to CO2" and deride my concerns as "an example of 'Perfect is the enemy of good'."

But some organizations have been looking beyond CO2 at the issues of health. A new report by Energy Efficiency for All (EEFA)Making Affordable Multifamily Housing More Energy Efficient: A Guide to Healthier Upgrade Materials is a real eye-opener. It was developed by the Natural Resources Defense Council in collaboration with The Healthy Building Network (HBN), Vermont Energy Investment Corporation, Three3, and the International Living Future Institute, to determine which are the healthiest. Why is this necessary?

Building materials matter to our health. So why do so many of the products commonly used to insulate and air seal our multifamily buildings contain chemicals that are hazardous? We believe that three primary factors are at work: a weak regulatory environment allowing the use of hazardous chemicals in products; misconceptions about chemicals in building products and their impacts; and the lack of disclosure and transparency about chemicals used in products.

Making Better Choices for Materials

formaldehyde is natural

Formaldehyde facts/Screen capture

The regulatory control of chemicals in the USA is particularly weak, with the attitude that they are safe until proven otherwise. An amazing 62,000 chemicals were grandfathered in when the Toxic Substances Control Act was passed 45 years ago and only 200 have been tested since. So according to the EPA many of the chemicals in the list above are perfectly fine. Some of them even have their own promotional organizations. When you are up against the American Chemistry Council, Formaldehyde Facts, and this gem from the Kitchen Cabinet Manufacturers Association, it is hard to know what to believe.


Formaldehyde facts/Screen capture

Toxic chemicals aren't necessarily safe if they are behind walls, either. "A 2009 Healthy Building Network analysis of fiberglass insulation emissions studies revealed that formaldehyde from binders readily migrated through drywall and air barriers."

Using a four-step methodology, NRDC and its partners ranked insulation products on the basis of health impacts. They also include relative costs.

Insulations table

Energy Efficiency for all/via

Regular readers will probably not be surprised to see cork up at the top of the list, but unfortunately it has the highest relative cost of any insulation.

What was really surprising to me was that fibreglass came next; I always thought it should be avoided. The industry replaced formaldehyde binders with acrylic binders a decade ago, but I still believed that the fibres were a health hazard. It also has a bad reputation because of really terrible installations.


© Rockwool

I have been a fan of rock wool instead and once made the case that it was the greenest insulation, but it apparently still has formaldehyde. The Living Building Challenge gives it an exemption for exterior use on foundations because there are not a lot of options, particularly if you want to avoid foam.

Better Insulation Options

Cellulose, which is hugely popular because of its low embodied energy, rates lower than fiberglass because of the large quantity of boric acid flame retardant, "a potential concern because of its associated developmental and reproductive hazards."

There are other insulations that have been excluded because of cost or limited availability, including foamed glass, mushrooms, polyester, Airkrete and sheep's wool. Given that the report is directed toward retrofits of multifamily housing, this probably makes sense. But it would be nice to know where they all sit on the table.

The focus on health in multifamily buildings makes sense, given the higher population density and as noted recently, the often crappy ventilation systems. But the lessons can be applied to any building, the most important being that health matters as much as R-Value. It's a wake-up call:

It is time for a discussion about the connections between people’s health and buildings. While the impacts of housing quality on health are well known to public health professionals, this understanding has only recently gotten traction in the energy-efficiency and building performance industry.

The tighter the building envelope, the more critical it becomes to eliminate these harmful chemicals. That's why it is so important that efficient buildings be healthy buildings. This document is a great place to start.