September, 2007


SYNOPSIS – Organic material and mold is a marriage made in heaven for the simple reason that organic material is food for mold.  Tightly packed cellulose insulation sandwiched in a wall spells troubles if water ever infiltrates where natural ventilation is nonexistent.  Experts in various fields, including mold experts, must share their knowledge to make sure that good intentions in building green do not lead to disasters.  The choice of insulation material must make sense otherwise practicing mold prevention will not do much good.


Charles and Danielle Dobbs


The future looks rosy, or we should say green, because the green movement is here to stay.  For those of us looking for a holistic lifestyle approach and leaving a green legacy for future generations we applaud every effort made toward this goal.  Along the way mistakes will be made with all good intentions, because of lack of knowledge or because things do not always behave in the real world as they do in a laboratory.  We live in an imperfect world and many variables come into play in the building industry.  Experts in various fields must share their knowledge so that adjustments and compromises are made to optimize green buildings without creating problems.

At the September meeting of the Central Florida USGBC Chapter meeting we were fortunate to hear Mr. Cherry, president of the Community Environmental Center in New York.  He shared with us excellent tips on recycling building materials, and he informed us that the city of New York was taking the lead in building green.  However, he mentioned something we are very familiar with – organic material and mold.  He said that cellulose and boric acid work very well as insulation.  That concerns us because as mold inspectors we know that cellulose is candy for mold.  Searches on the Internet are inconclusive because most articles come from manufacturers promoting their own cellulose brand.  The future will tell how this type of insulation will behave under different conditions - with slow leaks or with major water intrusion, such as plumbing leaks, hurricane, or having the building soaked at the time of a fire.

Cellulose insulation is being touted as the “greenest of the green”.  It is recycled from paper products, and laboratory testing has shown that cellulose fiber has a higher R-value over mineral fiber – as much as 38% better.  Researchers at the University of Colorado concluded that cellulose achieves a “tighter building cavity”, thus reducing heat lost.  In addition, cellulose fiber takes 25 to 30 times less energy to make than mineral fiber insulation, and being 3 times denser than fiberglass it provides noise reduction.

Since cellulose burns easily it is necessary to treat it with a fire retardant, such as borax.  However, boric acid is toxic if inhaled, thus installers must wear proper respiratory gears to protect themselves.  Some claim that boric acid is a natural anti-fungal.  On the other hand, the National Insulation Association states that cellulose-based insulation “is the ideal food source for mold if it becomes wet.”  They claim that other biodegradable insulating material, like soybean is superior to cellulose and less susceptible to mold.

What are we to choose?  With time, our imperfect world will tell how cellulose, soybean, corn, or other products will fare against each other.  All manufacturers put disclaimers on their product “ . . . when properly installed, it should . . .”  That’s all nice and dandy but we all know that ideal conditions seldom exist out there, especially during construction, but after owners move and settle in, pipes will leak at one time or another, roofs, doors and windows will sprung a leak, and wind-driven rain during hurricanes, which seems to defy the laws of gravity, will enter buildings in ways previously never thought possible.  Since we live in Florida, we know, we’ve seen it all!  But, if one has to choose between a material that is prone to mold or not, the answer is obvious. One thing is certain - regardless of insulation chosen we must all practice mold prevention.

As mold detection experts we find that many of the mold problems we are investigating could be prevented with simple preventive measures and prompt repairs, and for years, we’ve been preaching mold prevention.  Unfortunately most people wait for something to happen before becoming informed and starting to be proactive.

To prevent mold, one has to understand why and how mold grows in the first place.  The following excerpts from our book: Mold Matters – Solutions and Prevention explain: 

If a mold colony is growing somewhere it sends spores into the air to reproduce itself.  Spores need three things in order to grow: food, a surface to grow on, and water.  When conditions are right, mold can start to grow and propagate in as little as 24 to 48 hours.

Of these three things, water is the only one we can control.  For better or for worse, buildings will continue to be made from organic material: wood studs, pressboard, drywall, and many other common building materials that provide a food source for mold.  Once water has been allowed to infiltrate into the home or building, time is the crucial element.  The faster repairs are made, and the faster drying is implemented, the less likely that mold will gain a foothold.

The increase in incidence of mold contamination in recent times can be attributed in great part to energy conservation measures.  This has made our homes much tighter than they used to be.  In so doing, natural ventilation has been cut down, which would otherwise help dry water infiltration, condensation, or leaks when they happen.  Other factors contributing to mold are cheaper building materials, poor workmanship, leaving building materials on job sites unprotected from rain, and cutting down on time allowed to cure materials.  All this and more has contributed to making homes and buildings more susceptible to mold.

When mold attacks solid pieces of wood, it takes longer to deteriorate, because its cells are not fractured.  Pressboard, on the other hand, has fractured cells and cellulose-based glues (sugar).  This means that the rate of decomposition in pressboard is much higher than in solid wood and the glues used are candy for mold.

Knowing the above, one has to wonder whether organic material is the right choice for insulation in green buildings.  We need to remember that if water infiltrates inside the wall cavity packed with cellulose, tightly sandwiched between two walls with no ventilation, we are looking for trouble.  This brings us to our next question.  What type of insulation should we use in green buildings that is both environmental friendly and mold deterrent?

The concept of Green is in its infancy and many mistakes will be made before we learn what works and doesn’t.  It is imperative that experts in various fields, including mold experts, share their knowledge and experience so that good intentions in building green do not lead to disasters.  Mold not only affects building structures, it can also make people sick.  It is imperative that researchers test insulation under various conditions, including water, to select a type of insulation that is environmentally sound and not prone to mold growth.  We have no doubt that in the end common sense will prevail.

ABOUT THE AUTHORS: Charles and Danielle Dobbs are owners of Dobbs Enterprises, Inc., a water/moisture intrusion and mold detection expert company based in Maitland, Florida.  They are authors of MOLD MATTERS – Solutions and Prevention, and together have written many articles.  More information can be found on their website:

Dobbs, Charles and Danielle. Mold Matters – Solutions and Prevention. Dobbs Enterprises, Inc. 2006.
Lea, Daniel. Cellulose: Building Insulation with High Recovered Content, Low Embodied Energy.  June 24, 1996.



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