Functional Availability of Climate and Ventilation Systems

Functional availability is used to quantify the probability of a system’s capability both to be in an
operational state and, at the same time, maintain the intended levels of the functions. The purpose of the work described in this paper is to determine if functional availability can be used for the evaluation of performance procurement contracts.
This study involved making measurements in an office building over eight consecutive periods during July and August. This monitoring showed that the HVAC-system did not perform as well as it should and that, in each case, the system functional availability was found to be below 0.7 (sometimes much less). This meant that the performance criteria studied were attained for less than 70% of the monitoring time. Although there was no contract regarding the level of functional availability, it is evident that the situation was not acceptable.
In this building, only the operational staff handled the malfunctions and they were unable to secure desirable conditions. Using the functional availability as an active tool, during the whole building process, helps all of those involved to focus on functions. This, in turn, should increase co-operation to reach these aims.
This study showed that the use of functional availability could form a basis for determining how well
functions are maintained. However, there is still much work needed before it can be used for performance procurement contracts.