Mold in Homes – Reference Guide

Introduction

The purpose of this booklet is to enable you to identify the signs and probable causes of moisture and moisture-related air quality problems in your home, and to offer practical solutions.

Many problems can be solved if you implement the following solutions:

adopt strategies to prevent excess moisture in your home;
perform minor repairs and maintenance work;
hire a competent contractor to perform major repairs.

Tenants: Report plumbing leaks and moisture problems immediately to the landlord, building manager, or caretaker. If persistent water problems are not resolved, contact the local or provincial health or housing authorities.

Moisture and Air Quality Problems

Moisture production is constant in a home: from 10 to 50 liters (2 to 10 gallons) per day. During a 200-day heating period, when doors and windows are closed, 2,000 to 10,000 L (400 to 2,000 gal) of moisture can be trapped inside. For example, a cord of wood stored in a house can release more than 270 L of moisture. Excessive moisture can cause dampness problems, which in turn can lead to air quality issues.

Moisture Problems

There are two sources of moisture problems – water leaks and condensation. This publication focuses primarily on condensation issues. If warm, moist air comes into contact with a surface that is too cold, the moisture it contains condenses. Water and frost accumulating on windows are obvious examples. Condensation can also occur in the attic space and within exterior walls. Over time, if the air in your home is too humid, it can result in damage to the structure, your belongings, and potentially even your health. Controlling the humidity in your home is the best defense against mold problems.

Air Quality Problems

The air you breathe at home should be clean (i.e., as free of pollutants as possible). For your health and comfort, indoor air should be replaced by fresh air from the outside. Without this air exchange, moisture will build up, mold could become a problem, and the quality of the air you breathe may then deteriorate.

Molds growing at home can produce spores, toxins, and odors.

Synthetic fabrics, furniture, decorative accessories, and household products can emit harmful chemicals. Other sources of indoor pollutants include cigarette smoke, candles, as well as poorly maintained or poorly ventilated combustion appliances, such as gas or propane stoves, heat generators (furnaces), water heaters, wood stoves, and fireplaces.

Replacing stale air with fresh air decreases the possibility of indoor air quality problems.

Causes

Condensation occurs on cold surfaces. It results from:

from excessive moisture production:
- ventilating the basement with warm air in the spring or summer can cause a tremendous amount of condensation in basements;
- through the inappropriate use of humidifiers;
- through evaporation during showers, dishwashing, laundry, and cooking; it also comes from aquariums, standing water, people, pets, and plants;
- in damp basements;
- in basements and crawl spaces with dirt floors.
from inadequate air exchange:
- indoor air is not replaced by outdoor air (generally, cold outdoor air will help dry out indoor air).
from cold surfaces caused by:
- a deficient heating system or inadequate heating of certain rooms (e.g., heating for a guest room that is blocked because it is not used often enough, an unheated basement);
- large variations in indoor temperature (e.g., turning down the thermostat, uneven heat distribution from wood stoves, unheated rooms);
- insufficient air circulation in a room due to furniture placed against exterior walls;
- poor quality windows or heat being blocked by blinds or curtains;
- a lack of insulation in walls and ceilings.
from cold surfaces in basements during the summer.

Solutions

First, moisture production must be reduced:

eliminate sources of moisture;
decrease water infiltration in the basement;
stop using humidifiers;
use a dehumidifier in the basement during the fall, spring, and summer.

Secondly, surfaces must be kept warm:

replace windows with energy-efficient models;
insulate walls and ceilings adequately;
provide sufficient heat to all rooms in the house.

Good ventilation, sufficient air circulation, and proper heat distribution are important and effective measures to prevent moisture-related problems.

Measure the humidity level in your home

The amount of water vapor in the air is usually evaluated using relative humidity.

A relative humidity sensor (or hygrometer) allows you to measure the humidity level in your home.
You can purchase one at a hardware store or from a building materials supplier.
During extreme cold, relative humidity should be maintained at 30% or less to prevent condensation from forming on windows.
In winter, relative humidity should not exceed 45%.
By installing improved energy-efficient windows, you can maintain a higher relative humidity level without the risk of condensation.

Mold

Molds belong to a group of microorganisms that include fungi and yeasts. Most people are familiar with molds due to their effect on food spoilage, such as with bread and fruit. In the food chain, molds act as natural decomposers. If mold grows inside your home, it can cause problems.

Problems Related to Mold

Mold can lead to:

the appearance of unsightly stains;
damage to paint, wood, drywall, ceiling tiles, and fabrics;
damage to personal belongings;
allergies;
illnesses.

Common Symptoms

discoloration on wall and ceiling surfaces, furniture, or decorative accessories
stains on carpets
mold behind furniture and on curtains
stains on personal items placed near affected areas, such as storage boxes and clothing
musty odor
rotting wood

Prevention

Mold requires high levels of humidity to grow. Some types of mold require the presence of condensation before they proliferate.

If mold is present, clean the contaminated areas as soon as possible, and then identify the source of moisture that allowed the mold to multiply in that spot. This booklet will help you identify possible sources of moisture and suggest solutions.

Cleaning Methods

You can clean small moldy surfaces yourself using unscented detergent and water. A moldy surface is considered “small” if there are fewer than three patches, each of which is less than 1 m2. If you find more than three patches or if the affected area is larger, you should call a qualified professional to have your home inspected. You will also need a specialized contractor to clean large areas of mold.

When cleaning:

wear rubber gloves;
wear a mask, rated N95, capable of filtering fine particles;
wear protective goggles;
rinse thoroughly using a clean damp cloth;
dry the surfaces.

Moldy ceiling tiles and carpets must be removed and disposed of. Drywall that remains stained after being cleaned with detergent and water may need to be replaced. Attempt to wash fabrics, and if odors or stains persist, discard them.

To clean properly, all mold must be eliminated. The use of chemicals such as bleach and fungicides is not recommended. It is important to remove all mold residue since it can cause allergies and illnesses.

General Inspection of Your Home

Now that you have a general idea of the causes of moisture and air quality problems in the home, know how to prevent excessive moisture production, and know your home’s relative humidity level, conduct a full inspection of your home using this booklet. For each room, common signs, probable causes, and practical solutions are described.

During your inspection, use the checklists provided on the following pages to note the signs found in your home, the possible causes relevant to your situation, and the practical solutions you could implement.

Problems in Your Living Areas

Common Signs

Condensation on windows
Rotting windowsills
Damaged drywall
Musty odor
Mold on walls
Mold on curtains, carpets, or furniture
Mold in closets

Probable Causes

Humidifiers
Excess moisture in the basement or crawl space
Moisture produced by numerous occupant activities
Too many people and pets
Uncovered aquariums
Large number of plants
Indoor firewood storage
Poor air circulation within and between rooms
Cold surfaces resulting from a lack of insulation
Significant air leaks around electrical outlets, window frames, etc.
Closed curtains that prevent warm room air from heating the window glass
Overfilled closets and content placed too close to the exterior wall
Insufficiently heated rooms
Inadequate ventilation
Poorly maintained air conditioner

Practical Solutions

Stop using humidifiers.
Use a dehumidifier in the summer.
Eliminate sources of moisture in the basement or crawl space.
Apply a sealant to the joint between the floor and the basement walls.
Install exhaust fans in the kitchen and bathrooms.
Cover the aquarium.
Reduce the number of potted plants.
Circulate air between rooms.
Insulate cold surfaces properly.
Seal major air leaks.
Decrease the amount of stored goods.
Open the curtains.
Create a one-inch gap at the bottom of closet doors or leave them open.
Heat all rooms.
Install a balanced ventilation system—and use it regularly.
Clean air conditioner condensation pans, and ensure water flows freely through the drain lines.

Problems in Your Basement

Common Signs

Damp or wet floors or walls
Powdery white stains on the concrete of walls or the floor
Stains on carpets
Condensation on windows
Rotting windowsills
Musty and damp odor
Presence of mold on rim joists behind insulation
Mold growth on stored goods (i.e., cardboard boxes, clothing, etc.)
Mold in the cold room
Mold in the corners of walls or the ceiling
Water leaking through cracks in the chimney
Water beading on cold water pipes

Probable Causes

Dirt floor in the crawl space or basement
Cracked concrete walls and floor
Water leaks from appliances or the plumbing system
Rain penetrating the walls
Flooding
Shallow water table
Runoff water running along foundation walls and then flowing toward the floor drain
Poor grading of the ground near the foundations
Defective sump pump
Open sump pit
Furnace humidifier
Carpet laid on the concrete floor
Hot tub or pool inside the house
Firewood storage in the basement
Dryer vent not connected to the outside
Laundry hung inside the house to dry
Absence of an exhaust fan in the bathroom
Storage of items against walls or on the floor
Unheated basement or crawl space
Clogged foundation drains
Condensation of combustion gases from the chimney
Backdrafting of combustion gases from the furnace or water heater

Practical Solutions

Cover the dirt floor in the crawl space or basement with polyethylene, or install a concrete floor.
Seal foundation cracks and water infiltrations.
Repair plumbing and appliances.
If water or mold damage was caused by sewage or other wastewater, call a professional experienced in cleaning and repairing buildings damaged by contaminated water.
Regrade the ground around the house.
Repair the sump pump.
Install an airtight cover on the sump pit.
Do not humidify the whole house unless absolutely necessary.
Remove carpets.
Cover or empty the hot tub when not in use to prevent evaporation.
Store firewood outside.
Connect the dryer vent to the outside.
Do not dry clothes in the basement.
Ensure the bathroom fan exhausts air to the outside.
Minimize the number of items stored in the basement.
Provide sufficient heat to the basement.
Inspect the foundation drain and improve it if necessary.
Dehumidify the basement during the summer months.
Remove ceiling tiles that show mold.
Insulate cold water piping.

Problems in Your Bathrooms

Common Signs

Condensation on windows
Condensation or stains on walls and the ceiling
Water dripping from the exhaust fan grille
Mold in ceramic tile joints (grout)
Rotting windowsills
Damaged drywall under windows
Bulging drywall
Peeling paint or wallpaper
Musty odor
Visible damage caused by mold: stains or growth of microorganisms on the floor or carpet
Lifting floor tiles
Water pooling around the toilet, sink, or bathtub
Unexplained increase in the water bill
Mold on walls or the ceiling
Condensation on the toilet tank
Mold under the toilet tank

Probable Causes

Excess humidity in the bathroom
Moisture generated by baths and showers
Absence of an exhaust fan
Fan not being used
Uninsulated ventilation ducts
Inoperable backdraft damper on the fan
Plumbing leaks
Plumbing leaks inside walls
Moisture from bath mats, wet towels, and clothes hung to dry
Inadequate ventilation
Temperature kept too low
Leaking seals around the shower or bathtub
Uninsulated ventilation ducts
Uninsulated toilet tank

Practical Solutions

Run the fan whenever you take a shower or bath.
Install an exhaust fan that vents air to the outside (it is unrealistic to believe that a window can provide adequate ventilation).
Leave the fan running for at least 15 minutes to eliminate moisture.
Use a rubber squeegee or a towel on the shower stall or bathtub enclosure after use.
Close the bathroom door when taking a shower.
Install a humidistat that automatically starts and stops the exhaust fan.
Repair plumbing leaks.
Provide sufficient heat and ventilation.
Apply sealant around the perimeter of the shower stall, bathtub, and sink.
Properly insulate the walls and ceiling.
Consult a competent contractor for the replacement of walls displaying mold.
Ensure that ventilation ducts are correctly installed.
Remove the carpet.
Install a 6 L toilet—its tank does not sweat.
Clean surfaces periodically.

Problems in Your Kitchen

Common Signs

Condensation on windows, walls, or the ceiling
Damaged walls under windows
Peeling paint or lifting floor tiles
Presence of moisture under the sink or kitchen counter
Rotting wood components under the sink
Mold in cabinets and in the corners of exterior walls
Musty odor

Probable Causes

Excess humidity in the home (other moisture sources exist in the house)
Absence of a range hood over the stove
Prolonged cooking of food or long-simmering of foods and liquids
Combustion moisture produced by a natural gas stove
Leaks around the sink and faucets
Plumbing leaks
Wet waste or objects contributing to moisture
Mold growth behind the refrigerator or in the condensation pan
Items in cabinets against the exterior wall preventing air circulation
Temperature that is too low or fluctuates

Practical Solutions

Control humidity throughout the entire dwelling.
Install a quiet exhaust fan in the kitchen connected to the outside and use it.
Cover liquids and food when simmering or boiling.
Turn on the range hood fan when cooking.
Seal the joint between the sink, faucets, and the counter.
Repair leaks.
Clean the condensation pan occasionally.
Store items a few inches away from the exterior wall. Open cabinet doors occasionally to allow heat to enter.
Store compost or trash in a closed container under the sink.

Problems in Your Bedrooms

Common Signs

Condensation on windows
Rotting windowsills
Mold around windowsills
Damaged or stained drywall walls or ceiling; peeling paint
Lifting wallpaper
Bulging or cracked ceiling
Musty odor
Damp and musty odor in closets
Mold in closets, on exterior walls, behind furniture or frames hanging on walls, etc.
Water dripping from ceiling lights

Probable Causes

Too frequent use of a humidifier
Excessive humidity level (moisture may be coming from elsewhere in the house)
Poor air circulation in the room
Inefficient windows
Closed blinds and curtains preventing heat from reaching the windows
Lack of air circulation in closets
Insufficient space at the bottom of closet doors
Temperature set much lower than in other rooms
Bed and furniture too close to exterior walls preventing free air circulation
Too much furniture and decorative accessories, which prevents proper air circulation
Old, moldy carpet
Deficient insulation in exterior walls or the attic space

Practical Solutions

Run the humidifier for short periods of time, monitor the relative humidity, and ensure the room dries out.
Reduce humidity throughout the entire house.
Clear any blocked heating vents.
Leave bedroom doors open to allow better air circulation or trim the bottom of the door to create a gap.
Windows may need to be replaced.
Open blinds and curtains to allow surfaces to warm up.
Do not store items from floor to ceiling in closets located against an exterior wall.
Open closet doors or install louvered doors.
Heat bedrooms properly.
Place furniture 15 cm (6 in) away from the exterior wall, ducts, and air return vents.
Properly insulate cold walls and the ceiling.
Reduce the amount of furniture and decorative accessories.
Consider installing hard surface flooring.

Problems with Your Roof and in Your Attic Space

Common Signs

Ice dams
Condensation, frost, and mold on trusses and roof sheathing
Condensation near vents and plumbing stacks
Condensation near wiring and electrical fixtures
Water dripping from soffit vents

Probable Causes

Ice dams
Gaps and cracks in the ceiling allowing warm air to escape into the attic space
Attic access hatch that is uninsulated and not airtight
Absence of a chimney firestop
Kitchen and bathroom fans exhausting stale air into the attic space
Unsealed electrical or plumbing fixtures, vents, etc.
Leaking roof
Unsealed and uninsulated ducts in the attic space

Practical Solutions

Seal all openings to prevent indoor air from entering the attic space.
Seal and insulate the attic access hatch.
Install a firestop around the chimney or seal the existing one to reduce air leaks into the attic.
Extend all exhaust air ducts to the outdoors.
Seal all ceiling lights.
Repair the roof and flashings.
Reduce excessive humidity levels in the house.
Seal and insulate ducts passing through the attic space.

Problems in Your Exterior Walls

Common Signs

Exterior siding that is bulging, warped, or rotting
Peeling or blistering paint
Presence of condensation in the form of frost
Moisture stains or chalky deposits on brick or stucco
Cracks in the foundation
Water puddles near the foundation

Probable Causes

Warm, humid indoor air passing through the air barrier into the wall
Wind-driven rain penetrating gaps in the exterior siding
Deficient or missing flashings
Rain barrel overflow discharging water toward the foundation
Defective downspouts or those discharging near the foundation
Absence of gutters
Broken or clogged gutters
Deficient leveling and drainage and missing deflector
Poor ground grading
Deficient grading under verandas and decks
Water leaks from the outdoor faucet or garden hose

Practical Solutions

Seal all openings in exterior walls.
Reduce excess humidity in the house.
Improve ventilation.
Install flashing to direct rain away from the wall, or repair existing flashing.
Direct rain barrel overflow away from foundations.
Repair defective downspouts.
Install gutters and extend them away from foundations.
Repair or clean gutters.
Regrade the ground to move water away from foundations.
Repair leaking outdoor faucets.
Add an extension hose to minimize water accumulation near foundations.

Ventilation Options

After cutting off all sources of moisture, indoor air quality can be improved through ventilation. All ventilation installations must be balanced, meaning that as much air must enter as leaves. Air intakes must be large enough for air to enter easily and supply all exhaust devices.

Types of Ventilation

Passive Ventilation

In winter, open one or more windows for a short period of time. This method can provide temporary ventilation, but it is not always effective or economical.

Exhaust-Only Ventilation

At a minimum, an exhaust fan is needed in both the kitchen and the bathroom, and they should be run for a significant amount of time each day. Warning: When using powerful exhaust fans, combustion appliances connected to a chimney may not function properly.

Balanced Active Ventilation

Exhaust fans work in conjunction with fresh air intakes connected to the furnace’s air recirculation system.

In some homes equipped with combustion appliances—such as a furnace, water heater, fireplace, etc., running on gas, oil, or wood—a fresh air supply system may be required to replace the air extracted by fans.

Ventilation and Heat Recovery

Combustion appliances with paired fresh air (combustion air) intakes and exhaust flues will operate without issues.

Ventilation Combined with Air Circulation

If the house is equipped with a forced-air furnace, run its fan continuously or intermittently. In conjunction with opening windows or using exhaust fans, this measure will improve air quality throughout the house. One drawback is that most fans consume a lot of energy.

Protect Your Home and Your Health

Many ventilation options can affect the performance of combustion appliances, particularly in the case of powerful fans. Learn more by consulting the CMHC *About Your House* series of fact sheets or a qualified heating and ventilation contractor.

You can protect yourself against the worst effects of combustion gas backdrafting by installing a CSA-certified carbon monoxide detector and smoke alarm.

Glossary

Forced Air – Air pushed through ducts inside the house by means of a fan installed on the heating appliance frame.

Condensation – The transformation of water vapor contained in the air into liquid water upon contact with cold surfaces.

Air Sealing – The application of weatherstripping such as caulking or expansion foam to seal small cracks and spaces in windows, doors, walls, and ceilings to reduce air infiltration or leaks and heat loss.

Backdrafting – The return of air from the outside to the inside of a building through a barometric damper, a hood, or a burner due to a blocked chimney or pressure higher than the chimney’s draft. Backdrafting brings odors, fumes, or toxic gases back into the building.

Sump Pit – A sealed tank that receives water discharged by a floor drain or foundation drain and pumps it into the sewer line using a pump.

IAQ – Acronym for “Indoor Air Quality.” A generic term concerning the presence of chemical and biological contaminants in the air of a building and their potential health effects.

Flashing – Sheet metal or other material used in roof and wall construction to prevent water infiltration.

Maintaining Homes to Prevent Mold

The information in this chapter is intended for First Nations housing departments, bands, and technical service providers.

First Nations housing departments and bands can reduce mold contamination problems by adopting the following means:

follow a simple maintenance checklist to detect problems related to the roof, exterior siding, basement, plumbing, as well as heating and ventilation systems;
repair as quickly as possible all leaks and resolve all reported problems; and
inform occupants and encourage them to follow the recommendations above.
Suggestions for specific locations in the house: Basements and crawl spaces
Cover all dirt floors with a sealed 6-mil polyethylene sheet, followed by 50 mm
(2 in.) of clean gravel or bricks, or a concrete slab at least 75 mm (3 in.) thick.
Properly seal foundations, insulate them (preferably from the outside), and ensure proper drainage.
Discourage the setup of a cold cellar in the basement. The conditions favorable for food storage (cold and moisture) are also conducive to mold growth. The technical service provider should give advice on recommendations regarding the cellar. If mold is not a concern, the cellar can be maintained by periodic cleaning with trisodium phosphate and by insulating it from the rest of the house with airtight, isothermal doors. The cellar must have its own fresh air supply and exhaust system (a small fan). A cold cellar showing significant mold that is a continuous source of mold for the whole house must be completely cleaned and maintained in the same way as the heated living area.
Install an airtight cover on the sump pit. If a manufactured cover is not available, use a piece of metal or plywood wrapped in plastic.
Install an airtight backwater valve on the floor drain.
Discourage interior insulation, but if there is exposed insulation in the basement, seal the air barrier and vapor barrier covering the insulation inside the basement walls or between floor joists.
Discourage the use of carpet on the basement slab. The floor can be painted. Likewise, raised floors are not recommended, as the cavities created can hide mold.

Bathroom

Install a fan exhausting air directly to the outside or a central heat recovery system to exhaust humid and stale air.

Kitchens

Install a range hood exhausting air directly to the outside.

Mechanical Systems

Do not install furnace humidifiers.
Ensure that all forced-air systems are capable of circulating air freely throughout the house. Leave a space at the bottom of doors to allow air to return, if necessary, to the central return circuit.
It is preferable to ensure continuous air circulation using energy-efficient two-speed fans.
Install a portable dehumidifier in the damp basement to lower humidity in the summer, helping to prevent condensation on cold surfaces.
Replace fiberglass furnace filters with one-inch pleated filters.
Install a whole-house heat recovery system, following recommended installation practices.

Laundry Areas

Ensure the dryer exhausts air directly to the outside through short, straight runs of aluminum ducting with sealed joints.

Closets

Cold walls and poor air circulation in closets can lead to condensation and mold growth. Ensure exterior walls are fully insulated with an effective air or vapor barrier.

All Living Areas

Replace all carpets with vinyl tiles.
Seal all openings and leaks in the wall or in the air/vapor barrier.

Exterior

Regularly check the condition of the roof and exterior siding to detect any areas where water could enter. Resolve all problems quickly.
Install gutters, downspouts (extending at least 3 m or 10 ft from any wall), and grade the ground to move water away from the house.
Caulk and seal the house to prevent the penetration of dust, pollen, and other outdoor particles.

Renovating Homes to Prevent Mold

The information in this chapter is intended for First Nations housing departments, home builders, renovators, housing policy developers, and technical service providers.

Key Points:

Correct the conditions leading to mold growth. Keep the house dry.
Repair all water leaks through the roof, windows, doors, siding, and foundations.
Repair all plumbing leaks.
Ventilate and dehumidify the house to maintain relative humidity between 30% and 45%.

Strategy

To solve mold problems in the long term, the cause must first be understood. Measures must be taken to prevent the problem from recurring. Temperature and air conditions that are comfortable for people are also favorable for mold. The only factor we can control is moisture. Houses must be kept dry!

For the Building Envelope

Stop water leaks through all parts of the roof, exterior walls, or foundations below ground level.
Cold surfaces can lead to condensation and mold growth, so they must be insulated to keep all interior surfaces warm.
Implement air sealing measures.

For Mechanical and Ventilation Systems

Repair all plumbing leaks.
Manage relative humidity (maintain it between 30% and 45%).
Exhaust stale air and bring in fresh air.
Circulate fresh air throughout the entire living area.

Renovate by considering the house as a system where the building envelope, mechanical systems, and occupant lifestyle all interact. Many houses with a mold problem have damp crawl spaces. The crawl space must be considered either “open to the outside air” or part of the house’s living area, and not something vague in between. Any crawl space containing a furnace or ductwork must be treated as part of the living area and kept as clean as the rest of the house.

Other houses have basements with framed walls that are insulated and finished on the inside, and a foundation made of poured concrete or blocks. These contain interior cavities prone to moisture and mold problems inside the stud wall. It then becomes more difficult and expensive to renovate in the event of a basement leak or flooding. Internal reinsulation of any moldy basements is strongly discouraged. External insulation eliminates hidden cavities and makes it much easier to detect and repair any future mold problems. It is also recommended not to cover bedroom or basement floors with carpet.

Building Envelope Renovations

Cost-Effective Foundation Options

All exposed soil in the basement or crawl space must be covered with a sealed layer to prevent water or soil gases from entering the house. The ground can be covered with a continuous and intact 6-mil polyethylene sheet (extended above ground level and sealed against the walls). The sheet must be secured by a 50 mm (2 in.) layer of clean stone or gravel, or held in place by bricks. A more expensive option is to cover it with a 75 mm (3 in.) thick concrete floor.
If necessary for drainage, install a sump pit with a sealed cover, and a basement drain with a backwater valve (backflow prevention device). Install a submersible sump pump connected to a suitable discharge point. If the sump pit is not connected to the exterior perimeter or underfloor drainage pipes, it may be necessary to establish a flow path for the sump, depending on the soil type.
Seal all formwork tie holes and all cracks in walls and floors from the inside using an appropriate epoxy adhesive, following the manufacturer’s recommendations.
Insulate the foundations from the outside, from the top of the concrete or block wall down to 600 mm (2 ft.) below finished grade, using extruded polystyrene sheets with a foundation protective coating and a metal drip edge. A further improvement would be to install a 600 mm (2 ft.) wide sheet of extruded polystyrene laid horizontally (with a slight outward slope) at the bottom of the wall insulation.
When backfilling around the insulation, create a slope away from the foundations of at least 15 cm (6 in.) over 3 m (10 ft.). This might require the installation of window wells. A window well should be placed so that the top is clearly above the finished grade, fastened and sealed to the wall, and the bottom should be connected to its own water collection and drainage system.
Install insulation and an air/vapor barrier in the spaces between joists located along the inner face of the rim joists, from the inside of the floor sheathing down to the top of the foundation wall. Alternatively, when insulating the foundation from the outside, remove the exterior siding up to the top of the floor framing and insulate this area in the same manner as the foundation wall.

More Expensive Foundation Options

Excavate around the foundation walls and waterproof them from the outside.
Install drainage-promoting insulation panels over the full height of the foundations.
Install perimeter drains sloping at 1:50 to a clear outlet, or connect them to the local storm sewer system or the sump pit.
Install a waterproofing membrane over the current floor and pour a new concrete slab over it.

New Foundation

If the current location is too damp and it is very difficult and expensive to prevent water from entering the existing basement, a new foundation might be required. In this case, on the current site or a drier one, proceed as follows:

Build a new 1.2 m (4 ft.) high poured concrete crawl space foundation with footings, following a slope equal or approximately equal to the current one.
Waterproof and insulate the exterior of the foundation walls.
Install perimeter drainage, a floor drain, and a sump pit.
Implement thermal insulation under the slab along with a polyethylene air/vapor barrier or moisture barrier.
Pour a floor slab at least 75 mm (3 in.) thick.
Move the house onto the new foundations.
Backfill with well-draining material (if available) and grade the ground sloping away from the house.
Use the existing stairwell, if space permits, to place the laundry room, a utility room, or the water heater, in addition to providing an access hatch to the crawl space.

If the house is to be moved onto a new foundation, it is important to clean the mold throughout the portion being moved, as well as in furniture and other belongings; otherwise, the mold will also spread to the new foundation.

Building Envelope Recommendations Above Grade

Repair the roof. Replace all missing shingles or flashings as needed; design flashings so that they do not rely on caulking. Ensure all gables and soffit vents are protected.
Gutters and downspouts must be installed with connections that discharge water onto splash blocks at least 3 m (10 ft.) from the building.
Repair the exterior siding. Have drip edges installed above windows and doors as needed. Caulk windows and doors. Replace deteriorated siding.
Replace all broken window panes or insulated glass units with broken seals. Replacement windows, if applicable, should be at least double-glazed with insulating spacers and effective seals. Ensure all window installations are secure, uniform, plumb, level, operate smoothly, are made airtight with polyurethane foam, and are properly caulked and sealed.
Seal the building envelope: replace porous or detached weatherstripping on doors, windows, or attic access hatches. Seal holes around penetration points.

Interior Water Sources

Many mold problems stem from plumbing leaks. Those occurring under kitchen or bathroom sinks, from bathtub pipes or drains, or from toilet connections, can cause water to seep into hidden cavities under cabinets or in the floor framing, causing invisible mold growth. Water pumps and pressure tanks are also common sources of water leaks or condensation. Mold can grow in a small damp area even if the rest of the house is very dry.

Mechanical and Ventilation Systems

Common Problems

Many homes have no mechanical ventilation. Due to our cold climate, there is often very little natural ventilation through windows, which are kept closed for long periods. Moisture and other air pollutants can accumulate, especially in homes with many occupants. Other homes may have mechanical ventilation using poor-quality bathroom fans that cannot adequately exhaust stale, humid air, or recirculating kitchen hoods that do not actually function as ventilation equipment.

Supply ducts are often used to provide fresh outdoor air into the return circuit of a forced-air furnace. Air intake locations may be poorly placed. The supply of fresh air is limited by the operation of the furnace fan. Dryer air is often exhausted indoors, or outdoors through long, winding loops of flexible ducting.

Solutions

In many homes, heating and ventilation equipment is a collection of parts rather than a coordinated system. The requirements of the National Building Code of Canada 1995 attempt to correct this situation and should be considered the minimum standard. Balanced whole-house heat recovery ventilation (HRV) systems are recommended to better eliminate moisture and pollutants caused by high occupancy in small houses in such harsh climates.

Cost-Effective Ventilation Options

Ensure that the exhaust fan in the bathroom ceiling vents directly outside through sheet metal pipes with sealed joints.
Insulate the ductwork and slope it toward a clear hood exit leading outside or away from the soffit. Avoid exhausting air into the attic or soffits.
Alternatively, install a new centrifugal exhaust fan in the bathroom ceiling with a noise level of 2.0 sones or less, complying with the primary ventilation requirements of the National Building Code of Canada 1995. This type of fan will provide higher airflow. Additionally, a quiet fan is more likely to be used for longer periods. Note that a separate bathroom exhaust fan is unnecessary if a Heat Recovery Ventilator (HRV) is installed.
Install or upgrade kitchen hoods to vent directly outside. All appliances should have speed controls and short runs of rigid sheet metal ducting with sealed joints. All ducts passing through unheated spaces must be insulated. Ducts must be accessible for cleaning or include a grease filter.
Ensure the current fresh air intake hood is not located near driveways or other exhaust hoods to provide the home with clean air.
Improved ventilation will not reduce indoor humidity if the outdoor weather is warmer and more humid than indoors. Cool basement surfaces are particularly vulnerable to condensation in summer when warm, humid air can enter the basement. Dehumidification is often required. Install a portable dehumidifier; empty it as needed or connect it directly to the floor drain. Clean it periodically.
Replace all flexible dryer ducts with aluminum ducting using taped joints and short, direct runs.
If the house has a forced-air heating system, have warm air registers installed in every room. Ensure return airflow from each room through return air ducts or by creating gaps at the bottom of doors, or by using louvered doors, allowing air to circulate through central return air registers. Ideally, air should circulate continuously, but this is not a comfortable or energy-efficient option with a single-speed furnace fan. Energy-efficient two-speed fans are recommended.
When installing exhaust equipment, ensure the amount of extracted air does not cause backdrafting in wood stoves, fireplaces, or wood, oil, gas, or propane heating appliances, or any other combustion devices. Installations must meet the safety requirements of the National Building Code of Canada 1995 regarding make-up air systems and carbon monoxide detectors.

More Expensive Ventilation Option

Install a balanced Heat Recovery Ventilator (HRV) system, either with its own duct system or integrated into an existing forced-air heating system. This type of system makes individual bathroom fans and fresh air intakes unnecessary in most cases. If integrating the ventilation system with the heating system, install a two-speed fan with a high-power blower motor, and run the fan at a continuous low speed for air circulation and at high speed when heat is required.

Interior Finishes

Renovating after mold cleanup often includes interior finishing. This is a good opportunity to further protect the home against mold and also reduce other indoor air pollutants. Opt for low-pollutant finishes such as:

Low-odor paints for drywall, specifically paints that release low levels of volatile organic compounds (VOCs);
Vinyl tiles (avoid carpets, which can be a source of chemical pollutants and harbor dust, mold, and dust mites);
Water-based, low-VOC finishes on doors and trim;
Cabinet materials selected for low emissions, such as locally available hardwoods or softwood plywood.

Design and Construction of Houses Less Vulnerable to Mold

The information in this chapter is intended for tribal councils, First Nations housing departments, bands, home builders, housing policy developers, and technical service providers.

A more mold-resistant house has the following characteristics:

a simple, proven, and affordable design;
the lowest floor is located above the water table or predicted flood level;
no basement (insulated, frost-proof slab-on-grade foundation);
an airtight and energy-efficient envelope;
an effective heating, dehumidification, and air circulation system;
heat recovery ventilation (HRV);
an exhaust hood venting to the outside;
finally, materials selected for their durability, low chemical emissions, and ease of maintenance.

What to Avoid

The moisture leading to mold growth in existing homes often stems from one or more of the following conditions:

poorly drained construction sites;
houses built to standards unsuited to the site, climate, or number of occupants;
basement leaks;
basements insulated on the inside, creating a hidden cavity conducive to mold growth;
poorly maintained roofs that leak;
leaking plumbing;
no mechanical ventilation;
weak exhaust ventilation in the bathroom;
weak kitchen ventilation, including recirculating range hoods;
low or non-existent fresh air supply;
uncontrolled air leaks;
cold interior surfaces.

Construction Sites

Building houses, especially with full-height basements on damp sites, has sometimes caused problems in the past, resulting in chronic basement leak issues leading to mold growth. Community planning must take into account that certain sites should be left vacant.

Specifications

To build houses less vulnerable to mold, detailed specifications must be established for contractors and inspectors. Similarly, occupants must be willing to adapt to changes in residential construction. However, specific designs must meet the requirements of the occupants’ cultural and daily activities. The National Building Code of Canada 1995 provides a minimum standard. All new constructions can be developed from a set of standard features incorporating details compliant with the National Building Code of Canada 1995, as well as the R-2000 standard, and adapted to the specific needs of a community in a given location. Improvements and different concepts can be developed over time, but the basic house system remains the same.

Basements

The easiest way to avoid basement problems—such as leaks, hidden cavities conducive to mold growth, cold and damp surfaces, and excessive accumulation of mold-prone items—is to avoid building basements altogether. Slab-on-grade bungalows are recommended. It must be recognized that crawl spaces are sometimes the only viable option. Unfortunately, many current crawl spaces are very vulnerable to moisture and mold, which are easily transferred to the rest of the house. Most crawl spaces are built and maintained as if they were located “outside” the house. Since they often contain forced-air heating units (with leaking ducts) and are only separated from living areas by non-airtight floors, they are, in fact, “inside” the house. At the design stage, it must be decided whether the crawl space should be “conditioned” or not.

A conditioned crawl space is one that is not separated from the heated parts of the house. The temperature may be different, but the air in the crawl space is connected to the air in the house. This type of crawl space must be built as if it were a shallow foundation, with an air barrier, vapor barrier, insulation, heating, air conditioning, and ventilation similar to those in the rest of the house and adapted to the climate.

An unconditioned crawl space is distinct from the heated or conditioned areas of the house. It is located “outside,” so the floor above must be treated as the bottom of the building envelope and include the air barrier, vapor barrier, and insulation adapted to the climate. Household services, including ducts, should not be placed there.

Ground Floor Construction

There are several options for ground floor construction. Consult construction manuals such as the Canadian Home Builders’ Association Builders’ Manual, or various CMHC publications on mold elimination.

Maintenance

Occupants must be informed of their responsibilities and provided with the necessary tools and resources to perform all essential maintenance tasks.

Heating and Ventilation

The construction of better building envelopes will lead to better heating systems. The choice of fuel depends primarily on price and availability. Any heating fuel can be used in a house that is less vulnerable to mold, provided the necessary precautions for that fuel are taken. All exhaust equipment must be carefully planned and matched with the heating system to avoid dangerous backdrafting of combustion gases.

The heating and ventilation system can be used to ventilate surfaces, keep them warm, provide drier air, and exhaust humid air. Heating and ventilation systems can be either combined or entirely separate, but it is advisable to ensure air circulation, fresh air supply, and stale air exhaust. Balanced heat recovery ventilation is recommended as the best method to exhaust humid and stale air and provide an equal amount of fresh air. If such a central system is installed, bathroom exhaust fans are normally no longer necessary. However, a range hood that exhausts to the outside is still recommended to remove cooking odors and excessive moisture from the kitchen. The dryer must also be vented directly to the outside.

Interior Finishes

Apply low-polluting finishes:

Drywall painted with low-VOC paint;
Vinyl tiles or prefinished hardwood floors;
No carpet;
Water-based, low-VOC finishes on doors and trim;
Cabinet materials selected for their low emissions.

“Small” Mold Level

How much mold is present?

Mold is considered to cover a small area if there are no more than three patches, each with an area of less than one square meter. Clean small areas yourself with a detergent solution, wearing rubber gloves and a dust mask for protection. Small mold spots in homes can grow over time if ignored, so it is important to clean and remove even tiny spots. Note that people with asthma or allergies should refrain from performing the cleaning.

How to clean small mold spots

Key points:

Occupants can clean small mold spots themselves.
A mask, safety glasses, and rubber gloves must be worn.

Cleaning small surfaces

You can clean small moldy surfaces (one to three patches of at most one square meter), but wear at least:

Goggles or safety glasses;
An N95 respirator (3M 8210 or equivalent);
Rubber gloves.

Occupants suffering from asthma, allergies, or other illnesses should avoid the area being cleaned.

Procedure for cleaning small moldy surfaces

Wear rubber gloves, goggles or safety glasses, and a mask. When purchasing a mask, choose an N95-rated model, as it traps finer particles than ordinary dust masks.

Washable surfaces

Scrub with a detergent solution, then
Wipe with a sponge and a clean damp cloth and dry quickly.

Moldy drywall

Clean with a damp cloth and baking soda or a little detergent, without getting the wall too wet.

Moderate, large, or very large amounts of mold require more rigorous precautions and even better protective clothing.

Minimum Personal Protective Equipment (MPPE) and other requirements

The following recommendations comply with New York City Department of Health guidelines regarding mold cleanup. In addition to addressing the affected area, the time required to remedy the situation must also be considered. An N95 respirator is the minimum respiratory protection for small cleanups. It can be replaced by a more effective half-face respirator if the mold growth is significant and if cleanup and decontamination operations are expected to take hours instead of a few minutes. If the work extends over several days, it would probably be better to use a full-face respirator equipped with HEPA filters.

Small-scale cleanups do not require additional preparation for the work area. However, for larger operations, work areas must be isolated to prevent contamination of other rooms in the house. An exhaust fan installed in a window prevents air movement to other parts of the house and provides ventilation for workers.

MPPE for cleaning small sites

Cleaning one to three patches with an area of less than one square meter should only take a few minutes.

N95 respirator, for example 3M 8210 model
Goggles or safety glasses
Household rubber gloves

Who does the cleaning?

Occupants of the house who are reasonably healthy. High-risk individuals must not be present at the work site.

“Moderate” Mold Level

What should be done if mold occupies a large surface?

The mold surface is considered moderate if a) it consists of more than 3 patches, each having an area of less than one square meter, or b) at least one patch covers less than one square meter, but less than a full sheet of plywood. Clusters of spots (separated by a distance of less than two garbage bag lengths) must be considered as a single patch.

You can clean moderate amounts of mold only if you proceed correctly and are able to obtain the proper protective equipment: a dust mask (a half-face respirator with a carbon cartridge is optional), safety glasses, and rubber gloves. Scraping a moldy surface will launch debris into the air and expose you to more mold. Ask your First Nations housing department or your band for the procedure to clean moderate amounts of mold, and buy or borrow a breathing apparatus and safety glasses.

Preparing the Home for Cleaning

The information in this chapter is intended for First Nations housing services and bands.

Key Points:

A plan is required for every cleanup.
The work site must be properly prepared according to the scale of the cleanup.
Occupants and workers must be protected against mold exposure during cleaning.

Establishing a Work Plan and Cost Estimate

Smaller mold cleanups can be performed by the occupant or community volunteers. Larger tasks will likely require a specialized mold remediation contractor. Another contractor may be needed to renovate the house and make it more mold-resistant. Agreements with both contractors must include clear specifications regarding work and costs. Discuss the plan with the contractors, as their experience can be valuable. However, be cautious and do not necessarily accept all advice on mold cleaning and renovation for mold resistance from the contractors hired to perform the work. Independent inspections by a technical service provider competent in indoor air quality are necessary to confirm that the work is performed as planned and that the initial plan is still appropriate despite any unforeseen conditions.

Preparing for an Effective Cleanup

Depending on the type of mold and the dimensions of the contaminated surface, proper preparation may include the following steps:

Ensuring the safety of occupants during cleaning.
Reviewing safety requirements.
Ensuring that cost estimates are still up to date and cover all required work.
Reviewing the work procedure with the workers, the band housing representative, the technical service provider, as well as the nurse or community health representative or environmental health officer.
Preparing the work site according to the scale of the cleanup.
Sealing all openings and duct penetrations to prevent air from the work area from mixing with the rest of the house.
Organizing the disposal of moldy waste and other debris.
Organizing post-cleanup monitoring.

Worker Protection for Working in Mold-Contaminated Homes

All persons called upon to perform small mold cleanups or to remove and decontaminate objects in very moldy houses before the arrival of a professional cleaning contractor must consider the following.

Basic Requirements

No worker suffering from any form of immune suppression, asthma, or mold allergy should work on the cleanup. The risk of severe reactions in case of inadvertent exposure is too great. All workers who have recently suffered from a severe cold or flu must delay their work in moldy locations until their full recovery. Contractors must establish a worker protection program in accordance with provincial and federal regulations. All persons must be familiar with their personal protective equipment, how to repair, maintain, and clean it, as well as the hazards associated with handling mold-contaminated materials and bleach solutions.

MPPE for Cleaning Medium-Sized Sites

The cleaning of more than three patches with an area of less than one square meter, or at least one patch with an area greater than one square meter but covering less than a sheet of plywood, will take hours.

Work site preparation: Isolate the area to be cleaned using plastic sheeting. An exhaust fan would be useful. High-risk individuals must not be at the work site or in adjacent spaces.

PPE

An N95 respirator, such as the 3M 8210 model, is the recommended minimum; however, it is preferable to opt for a half-face mask equipped with a carbon cartridge.
safety glasses.
heavy-duty rubber gloves.

Who does the cleaning? Maintenance personnel who have received training in mold removal; occupants under the supervision of a trained person.

“Advanced” Mold Level

The moldy surface is considered large if a single mold patch is larger than a standard sheet of plywood or drywall. The house is considerably contaminated when many large mold patches are present. Exposing oneself to such an amount of mold is risky. Do not attempt to clean it yourself; instead, contact your First Nations housing department or your band.

PPE for Large-Scale Cleanups

(moldy surfaces equal to or larger than the dimensions of a standard sheet of plywood; cleaning will take place over several days)

PPE

the N95 mask, such as the 3M 8210 model, is the recommended minimum; however, it is preferable to opt for a half-face mask equipped with a carbon cartridge.
adequate eye protection.
heavy-duty rubber or neoprene gloves.
disposable clothing covering the head and shoes.

A health and safety professional must be consulted.

Who does the cleaning? Maintenance personnel and others who have received training in mold removal.

Work site preparation: Isolate the area to be cleaned using plastic sheeting taped to the walls and ceiling. Use an exhaust fan to depressurize the work area. Only members of the cleaning team should be at the work site. When contamination is very significant, the work must be entrusted to specialists trained in handling hazardous materials. A health and safety specialist with experience in mold should also be consulted. Workers must be protected by full-face respirators equipped with HEPA filters and disposable clothing covering the head and shoes. The work area must be isolated and depressurized.

What to reasonably do or avoid, as the case may be:

To do

wear protective clothing to avoid exposure to mold during cleaning, handling of moldy materials, or renovation of moldy houses;
ensure that the respirator is in good condition and suited to the circumstances;
apply the correct procedure for preparing the site;
remove mold-contaminated clothing and wash hands before eating;
wash your gloves (if they are washable) at the end of the work;
replace your disposable mask or respirator filters as needed, and store masks in clean plastic bags;
finally, wash work clothes separately and take a shower at the end of the workday (so as not to expose your family to mold).

To avoid

assuming that one is resistant and that mold cannot cause harm;
working in a mold-contaminated area without personal protective equipment;
eating at a mold-contaminated site;
touching your face or skin with work gloves.

Mold Cleanup

The information in this chapter is intended for First Nations housing services, bands, mold cleanup contractors, and renovators. The procedure for cleaning mold and ensuring safety depends on the type and surface area of the mold. Small amounts of mold can be cleaned by the occupant or by a community team.

Key Points:

Cleanup and safety procedures depend on the type and surface area of the mold.
The use of a high-efficiency vacuum is a very useful way to reduce mold exposure before, during, and after renovation.
A mold problem in one area can contaminate the rest of the house.
Furniture, clothing, and belongings must all be cleaned before being returned after mold cleanup or transported to another home.
Cleanup is not complete without ongoing monitoring.

General Guidelines

There are several general strategies to be employed simultaneously:

Disposal of mold-contaminated belongings and furniture;
Decontamination of belongings and furniture;
Decontamination of wood;
Removal or replacement of moldy drywall;
General cleaning;
Decontamination of the building’s concrete surfaces.

Disposal of Mold-Contaminated Belongings, Furniture, and Building Materials

Furniture that has been dampened or kept for a long time in a moldy location, or that is visibly very moldy or emits a musty odor and is not washable, must be disposed of. Contaminated belongings, furniture, and building materials to be disposed of must be wrapped in heavy-duty double garbage bags, sealed and labeled accordingly, and then taken to the landfill.

Decontamination of Belongings and Furniture

Items to be salvaged must be cleaned as follows:

Washable items should be washed with detergent, rinsed, and dried. Repeat as necessary. Airing them out outside on a sunny, dry day can be helpful.
Furniture with a hard, washable surface can be scrubbed with detergent, rinsed, and dried as above.
Surfaces likely to be damaged by excess water can be cleaned with baking soda. Add just enough water to make a paste, then apply the mixture to the surface to be cleaned and leave it for half an hour or longer. Wipe or vacuum. Repeat as necessary. Air the item in the sun.
Certain non-washable clothes can be dry-cleaned.

Place cleaned items in 6-mil plastic bags, label them, and store them separately.

Use of High-Efficiency Vacuum

Mold exposure can be reduced by using a high-efficiency vacuum before cleaning moldy surfaces. Vacuuming can be done again during cleaning and once more after renovation. Using a high-efficiency vacuum is also a useful interim measure to reduce mold exposure when it is impossible to correct the situation immediately.

Decontamination of Wood

Visually rotted wood must be discarded and replaced. Frames and other wood surfaces can be cleaned using either of the following two methods:

Method 1. Use a high-efficiency vacuum on moldy surfaces. Omit this step if the wood is damp. Wipe with a cloth soaked in an odorless detergent solution and water, then sponge with a clean damp cloth. Extract excess water using a wet/dry vacuum and use dry cloths to blot water from surfaces and all nooks and crannies. Speed up drying with fans and open windows (if outdoor relative humidity is low) or with dehumidifiers (keep windows closed). Wood should not remain wet for more than one day. Measure the relative humidity of the air near the frame. It is dry enough if it is less than 60%.

Method 2. Use a high-efficiency vacuum on visible moldy sites. Simultaneously, sand and vacuum until all traces of mold disappear. It is important to prevent dust from dispersing during sanding.

Removal and Replacement of Moldy Drywall

Cover the moldy surface with a piece of 6-mil polyethylene large enough to cover the surface and at least eight inches around it.
Seal the edges of the polyethylene sheet with sheathing tape or duct tape.
Cut around the edge of the area bounded by the tape and remove the material.
Place the moldy material in a heavy-duty garbage bag or wrap it in a 6-mil polyethylene sheet, sealing the joints with tape. Take it all to the landfill.
Wash the surrounding area with a mild detergent solution and dry quickly.

Check the back of the cut surface. If there are traces of mold in the wall cavity, it means that much more work than replacing the cut portion will be required. It may be necessary to remove moldy insulation, clean the framing, or even replace a larger area of the drywall. If the work is not done immediately, cover the hole temporarily with polyethylene to protect the area and prevent the spread of mold.

General Cleaning

First, vacuum the surfaces with a high-efficiency vacuum. Scrub or brush the moldy surface with a mild detergent solution, then rinse by sponging with a clean, wet cloth. Repeat. Dry quickly.

Decontamination of Concrete Surfaces

Vacuum the surfaces with a high-efficiency vacuum.
Follow the steps indicated above for concrete surfaces showing no visible traces of mold.
For concrete surfaces with visible traces of mold, use trisodium phosphate (TSP), at a rate of one cup per two gallons of hot water. Stir for two minutes. Note: Avoid getting trisodium phosphate in contact with skin or eyes.
Saturate the moldy concrete surfaces with the solution using a sponge or cloth. Leave the surface wet for at least 15 minutes.
Rinse the concrete surface twice with clean water. Wash the sponge or cloth well between wipes.
Dry completely as quickly as possible.

Cleaning a Moderate Surface

These guidelines apply to surfaces larger than a garbage bag folded in half, but smaller than a standard sheet of plywood.

Follow the safety procedures outlined in the previous chapter, including occupant and worker protection, isolation of the contaminated area, and ventilation.
If possible, dispose of moldy material as indicated above.
Remove contaminated carpet, underpad, and furniture for cleaning or disposal.
Decontaminate surfaces as indicated above.
Wash the surrounding area with a mild detergent solution.
Vacuum the ducts and the heating unit (stricter measures may apply when the heating and ventilation system is directly affected by mold). Do not use biocides (chemicals intended to kill mold) on the ducts.
Ensure that all work areas have dried completely before using a high-efficiency vacuum as the final step of the work.

All mold growing in the house can eventually affect health. Perform a full “spring cleaning” from cellar to attic. Clean walls, ceilings, and floors with a mild detergent solution. Use bleach on wood framing if necessary, and trisodium phosphate on concrete.

Cleaning a Large Surface

If the amount of mold in a single patch occupies a surface larger than a standard sheet of plywood and several patches are found in the house, stricter cleaning rules apply. This type of cleaning requires greater knowledge and better equipment, and it is best left to a qualified specialist. The rules for occupant and worker protection are much stricter.

For All Renovations

If the repair or renovation occurs in only one or two places in the house, build an enclosure around the work sites consisting of framing elements and polyethylene sheets or tarps. If the moldy surface is very large, use exhaust ventilation while working to prevent dust and construction debris from spreading throughout the house.
Store all debris in closed containers.
Remove all demolition debris as soon as possible.
Remove construction debris no later than the end of the work.
Clean all marked or soiled surfaces, and repair all damaged areas.
Remove all enclosures and clean the spots one more time.

“Spring Cleaning” of the Entire House

Due to air movement inside, a localized mold problem will eventually contaminate the entire house by spreading spores, even those growing behind walls. Walls are never perfectly airtight, and drafts can pull spores out of wall cavities. If conditions are favorable, mold will begin to appear in a new location. It is recommended to clean the house thoroughly from cellar to attic.

Vacuuming

It is preferable to use a vacuum equipped with a high-efficiency filter.

Heating and Ventilation Ducts

The heating, ventilation, and air conditioning ducts of a house where mold is present almost certainly contain dust contaminated by that mold. Both the supply and return air ducts must be dismantled, vacuumed, and washed with a detergent solution. Supply ducts from the outside and exhaust ducts from the bathroom, range hood, or vacuum, etc., must be inspected and cleaned.

Washing

All hard surfaces must be washed with a detergent solution after having been vacuumed. Dry by wiping, then rinse and wipe again.

Salvage or Dispose?

Any furniture or items such as sofas, cushions, or mattresses originating from a basement or other room obviously affected by mold must be disposed of. All furniture and belongings from other rooms on the ground floor must be removed from the house during cleaning and either disposed of or cleaned before being brought back to the house or transferred to another. Otherwise, they will be a source of mold spores. To clean furniture and clothing, apply the general guidelines. Non-washable furniture must be evaluated individually based on the risk of mold contamination. Moisture and mold can penetrate soft or upholstered furniture. Any attempt to disinfect mold on the surface of such items is unlikely to succeed, especially if the furniture has been exposed for a long time to conditions favorable to mold. Furniture subjected to high humidity for several weeks should be suspected of being sources of recontamination and, therefore, disposed of.

Monitoring Homes After Cleanup in Case of Future Mold Appearance

The information in this chapter is intended for First Nations housing services, environmental health officers, community health nurses or representatives, and technical service providers.

Main Point: Monitoring is recommended to ensure that all mold has been removed and that no new mold appears unnoticed.

After the cleanup is finished, it is recommended to have a competent person perform periodic visual inspections to ensure no new mold appears without being noticed. It is also necessary to advise the occupant to constantly monitor the house for possible signs of mold growth. The effectiveness of the renovation can also be verified by air tests, and by observing all surfaces that still appear marked or stained. Such tests are useful, especially if the contamination was significant or if there were toxic molds. Decisions regarding testing will be made by the First Nations housing service, in collaboration with the environmental health officer and the technical service provider competent in indoor air quality. The nurse or community health representative, or the environmental health officer, will need to conduct the tests.

Here is the suggested procedure:

Indoor air can be tested one to three days after the end of the cleanup, in at least four locations (two at the site of visible mold and two elsewhere in the house). Tests should take place twice, in the morning and the afternoon.
Outdoor air on the windward side of the house must be tested once in the morning and once in the afternoon.
Surfaces that are still marked or stained, or that show new marks, must be tested by scraping or surface sampling.
Before the site is declared ready for re-occupancy, all test results must be within normal limits for the location and site of each test, as judged by a competent on-site sampling specialist. The American Industrial Hygiene Association (AIHA) guidelines provide examples of normal limits for mold contamination. In general, no species should proliferate significantly better indoors than outdoors.

Before Occupants Return

The information in this chapter is intended for First Nations housing services and bands.

Key Points:

Construction-related damage or debris must be cleaned up.
Confirm with the environmental health officer or the nurse or community health representative that the house is ready for re-occupation.
Occupants must be shown how to use and maintain any new heating or ventilation equipment.
Occupants must take necessary measures to prevent mold growth.

A thorough cleaning is necessary after the mold cleanup and after the completion of renovations. Then, proceed as follows:

Have the house checked by the nurse or community health representative, or by the environmental health officer, to confirm that it is ready for re-occupation.
The renovation contractor or another competent person must explain to the occupants the operation of any new heating or ventilation equipment, or other new features of the house. Printed instructions on the maintenance of new and unfamiliar equipment such as heat recovery ventilators must be left with the occupants. Indeed, verbal instructions are likely to be forgotten.
Occupants must be given a copy of the “First Nations Occupant Awareness Guide to Mold” and urged to follow preventive measures, encouraging them to recognize and clean small mold spots.
It is important to help occupants understand their responsibilities and know when and to whom to turn to ask for help regarding all questions relating to mold, maintenance, or mechanical systems.

“About Your House” Fact Sheets

The About Your House fact sheets are intended to help owner-occupants take the right measures regarding existing problems in their homes, or to make informed decisions when planning renovations or improvements.

The following fact sheets contain more information on a variety of topics related to moisture and indoor air quality.

To obtain these About Your House fact sheets or to learn more about our wide range of information products, visit our website at the address www.cmhc.ca

You can also contact us by phone: 1-800-668-2642 or fax: 1-800-245-9274.

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