Mold in Homes

INTRODUCTION

This fact sheet provides information for people whohave mold problems in their homes. It presents thehealth concerns associated with mold exposure andadvice on finding and removing mold contamination.

What is Mold?Molds are fungi. Molds grow throughout the naturaland built environment. Tiny particles of mold arepresent in indoor and outdoor air. In nature, moldshelp break down dead materials and can be foundgrowing on soil, foods, plant matter, and other items.Molds produce microscopic cells called “spores”which are very tiny and spread easily through the air.Live spores act like seeds, forming new mold growths(colonies) when they find the right conditions.

What does mold need to grow?Mold only needs a few simple things to grow andmultiply:• Moisture• Nutrients• Suitable place to growOf these, controlling excess moisture is the key topreventing and stopping indoor mold growth.

Should I be concerned about mold in my home?Mold should not be permitted to grow and multiplyindoors. When this happens, health problems canoccur and building materials, goods and furnishingsmay be damaged.

HEALTH EFFECTS

Can mold make me and my family sick?Mold can affect the health of people who areexposed to it. People are mainly exposed to moldby breathing spores or other tiny fragments. Peoplecan also be exposed through skin contact with moldcontaminants (for example, by touching moldysurfaces) and by swallowing it.

The type and severity of health effects that mold mayproduce are usually difficult to predict. The risks canvary greatly from one location to another, over time,and from person to person.

What symptoms might I see?The most common health problems caused by indoormold are allergy symptoms. Although other and moreserious problems can occur, people exposed to moldcommonly report problems such as:• nasal and sinus congestion• cough• wheeze/breathing difficulties• sore throat• skin and eye irritation• upper respiratory infections (including sinus)

Are the risks greater for some people?There is wide variability in how different people areaffected by indoor mold. However, the long termpresence of indoor mold growth may eventuallybecome unhealthy for anyone. The following types ofpeople may be affected more severely and soonerthan others:• infants and children• elderly people• individuals with respiratory conditions or

sensitivities such as allergies and asthma• persons having weakened immune systems (for

example, people with HIV infection,chemotherapy patients, organ transplantrecipients)

Those with special health concerns should consult amedical professional if they feel their health is affectedby indoor mold.

Are some molds more hazardous than others?Some types of mold can produce chemicalcompounds (called mycotoxins) – although they donot always do so. Molds that are able to producetoxins are common. In some circumstances, thetoxins produced by indoor mold may cause health

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problems. However, all indoor mold growth ispotentially harmful and should be removed promptly,no matter what type(s) of mold is present or whetherit can produce toxins.

HOME INVESTIGATION

How do I tell if I have a mold problem?Investigate – don’t test. The most practical way tofind a mold problem is by using your eyes to look formold growth and by using your nose to locate thesource of a suspicious odor. If you see mold or ifthere is an earthy or musty smell, you should assume amold problem exists. Other clues are signs of excessmoisture or the worsening of allergy-like symptoms.

• Look for visible mold growth (may appearcottony, velvety, granular, or leathery and havevaried colors of white, gray, brown, black,yellow, green). Mold often appears asdiscoloration, staining, or fuzzy growth on thesurface of building materials or furnishings. Whenmold is visible, testing is not recommended.

• Search areas with noticeable mold odors.• Look for signs of excess moisture or water

damage. Look for water leaks, standing water,water stains, condensation problems. Forexample, do you see any watermarks ordiscoloration on walls, ceilings, carpet,woodwork or other building materials?

• Search behind and underneath materials (carpetand pad, wallpaper, vinyl flooring, sink cabinets),furniture, or stored items (especially things placednear outside walls or on cold floors). Sometimesdestructive techniques may be needed to inspectand clean enclosed spaces where mold andmoisture are hidden; for example, opening up awall cavity.

Should I test for mold?The Minnesota Department of Health does notrecommend testing for mold. Instead, you shouldsimply assume there is a problem whenever you seemold or smell mold odors. Testing should never takethe place of visual inspection and it should never useup resources that are needed to correct moistureproblems and remove all visible growth.

Sometimes, mold growth is hidden and difficult tolocate. In such cases, a combination of air (outdoorand indoor air samples) and bulk (material) samplesmay help determine the extent of contamination andwhere cleaning is needed. However, mold testing israrely useful for trying to answer questions abouthealth concerns.

MOLD CLEAN UP AND REMOVAL

To clean up and remove indoor mold growth, followsteps 1-6 as they apply to your home.

1) Identify and Fix the Moisture Problem - themost important step in solving a mold problem is toidentify and correct the moisture source(s) thatallowed the growth in the first place. Common indoormoisture sources include:• Flooding• Condensation (caused by indoor humidity that is

too high or surfaces that are too cold)• Movement through basement walls and slab• Roof leaks• Plumbing leaks• Overflow from tubs, sinks, or toilets• Firewood stored indoors• Humidifier use• Inadequate venting of kitchen and bath humidity• Improper venting of combustion appliances• Failure to vent clothes dryer exhaust outdoors

(including electric dryers)• Line drying laundry indoors• House plants - watering them can generate large

amounts of moisture

To keep indoor surfaces as dry as possible, try tomaintain the home’s relative humidity between 20-40percent in the Winter and less than 60 percent the restof the year. You can purchase devices to measurerelative humidity at some home supply stores.Ventilation, air circulation near cold surfaces,dehumidification, and efforts to minimize theproduction of moisture in the home are all veryimportant in controlling high humidity that frequentlycauses mold growth in our cold climate.

2) Begin Drying All Wet Materials - as soon aspossible, begin drying any materials that are wet. For

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severe moisture problems, use fans and dehumidifiersand move wet items away from walls and off floors.Check with equipment rental companies orrestoration firms to see if you can rent fans anddehumidifiers.

3) Remove and Dispose of Mold ContaminatedMaterials - items which have absorbed moisture(porous materials) and which have mold growing onthem need to be removed, bagged and thrown out.Such materials may include sheet rock, insulation,plaster, carpet/carpet pad, ceiling tiles, woodproducts (other than solid wood), and paperproducts. Likewise, any such porous materials thathave contacted sewage should also be bagged andthrown away. Non-porous materials with surfacemold growth may be saved if they are cleaned welland kept dry (see step 4).

Take Steps to Protect Yourself - the amount ofmold particles in air can increase greatly when mold isdisturbed. Consider using protective equipment whenhandling or working around mold contaminatedmaterials. The following equipment can help minimizeexposure to mold:• Rubber gloves• Eye goggles• Outer clothing (long sleeves and long pants) that

can be easily removed in the work area andlaundered or discarded

• Medium-efficiency or high-efficiency filter dustmask (these can be found at safety equipmentsuppliers, hardware stores, or some other largestores that sell home repair supplies) -- at aminimum, use an N-95 or equivalent dust mask

Take Steps to Protect Others - plan and performall work to minimize the amount of dust generated.The following actions can help minimize the spread ofmold spores:• Enclose all moldy materials in plastic (bags or

sheets) before carrying through the home• Hang plastic sheeting to separate the work area

from the rest of the home• Remove outer layer of work clothing in the work

area and wash separately or bag• Damp clean the entire work area to pick up

settled contaminants in dust

4) Clean Surfaces - surface mold growing on non-porous materials such as hard plastic, concrete, glass,metal, and solid wood can usually be cleaned.Cleaning must remove and capture the moldcontamination, because dead spores and moldparticles still cause health problems if they are left inplace.• Thoroughly scrub all contaminated surfaces using

a stiff brush, hot water and a non-ammonia soap/detergent or commercial cleaner

• Collect excess cleaning liquid with a wet/dryvacuum, mop or sponge

• Rinse area with clean water and collect excessrinse water

5) Disinfect Surfaces (if desired) - after cleaninghas removed all visible mold and other soiling fromcontaminated surfaces, a disinfectant may be used tokill mold missed by the cleaning. In the case ofsewage contamination, disinfection must beperformed -- contact the Minnesota Department ofHealth for appropriate advice.

• Mix 1/4 to 1/2 cup bleach per gallon of water andapply to surfaces where mold growth was visiblebefore cleaning. The solution can be applied witha spray bottle, garden sprayer, it can be spongedon, or applied by other methods.

• Collect any run-off of bleach solution with a wet/dry vacuum, sponge or mop. However, do notrinse or wipe the bleach solution off the areasbeing treated -- allow it to dry on the surface.

Always handle bleach with caution. Never mix bleachwith ammonia -- toxic chlorine gas may result. Bleachcan irritate the eyes, nose, throat, and skin. Providefresh air (for example, open a window or door). Protectskin and eyes from contact with bleach. Test solution ona small area before treatment, since bleach is verycorrosive and may damage some materials.

6) Remain on MOLD ALERT - Continue looking forsigns of moisture problems or return of mold growth. Beparticularly alert to moisture in areas of past growth. Ifmold returns, repeat cleaning steps and consider using astronger solution to disinfect the area again. Regrowthmay signal that the material should be removed or thatmoisture is not yet controlled.

When can we rebuild?Rebuilding and refurnishing must wait until all affectedmaterials have dried completely. Be patient – it takestime to dry out wet building materials. A moisturemeter may help measure drying progress. Contactyour county Minnesota Extension Service office tosee if they loan moisture meters.

Can ozone air cleaners remove indoor mold?Some air cleaners are designed to produce ozonewhich is a strong oxidizing agent and a knownirritant of the lungs and respiratory system.Studies have shown that ozone, even at highconcentrations, is not effective at killing airborne moldor surface mold contamination. Even if mold waskilled by ozone, the health threats would not bereduced until mold contaminants are removed throughcleaning. Health experts, including the MinnesotaDepartment of Health, do not recommend the use ofozone to address mold or any other indoor airproblems.

Questions ?Minnesota Department of Health - Indoor Air Unit121 East Seventh Place, Suite 220P.O. Box 64975St. Paul, Minnesota 55164-0975Phone: 651-215-0909 or 1-800-798-9050

To request this document in another format such as large print, Braille, or cassette tape, contact the MinnesotaDepartment of Health Indoor Air Program at (651) 215-0909; TDD (651) 215-0707; or toll-free through the

Minnesota Relay Service at (800) 627-3529.

02/01 IC# 141-0288

Ventilation forOlder HomesVentilation forOlder Homes

• Bathroom fans andrange hoods can provide adequateventilation in manyolder homes.

• Fans must be properlysized and ducted.

• Ventilation won’talways solve mouldand mildew problems.Other measures mayalso be necessary.

• Dehumidifiers helpcontrol basementmoisture problems in summer.

IntroductionMany older homes suffer from condensation and mould growth. If serious moisture problems areignored, permanent damage to ahome’s windows, interior finishes and structure can occur. Prolongedexposure to some moulds may alsocause health problems.

This fact sheet examines commonmoisture problems and suggests possible solutions, including somesimple, inexpensive, do-it-yourself projects. Low to moderate cost ventilation options for typical olderhomes are also discussed.

What causes moisture problems?

Condensation occurs when humid air is cooled below its “dew point.”Mould growth usually occurs on anysurface that remains wet or damp for a prolonged period of time. The twofactors that determine whether condensation will or won’t occur arethe “relative humidity” of the air andtemperature of the various cold surfaces(particularly windows) in the home.

Can you explainrelative humidity?

The amount of water vapour air can hold depends on its temperature.For example, air at room temperaturecan hold over ten times more watervapour than air at –5º Celsius.

Relative humidity tells us how “wet”or “dry” the air is. As air is warmed,it expands and its relative humiditydecreases, because warmer air canhold more moisture. Conversely, as air is cooled, it shrinks and its relativehumidity increases. Condensationoccurs when relative humidity reaches100 per cent.

To reduce the relative humidity ofthe air in your home, you can:

1) increase air temperature (turn up the heat)

2) reduce the amount of moisture in the air by:

• eliminating moisture sources (storing firewood outside, etc.)

• diluting it with air that is drier (ventilation during the heating season)

• removing moisture from the air (dehumidification)

Key Points

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February 2000

Why does surface temperature matter?

Cool surfaces reduce the temperature of nearby air. If air is cooled enough that its humidity reaches 100 per cent, condensation occurs and problems begin.Condensation typically first starts on windows becausethey are the coldest surfaces in most homes. If indoorhumidity continues to rise, condensation and mouldgrowth may also occur on other cooler surfaces, such as outside corners, behind furniture, or in closets withoutside walls.

Do I need more ventilationin my house?

It depends on your home and your habits. Every buildingcan tolerate some moisture before problems begin tooccur. And each household’s cooking, bathing, and livinghabits are different. But if window condensation ormould growth occur frequently, it is time to take action.The “Assessing Your Home’s Moisture Problem” sidebarprovides suggestions on how to solve common moistureproblems.

Does my existing exhaust fan work?

Check air flow at the exhaust hood by holding a garbagebag over the exhaust hood and timing how long it takesto inflate the bag. If it takes more than a few seconds,the fan system needs to be upgraded and/or replacedwith a more powerful unit, or the ductwork needs to be improved.

Should I buy a heat recovery ventilator?

Heat recovery ventilators (HRV) are designed for, andwork best in, a new home that is air tight. In this type ofhome, virtually all fresh air is distributed by the HRV.

In an older, leakier home, air continues to enter thehome through cracks and holes, so the heat recoveryand fresh air distribution advantages of an HRV are, forthe most part, lost. It can also be expensive and difficultto properly install a fresh air distribution duct system ina finished house. A less elaborate and expensive centralexhaust system can provide enough extra ventilation tocontrol humidity in most older houses.

How about opening windows?

Windows are just as likely to allow outside air into thehouse as let inside air out—and incoming air tends topush the moist air into the rest of the home. On calmdays, air may not move at all. Worse still, hardly anyonewill leave windows open on cool days, when you mayneed ventilation the most. Fans, on the other hand, positively remove air from the building.

So what are my options?Bathroom fansGood-quality bathroom fans can solve minor bathroommoisture problems ... if they are properly sized andinstalled. Look for a fan with a rated capacity of at least100 cubic feet per minute (cfm), a minimum 4-inch (10 cm) outlet and a “squirrel cage” type blower. The

Typical higher capacity design. Note blower wheel and four inch outlet for duct.Minimum recommended.

Removeable filter and grille for in-line fan or exhaust vent.Suitable for kitchen and bathrooms.

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What should I do first? Start by checking your home for ways to reduce moisture levels through source control. It is always better to control moisture at its source than to dependon ventilation to remove moisture that could have beenprevented in the first place. After all, it costs money toinstall and operate a fan.

Six suggestions for reducing an older home’s moisture levels are:

1) Dry and store firewood under cover outdoors.

2) Cover any exposed earth in crawlspaces or basementswith heavy polyethylene to stop evaporation into thehouse. This is extremely important!

3) Fix basement leaks and make sure downspouts direct water away from the foundation.

4) Vent clothes dryers outdoors.

5) Operate existing fans more often.

6) Avoid drying clothes indoors.

What is the next step?If moisture problems continue, the next step is to thoroughly examine your house to determine where andwhen problems are occurring. Common problems arediscussed below. Possible solutions are listed from leastexpensive to most.

1) Problems are not widespread, and occur onlyin (or near) ”wet” areas such as bathrooms orkitchens.

Likely cause: Moisture generated by cooking or showering isn’t removed fast enough.

Possible solutions:

• Reduce moisture generation when possible. Use lids on pots, shorter showers, etc.

• Improve existing ventilation. Increase air flow by operating your existing fan longer, upgrading ducting, or replacing the fan with a more powerful unit.

• Add more ventilation. Install quality bathroom,kitchen, or central exhaust fans as appropriate.

Assessing Yocost of this type of fan starts at about $65. Don’t buy afan with a sone rating above four. More expensive fanunits tend to be quieter (a sone rating of two or less) andbetter constructed. The 1995 National Building Coderequires that all fans in a new house must have a sonerating of two or less.

Low-cost, low-capacity (50 to 60 cfm) bathroom fansaren’t a bargain at any price. They don’t exhaust aireffectively, are noisy, and won’t stand up to frequent use.

Range HoodsRange hoods vented to the exterior are an effective wayto exhaust odours and moisture from cooking, particularlyif grease or fat is present. But range hoods can’t meet all of a home’s ventilation requirements. The capacity,quality, and noise levels of range hoods vary greatly.Downdraft range hoods can have exhaust capacities ashigh as 600 cfm and may be powerful enough to pullflue gases from the furnace or wood stove into the home.

Central exhaust fansThese systems are ideal for many older houses thataren’t particularly air tight but still need some extra ventilation. Most central exhaust systems have enoughcapacity to exhaust from several areas of the house, sothey can replace several smaller exhaust units, which can help to justify their higher cost ($250–$350 plusinstallation). Quality central exhaust systems are quietand suitable for continuous operation.

Typical low capacity, propeller-type design with blades. Not recommended.

Blower-style fans are quiet and effective.

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our Home’s Moisture Problems

2) Problems are concentrated in the coldest room(s)in the house such as an unused bedroom.

Likely cause: Room is too cold. Lower temperaturesincrease relative humidity and reduce exterior wall andwindow surface temperatures. Both make condensationmore likely.

Possible solutions: Add heat by

• turning up the thermostat

• opening air dampers and registers

• removing any blockages over heaters

• opening or undercutting doors to increase circulation

• increasing heat distribution system capacity to affected areas

3) Mould formation limited to a few defined areas

Likely cause: Missing insulation or large air leakshave cooled surfaces enough to cause condensation.

Possible solutions:

• If problems are found, air seal or insulate as required.

4) Your basement is damp or musty during warmer weather

Likely cause: The ground cools below-grade concretewalls and floors enough that they become the coldestsurface in the building in the summer.

Possible solutions:

• Best: Insulate walls and floors to raise concrete temperatures (exterior insulation) or to keep humid indoor air from reaching the cold concrete(interior insulation and an air barrier).

• Most practical in older home: Close windows and doors to avoid bringing in more moisture-laden air, then use a dehumidifier to control basementhumidity levels.

5) Window condensation on only a few windows

Likely cause: Problem windows are cooler than rest of windows in the house.

Possible solutions:

• Leave tight-fitting drapes open during cold weatherto keep windows warmer.

• Weatherstrip and air seal windows and frames.

• Add a permanent or temporary storm window.

• Insure window isn’t isolated from heating source.

• Replace window with an energy efficient window.

6) Widespread window condensation throughouthome and some mould growth on drywall

Likely cause: Humidity levels are too high.

Possible solutions:

• Install additional ventilation. Choose quality equipment that is quiet and capable of continuousoperation.

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Installing a bathroom fanTo exhaust enough air to keep moisture from damagingyour bathroom, you need a quality bathroom fan and agood installation. Scrimping on either the fan or exhaustductwork usually results in an exhaust system that doesn’tdo the job. That’s no bargain at any price.

Here are a few tips.

Where should I put the fan?Most bathroom fans are mounted in the ceiling andvented out a gable end wall. In retrofit applications orwhen the attic isn’t accessible, it may be easier to installthe fan in the top of a storage cabinet or adjoining closetand run the exhaust duct out the wall below ceilinglevel. This also keeps the exhaust duct short and warm.

Where should the exhaust hood be?Exhaust hoods work best when located on a wall.Terminating a duct into the roof overhang is not recom-mended, since incoming attic ventilation air may carrythe moist bathroom air back into the attic, and the backdraft damper won’t work when hanging upside down.Roof-mounted vents add an unnecessary hole to yourroof and if duct condensation occurs, it can drip into the bathroom through the fan.

Bathroom Fan InstallationUsing Adjacent Storage Space

Fan and ductwork are inside to minimize condensation

Ductwork is short and

directSeal duct to exterior

wall

What about ductwork?Ducts should be at least 4'' (10 cm) in diameter (or nosmaller than the fan’s outlet if it is greater than fourinches) and be as short, smooth, and straight as possible.Ducts in cold spaces should be sloped to the outside andmust be sealed and insulated to prevent condensationand moisture damage to the attic. Flexible plastic dryerhose should not be used, because the duct’s rough surfacewill restrict the fan’s air flow.

Any control suggestions?Wind-up timers (availablefor about $20) are usefulbecause wet towels, showerenclosures, etc. continue to produce moisture afteryou leave the bathroom.

Who installs bathroom fans?Most ventilation contractors and some carpenters or electricians install bathroom fans, but no trade specializes. Be sure to discuss the points raised in this fact sheet with prospective contractors before deciding who to hire.

Typical Ceiling Installation

Slope pipe to exterior

Insulate and seal all attic ductwork

Seal fan at ceiling level to drywall

Use smooth pipe with minimum diameter of

four inches

Vent exits throughgable end

Installing a central exhaust fan

Adding a central system to an older house is usually notdifficult as long as either the attic is accessible or thebasement isn’t finished.

In an attic installation, choose a fan unit approved foruse in cold temperatures and use insulated flex ducts toprevent condensation. Nearly all work can be done inthe attic or through closets without disturbing the livingareas of your home.

What’s the best way to control a central exhaust system?Wind-up timers are a good choice in bathrooms or otherareas with short-term ventilation requirements. If thesystem is also expected to control indoor humidity levels,consider a humidistat located in a central area or a 24-hour timer to automatically turn on the fan at scheduledintervals.

Ask ENERINFO Please address requests for more information,publications, or videos to:

ENERINFO at 1-800-670-4636 (toll-free)Web Site: http://www.gov.ns.ca/natr/meb/energy.htm

or write

ENERinfoEnergy UtilizationNova Scotia Department of Natural ResourcesP.O. Box 698, Halifax, N.S. B3J 2T9Fax: (902) 424-7735

The ENERinfo Advisor SeriesFact sheets available in this series include:

• Building an Energy Efficient Home• Hot Water: How to Heat and Use It Efficiently• Passive Solar Homes• The Energy Code and You• Ventilation for New Homes• ENERINFO Video Library Request Form• ENERINFO Information Request Form

Other Information Sources• www.cmhc-schl.gc.ca/cmhc.html• oee.nrcan.gc.ca/oee_e.cfm

Attatching insulated duct fan ceiling inlet. Ensure gap around duct is sealedwhere it penetrates the drywall or vapour barrier. Tape ducting to duct fitting.

Quality in-line fan unit mounted in an attic. Quiet, capable of continuousoperation, and has a high capacity.

How does the fresh air get in?Most older houses have enough air leakage pathsthrough or around windows, doors, and other buildingcomponents that the air exhausted by a moderate-sizefan can be easily replaced. But air leaks in your homemay not be located exactly where you want more freshair, so exhaust-only systems can cause cold air drafts. Airquality throughout the home may also vary. If more freshair is needed in a particular area, intentional holes to theoutside (small ducts) can be added to bring in fresh air.These ducts must be carefully located to avoid drafts.

Designed by Paul T. Cormier, Creative Services, Communications Nova Scotia.Film by Maritime Photoengravers. Printed by McCurdy Printing Limited.