Renere teknologi til undgåelse af biologisk vækst på murværk, tegl- og betontage
Summary and conclusions
The background for the project is a desire to find environmentally friendly methods for preventing and combating biological growth on masonry, clay tiled and concrete roofs. A number of the pesticides and disinfectants that are frequently used to remove growth on masonry, clay tiled and concrete roofs cannot be used in accordance with current legislation.
Therefore it is important to find alternative methods to prevent and combat biological growth in order to comply with the legislation in practice. As the situation is today there are no alternatives to chemical prevention agents and disinfectants, consumers turn a blind eye to the legislation.
The purpose of this part 1 of the project is to
 | analyse the methods used in practice to prevent and combat biological growth |
| analyse in which circumstance the agents/methods are used |
| analyse the quantities of the pesticides being used |
In the project, the term "biological growth" is used as a generic term covering
| bacteria |
| algae |
| fungi |
| lichens |
| mosses |
Higher plants such as facade plantings are not covered by the project.
The project only includes organisms occurring in Denmark on the materials below:
| masonry materials including bricks calcium silicate bricks granite/gneiss masonry mortar rendering mortar white-washed masonry surfaces painted masonry surfaces |
| clay tiles |
| concrete tiles |
Conclusions
Investigation of methods used in practice to combat biological growth
The investigation has indicated that there is a wide range of different chemical agents for cleaning biological growth on masonry, clay-tiled and concrete roofs.
The chemical agents can be divided into the following main groups:
| agents containing quaternary ammonium compounds |
| agents containing hypochloride |
| agents containing organic fatty acids and soaps (salts of organic fatty acids) |
| agents containing inorganic or organic acids |
| agents containing inorganic alkaline compounds |
| various other agents |
The investigation has confirmed that a wide range of the most commonly used agents cannot be used in accordance with current legislation. The few agents that can be used legally have not been fully tested by the trade.
Regarding mechanical methods, the following methods appear to be used:
| blast cleaning, wet |
| blast cleaning, low pressure |
| high-pressure cleaning, 250-700 bar |
| high-pressure sluicing |
| high-pressure sluicing with warm water/hot-water cleaning/steam cleaning |
| raking out joints, brushing with steel brush etc. |
The most frequently used mechanical methods are hot-water cleaning and low-pressure blast cleaning. Mechanical methods are often used in combination with one of the chemical agents.
Investigation of circumstances in which the agents/methods are used
With a few exceptions, all chemical agents are generally used on all material and construction types covered by the project. The chemical agents are used by private homeowners, by housing associations as well as by professionals. Professionals often use a combination of chemical agents and mechanical methods.
On the other hand, mechanical methods are primarily used by professional cleaning firms, however smaller high-pressure cleaners are also used by private persons. Different types of high-pressure methods have been seen in use on all material and construction types covered by this project. Blast methods have only been seen in use on masonry constructions and not on roofs. The investigation indicates that biological growth is primarily cleaned for aesthetic reasons, although damage is expected to occur if the growth remains. Next cleaning is often carried out as part of preliminary treatment before applying another surface treatment (white-wash, paint, graffiti protection, etc).
Quantities used to combat biological growth
It has been difficult to analyse the quantities of chemical agents. To a great extent the manufacturers were reluctant to contribute information about quantities. Most manufacturers are familiar with the fact that the products must not be marketed as pesticides against biological growth, and they do not like stating sales figures for products which in practice are often used illegally.
Even when the manufacturers have stated quantities, it has been difficult to Determine the fraction of the quantities sold used to combat biological growth on masonry, clay-tiled and concrete roofs.
As the project continues, efforts to analyse the quantities will carry on. Among other things the project will examine whether the relevant information can be found by searching the product register of The Danish Environmental Protection Agency. It is considered essential to know the quantities of chemical agents being used to remove biological growth on masonry, clay-tiled and concrete roofs in order to estimate the extent of the problem in relation to the use of equivalent chemical agents for other functions. This estimate is essential to The Danish Environmental Protection Agency in order to be able to give priority to achievement areas.
Investigation of agents used in practice and methods for prevention of biological growth
Preventive agents and methods are only generally used by professionals. Agents for prevention can by divided into the following main categories:
| preservative agents |
| sealing agents |
| paints |
Use of preservative agents is particularly widespread. A differentiation is made between the following types of preservative agents:
| monosilan type |
| oligomersilan type |
| siloxan type |
| silicone resin type (polymere) |
Professional cleaning firms typically recommend treating vertical masonry after cleaning biological growth. It seems treatment of roofs is about to become more common.
Sealing masonry and roofs has only been used to a limited extent in practice. Some of the listed products are relatively new on the market and experience with them is limited.
Paint is not used to prevent biological growth in practice.
Prevention of biological growth however is necessary in connection with painting because the paint layer can be damaged by biological growth. These conditions have been examined further in the project phase "Examination of occurrences". Many paints therefore contain compounds to prevent biological growth.
The types of paint being marketed as having an effect against biological growth
| contain a biocide and/or |
| contain compounds that affect the moisture conditions of the structure, often in the shape of the same compounds as in preservative agents. |
Value of the initial investigation phase in relation to the further progress of the project
The initial investigation has
| created a survey of existing experience concerning agents and methods to combat and prevent biological growth. This survey is an essential precondition for producing a proposal for action plans for cleaner technologies that are the ultimate objective of the project. |
| confirmed the need to document when growth can cause damage. This will be covered by the later phases of the project. |
| revealed an uncertainty among the users of whether mechanical methods in some cases are sufficient without also applying chemical agents. This uncertainty results in most professional firms combining mechanical methods with chemical pesticides. This confirms the need to develop a method for testing agents and methods for combating and preventing biological growth. The later phases of the project will cover development and testing of such methods. |
Many of the agents used today outside the environmental legislation, are characterized by being rather easy to use and they do not require much equipment. The agents are marketed as giving an immediate, though not always sustained effect against the growth. In order that possible future suggestions for cleaner technology solutions become generally accepted in practice, these criteria must be fulfilled if possible.