Mold: The Unwelcome Houseguest

mold on ceilingMold is a frequent and unwelcome guest in homes across America. So much so that the U.S. Environmental Protection Agency has designated September as Mold Awareness Month.

We at CertainTeed agree that mold is an issue worth addressing. As a manufacturer, we are able to help reduce the threat of mold by developing products that discourage its growth. We also devote significant building science resources to keep building professionals apprised of new information on this complex issue. Perhaps it’s this education, which ultimately trickles down to the homeowner that has the largest impact on mold. After all, it’s not just good materials and proper construction that keep a home mold-free. Good home maintenance is a key defense against the pesky guest.

We often refer to mold as the four-legged stool. It grows easily because it only requires air, water, a food source like dust, paint or fabric, and for the temperature to be between 41 to 104 degrees. In a home, these elements come together frequently so mold has the potential to flourish. Flooded basements or attic space beneath a leaky roof are high-risk areas for mold proliferation, but so are less obvious spaces like carpet near a wet potted plant. Mold spores can also enter a home through open doors, windows, heating, ventilation and air conditioning systems with outdoor air intakes. Spores can even attach to pets and people who unknowingly bring them inside on their bodies, clothes, and bags.

Homeowners are often able to remediate small areas affected by mold. A solution of one cup of bleach to one gallon of water can remove the unwanted fungus from nonporous surfaces. It’s important, however, that homeowners know to be careful to not mix bleach with other household cleaners and to wear disposable gloves and a protective N95 respirator during the remediation process.

For larger mold removal projects, or those affecting porous surfaces like drywall or insulation, building professionals with a solid understanding of building science should be the ones to clean away the mold. These professionals will also be able to safely remove materials and replace them with mold-resistant materials like fiber glass insulation or mold-resistant gypsum wallboard.

The good news is mold does not have to happen. Our building scientists often tout the five Ds to controlling mold. De-leak fixtures and holes, de-bubble wallpaper, dehumidify the indoor air, dry wet furnishings within 24 to 48 hours, and de-odor or fix the source of musty smells.

For more information on mold or Mold Awareness Month, visit


Tips for Checking for Mold Following a Wet Winter


Following this incredibly wet winter, it is a good idea to check to make sure that mold growth is not beginning inside or on your home. You may have noticed that the media has been talking about this on news programs of late.

Mold needs four things to thrive and liquid water is perhaps the most critical as it is the only one we have a chance of controlling. Having liquid water coupled with available oxygen, food and the temperature sweet spot, 41° to 104° F, is the perfect storm for mold growth. Here is what you should do:

  • Inspect your basement for damp walls or cracks where moisture can come in and seal them.
  • Fix plumbing leaks and other water problems as soon as possible. Dry all items completely. 
  • Scrub mold off hard non-porous surfaces with detergent and water, and dry completely.
  • On porous surfaces, in addition to surface cleaning you need to completely dry the material in order to prevent its reappearance. If that can’t be done, you may need to remove the material.
  • Inspect the exterior of your home at ground level. If water is collecting there, divert it away from the foundation.
  • If you find mold, make sure to cover your face and hands to minimize exposure when cleaning the area. It is also important to put a fan in a window and blow air from the room out of the house when you are working around the mold or you may disturb it. If it is a significant area affected or if you begin to feel “allergy type” symptoms when working around mold, call an expert to clean it out.

What humans typically react to are the mold spores which become airborne when it is in its “happy place” with food, water, and a cozy temp or when the mold is physically disturbed.  

We’ve made a lot of changes to how we build in recent years in order to conserve energy and live more sustainably. Many of the things we’ve done to improve our habitat have unfortunately created an ideal environment for mold to thrive. The only chance we have to keep mold from becoming a full-time member of our households is to eliminate the presence of liquid water in or on the materials we use to construct the dwellings.


If It Smells Bad It Is Bad

 September is Mold Awareness Month and I thought it would be a good time to provide some helpful tips about mold.  This was prompted by a discussion that came up the other day when I was conducting a webinar on “The Future of Building Materials and Their Impact on How we Build”.  Mold is not always visible but early detection of a mold problem is critical to the health of a building.

Mold-in-basement2Mold has a long history, in fact, references about mold can be found in the Bible (Leviticus 14: 33-53). When you are dealing with living things that have that much staying power, it is clear that you can’t or won’t get rid of them easily.  In a previous blog, I discussed the four things that mold needs to grow: the right temperature, sufficient water, oxygen and food.  But you can control the growth by eliminating one of the elements. If the problem is moisture in the wall cavity you need to remove all the wet insulation and drywall and thoroughly dry the assembly.

One of the best ways to identify a mold problem early is through smell. Often you can smell it before you see it. If you smell something that doesn’t smell right, trust your instincts and check it out.  This is your learned response to protect you from dangerous materials.

If you think you may have mold, get on your hands and knees and sniff around the outlets in your walls. If you have it – you will smell it.  Also, check areas that do not have adequate ventilation (closets or other spaces with no vents or registers).

If you smell it that means the mold spores are airborne and that is when they present the most health risk. When it’s dormant you are not going to smell it but if the spores go aerosol, you need take action.


Mold Awareness Month: The Five “D’s” to Controlling Mold

Lucas Hamilton

The U.S. Environmental Protection Agency (EPA) estimates that 50 percent of schools nationwide have issues linked to poor indoor air quality.  In many cases, this condition is linked to mold growth in buildings. Mold poses a serious health risk to individuals with respiratory health issues.

This has been a summer of record high temperatures and humidity across the country. This is a perfect storm for the propagation of mold.  As I discussed last year, mold is like a four legged stool.  Mold needs four things in order to grow:  food, water, oxygen and temperature between 41 and 104 degrees.  It is almost impossible to eliminate the potential for molds and mold spores to infiltrate an environment unless you control the elements that give mold it’s ‘legs.’

Controlling the moisture in and around a building is one of the best methods for maintaining a mold-free environment.  By following the five “D’s” you can protect against any opportunity for mold growth or infiltration:

De – Leak – Check for leaky roofs, walls, windows, foundations, facets and pipes regularly and repair them as soon as possible.

De – Bubble – Moisture trapped behind wallpaper paired with wallpaper glue is a perfect recipe for potential mold growth.

Dehumidify – Use dehumidifiers and air conditioners, especially in hot, humid climates to reduce moisture in the air.  Exhaust fans should be used in bathrooms and kitchens to remove moisture to the outside.

Dry – Clean and dry any damp furnishings within 24 to 48 hours to prevent mold growth.

De – Odor – Keep in mind, if you have had a leak, the first sign of mold may be musty or moldy odors. But do not sniff or touch mold.  If you suspect mold, contact a certified mold inspector.

Mold has a long history and a survival instinct that is almost unmatched in nature.  But let’s keep mold outside by making sure that moisture is managed in our buildings.

Lucas Hamilton is Manager, Building Science Applications for CertainTeed Corporation

Proper Roof Ventilation is Critical

Lucas Hamilton

I was in Pittsburgh recently and had the pleasure of visiting a home that was about to be reroofed again – it has been reroofed several times in the last few years.  The house was between 30 – 40 years old and originally had wood shakes which were replaced with asphalt shingles.  The roof was under ventilated to begin with but when they went to the new system it made the problem worse. Each contractor that came along tried to do different things to deal with the problem that the homeowner was encountering.

While putting away Christmas decorations a few years ago, the homeowners noticed ice forming in her attic.  Originally, they thought it was from a roof leak so they replaced the roof.  However, the next winter the ice returned. The roof leak wasn’t the cause. It was insufficient attic ventilation. The house had a great deal of moisture build up in the attic space which was causing ice to form in the winter on the underside of the roof. 

The second contractor tried to add roof ventilation but did it in a way that didn’t help the situation.  He installed a power vent up high on the roof next to the ridge vent.  They put a humidistat on the power vent to activate the vent when the humidity rose in the attic.  The problem was that when the power vent kicked on, because of its position next to the ridge vent, it was pulling air in through the ridge vent and right out through the power vent which did not correct the humidity in the attic or solve the ventilation issue.

I met with them to discuss what was happening to the roof, make recommendations and work with the roofer to correct the ventilation issue. The roofer is going to optimize the power venting and eliminate the ridge vent. This was chosen because there is a concern that with the shape of the roof, you may never get sufficient soffit intake for the ridge vent alone to be sufficient.

As a result of the moisture in the attic, mold was developing on the roof decking.  While there are many ways to remediate mold, the homeowners wanted to take the most certain route which is to remove the contaminated wood. Of course, that adds cost to the project but is the best method of remediation.

Even though the knowledge base on ventilating residential roofs has expanded tremendously over the past 50 years,  professionals can sometimes have a difficult time properly ventilating a unique or challenging roof.  The homeowners were frustrated because they received different information from each contractor.  That can happen.

It is always a good idea to research the issues and ask questions.  In buildings where the attic ventilation requirements are not straight-forward the professional needs to look at the situation  from many angles to come to the right conclusion that solves the problem.   

Lucas Hamilton is Manager, Building Science Applications at CertainTeed Corporation

Moisture Management Remains Key Issue Across America

Lucas Hamilton

Lucas Hamilton

I recently spent some time in the St. Louis area and New York conducting workshops and trainings on moisture management. To my surprise the interest level in this topic remains sky high. The design community as well as contractors still have extreme need for knowledge around moisture management and design options to control this problem.

I guess because I have been dealing with the moisture and mold issues for so many years I feel that just about everyone knows how to protect against it but the truth is there are mold remediation cases from New York to California and it continues to plague the construction industry. But there are solutions to this age old problem – proper wall assembly design and product selection.

Following a training one my co-workers gave there were an hour’s worth of questions about moisture and mold issues. Questions such as:

• What is best assembly to prevent moisture?
• Higher insulation systems vs regular insulation systems?
• What about changes to the building codes regarding vapor retarders?

In a previous blog we did address the conditions that need to exist for mold to grow and we continue to develop solutions around this very critical issue.

We are in the solutions business and have crafted solutions and created balanced systems with products that can help to minimize moisture build up in wall assemblies and continue to conduct presentations and trainings to assist in the understanding of the best practices in resolving moisture issues in construction.

We will continue our efforts to help people build more robust assemblies and welcome the opportunity to respond to questions.

We need to fight the fight because this effects construction costs. The point is if you build it right to begin with you can solve half the problems that result in moisture and mold damage.

Lucas Hamilton is Manager, Building Science Applications at CertainTeed Corporation.

Mold Awareness Month: A Historical Perspective on Mold

Lucas Hamilton

Lucas Hamilton

As we come to the close of Mold Awareness Month, I thought I would offer some perspectives on the history of mold as a follow-up to my earlier blog “Mold is Like a Four-Legged Stool.”

Mold has a long and colorful history. It is a living and very dynamic organism.  Mold spores are everywhere; on clothing, items you buy in the store, in walls and buildings.  It can exist in pores within materials not visible to the eye but once that material is exposed to a temperature of 41° – 104°, has moisture, oxygen and food, it will grow.

Historical References to Mold

  • One of the first references to mold remediation occurs in the Bible in the book of Leviticus chapters 13 and 14 in which God not only reveals that he placed mildew in a home, but offers specific directions about how to remediate the mold using the blood of a dead bird.
  • The Curse of King Tut’s Tomb was Aspergillus mold the most common genus of fungi with 160 species.  In 1922 archaeologist Howard Carter and his team discovered King Tut’s Tomb. Shortly after attending the opening of the tomb in 1922, Lord Carnarvon, as British sponsor of the expedition, died.  It was speculated that supernatural forces were at work. Within five years, 11 of the people who had entered the tomb with Carter were also dead. 
  • The Salem Witch Trials – It has been discovered that Claviceps purpurea a fungus that grows on rye wheat which was used to make bread can cause Ergotism, a disease which affects the pores and can cause hallucinations and convulsions.  In testing artifacts from that time period and exhuming the bodies of those thought to be witches, the bacteria was found.
  • The Irish Potato Famine was caused by Phytophthora infestans, a water mold that attacked the potato crop in Ireland between 1845 -1849 causing thousands to starve and others to flee the country.

Of course there are beneficial uses for mold.  Molds help to breakdown organic matter. Some of my favorite cheeses are ripened using molds. Antibiotics, such as Penicillin are created from molds.

But perception is always in the eye of the beholder.  If you think your neighbor is possessed or if you suffer from headaches, redness and skin irritation, sneezing, watery eyes or more seriously, vomiting, diarrhea, or constant fatigue, it could be from exposure to mold. While it seems mold can cause many symptoms one must remember that there are thousands of species of mold and different species can produce different reactions within different people.

I have come to view human beings as Portable Organic Detection Systems (PODS). We have genetically learned what things are bad for us. Things that smell bad we generally assume are bad for us. It is a learned response that is grounded in a perception as well. If you suspect you may have mold in your walls, get on your hands and knees and sniff at the wall outlets. If there is mold in the walls, in many cases you will smell it there.

Mold has been around for thousands of years and will probably be around for thousands more. Mold is nothing to be afraid of, but it is something we need to control for our health and well being as well as the health of our buildings.

Lucas Hamilton is Manager, Building Science Applications at CertainTeed Corporation. 

Mold Awareness Month – Mold is like a Four Legged Stool

Lucas Hamilton

Lucas Hamilton

Since there is a “month” for just about everything else, why not "mold awareness?"  While some may think this is a non-issue, I assure you, it is not.  Last year the governors of several major states proclaimed September of 2008 to be Indoor Mold Awareness Month.  Other states have now joined the push to raise public awareness of this potential health issue.  For people who have been exposed to mold and have had an allergic reaction, because that is what it is in most cases, it can be a serious problem. Reactions such as a rash, itchy skin, difficulty breathing or headaches have been a result of inhaling mold spores. Over the past 20 years, mold has become very well understood in buildings because of litigation, which bolstered research and conversation regarding the cause, effect and damages that result from mold.

Mold needs four things to live:  a temperature of 41 to 104 degrees; sufficient moisture content; oxygen and food. Mold is like a four legged stool, if you knock one leg out the stool falls over. If mold does occur in buildings there are very well established guidelines for remediation. Mold does not consume building materials, it does not cause structural issues – fungus does – which occurs at a higher moisture content than mold.  Mold is more common and can be dried out, killed, and wiped away.  If you keep the area dry from that point on, you will not have further problems.  People develop issues with mold when it becomes active and releases spores into the air.  Those spores are inhaled and, like ragweed, can cause an allergic reaction.  The trick is to control the elements of the four-legged stool. But how do we control these elements?

Temperature is something we create. We know that mold’s sweet spot is 41 to 104 degrees and I guarantee that you can find that temperature range in just about any wall anywhere in any season. 

Oxygen – you’re not going to get rid of oxygen unless you build your building on the moon. 

Food – starch or sugar typically are the food sources for mold. You can try to build a building that is food free but I guarantee you food will show up. A perfect example of how a food free environment doesn’t last is your shower, which is generally ceramic, glazed tile, glass, chrome, vinyl – there are no starches or sugars in these materials – but mold will grow because food shows up in things like soap.   Starch is one of the binders for soap. That’s the problem with trying to develop buildings without food sources, because food will show up in the form of contamination through the use and occupancy of the building.

The accepted strategy among building designers and construction professionals is to control the moisture so that you do not have a17% wood moisture content in materials. This is the moisture content at which mold will appear.  

We’ve never really been able to completely keep moisture out of our building constructions. The trick is to build living, breathing, drying assemblies that keep moisture content levels low. You can live with bursts above the 17% as long as you get the water out before the mold begins to propagate. If mold does occur in your building, deal with it in a considerate and rational approach: Protect people from exposure to the airborne spores, clean it up, dry out the substrate, and prevent the surface from achieving elevated moisture contents in the future.

 Lucas Hamilton is Manager, Building Science Applications at CertainTeed Corporation.  

                                   Nolan Mug shot             

Nolan Day, Architectural Systems Manager at CertainTeed Corporation contributed to this blog.