Mold and mildew
- a problem in Danish buildings?

In recent years, there has been an increased focus on mold in the home. Despite several medical, biological and construction studies, the effects of mold on the indoor climate are still unclear. There is a lack of clear threshold values for when mold is unacceptable in the home. This ignores people who are actually hypersensitive to mold. It requires in-depth specialist medical knowledge to assess these conditions and as long as there is no consensus within the medical expertise, it is extremely difficult for "the rest of us" to assess the health aspects. Among the advisors, there is also disagreement about how the building should be examined, as well as which analysis methods are best to use when mold is present. It is understandable that consumers find it difficult to relate to fact or fiction.

This article describes the issues surrounding mold from a biological and construction angle. Please also refer to the latest BYG-ERFA Foundation experience sheet on mold.

What is mold?

Molds originate in nature and are found everywhere. Just like plants and animals, molds (along with other types of fungi) have their own biological group. Molds are primitive fungi that are unable to form fruiting bodies.


	Mold on contact prints		Molds originate from nature

Under favorable conditions, the mold spores will germinate and grow as hyphae (cell threads), forming a mycelium (tissue of the fungus' cell threads) that can typically be seen as black, whitish, brownish or blue-green colonies on building materials, food, etc. In the mycelium, millions of new spores are formed and spread by the wind. During the winter months, when nature is dormant, the concentration of mold spores in outdoor air is very low. During spring, nature awakens from hibernation and mold spores can again be detected in outdoor air. In late summer, the highest concentrations of mold spores are seen, with many thousands of spores/m3 of outdoor air.

Why does mold occur in buildings? - Growth conditions

The mold spores are brought into the home with the outside air and if the right conditions are present in the home, the spores will germinate and mold growth has started. A prerequisite for mold growth is the presence of moisture. Moisture can occur in many ways. Typically, dampness is caused by poor living habits, condensation due to thermal bridges, leaking water installations, leaky building envelope, flooding and fire-fighting water. Finally, combinations can of course occur. When the relative humidity in the home exceeds 75-85% for an extended period of time, mold growth will certainly occur. Temperature is also important. Most molds grow best at 15-28 degrees C. Some types can grow at low temperatures (5-10 degrees C) while others can grow at high temperatures (50 degrees C).


	Mold growth on floor joists after water damage		Black mold on roof window

Where does mold occur in the building?

Mold growth can occur anywhere in a building if the right conditions are present. Building materials consisting of organic materials such as plasterboard, wallpaper, wood, veneer, etc. are particularly vulnerable, but mold can also thrive on wet concrete and masonry. Mildew, which is caused by black-pigmented molds, is typically seen at lower temperatures on e.g. thermal bridges, window slits, cold water pipes, etc. Inadequate cleaning in the home can also provide a breeding ground for mold growth. House dust consists of organic materials that molds can feed on.

Is mold harmful to indoor air quality?

Mold consists of and contains components that under certain conditions can be a nuisance in the indoor environment. In addition, actively growing molds can release volatile organic compounds (VOCs) into indoor air and release fungal toxins (mycotoxins) into the material they grow on. Some mold species can release substances that give off a characteristic pungent and unpleasant moldy odor that is familiar from damp summer houses, basements, clothes hanging in damp conditions, etc.

If mold is present in the home for a longer period of time, it can cause indoor air quality issues such as mucosal irritations in the eyes, nose and throat. Symptoms such as fatigue, headaches and difficulty concentrating can in some cases also be attributed to mold growth in the home. However, these symptoms can also be caused by other conditions such as asthma, psychosocial conditions (poor working conditions, bullying, conflict, etc.)

It is unlikely that either mycotoxins or VOCs will be released in such high concentrations in a home that they could cause indoor climate problems. However, it is known that mold spores and fragments (particles) from mold can cause discomfort for people who are hypersensitive (allergic) to mold. Mold spores and hyphae contain both foreign proteins and carbohydrates (glucans) that can be allergenic to hypersensitive people. It will therefore be difficult or impossible for these people to live in homes with mold. If you want to know more about these conditions, you can download the Danish Health Authority's pamphlet on mold.

How should you proceed?

We should not accept mold growth in the home beyond what is normal. If a tenant suspects mold growth, landlords should always take the problem seriously. Start by investigating if there is a problem that requires action. Often it will be a minor problem that can be solved by simple cleaning. In other cases, it may be appropriate to seek advice from one of the consulting companies that have experience in inspecting a building for mold.

Consider the home as a place with both indoor and outdoor zones. Mold in an outdoor zone such as. an attic or crawl space means less than if mold is found in an indoor zone such as the living area of the home, where you spend many hours during the 24 hours of the day.

How do you check for mold?

An investigation for mold infestation in the building should always be destructive. This is the only way to adequately uncover hidden mold growth. Particularly in damp buildings, care must be taken in hidden structural elements where moisture has difficulty escaping and therefore provides a breeding ground for mold growth. After water damage, extra care should be taken to check cavities in partitions, floors, etc. If these areas are left to dry out, mold growth will often occur after just 1-2 weeks.

There are several analytical methods for detecting mold. None of the methods can be directly compared. It is therefore very important that the analyst knows both the strengths and weaknesses of the chosen method. The following are brief examples of methods for detecting mold in the home. There are significant price differences between the analysis methods mentioned.


	Mold on an exterior wall Thermal bridge		ProClean test Purple color indicates mold

Contact print - is a small plastic dish with a culture medium (usually tomato juice gel, called V8) that can be imprinted on a surface, transferring mold growth, spores etc. to the culture medium and then brought back to the lab for cultivation for about 7 days. The resulting mold colonies can then be counted and named

The following criteria are used to describe the extent of mold growth:

Poor growth < 10 colonies
10 < moderate growth < 50
Massive growth > 50 colonies

Air analysis - are samples collected directly from the air using special collection equipment (slit samplers) or on agar plates with culture medium. The air analysis can give the investigator a picture of the extent to which indoor air is contaminated with molds and if so, whether these originate from the home or are introduced from the outdoor air (nature).

Material samples including tape prints - is an analysis method where you take e.g. wallpaper samples or tape prints are taken from the surface and then under a microscope you can see what and how much mold growth is present on the examined surface.

The following methods are all so-called rapid methods, performed by swabbing the surface with a cotton swab and subsequent chemical analysis:

Mycometer - Analyzes for an enzyme that is characteristic of mold. Operates with 3 categories, A: 25 and 450.

ATP - analyzes for the chemical adenosine triphosphate, which is found in all living cells. ATP numbers below 100-200 (not definitively determined) will usually be acceptable.

ProClean - is a protein test that requires no instrument, but gives a clear violet color reaction if proteins are present.

Remediation after mold infestation

It is important that the cause of the mold growth is found and removed. If necessary, a proper drying process must be initiated. It is often wise to hire a professional drying company that has both the experience and the right equipment for the task at hand. When starting a mold remediation project, it is important to set aside the necessary time to both plan the process and inform everyone involved. The renovation can then be carried out in peace and quiet, with due consideration for quality control and safety in the execution.

Choice of method

Before starting a mold remediation project, a decision must be made whether the mold-affected materials should be discarded or whether they can be cleaned and reused. This will usually be based on an economic assessment.

Basically, the mold growth must be removed, not just killed or dried out. The dead mold spores and mold particles will contain foreign proteins and carbohydrates that will be allergenic to sensitive individuals.

Remediation methods

When repairing mold infestations, both mechanical and chemical methods can be used and are often performed in combination. The method chosen will always depend on the specific damage, building conditions, building materials, etc. Mechanical methods include techniques such as grinding, planing, milling, steam cleaning (dry steam), high-pressure cleaning with hot water, ice removal, etc. For larger jobs, it is advisable to test the chosen method on a small area to avoid costly re-treatments.


	Ice cleaning of roof rafters		ProtoxBiox Treatment of Mold on concrete floors

Disinfection neutralizes and removes mold growth. For disinfection use ProtoxHysan and/or ProtoxBiox. Neither of the 2 mentioned agents leave chemical residues that can subsequently have any negative impact on the indoor climate.

In some cases, it may be necessary after disinfection to take preventive measures to prevent mold growth from reoccurring. This will typically be on a thermal bridge, damp foundations, wood veneer underlayment, etc. In these cases, the product is used Protox mold containing fungicide. A degassing study carried out by Eurofins Miljø A/S shows that no degassing can be detected from the product.

How to use ProtoxHysan, ProtoxBiox and Protox mold?

Please refer to the technical data sheet and product descriptions for each product:

ProtoxHysan – Product description, application and indoor climate report.
ProtoxBiox – Product description, application and BST report.
Protox mold – Product description, application and indoor climate report.

How to prevent mold?

Check the house/residence for penetrating moisture and make sure to repair all moisture damage - check gutters, drains, wells, windows, doors, roofing, bulkheads, etc.
Do not dry clothes in your home - even in the bathroom, hang damp towels outside on the clothesline after bathing.
Use the hood when cooking, check that the extraction is working properly.
Ventilate frequently but briefly to avoid cooling of surfaces.
Turn up the heat.
If there is dew on the double glazing, it is a sign of excessive humidity in the indoor air. Get a hygrometer and check that the humidity never exceeds 60% relative humidity.

Mold and mildew

Mold and mildew- a problem in Danish buildings?