the service life of any given element may vary significantly from building to building, since each building is a prototype that responds to unrepeatable conditions.

Degradation agents (whether physical, chemical or mechanical) and the natural ageing process. design and construction errors, or the application of inadequate materials.

The functional service life is directly related with the
expectations and demands of the users.

Economic service life can be defined as the time elapsing since the construction is placed into use until the instant that it is replaced by a more profitable solution.

Three main drawbacks

1. complexity of the mathematical expressions
2. large amount of data required necessary to validate the model, which should preferably be collected over a long period of time.
3. the great dependence of the fieldwork.

Most literature focus one type of material only—usually reinforced concrete—subjected only to a degradation agent (usually chloride attack)

MEDIC method : evaluating the residual service life of the buildings

Advantages:

1. Easy to understand and apply;
2. can be easily implemented, and maintain their operability even when all the variables related to the modelled phenomena are unknown.
   
   

Disadvantages:

1. Unable to capture the random nature of the degradation phenomena.
2. Does not provide any information regarding the degradation process or related to the probability of transition from one degradation condition to another

The European project Energy Performance Indoor Environment Quality Retrofit (EPIQR)

Performance Limits method: to evaluate the durability of
building components by simulating their performance over time.

Factorial method