Acoustic Insulation

The design consists of large areas of exposed insitu concrete walls, both on the interior and exterior faces of the building. To counteract this, acoustic insulation will be provided in the form of the formwork cladding system which has been designed. Through acoustics calculations, formwork will be permanently left in place to provide acoustic insulation. These bespoke panels will consist of an extra layer of acoustic boarding which has been specified and installed during the off-site manufacturing process.

We will look at the worst case scenario: the gym area, where the walls and ceiling are cast in-situ. The floor is finished in conrete screed.

We expect a very poor reverberation time calculation for this space due to the concrete core structure.

We will be using Sabine’s equation (above) to determine the Reverberation time for the gym space. The volume of this space is calculated to be 2120m 3

Area (m2) Absorption Co-efficient (at 500 Hz) Material 335 6.7 Concrete Poured (0.02) 335 6.7 Concrete Poured (0.02) 530 10.6 Concrete Poured (0.02) 100 18 Ordinary Glazing (0.18) 42

The information above calculates effective/average absorption rate at 500Hz frequency, to be a total of 42. V=2120m3 0.161 x V 0.161 x 2120 = 341.32 T = 341.32/42 T = 8.12s Area (m2) Absorption Co-efficient (at 500 Hz) Material Floor 235 4.7 Concrete Poured (0.02) Ceiling 235 4.7 Concrete Poured (0.02) Wall 280 5.6 Concrete Poured (0.02) Glazing 100 18 Ordinary Glazing (0.18) Acoustic Insulation 450 405 Ordinary Glazing (0.9) Total Absorption 420

An acceptable reverberation time is around 0.8s. This result informs us that having a bare concrete interior would result in a very poor acoustic space with a reverberation time which is x10 times worst than the accepted parameters.

Cross Section - Acoustic Insulation of permanent formwork cladding

Acoustic Insulation - Absorption coefficient of 0.9. Image provided by VINCO

In order to acheive an acceptable acoustic space, we will recalculate the absorption co-efficient with the addition of acoustic insulation. This insulation comes in the form of wood cladding. The cladding has a co-efficient of 0.9. Area (m2) Absorption Co-efficient (at 500 Hz) Material Floor 335 6.7 Concrete Poured (0.02) Ceiling 335 6.7 Concrete Poured (0.02) Wall 530 10.6 Concrete Poured (0.02) Glazing 100 18 Ordinary Glazing (0.18) Total Absorption 42

Floor Ceiling Wall Glazing Acoustic Insulation Total Absorption

Area (m2) Absorption Co-efficient (at 500 Hz) Material 235 4.7 Concrete Poured (0.02) 235 4.7 Concrete Poured (0.02) 280 5.6 Concrete Poured (0.02) 100 18 Ordinary Glazing (0.18) 450 405 Ordinary Glazing (0.9) 420

The calculation above shows the addition of the acoustic insulation which would cover 1/3 of the floor and ceiling spaces as well as 1/2 of the interior walls.

V=2120m3

0.161 x V 0.161 x 2120 = 341.32 T = 341.32/420 T = 0.8s

An acceptable acoustic performance level is acheived by the introduction of this cladding. In terms of Architectural design intent, the play on pattern between formwork and exposed concrete can be designed within these acoustic parameters.

Formwork panels specified to act as Acoustic insulation must cover 50% of the wall area in order to acheive an internal reverberation time of 0.8s

Vibration Control:

Another issue is the vibration caused by the gym area which is on the first floor. The ground floor level contains retail units, therefore actions must be taken to restrict the acoustic vibration through the concrete floors.

We will be adding an extra layer of insulation on top of the structural concrete floor to restrict this vibration. TVS RESi Foam is a low cost, under screed acoustic insulation which is Part E Compliant. The material is a cross-linked, closed cell polyolefin foam which reduces the transmission of impact sound through in-situ concrete floors. The foam is 8mm thick and is a rigid material.