CASE STUDIES OF MOLDY HOUSES



CASE STUDIES OF MOLDY HOUSES

Jeffrey C. May, M.A.

J. May Home Inspections/JMHI, Inc., Cambridge, MA 02139

Abstract- JMHI has inspected approximately 60 "sick houses." (as of 1991) Occupant symptoms included asthma/allergy, chronic respiratory problems, and sinus congestion. Based on our visual inspections, the most common factors associated with these residential health risks are: forced air systems, humidifiers and mold growth resulting from interior or exterior moisture sources. In most problem houses, the only remediation undertaken was source removal or mitigation.

Key word index: Sick house, airborne spores, humidifiers, ducts

INTRODUCTION

JMHI, Inc. conducts property inspections for home buyers, as well as environmental surveys for homeowners and building operators who are experiencing building-related health and/or odor problems. We have inspected about 1000 homes and buildings, approximately 5% of which could be considered "sick." Improper maintenance of forced air systems, and decay of construction materials or house contents from excess building moisture are most often responsible for occupant symptoms. Pets and pests such as dust mites are additional significant factors.

Architects and builders are sometimes responsible for problem houses, but the occupant's lifestyle or negligence is usually responsible for the excess moisture conditions that lead to mold problems. Representative egregious activities include improperly vented dryers, careless showering, neglect of gutters and poor drainage of foundation water.

METHODS

Inspection

Each environmental survey begins with an initial telephone contact followed by an on-site interview to discuss occupant symptoms, concerns and observations; site observations and appropriate testing are subsequently undertaken.

The physical survey begins at the exterior where the condition of the roofing, gutters and siding is noted. Areas where there are stains on painted wood surfaces are tested for moisture content with a Tramex encounter and mechanically probed for decay.

The grading around the house is observed as well as the discharge areas of downspouts. These areas are noted in order to locate possible sources for basement water entry or moisture. Indoors, areas opposite locations where roof or surface water accumulate are examined closely. Moisture content measurements at walls and floors may be taken with the Tramex encounter or a Delmhorst Moisture Meter. All surfaces in the basement are examined for staining and discoloration that may be the result of mold growth.

Mechanical systems examined in the survey include heating, air conditioning, and humidification. Access doors are opened and visible filters, ducts, blowers, and other components inspected for possible contamination. (Since spillage of combustion gases is quite common, a routine part of any inspection includes testing all combustion equipment for spillage, regardless of complaints, using a TIF 8800 Combustible Gas Detector, TIF Instruments, Miami, FL). If accessible, the chimney flue interior is inspected with a mirror and flashlight from a clean-out or vent pipe.

Interior surfaces are scrutinized for signs of mildew or staining that might suggest entry of exterior water into walls, or plumbing leaks. Bathroom floors and walls may be checked for abnormal moisture content. Occupant portable humidifier use is detailed, and dryer ventilation checked.

Air Sampling

Air sampling for fungal spores and other suspended particles is conducted with a Burkard Personal Volumetric Air Sampler (Burkard Manufacturing, Herdfordshire, England). Glass slides for sample collection are prepared by placing a Scotch Tape "mask," consisting of four strips of tape placed so as to leave a rectangle, about 16 mm x 6 mm, of uncovered glass at the center of the slide. A razor blade is used to coat a film of Dow-Corning High Vacuum Grease at the center of the slide. The tape mask is removed, leaving behind a flat, rectangular layer of the silicone grease about 60 microns thick.

A sampling time of 3 minutes is employed indoors and 5 to 10 minutes outdoors (at the predetermined flow rate of 10 l/Min.). Outdoor and indoor air samples are deposited for convenience of comparison on the same slide by reversing the slide in the Burkard sampler. Burkard samples are stained with acid fuchsin in lactic acid. Spores are counted using a light microscope at 400x or 1000x magnification. Culturable fungi are collected using an Andersen N6 single-stage sampler (Andersen Instruments, Atlanta, GA). Air samples of from 1 to 3 minutes in duration (at 28.3 L/min) are collected on Petri dishes containing Sabouraud (dextrose) medium and incubated at 28¡C. Colonies are counted after 5 days and recoveries reported as CFU/m3.

Dust mite antigen levels are obtained by vacuuming surfaces for three minutes with an ALK filter cassette and vacuum adaptor (ALK Laboratories, Milford CT) and subsequent analysis by ALK.

Surface samples were obtained by pressing Scotch Tape on the surface to be sampled. An approximately 1 cm square piece of tape is cut and placed in a drop of mounting jelly on a microscope slide; a second drop of jelly is placed on top of the tape and a cover slip pressed into place. The prepared slide is observed with a microscope.

GENERAL OBSERVATIONS

Basement Moisture

Between 5% and 10% of houses have some type of moisture problem. The most frequent cause of basement moisture is improper dispersal of roof water; rarely is the level of the water table responsible for a wet basement.

In houses with wet basements, everything and anything can be decayed. Even in basements with little or no stored materials, accumulations of biodegradable dust from the air on foundation walls may become mold-decayed.

In the Northeast, the worst season for interior mold decay is summer when the relative humidity is high and the temperature of the basement masonry floors and walls is below the dew point. During the summer, it is preferable to operate a dehumidifier in a closed basement than to leave the windows open for ventilation. Without dehumidification, foundation walls and carpeting on concrete become wet. It is not uncommon to find visible mildew growth on wallboard, wood trim and partition wood near the floor in basements, though such growth is not necessarily associated with elevated airborne spore counts.

Moldy Carpets

Burkard air samples from carpeted rooms appear to reflect the degree of biological growth in the carpet. For example, the photomicrograph in Figure 1 illustrates two 3-minute air samples collected side-by-side on a single slide in a bedroom with clean carpet. The first sample (left side) was obtained in quiescent room air, the second after agitating the carpet and bedding. There is a lack of spores in both samples, despite a great increase in the number of airborne fibers and skin scales.

The air sample in the photomicrograph in Figure 2A was obtained in a carpeted basement condominium with a strong odor that, in the opinion of the real estate agent selling the property, was the result of "the inhabitant's exercise habits;" the Burkard sample in quiescent room air clearly indicated other sources for the odor, as large numbers of spores and hyphal fragments were present. Just prior to purchasing the unit, the client removed the carpeting; the subsequent Burkard air sample (Fig. 2B) yielded a significant decrease in the spore and debris content.

Furnace Spillage

Spillage of combustion products from gas-fired furnaces, boilers and hot water heaters is most often associated with carbon monoxide; however, moisture is also a combustion product, and a leaking furnace in a house can contribute up to several pounds of combustion moisture per hour of operation. Very often, spillage from combustion equipment continues for years without significant production of carbon monoxide or occupant symptoms or knowledge. There may, however, be building effects such as peeling paint at the exterior and mildew growth in attics or at cold interior corners of ceilings or walls resulting from the excess moisture.

Humidifiers

Humidifiers in houses are either furnace-mounted or portable. In the Northeast region of the country, furnaces are less common than boilers, and of all furnaces, less than 25 % have been equipped originally with humidifiers. Less than 1% of the furnace humidifiers observed on home inspections have been operable; many furnaces previously equipped with humidifiers have obvious signs of rust .

The reservoirs of broken furnace humidifiers are either dry or water-filled, depending on the operability of the float valve. The reservoirs, wet or dry, are always filled with substantial amounts of inorganic and organic debris. I have seen as much as 1 cm of solid crystalline mineral material on the bottom of a dry reservoir. Wet reservoirs (Fig. 3) often have powerful odors resulting from decay of airborne materials such as skin scales, animal hairs and carpet fibers deposited in the water, or mice that have unfortunately found their way into it.

Ultrasonic, steam and atomizing types of portable humidifiers are quite popular consumer items, and major department stores have floor to ceiling stacks on display during the winter. Though the potential for bioamplification and dispersal is substantial, there has not yet been a great deal of demonstrated health effects resulting from residential inhalation of humidifier-generated bioaerosols. The impact of over-humidification on indoor air quality, however, is far less controversial, and the importance of relative humidity to mold and mite growth is clearly recognized.

Burkard air samples containing large numbers of spores and hyphal fragments have been obtained from bedrooms (with carpeting) in which humidifiers were operated for long periods of time.

(As an indicator of the potential for carpet mold growth, one testing method of possible promise is the collection of an agitated-carpet Burkard air sample on silicone grease and subsequent incubation of the glass slide supported above a small amount of water in a sealed container. Extent of mold growth on the slide can be readily observed under a microscope.)

Air Ducts

The average homeowner never has the furnace or air conditioning ducts cleaned. The debris content in ducts depends to a large extent on occupant lifestyle and housekeeping practices; homes containing pets and high-pile carpets that are rarely vacuumed have the dirtiest ducts, particularly if the blowers are operated without filters. A substantial portion of the debris that ends up in a vacuum bag of a clean home comes to rest in the ducts of an unclean home. Generally, the single largest component of the debris is skin scales. Other components are equally well suited for biodegradation by molds under appropriate moisture conditions. The round duct in Figure 4 passed through a damp crawl space and has an approximately 2 cm coating.

CASE STUDIES

Case 1: Rotting Walls

In at least two houses, decay in the cavity of exterior walls is very likely to have been responsible for asthma and/or allergies. In one case, water leaking from the end of a gutter entered a wall (Fig. 5), allowing fungal growth that decayed the entire interior of the wall at the first floor down to the sill (on top of the foundation). Decay spread to the interior side of the wall where the baseboard trim of the bedroom closet was visibly decayed at the interior. The tenant reported that he coughed whenever he was in the bedroom, and the real estate agent noted that a previous tenant with mold sensitivities had been hospitalized twice with asthma attacks the year before.

Case 2: Basement with Fungus

A young couple with no previous allergy history was renting a house in which the basement was used as an exercise room. They had been renting the house for about a year when the wife had her first asthma attack; the husband reported that he had been experiencing chronic sinus congestion. During a casual conversation, the husband observed that puffs of smoke came out of his basement carpet when he jumped on it. Inspection of the home revealed significant drainage, grading and water table problems, with extensive water entry into the finished basement. There was widespread fungal growth on walls and in carpeting (Fig. 6).

Major remediation efforts were recommended that included installation of gutters and perimeter drains, improvement of grading, and replacement of all contaminated walls and carpets; the tenants vacated, nonetheless.

Case 3: Solar Greenhouse Return Air

An older female asthmatic with worsening symptoms requested help because she was only comfortable in the sun porch of her house, where there was no forced air heat register. To conserve energy, the homeowner 10 years earlier had built a solar greenhouse at the rear and ducted the return air for the furnace into the structure. With the heating system operating, air was drawn into the greenhouse from the kitchen at the first floor and into the furnace from the greenhouse at the basement level. No plants were grown in the greenhouse, only mold on soil and wood chips.

The homeowner eliminated the moldy greenhouse from the heating system return and sealed leaky basement ducts; his wife experienced significant relief.

Case 4: Basement, Bedroom and Bath Mold

A middle-aged male with a history of allergy reported wheezing within an hour of arriving home from work. His wife who never had allergy problems was beginning to experience symptoms. Both young children were also experiencing allergies. The basement and bedrooms were sampled with the Andersen and Burkard samplers; and the bedding was sampled for dust mite antigen with an ALK cassette. Viable colony counts in the basement, boys room and master bedroom were, respectively, 4,205 CFU/m3, 2400 CFU/m3, and 2700 CFU/m3, consisting largely of Penicillium and Aspergillus. The basement has a dirt floor and the occurrence of taxa there and in the bedrooms was similar. Burkard samples indicated substantially higher spore counts and numerous respirable fibers that included possibly fiberglass (from insulation), cellulose (from bedroom matting) and asbestos (from friable basement pipe insulation).

The bathroom contained mold growth on the ceiling and both Burkard air and Scotch Tape sampling (with subsequent growth on Sabouraud agar) suggested Cladosporium. No Andersen sample was obtained, but the total count on the bathroom Burkard slide was probably in the range of tens of thousands of spores per cubic meter. The level of total dust mite antigen in the couple's bedding was high: 60 micrograms per gram of dust.

Installation of a basement cement floor and a bathroom exhaust, and institution of dust mite environmental controls were recommended. Elimination of the bedroom mat and disinfecting the bathroom mold was also suggested. (Figure 7 illustrates Aspergillus growth on the ceiling and walls of a bathroom in another home.)

Case 5: Unvented Dryers

A young client with sensitivity to Aspergillus (according to his physician) reported feeling lethargic at home. The family had been venting the dryer into the closed garage and showered very carelessly. There was fungal growth and laundry lint at most garage surfaces as well as floor decay under the bathtub all along the bottom edge. Judging from the odor, a bathroom mat beside the tub had significant microbiological growth. Dryer vent moisture in the garage migrated upward to the attic where the north facing underside of the roof sheathing was all stained by mold proliferation. Venting the bathroom and dryer to the exterior were recommended.

Another homeowner reported that shortly after purchasing his dryer, mold and plaster efflorescence began to appear in one corner of his second floor bathroom. In this case, the dryer was operating unvented in the basement directly below the plumbing chase which was open to the attic. Warm, moist air from the dryer rose through the chase into the attic, where it condensed on a cold horizontal section of vent pipe and dripped down. Curiously, all the stack pipe joints in the attic had been heavily caulked and a roasting pan placed under the pipe, as the owner must have believed that there was a pipe leak. The pan was full of water and overflowing at a point directly above the bathroom ceiling location where the damage was observed. Sealing the chase in the basement and venting the dryer were recommended.

Case 6: Humidifier Irritant/Allergen

An asthmatic real estate broker called because she was having difficulty breathing every morning. She noted in our conversation that she was using a portable ultrasonic humidifier in her bedroom. I recommended that she stop running the humidifier and replace her pillow. Her mornings improved immediately.

I experienced similar relief on two occasions after terminating humidifier use. In our first house, every time the furnace blower started both my son and I would start to cough virtually simultaneously wherever we were. This occurred before I was familiar with the potential problems associated with humidifiers. I was brought to sudden awareness when I looked at the reservoir water under a microscope and found the abundance of life within it to be most similar in appearance to that in stagnant pond water.

Having learned nothing from this experience, I abandoned the furnace humidifier for a bedroom ultrasonic unit. Needless to say, the results were not too different, though with regular cleaning the irritation caused by the humidifier was intermittent. The apparent lack of consistency in clean room humidifier's impact on the allergenicity of the air may have to do with periodic variations in the microbiological content of the water which is supplied from a city reservoir that is under the local pigeon flight path and that is a favorite swimming hole for dogs and ducks.

Case 7: Accidental Mold Growth

In my own house, two typical examples of accidental mold contamination occurred. At one time, I coughed unpredictably in the kitchen of my house. Ultimately, I realized that the coughing began as soon as the refrigerator compressor started running. I removed the drip pan and found a moldy onion resting in a puddle of condensate water. Each time the compressor ran, air was blown over the moldy onion and into the kitchen. On another occasion, I found the dictionary under my son's fish tank filled with Penicillium from long-term leakage of his fish tank pump.

In the home of an asthmatic nurse, moldy grass on a stored lawn mower in the basement appeared to be the most likely irritant source. In the home of a pulmonary physician, water had been leaking unobserved from the washing machine hook-up hose and dripping onto floor lint and debris. The exhaust hose for the adjacent dryer was crimped creating excessive back-pressure that caused the hose fittings to leak hot air that probably distributed the moldy debris under the washer.

CONCLUSION

From my perspective as a home inspector, mold contamination of buildings is of far greater consequence than is generally recognized, and in fact could easily be the source of interior pollutants with the most widespread impact on health.

The prevention of mold problems is generally not a complicated matter but will require that homeowners and building operators be educated and made aware of the connection between mold contamination and health.

Both of my children have allergies and I wonder if there is any coincidence in the fact that they each spent part of their early childhood in damp basement child care facilities crawling on carpets that were probably infested with mold and mites.

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