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Copy of a report prepared for Taylor Construction and their client.

For several decades, Canadian homes have been built over dirt crawl spaces because it was simple and cheap. Unfortunately, many of these dirt crawl spaces were vented based on the faulty assumption that these vents would allow moisture to escape from the crawl space. We now know that these vents actually increase the relative humidity level. The natural upward air movement draws air from the crawl space vents up into the living space of the home. Did you know that up to 40% of the air you breathe in your home was once in the crawl space?

Vented dirt crawl spaces create a ticking time bomb of potential problems. The bare soil contains high levels of humidity that natural airflow patterns move upwards into your home. This is referred to as the "Stack Effect". This means that not only are mould spores and allergens entering your living space, but that moisture is entering the entire floor framing system under the house, paving the way for damaging wood rot. This can result in expensive structural repairs to girders, floor joists and sill plates.

Typical Crawl Space
Typical Crawl Space

Benefits of Unvented Crawl spaces

Crawlspace vents effectively become the "determined hole" in a home. In winter, warm air exiting the attic or ceiling creates a negative pressure at the lowest openings in the home. This negative pressure causes cold air to enter through the crawlspace vents and rise through holes in the subfloor to the first floor. This phenomenon creates the "cold floor syndrome" prevalent in cold climatehomeswith vented crawlspaces.

The cold air can also carry unwanted moisture and gases from the soil, and odours from the crawlspace into the home. Typically, the floor above a vented crawlspace is insulated. In unvented crawlspaces, the walls, instead of the floor, should be insulated to limit heat transfer from outside to inside the crawlspace, and vice versa. When properly built, an unvented, insulated crawlspace helps to eliminate problems with comfort, odour, and health associated with mould, mildew, and bacterial growth.

Conditioning the Crawlspace

Once the crawlspace is insulated and unvented, it should be treated the same way as any other space in the house-supplied with a certain amount of heated or cooled air from the mechanical system. Conditioning the crawlspace can help the mechanical components that are housed in the crawlspace (the air handler, ductwork for the first floor zone, and plumbing line, for example) operate more efficiently and last longer because they are not subject to temperature and humidity extremes. Ideally, the crawlspace temperature should be about 55°F to 65°F year-round. All ducts should be well sealed with mastic to prevent unwanted air leakage. This air leakage increases energy consumption because the outside air has to be heated in the winter and cooled in the summer.


Foundation ventilators also known as crawl space vents play an important part minimizing potential wood decay to your home's foundation caused by excessive moisture intrusion into the crawl space of foundation area. The unfortunate result of less foundation ventilation has been the increase of wood rot in crawl spaces and moisture problems in the living areas of homes. Moist climates require you to provide and maintain adequately ventilated crawl spaces. A crawl space vent system, in addition to venting moisture vapour, serves to vent out other gases, such as those formed from residues in termite treatment, treated wood, and radon gases. The crawl space vent system protects the structure of the house and the health of its occupants. To aid natural crawlspace ventilation, mechanical ventilation should exchange the crawlspace air at least four times an hour or once complete air exchange every 15 minutes. To determine this, multiply the square footage of the crawlspace by the height to calculate the cubic feet of the crawlspace and then divide by 15 to determine the CFM needed to properly ventilate your crawl space.

110 CFM Ventilator Fan

110 CFM Ventilator Fan

Length x width x height = total cubic feet of crawl space Divide = total cubic feet of crawl space / 15 = CFM needed for proper foundation ventilation.
21' x 18.5' x 2' crawl space = 777 cubic feet of area
divide 777 cubic feet by 15 = 51.8 cubic feet per minute (c.f.m) of air flow needed to ventilate your crawl space

Therefore, 1 unit would be required to properly ventilate a crawl space at18 Ronan Avenue. As with all powered exhaust systems, proper intake air vents should be used. Generally, one air intake vent is recommended as a minimum for air intake. Having 3-4 intake vents would be ideal. These crawl space ventilators should be installed on opposite ends of the intake vents, to allow air movement across the entire space to be ventilated.

110 CFM Ventilator Fan Diagram
110 CFM Ventilator Fan Diagram

By incorporating the crawlspace vent into your homes crawlspace ventilation system, you can help stop "mould growth", mildew, rot, pest /insect infestation and decrease high humidity levels while increasing the overall airflow within your foundation.

Whether or not to ventilate a crawlspace is probably the most controversial issue concerning crawlspace design. Many building code require vents to circulate outside air. Research has now shown that crawlspace vents can be counterproductive. Introducing outside air into a cool crawlspace during summer, when temperatures are most conductive to mold and decay actually raises crawlspace relative humidity. This practice can easily produce relative humidity of 80-95%, even in dry crawlspaces with dry soil or vapour barriers. Experts recommend, after addressing all other moisture concerns, to seal the crawlspace and install a proper vapour barrier. If needing, a dehumidifier can be installed to condition the crawlspace.

Typical Vent In A Crawl Space
Typical Vent In A Crawl Space

Standing water in a crawlspace is a serious concern. All attempts need to be made to divert water from draining towards your home. Rain gutters need to be clean and large enough for the size of the home. The ground outside the foundation must be graded away from the home to keep water from pooling next to the foundation. Sprinkler heads need to be properly maintained to prevent them from soaking the foundation and crawlspace vents. Water pipes or drain pipes need to be checked for cracks and leaks. Furnace drain lines need to be drained properly. When all of these concerns are addressed and there is still water pooling in your crawlspace, a drainage system may be required. Sometimes because of a high water table or a spring located within the crawlspace, the problem can not be corrected from inside.
Crawl Space Soaked With Water
Crawl Space Soaked With Water

If the floors in your home are sagging or bouncy, extra supports may be needed. When floors sag the drywall often cracks especially on the corners of the windows or doors. The floor can often be raised back to its proper position and held in place with stronger piers. Sometimes additional piers need to be added when the spans between them is too large. Special care needs to be taken when the floors have been tiled. When the floor is lifted the probability that the tiles will come loose is very high.

Sagging Floor Held Up With Added Piers
Sagging Floor Held Up With Added Piers

It has been a standing practice for contractors to insulate the underneath of the floor joists in a crawlspace. The theory has been if you are going to ventilate your crawlspace with foundation vents, the only way to keep the home insulated was to place the insulation on the floor joists. Most of the time the insulation was installed with the paper vapor barrier facing the crawlspace instead of facing the floor as it should be. This was done so that the insulation could be easily stapled to the floor joists. When hot humid air would enter the crawlspace it would condense and the paper backing would become wet. The weight of the insulation would eventually pull the paper through the staple and the result would be insulation falling to the floor or the crawlspace. The other option would be to have the expose fiberglass facing down and be held up with metal rods. The rods would eventually come loose and then the insulation would fall to the crawlspace floor. In either case rodents usually aided in the deterioration of the fiberglass insulation. With the theory of sealing the vents and properly insulating the foundation walls, the moisture concerns are eliminated and the need to fix or replace the insulation every 7-10 years has been eliminated

Improper Insulation Methods Can Lead To Trouble
Improper Insulation Methods Can Lead To Trouble

The crawlspace of a home is a favorite place for contractors to leave debris behind. Most plumbers, heating and cooling technicians, electricians and every other person who works in crawlspaces seem to not have a problem leaving debris in crawlspaces. Out of sight, out of mind. The problem is rodents and insects enjoy the debris. They can utilize the debris for homes. Wood debris is very attractive to insects such as termites for a source of food. Mould also thrives on many of the materials left behind. Debris could also cause harm to any person who may have to enter the crawlspace to perform a service.

Junk Left behind By Contractors
Junk Left behind By Contractors

When humid air is allowed to enter the environment of a cool crawlspace, the result is high humidity which causes the furnace pipes to sweat. Properly controlling all sources of moisture will prevent this from happening. Sources of moisture include outside air entering through foundation vents, water penetrating through the foundation, broken or leaking pipes, furnace drains improperly drained, springs in the crawlspace, inadequate or missing vapour barrier and clothes dryers venting into the crawlspace. The result is high humidity and the perfect environment for mould and fungus to thrive.

High Levels Of Humidity Help Promote The Growth Of Mould And Mildew
High Levels Of Humidity Help Promote The Growth Of Mould And Mildew

Most homes have been constructed with foundation vents in the crawlspace. These vents allow cold air to enter the crawlspace even when they are closed. The cold air will lower the temperature of the crawlspace and therefore make the floors cold. A cold crawlspace also makes the heating system work harder to keep the house warm. Properly insulating the crawlspace would eliminate the vents and allow the crawlspace to stay warmer.

Insulated Crawl Space
Insulated Crawl Space

A musty or mouldy smell is a sign of mould. If the smell is in a room above a crawlspace the crawlspace should be checked for the presents of mould. A musty smell is caused by the mould spreading and establishing its territory.

Mould Infestation In The Crawl Space
Mould Infestation In The Crawl Space

Moulds produce tiny spores to reproduce. Mould spores waft through the indoor and outdoor air continually. When mould spores land on a damp spot indoors, they may begin growing and digesting whatever they are growing on in order to survive. There are moulds that can grow on wood, paper, carpet, and foods. When excessive moisture or water accumulates indoors, mould growth will often occur, particularly if the moisture problem remains undiscovered or un-addressed. There is no practical way to eliminate all mould and mould spores in the indoor environment; the way to control indoor mould growth is to control moisture.

  • Potential health effects and symptoms associated with mould exposures include allergic reactions, asthma, and other respiratory complaints.
  • There is no practical way to eliminate all mould and mould spores in the indoor environment; the way to control indoor mould growth is to control moisture.
  • If mould is a problem in your home or school, you must clean up the mould and eliminate sources of moisture.
  • Fix the source of the water problem or leak to prevent mould growth.
  • Reduce indoor humidity (to 30-60% ) to decrease mould growth by: venting bathrooms, dryers, and other moisture-generating sources to the outside; using air conditioners and de-humidifiers; increasing ventilation; and using exhaust fans whenever cooking, dishwashing, and cleaning.
  • Clean and dry any damp or wet building materials and furnishings within 24-48 hours to prevent mould growth.
  • Clean mould off hard surfaces with water and detergent, and dry completely. Absorbent materials such as ceiling tiles, that are mouldy, may need to be replaced.
  • Prevent condensation: Reduce the potential for condensation on cold surfaces (i.e., windows, piping, exterior walls, roof, or floors) by adding insulation.
  • In areas where there is a perpetual moisture problem, do not install carpeting (i.e., by drinking fountains, by classroom sinks, or on concrete floors with leaks or frequent condensation).
  • Moulds can be found almost anywhere; they can grow on virtually any substance, providing moisture is present. There are moulds that can grow on wood, paper, carpet, and foods. Asthma and Mould Moulds can trigger asthma episodes in sensitive individuals with asthma. People with asthma should avoid contact with or exposure to moulds. Floods/Flooding

I hereby authorize Air Detectives to perform mould remediation following these guidelines where necessary:

Stage 1: Demolition of all water damaged building material under the following conditions when mould remediation is performed after demolition.

Containment of the affected area is necessary to protect the occupants, remediation workers and the building itself from traveling mould spores. Only containment will offer proper protection to allow for inspection of wall cavities,removal or cleaning of mould. Containment involves plastic sheeting that is sealed with duct tape, Tuck Tape (or similar) to isolate and contain an affected or suspected area containing mould growth from the rest of the building. Full containment (similar to Level IV, NewYork City Guidelines, or Level 3 Canadian Construction Association) should be erected to contain the affected areas before mould removal and remediation activities commence. Complete isolation of CONDITION 3 areas from CONDITION I areas using plastic sheeting sealed with duct tape or similar and properly secured using staples (including ventilation ducts/grills, fixtures, and any other openings)are required.

The use of exhaust fans or negative air machines with HEPAfilters to generate negative pressurization within each containment area is required. Containment should be maintained via negative pressure to a minimum of 0.02 inches of water column. This should be checked periodically before and after any activities inside the contained area as well as periodically during the workday. Containment pressurization should be operated without interruption 24 hours/day until completion and continually logged using a digital differential pressure indicator with data logging capabilities.

Containment area should allow a minimum of 4ACH(air changes) per hour. Make up air into the containment area should be filtered air using a media filter with aMERV8 rating or better. Airlocks and sealed decontamination room for personnel and equipment at entrance/exit of containment is required.

Clean room for personnel dressing area and donning/doffing of Personal Protective Equipment PPE is required. All contained areas should include properly sealed plastic sheeting on the ceilings, walls and floors where possible.

All entry and exit points to the containment system (hot zone, decontamination chambers and clean rooms) must use proper opening and closing mechanisms consisting of either zippers or flaps located on both the positive and negative pressure areas.

Containment should be erected using fireproof plastic sheeting of the following densities:
Ceiling 4mil
Walls 6 mil
Floors 10 mil (where possible)

Containment may also be constructed using rip proof poly.

The contractor must secure the containment and no unauthorized or persons not trained in mould inspection or remediation should enter the containment at any time. All areas should be clearly marked as 'Clean Room', 'Equipment and Decontamination Room', 'Load Out Room' Regulated Area etc. Warning signs and restricted area signs should be clearly posted. All surfaces in the contained area including containment barriers and decontamination chambers should be HEPA vacuumed and cleaned with a damp cloth with a detergent solution and visibly clean prior to the post remediation inspection. Contractor must ensure that surfaces that are damp wiped are dried immediately.

A minimum of 3 passes for HEPA vacuuming for final cleaning is recommended. All equipment and tools in the containment areas should be cleaned and decontaminated prior to the removal of isolation barriers.

Cleaning inside the containment area should be conducted from clean working towards dirty areas. Cleaning of walls should be from top to bottom and towards the air filtration device.

All work should be performed using appropriate Personal Protective Equipment (PPE) and should be worn at all times when inside the contained work areas. Proper PPE consists of the following:

    * Full face respirators withHEPAfiltration cartridges for chemicals and organic vapours (P 100 cartridge).
    * Disposable protective clothing (Tyvek® or similar) covering head and shoes.
    * Latex, vinyl, neoprene or nitrile gloves (4 mil thicknesses).
    * Work gloves.

All containment procedures must include a sealed decontamination chamber where personal protective equipment is donned and doffed and where sealed bags of contaminated materials as well as contents and personnel are cleaned via HEPAvacuuming before exiting the containment area. All disposable suits, boots, and gloves must be sealed into a plastic bag and disposed of each and every time a person exits the work area into the decontamination chamber regardless of work performed or condition of the suit. Suits are not to be re used.Any building materials showing mould growth will need to be removed. Building materials that cannot be removed will need to have mould cleaned off by sanding, wire brushing or washing with a detergent solution. Several passes of thorough HEPA vacuuming as well as damp wiping of all surfaces in the affected area is required. All building materials which are removable (including but not limited to porous materials such as drywall, wall paper, studs, and carpeting) showing signs of water damage and/or mould growth should be removed in sealed plastic bags (6 mil) or rip proof bags and properly discarded into a secure refuse bin. Double bagging is recommended for added safety. The outside of the bags should be HEPAvacuumed and cleaned with a damp cloth and a detergent solution in the decontamination chamber prior to transport to uncontaminated areas of the building. All building materials and surfaces which are not removable (including but not limited to non porous and semi porous materials such as metals, glass, plastics, concrete, wood) showing water damage and/or mould growth should be thoroughly cleaned and scrubbed with a water and detergent solution, wire brushed, and/or sanded with a HEPA filter attachment to remove the mould. In some cases dry ice blasting of surfaces may be required.

50% of contract price $ _______________ to be paid in the form of a money order, certified cheque
or cash.

50% of contract price $ _______________ to be paid upon receiving an air sample report fromMBL
in the form of a money order, certified cheque or cash on ______________.



Date: ____________________________

Cleaning with dry ice! This new development is quickly expanding around the world. One system uses small rice size pellets of dry ice shooting them out of a jet nozzle with compressed air. It works somewhat like sandblasting or high-pressure water or steam blasting, with superior results. The frigid temperature of the dry ice -109.3°F or -78.5°C "blasting" against the material to be removed, causes it to shrink and loose adhesion from its sub surface. Additionally when some of of dry ice penetrates through the material to be removed, it comes in contact with the underlying surface. The warmer sub surface causes the dry ice to convert

back into carbon dioxide gas. The gas has 800 times greater volume and expands behind the material speeding up its removal. Paint, oil, grease, asphalt, tar, decals, soot, dirt, ink, resins, and adhesives are some of the materials removed by this procedure. Only the removed material must be disposed of, as the dry ice sublimes into the atmosphere.

Replaces Sandblasting:
This method is superior to sandblasting because the dry ice is soft enough not to pit or damage the underlying surface. The dry ice sublimes quickly into the air and only the removed material must be cleaned up. Dry Ice blasting eliminates equipment damage in two ways.

First, dry ice does not erode or wear away the targeted surface as traditional grit media and even wire brushes do. This means that surface integrity and critical tolerances are preserved and equipment will not have to be replaced due to surface erosion common with sand, glass beads, and other abrasive media.

Second, with traditional cleaning methods, equipment is often damaged (bumped, dropped, etc.) while in transit to or from the dedicated cleaning area. Instead most equipment and machinery can be cleaned while in place.

Uses For Dry Ice Blasting for Mould Remediation

Dry ice blasting accomplishes mould remediation faster and more completely than mechanical abrasion. Dry ice blasting does not require toxic chemicals and does not create a toxic dust hazard from remediation operations. Remediation operators have learned that one operator using dry ice blasting can accomplish the same mould removal as three operators using manual scraping and sanding. The range of available nozzles for dry ice blasting equipment enables operators to access tight corners quickly, and in many cases, clear mould from areas inaccessible to hand tools, such as inside corners of wood framing trusses and joists

Cry Ice Blasting          Cry Ice Blasting           Cry Ice Blasting

Dry ice blasting for mould remediation uses four physical properties of dry ice: velocity, abrasion, thermal shock, and evaporation. Dry ice is solid (frozen) carbon dioxide. For blasting uses, dry ice is manufactured in pellets of various sizes appropriate to the substrate to be cleaned. The pellets are hurled from a blasting gun by air pressure, which provides the velocity. When the pellets strike the surface to be cleaned, three things happen. First the velocity of the pellet strikes the substance to be removed. Because dry ice is at a temperature of -109 degrees F., the thermal shock helps loosen and lift the substance to be removed. Finally, the dry ice pellet flashes into carbon dioxide gas, providing more lift to the substance to be removed. The carbon dioxide gas is harmless, leaving no cleaning material such as sand or solvents to be cleaned up after the cleanup.



The flow of air from the crawl space is driven by the difference in building pressure between the first floor and the outside. Research shows that depending on the structure, well over 60 percent of the air we breathe inside the living space of our homes comes from the crawl space. It should be a concern to the homeowner that due to the high level of mould spores in the crawlspace, that areas outside have been contaminated. Once the crawlspace has been remediated that air quality tests should be made in the basement and first floors. An outside sample is taken to use it as a mean to base what the other samples will show. If the spore count is higher than outside, there should be further remediation.

Air Sampling Chart


How is your crawlspace growing mould while three seasons out of four, your home feels comfortable and dry? Sure, it may feel rather humid on the occaisional summer day, but most the time the house feels fineā€¦ So how does your crawlspace trap humidity? Even with your vapour barrier, moisture will condense and breed mould, termites, dust mites and more. Here's the answer. Air in your crawlspace is always more humid than the air in the house. And this is because cool ground temperature keeps the crawlspace colder than the air in your house. Because of this temperature difference, your home's living areas can feel dry, while below, crawlspace humidity runs rampid.

Here are a couple terms to know:

DewPoint=Temperature at which water vapour condenses
Relative Humidity (R.H.)=%of moisture present in relation to of moisture the air can hold.

In other words, relative humidity is the percent of water in the air. When R.H. hits 100%, water will condense, rain or snow. Dew Point is the temperature when this happens. Here are a few scenarios to show what happens in your home and crawlspace during typical weather conditions.

NOTE: Crawlspace R.H. (relative humidity) should try be 40% or less in order to keep Dew Point around 10-15 degrees below the crawlspace temperature. EPA recommends 40% - 50% R.H. This will control dust mite and mold populations. A crawlspace dehumidifier should always be used during humid or rainy weather. Humidity in the living area above, can be as high as 50% or 60%, based on comfort.

As the winter air enters, the humidity drops slightly within the crawlspace. Notice relative humidity is 62%, beyond what the EPAconsiders acceptable.As the air migrates upward, it warms greatly and relative humidity drops drastically. The house feels dry, but the crawlspace still requires dehumidification.To control dust mite populations, it is recommended that the crawlspace be kept at 40%R.H. all year long. Unfortunately, most dehumidifiers will not work at a 45° temperature.

Still winter time, but here we have a cold rainy day. It will still feel dry indoors, but notice as the outside air enters the crawlspace, relative humidity only drops to 70%. During this type of weather, your crawlspace dehumidifier should be running.

This is the type of weather where mould really thrives, especially if it were to rain. It's too cold to run the air conditioner, so high humidity goes unchecked. If it were raining, relative humidity outside would be 100%. This would raise the dew point to 55°.With the crawlspace at 58°, humidity would rise to a whopping 89%.All your cold water pipes and exterior walls would be dripping wet.

Here's a nice warm day with comfortable 50% humidity. But because it is so warm, dew point is also going to be warm. Any surfaces below 60° will form condensation. Look how high the relative humidity gets as the air cools to 65° in the crawlspace. At 83% relative humidity, your crawlspace is sure to grow a good amount of mould, as well as make a fine home for spiders, termites, cockroaches and other pests.

The mild summer night is the worse case scenario for allergies.As temperatures near the dew point, dust mites and mould will multiply and run rampid throughout your home. Notice how quickly food goes bad in this weather. Also, if you notice more bugs in your home, these are indications of high humidity.

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