Mold in tiny houses

Tiny houses often get moldy quickly. This is no coincidence, this post discusses the reasons and health consequences.

Why are tiny houses particularly prone to mold?

Humidity

In tiny houses, a similar amount of humidity often accumulates in a very small space as it does in much larger buildings. When used as a residential building, cooking, showering, breathing or even washing clothes may require several liters of air humidity to be removed every day. Window ventilation is generally not enough; “breathable walls” are usually more of a marketing term. The solution lies in a suitable ventilation concept (demand-controlled ventilation in the kitchen and bathroom, as well as continuous ventilation (controlled residential ventilation)).

Contrary to common belief, many mold fungi do not require liquid water to grow; a relative humidity above 75-80% is sufficient.

Type of construction

The minimum requirements in building regulations, especially in the areas of insulation and ventilation systems, are often not met. Solutions proven effective in conventional houses can only be partially applied to tiny houses. Construction is particularly complex in the case of mobile lightweight construction (weight restriction) with thin wall structures (maximum width according to German road traffic regulations 2.55 m). It is noticeable here that the tiny house sector in Germany is still quite young and there is no construction standard. Many tiny house wall structures are unsuitable in terms of building physics.

The risk of mold in the wall can be reduced by appropriate wall structures and, if necessary, the correct installation of a vapour barrier; a structurally tight & maintenance-free outer shell is helpful. To reduce the risk of mold in the interior, the insulation should be sufficient, thermal bridges should be reduced as far as possible, a ventilation system should be installed and the water installation and heating should be (frost) safe. Common mistakes include unnoticed cracking joints in the bathroom during transport, uninsulated wheel arches in low loaders, and ice-cold corners due to cramped and non-ventilated built-in furniture.

The post on winter-proof tiny houses and the mold prevention checklist may be helpful.

Health consequences

The German Federal Environment Agency writes in its 2017 guidelines on the prevention, detection and remediation of mold in buildings:

“Population-based studies have sufficiently shown that people exposed to indoor dampness/mould are at increased risk of multiple respiratory diseases. Particularly in the case of children who grow up in living spaces with visible mold infestation/moisture, the study results indicate an overall adverse health development of the affected children.”

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Even invisible mold is problematic.

“It should be noted that prolonged or periodically occurring dampness indoors, even without visible mold growth , is associated with an increased risk of respiratory illness, respiratory infection or the aggravation of an existing asthma condition.”

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In addition, there are of course considerable financial risks.

Credit: The cover picture is from Toshiyuki IMAI on Flickr.