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Frequently Asked Questions
PAGE8
Q. What about the acoustic performance of the raised access floor?
A. There are situations where the acoustic performance of the raised access
floor is of importance with regard to its ability to dampen the transmission
of airborne sound between adjoining rooms. The use of partitioning and stud
wall systems mounted off the raised access floor, thus creating a clear void
under partition walls does make the acoustic performance of the raised floor
of significant concern in sound sensitive installations.
Product attributes
In these instances there are certain attributes of the raised access floor that
become important. The construction of the floor panel with regard to the component
materials is an issue with regard to the
overall acoustic performance, as is the edge profile of the panel. The passage
of sound between adjacent panels is dependant on the level of gap between the
panels. This is dependant upon the manufactured quality of the panels and also
on the quality of the raised floor installation.
Performance Considerations
An indicative performance of the acoustic properties of a raised access floor
system can be derived from laboratory testing. In these tests an area of raised
floor is installed within a acoustic room and a standard partition wall is constructed
off the raised floor. As the acoustic performance of the room and wall are known
the only variable i.e. the raised floor, can be evaluated. The transmission
of airborne sound from room to room through the raised floor is measured at
a range of frequencies. These measurements allow the Floor Normalised Level
Difference to be determined across the test frequency range. This range of test
data is brought back to a single figure known as the Weighted Floor Normalisation
Level Difference that can be taken as the measurement of the amount by which
the raised floor will reduce airborne noise between adjacent rooms. Generally
these tests will be conducted on the raised floor alone, then with the addition
of a barrier under the partition line, and then with the addition of carpet
tiles on the raised floor.
Site Considerations
When required on site testing can be undertaken to determine the airborne sound
transmission between adjacent rooms. However in these situations the raised
floor is being measured in conjunction with the installed partitioning and the
installed suspended ceiling system. Whilst each individual system e.g. raised
floor, partition, ceiling may have its own test report on its acoustic performance
it is difficult to determine the performance of their combined installation.
Consequently in critical installations laboratory testing of a sample installation
i.e. raised floor, partition, ceiling etc should be considered.
Q. What is the fire resistance of a raised access floor system?
A. BS EN 12825 calls for compliance with provisional standard EN 13501-1 and
2 where required and discussions are still underway as to what level of compliance
is required for raised flooring. In order to meet the requirements of the PSA
MOB PF2 PS/SPU specification the raised access floor system has to comply with
the following:
- Class 0 fire rating which is obtained by achieving a Class 1 surface spread
of flame and appropriate fire propagation indices. These are determined by BS
476 Part 7 and Part 6.
- Pass the requirements of the small scale fire test as outlined in the PSA
specification. This test is undertaken on a complete raised floor system with
the floor subject to the system’s uniformly distributed
load for the duration of the fire test. The floor must not show excessive deflection
for the duration of the fire test.
- Provide information relating to the thermal insulation performance of the
raised floor. This is achieved by repeating the small scale fire test with measurements
taken of the temperature the raised floor surface reaches.
These tests provide information relating to the level of fire resistance and
reaction to fire of a raised floor system and have proved sufficient for a long
period of time and continue to be used until the requirements of EN 13501-1
and 2 are fully determined.
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