Monthly Archives: November 2013

Christmas Trees: a Source of Indoor Mold During the Holidays

A study presented at the annual meeting of the American College of Allergy, Asthma & Immunology in 2007 found that indoor mold increased over a two-week period after a live Christmas tree was placed in the room. The study, which was broadcast on CBS and NBC news, found that airborne mold counts increased from a normal count of 800 during the first 3 days to a high count of 5000 spores per cubic meter of air at day 12.

Although the study was of one tree in one home in the northeastern U.S., allergists from across the U.S. chimed in to agree with the study. Many of the allergists were not surprised by the result given the increase in allergies treated during during the thirty days following Christmas.

ESG has been collecting measurements of mold spore counts inside dozens of homes and businesses across North Carolina during the holidays for many years. Our data suggests that the lone study mentioned above is accurate: indeed, airborne mold counts seem to spike around the New Year and continue to be elevated, especially with a very allergenic mold called Myxomycete. Our office gets a number of calls from people who are suffering from allergies during this time, and in one case a young couple was so affected they stayed in motel until we could help figure out how to reduce the airborne mold counts in their home.

Here in North Carolina, the Fraser Fir is considered the finest Christmas tree, and many families enjoy the tradition of going to the mountains in western NC to cut a live Fraser Fir. What can a family do to help prevent a holiday-dampening allergic reaction? Medical professionals say that vigorously shaking a live tree before bringing it in the house will help. Some people use their leaf-blower to vigorously ‘wash’ the tree with air. Do not wet the tree down, as moisture will activate the mold to grow. Once brought indoors, keep the house around 68 degrees and locate the tree away from any air vents that could disperse the mold around the house. Finally, limiting a tree to a one-week stay inside the house should keep fungal counts low enough for most people to tolerate.

We will discuss the pros and cons of artificial trees in another post in a few days.


It’s a Great Time of Year to Fix Leaky Air Ducts


Craig Whittaker headshot smallCraig Whittaker founded Environmental Solutions Group in 2002 to provide impartial evaluation of properties relative to environmental health. He has assessed more than 1500 properties, has written thousands of environmental reports and is frequently asked to speak about building science issues.

If your home has central heating or air conditioning, your air ducts are one of the most important systems in your home. The air ducts are responsible for delivering conditioned air from the air handlers, which for most homes are located in the attic or crawl space. If the ducts are leaking air, you will spend an average of 20% more on heating your home this winter. For our friends north of the Mason-Dixon line, this can add up to hundreds of dollars worth of wasted energy.

Leaky ducts also draw unfiltered & unconditioned air from your attic or crawl space into the house. This can lead to poor indoor air quality from mold and bacteria, increased humidity during summer and cold spots in your home during winter. Even a small leak at a duct connection can cause the room served by the leaky duct to be several degrees colder than neighboring rooms where ducts may not be as leaky.

Leaking ducts also have more serious consequences. They often negatively pressurize a home, causing outside air to force its way in to balance the air pressure. This can cause a fireplace to backdraft, drawing deadly carbon monoxide (CO) down the chimney instead of allowing it to exit up the chimney. If you have natural gas appliances, the backdrafting from negative pressurization can also be dangerous, which is why it’s so important to have a functioning CO detector in your home.

You may be wondering if the ducts in your home are leaking. It’s best to assume that they leak as even newly-sealed ducts are not 100% airtight, and older systems often lose 35% of their heat through leaks.  In North Carolina and many other states, duct tightness testing is mandatory when new residential systems are installed, a vital step towards saving the power companies from having to produce more energy during peak demand.

The Department of Energy recommends having a qualified professional check for leaking ducts, followed by having them sealed and insulated. While gaps in conditioned spaces are relatively easy to repair, gaps at ducts in unconditioned spaces should be professionally sealed to ensure the use of appropriate sealing materials.

ESG’s sister company, ESG Energy, assesses hundreds of duct systems each year and can assist you in identifying leaks, or verify that leaks have been corrected properly.

In review, leaky ducts raise our heating and cooling costs and may lead to unintended health consequences such as allergies and more serious injuries from mold, bacteria and carbon monoxide. Before it gets cold outside is a great time to check your ducts.

Learn more at or visit for tips on sealing air ducts.