Let’s Talk Mildew !!

Mildew and Mold terms are used interchangeably


This writing is a Review of my education of the Mildew/Mold issue,

clarification comments are appreciated.


Did you know that Florida Insurance Companies are considering dropping coverage for Mildew damage in all of Florida?  This is why this is now a topic of high interest!


What does mold need to form and grow? 

          Water, warmth, medium for roots (dirt, paper, wood, dirt in voids, etc.)


Where does the water come from?

          Temperature differences between inside and outside.

          Water leaks from windows and from roofs.


How can you stop all water leaks?

You can’t stop all water leaks in all homes.  You can try, but construction is prone to human error and some problems will occur.


So the next question is How can homes be built the best to minimize Mold?  


Determine “Design Criteria”


You design the home with materials and methods to by ‘best effort’:

(1)   reduce the possibility of water intrusion and

(2)   when water does get in, the design will allow the water to leave at a rate faster

than mold can form.



To build a home that is moisture/mold resistant the structure needs to :


·         have the capability to not  weaken, or be damaged, when it gets wet; then be able to allow the water to be removed by nature’s dehumidifiers (heat of the sun and air flow/wind) or by manmade dehumidifiers (Air Conditioner Air Handlers and Stand alone Dehumidifiers) at a rate faster than mold can grow.

·         have a Moisture Barrier within the wall system, or on one side only,  to stop the moisture from going from one side of the wall to the other side of the wall.  This makes it so the path of least resistance of the moisture is straight to the outside edge of the wall where it is being pulled by the dehumidifiers. 


Even in Florida where the moisture is sometimes in the 70-90 percent range, this is less than the 100% moisture of the water in the wall, so the water will still travel toward the 70-90 percent exterior.  To keep the moisture (such as rain and water from a hose when cleaning the walls)out of the wall system, the material needs to be finished with a  paint that resists direct application of water  onto it, but allows any moisture that does get by the paint to escape THRU the paint.  This sounds like a hard thing to accomplish, but the house paints on the market today meet this criteria.  Once the water has penetrated the paint, or has been introduced behind the paint because of a water leak at a window or thru the roof, the material in the wall needs to be dense enough to absorb only the amount of water that can be removed by the methods above.  If the water does not get absorbed where it can be easily removed it will run off and the leak will be obvious.  So, little leaks will be handled by nature and is OK and big leaks will not be hidden in the wall and can be noticed and repaired, which is what we want.  We do not want the expense, or inconvenience, of having to repair the leak, but the cost to repair a leak when it is first found, is much less than the cost to repair the leak and the area ruined by mold.  The cost of the damage the mold is doing to our bodies can never be quantified. 



1)     Use Materials that can take a little moisture in and get rid of it without the material being damaged. 

2)     Use a material that repels large amounts of water from leaks so the leaks can be noticed and repaired prior to the forming of mold. 

3)     Use a moisture barrier near the middle of the wall. 


What is the best material to use to build a home?

It was once thought, that the more dense the material the better, but field experience and testing has shown that materials more dense than concrete can form mold in a very short period of time, even when directly exposed to sun and air.

The materials to best accomplish the goal of resisting mold is dense concrete

The bonding of the materials that make up concrete, and the PH produced, may resist the initial growth of mold. 

The water that makes its way in easily make its way back out prior to the forming of mold.  


For porous concrete - the water goes in and continues to travel further from the outside edges and then takes longer to remove, allowing mold to form.


Let’s compare these two methods:

All Wall System vs. Concrete Block


All Wall method of building walls

Wall materials listed from the inside out:

Cement Board

(which resists mold-water and does not deteriorate.  It can be soaked in water and when it dries it is stronger.)

Dense Concrete

4” Foam (as low as 1” thickness it is Impervious) Moisture Barrier

Dense Concrete

Cement Board

Cementious material (1/8” thick)



The All Wall System of building walls

COMPLETELY satisfies

the design criteria required to resist mold.

(hint as to why:  There is not any wood, or paper products to hold water.)

To help you understand the

Concrete Block method of building walls

We are going to list the wall materials listed from the interior of the room to the exterior of the wall:


Gypsum Wall Board (absorbs water and is weakened by water and wicks water)

¾” of wood, that absorbs water (furring strips that are nailed to the blocks)

Insulation material, usually sprayed cellulose(paper) that moisture is hard to get out of, once it is wet.

Porous concrete (concrete block)

Air Void

Porous Concrete (concrete block)

Stucco (cementious material 1” thick, applied in 3 coats)



·         The Concrete used is porous and will allow water travel and storage deep into the wall. 

·         There is no Vapor Barrier.

·         The air void will form moisture when the temperature difference between the interior conditioned air has approximately 40 degrees difference in temperature from the outside air. (Humidity, etc. affects this temperature difference.)

·         The concrete block method utilizes Gypsum Wall Board and wood that holds moisture which feeds mold. 

(Similar to a wood framed home.)


The Concrete Block method FAILS in 5 areas

of building a home to prevent mold problems


Mold from a more technical perspective:


Moisture concern in the Winter.

How to stop the environment that makes Mold form.


We are looking at two problems:


1.)  On the one hand we have traditional walls with semi-open cavities. Improper placement of vapor barriers can and will trap moisture in these cavities causing a variety of problems.  The design problem in this case is to create a wall cavity that breathes and doesn't trap moisture within the wall.


2.)  On the other hand, an almost impervious wall structure may not pass appreciable amounts of water vapor.

The design problem in this case is the internal volume of the house itself.  With an ACH of 0.05 and an impervious wall, the design problem is how to eliminate moisture build up in the house. We have to remind ourselves that our air conditioning firms are usually called H"V"AC companies.  "V" for Ventilation.  A member of the FBC, at a FBC meeting, brought up this very important point and phrase. This problem can be solve with Ventilation since it appears to be a winter time issue.  Long term, we need to look for a national AC firm that admits that the concept of a specifically designed outdoor air (OA) unit for   commercial concerns should probably be downsized for residential homes in the very near future. The additional cost,  complexity and energy penalty of separate de-humidifier should push some national concern to solve this in a more  integrated fashion.  Another way to attack this problem is to look at the effects of an additional 0.30 ACH of continuous mechanical ventilation. This value is the existing 0.05 ACH plus enough to reach the code requirement of 0.35 ACH. Of course all the attendant problems and issues of fresh air would have to be solved.  This is why Eco-Smart Homes have ventilation as a necessary component of their air conditioning systems.


One issue is clear:

When you minimize the skin loads and infiltration, the issue of ventilation moves to the front row. 


CFI (All Wall System) and ICF (Styrofoam Blocks filled with concrete) houses do this by their very nature so they will fortunately and unfortunately be solving this coming problem ahead of the rest of the construction industry. 


The other, obvious source of water is the concrete in the walls:

·         The All Wall System can express water both to the outside and inside as it cures, eliminating the possibility of mold. 

·         ICF (styrofoam blocks filled with concrete on site) forms will cause this water to be held more closely around the concrete, slowing down the cure of the concrete (a good thing for concrete strength) and slowing down the expressing of the water possibly allowing time for mold to form, though this is not a known issue to be concerned with.  The concern with ICF’s is when they have drywall boards on the interior of the wall, which holds water for mold to grow.




Mold is fast becoming one of the most important health, legal and business issues on the Florida real estate scene. Homeowners, landlords, lenders, real estate professionals, builders, and architects all face health, insurance, liability and property value issues related to mold.


Virtually any mold, when present in high quantities, can cause respiratory problems, such as sinus infections or asthma. Mold can cause severe allergic reactions in sensitive individuals and dangerous infections in persons with compromised immune systems. Some types of mold, like the “black mold” Stachybotrys produce deadly airborne toxins that can cause serious breathing difficulties, memory and hearing loss, dizziness, flu like symptoms, and bleeding in the lungs.


In the past few years hundreds of lawsuits have been filed in Florida and other states for mold damage to homes, schools, commercial facilities and government buildings. Liability issues have become a concern for landlords, and other commercial property owners. Insurers have reacted by raising rates, reducing coverage or exiting the market. Meanwhile, the cost of fixing mold-related problems, or remediation, continues to rise.


Only a complete professional inspection can determine if mold is a problem.  Then an accurate and objective report can be made.





Rampant mold growth has shut down new courthouse buildings in Palm Beach and Martin Counties and required multimillion remediation efforts before they could reopen. Homeowners and apartment tenants in Sunbelt states like Florida have won expensive verdicts and settlements for health concerns related to mold. Meanwhile, insurance companies are trying to reduce their risk by limiting or excluding coverage.


Indoor air quality (IAQ), especially mold growth, is fast-becoming one of the most important health, legal and business issues on the Florida real estate scene. Property owners, landlords, lenders, real estate professionals, builders, and architects all face potential liability issues related to mold.


While mold has gotten most of the recent headlines, it is far from the only IAQ issue faced by property owners and managers. Today’s tightly sealed buildings mean that occupants breath continually re-circulated air with high concentrations of dangerous chemicals, pet dander, dust mites, bacteria or viruses.  Substances in the air such as dust, pollen, or mold become "triggers" to the sensitized immune systems of people with allergies or to the inflamed airways of those who suffer from asthma. 


The U.S. Environmental Protection Agency (EPA) estimates that levels of pollutants are much higher indoors than outdoors, although most people spend 90 percent of their time inside offices, schools, warehouses and homes.  The quality of indoor air is a particular concern for schools, and daycare centers because young children cannot tolerate exposure to pollutants like adults. The costs of poor air quality include medical care, lost productivity due to absenteeism, lower efficiency on the job and material and equipment damages.


Health Problems


Mold can grow on any organic substance, provided moisture is present.  That means an opening in a roof or window, a plumbing leak or a flood can create ideal conditions for this naturally occurring fungus. Building materials such as drywall, plywood, plasterboard, wallpaper, and carpet provide the foods needed for molds to quickly grow and reproduce, releasing more and more of their reproductive spores into the air.  Although mold has always been present in homes and buildings, it has not received the nationwide interest that it is receiving today. Homeowners, tenants, and workers across the country are filing lawsuits in increasing numbers, claiming that indoor mold has harmed their health. Eighty percent of all IAQ issues are mold related.


Many health cases center around stachybotrys, known as “black mold,” which produces airborne toxins, called mycotoxins that can cause serious breathing difficulties, memory and hearing loss, dizziness, flu like symptoms, and bleeding in the lungs.  But stachybotrys is far from the only mold problem. Virtually any mold, when present in high quantities, can cause respiratory problems, such as sinus infections or asthma. Mold can cause severe allergic reactions in sensitive individuals and dangerous infections in persons with compromised immune systems. Prolonged exposure to mold can cause children and adults to develop a variety of respiratory symptoms.


A 1999 Mayo Clinic study pegged nearly all the chronic sinus infections afflicting 37 million Americans to molds.


Recent studies have linked molds to the tripling of the asthma rate over the past 20 years. “While we do not know all the causes of asthma, we do know that environmental factors such as air pollution, mold and second-hand smoke make asthma worse,” says EPA Administrator Christie Whitman.


Additional researched information.

Water Intrusion & Mold

An Overview

Mold and fungus claims against residential builders are increasing at alarming rates. Plaintiff attorneys are referring to mold and fungus as “Black Gold” and have targeted residential builders as their primary target!

Mold (or fungi) is an extremely complex topic for residential builders. It is an issue that must be taken seriously, and addressed appropriately by the builder community, especially since coverage for mold related issues are excluded from most general liability policies.

It is becoming more and more common for builders to be notified by their homebuyers that they are experiencing symptoms, which, in their opinion, may be associated with exposure to mold and/or fungus or that they have a moisture problem. Builders should immediately meet with the homeowner to determine if visible mold is present in the home, or if there is currently, or has been in the past, any form of water intrusion into the home. The builder should determine if there have been any plumbing leaks, window leaks, roof leaks, or water intrusion into the basement or slab. The builder should look for any signs of water damage or stains around windows, under sinks and vanities and at any other area that may be susceptible to water intrusion.  The most common reported symptoms of mold exposure are fatigue, nausea, headaches, cough, congestion, eye irritations, aggravation of asthma, and flu-like symptoms.  The likelihood of an individual developing symptoms after exposure to mold depends on what type of mold he or she is exposed to, the genetic predisposition of the individual, the person’s age, and general state of health.

It is important to note that measurements of exposure have not been standardized, and it is impossible to determine safe or unsafe levels of exposure for people in general. It is this ambiguity that is so frightening to builders, and also creates an atmosphere that is amenable to claims and litigation. While it may be difficult to prove that an illness is the result of exposure to mold, it can be even more difficult to prove an illness is not the result of mold exposure, especially if the presence of mold has been discovered in the claimant’s residence. It is perhaps the fact that so many illnesses are similar to those that may be caused by exposure to mold, as well as the difficulty in assessing if molds that are present are actually toxic to the homeowner that makes this issue so frustrating and dangerous!

Many of the general liability policies for residential builders now exclude coverage for property damage and bodily injury claims related to mold and fungus. These exclusions result in the builder’s assets and profits being exposed for the indemnity costs and the significant legal costs associated with mold and fungus claims.

Today’s homes are full of materials that are ideal for mold growth including but not limited to insulation materials, drywall, lumber, flooring, ceiling and floor tiles, carpet and carpet padding.

“Mold can grow on virtually any substance as long as moisture is present. Therefore, the only way to control your exposure to mold and fungus claims is to control moisture intrusion!”

This last information is an article within:   http://www.2-10.com/newhomebuilders/pdf/Constructive_Solutions


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