Encapsulation VS Removal of Asbestos containing Fiber Cement
Asbestos cement slabs are a widely used system to protect roofs from water, and there are several opinions from entities that say that, as a general rule, encapsulation of asbestos cement is preferable to its removal.
Taking this into consideration, Prudêncio thought of developing and applying an extremely efficient waterproofing and thermal insulation system, that would completely confine and protect asbestos cement from the causes that lead to its degradation: the encapsulation system, composed of a lightweight metallic reinforcement, PIR thermal insulation sheets and Köster TPO waterproofing membrane.
Continue reading the article to find out all the steps involved in this process and why we consider encapsulation to be the alternative to removing asbestos cement.
Background on fiber cement roofing
Regarding asbestos-cement roofing, corrugated sheets of this material, used on a large scale in building roofing, present several obstacles, such as the following:
- Asbestos-cement used in construction until December 2004 most likely includes asbestos in its composition, in a proportion ranging from 10 to 20%;
- Corrugated sheets have major weaknesses in terms of watertightness and lack of thermal insulation, which impairs the thermal efficiency of buildings and their energy rating;
- A wave of sensationalism and fear has been generated around this material, with no technical or scientific basis, which intends to remove, as a matter of urgency, all the fiber cement existing on the roofs of buildings.
Although there are asbestos fibers in fiber cement, they are strongly bound by cement (a non-friable material), and the probability of them being released from this material is almost zero. This means that fiber cement can be considered a very low risk material.
In fact, in most cases, removal represents a greater risk of fiber release by subjecting fiber cement boards to handling and direct aggression. Normally, encapsulation of asbestos cement is preferred over removal.
With this in mind, Prudêncio develops and applies a system that confines and protects asbestos cement from the causes that lead to its degradation – physical aggressions, sunrays and thermal amplitudes, rain and humidity – thus responding to all the weaknesses and risks posed by asbestos cement roofing.
Motivation for the project and objectives
Prudêncio developed this solution based on three main reasons.
1. The first reason concerns the reduction or even cancellation of the strong environmental impacts associated with asbestos-cement board removal and the high costs that such removal would represent.
In 2008, there were about six billion m² of this type of roofing in Portugal. In other words, removing this fiber cement to be deposited in landfills means a very high environmental risk of land and groundwater contamination, with costs and resource requirements that are impossible to bear.
2. The second reason is to eliminate health hazards.
This is because removal poses a greater risk of releasing a large number of particles.
3. The third reason refers to the presentation of an efficient solution, without the watertightness weaknesses of the “sandwich panel” type systems, traditionally used to replace fiber cement boards when these are removed.
At the same time, this solution should be comfortable and safe to apply, as it does not imply stopping the normal activities of the buildings, particularly industrial and commercial buildings, or the risk of flooding during application.
State of the art
Prudêncio found that the existing options for solving the asbestos-cement problem are very poor. These are summarized in two technically weak solutions, which carry environmental and health risks: the removal of asbestos cement to be replaced by sandwich panel systems or a supposed “encapsulation”, which, in fact, is nothing more than a simple cosmetic operation, by painting the asbestos cement boards with specific paints.
The option of removing the fiber cement, in addition to the health risks inherent to it, also brings the weaknesses of the sheet systems usually applied. We are referring to discontinuity in the gutters and other finishes that cause water ingress on windy days with high rainfall rates or in cases of clogging. We can see fragile and inefficient finishes on the various roof elements, such as walls, peaks, chimneys, skylights and stairwells, using metal ruffs with gaps in the joints or sealed with silicones and with apparent fixings. In addition, corrosion often appears earlier than expected, both in the roofing sheets and in the trim, cuts and fastenings.
Regarding the option of painting treatment, this should not be called “encapsulation”, since it does not protect the fiber cement from physical or mechanical aggressions and does not guarantee waterproofing. This is because, when the waterproofing material is applied directly over the fiber cement boards, the waterproofing becomes subject to the tensions of the support, rapidly presenting ruptures and detachments, especially in the overlapping joints of the fiber cement boards, where the effects of contractions and dilations are most felt. This problem becomes even greater because the direct placement of waterproofing materials over fiber-cement sheets does not provide for the application of thermal insulation, making them vulnerable to thermal amplitudes and the consequent effects of dilatations and contractions.
As serious or even more serious than what was mentioned above is the fact that the use of paints on fiber cement boards implies their prior washing or scraping, for proper adherence of the paints, which entails the risk of release of fibers harmful to the environment and to the workers who apply them.
Technical and scientific uncertainties
The system we thought of using for asbestos-cement encapsulation is similar to the one that has been used for many years in so-called “deck systems”, which is based on a simple metal plate, to which the coating solution consisting of thermal insulation boards and a waterproofing system is directly attached. This coating system was adapted to the solution of encapsulating fiber-cement roofing, but kept the general philosophy, which has proven itself for dozens of years.
The great challenge was to develop a system and application techniques that would strengthen the covering, ensure the safety of workers and cancel the risk of fiber release. This would avoid the risk of fiber cement board breakage during application of the encapsulation system, and ensure that the new system would be fixed without any kind of manipulation or perforation of the fiber cement boards. These last features are particularly important to give strength to our choice of encapsulation as an alternative to removal.
Another determining challenge was to devise a risk assessment that would demonstrate whether or not the asbestos cement in each specific job has asbestos in its composition, determine its condition, and clearly show that the exposure limit value for asbestos fibers (if the asbestos fiber result is confirmed) will not be exceeded in the work area during application of the encapsulation system.
The solution and working methods developed
Prudêncio’s solution is based on three important pillars:
1. Risk evaluation.
In order to implement an effective consensus risk assessment, it was first necessary to review all the legal and regulatory documents as well as the guide on good practice to prevent or minimise risks from asbestos in work that involves (or may involve) asbestos. This guide is intended for employers, workers and labor inspectors, and was prepared by the Senior Labour Inspectors Committee (SLIC – European Commission).
After analysing the documents, Prudêncio met with the competent entities to obtain their opinion and agreement on the methodology to be established and the assessments to be performed. We highlight the ACT of São João da Madeira, which was indicated to us as the most competent and experienced in matters related with asbestos, where we obtained essential information for our decision.
To conduct the evaluations related to the possible presence of asbestos in materials and in the air, we chose to use the services of INSA – Instituto Nacional de Saúde Dr. Ricardo Jorge, so that, given the sensitivity of the subject “asbestos”, there would be no doubts about the impartiality and technical rigor of the evaluations.
2. Development and dimensioning of the lightweight metal structure for fixing and reinforcing the roof.
As mentioned earlier, this solution allows the system to be fixed without manipulating the asbestos cement boards, reinforces the roofing and ensures safety for workers – from falling from heights and exposure to asbestos fibers – during the application of the system.
3. Application of Köster’s encapsulation system, consisting of PIR insulating boards and TPO waterproofing membrane.
This system, besides providing unique thermal and waterproofing efficiency, also ensures total mechanical protection to fiber cement boards, namely by the high compressive and mechanical strength that insulation boards and waterproofing membranes provide to the roofs.
Besides, it promotes sustainability and ecology, a philosophy intrinsic to Köster’s TPO membranes.
Results and conclusion
It is with great satisfaction that we feel that the goals that motivated us to invest in this solution have been achieved: the concerns about preserving the environment and public health, and the intention of presenting the market with a unique system in terms of energy efficiency, watertightness and asbestos cement protection and confinement.
We focus essentially on the exterior coating, because it is the one subject to the aggressions that lead to asbestos cement degradation. Normally, the interior of the slabs is in good condition, which can be verified by air analysis, through INSA, and which we propose to perform whenever there are doubts. When necessary, we present solutions for interior coating with paint suitable for fiber cement, which provides renewed and brighter environments, or we propose the realization of false ceilings.
We know that this is the ideal solution for a great number of situations, although we only recommend it after performing a risk analysis and understanding the function and typology of the buildings that contain asbestos cement roofing. However, there are cases in which, after weighing all the factors, we advise the removal of asbestos cement.
Our goal is to provide decision makers with all the existing information, enabling them to make the right choice regarding the renovation of this type of roofing.
We are proud of this asbestos cement roofing rehabilitation solution, to which we dedicate the motto “We transform a potentially dangerous roof into a sustainable system“, because we believe that we give our modest contribution for a healthier planet and for a better quality of life of its inhabitants.