Rain Noise …. Solutions for metal roof constructions!
Rain Noise? To some a relaxing diversion! However … Impact noise from rain on lightweight flat roof constructions can significantly increase indoor noise levels!
Rain Noise Building Regulations Approved Document E, 2004 Amendment requires construction of new school buildings to follow guidance provided by Building Bulletin 93. This includes a requirement to minimise rain noise on lightweight roofs.
Rain Noise Building Regulations BB 93 advises designers to consider the effect of impact noise from rain at an early stage of the roof design in order to minimise disturbance within the building. Whilst no limit is set, methods of control must be included and justified to building control.
BB 93 Section 3, Part 3.1 This highlights the need for: Sound absorption Acoustic damping The use of additional mass and / or an independent acoustic ceiling Laboratory measured data for comparison of roof constructions Rain Noise
New test standard A new test standard for impact sound from rain on the roof Draft ISO 140-18 is under development. The BRE were commissioned by Rockwool Limited and Euro-Clad to carry out sound intensity measurements of rain noise on specific roof constructions.
Rain Noise Testing Two types of rain are defined by Draft ISO 140-18 Intense rain – return rate of one in 2 years Heavy rain – return rate of one in 50 years The intention is that Heavy rain will be the preferred type of artificial rainfall for the comparison of products in Europe. Moderate rain defined by BS 7527-2.2 –Typical UK rainfall Used for testing
Rain Noise Testing How are the measurements made? A tank positioned above the test roof is filled with water and consistently recharged The flow rate is calibrated to ensure correct rainfall intensity
Rain Noise Testing How are the measurements made? All test constructions were assembled in accordance with manufacturers recommendations.
Rain Noise Testing How are the measurements made? Sound intensity measurements were taken below each roof construction by the BRE in the frequency range of 50 Hz to 5000 Hz
Rain Noise Testing …some definitions What is sound intensity? The sound power flowing per unit area, in a given direction, measured in W/m² Lower sound intensity levels represent improved acoustic performance.
Rain Noise Testing …some definitions Reverberant Sound Pressure level, L Aeq Sound in an enclosed space which results from repeated reflections at the boundaries. Lower reverberant sound pressure levels represent improved acoustic performance.
Profiled metal roofing Rockwool Cladding Roll Composite metal roof construction PIR insulation Standing Seam Constructions With perforated liner, Cladding Roll, RW3 With non perforated liner, Cladding Roll, RW3 Combined with Rockwool Acoustic Membrane Rain Noise Testing The constructions tested
Profiled Cladding Euro-Clad liner 19mm, 0.4mm Eurobar rail and bracket spacer system Rockwool Cladding Roll 180mm Euro-Clad outer 32mm, 0.7mm Test 1 Profiled metal roofing
Profiled steel outer, 35 mm deep, 0.5mm thick PIR Insulation foam, 80mm thickness Profiled steel liner, 20mm deep, 0.4mm thick Metal Roof Test 2 PIR Composite metal roofing
Summary of the results 50 dB 76 dB65 dB Profiled metal cladding Sound intensity level, L IA Reverberant sound pressure levels, L Aeq Classroom Reverberant sound pressure levels, L Aeq Gymnasium PIR composite panel 65 dB77 dB 62 dB A – weighted acoustic measurements
Test 3 Perforated liner Standing Seam Euro-Clad liner, 33mm, 0.7mm Top hat section Rockwool RW3 Slab, 30mm Vapour Control Layer Eurobar bracket & spacer system Rockwool Cladding Roll, 160mm Aluminium Halter Euroseam 400, 0.9mm
Test 4 Non perforated liner Standing Seam Euro-Clad liner, 33mm, 0.7mm Top hat section Rockwool RW3 Slab, 30mm Eurobar bracket & spacer system Rockwool Cladding Roll, 160mm Aluminium Halter Euroseam 400, 0.9mm
Summary of the results n/a 62 dB58 dB Sound intensity level, L IA Reverberant sound pressure levels, L Aeq Classroom Reverberant sound pressure levels, L Aeq Gymnasium Standing Seam 58 dB62 dB n/a A – weighted acoustic measurements Liner not perforated Liner perforated Not possible to measure at all frequency bands
Summary of the results n/a 76 dB58 dB Standing Seam roofing No RAM Sound intensity level, L IA Reverberant sound pressure levels, L Aeq Classroom Reverberant sound pressure levels, L Aeq Gymnasium PIR composite Panel 58 dB77 dB 55 dB 62 dB A – weighted acoustic measurements 2 layer RAM 3 layer RAM 44 dB 43 dB n/a Not possible to measure at all frequency bands
Overall Summary of results 11 dB Improvement compared with PIR composite Sound intensity level, L IA reverberant sound pressure levels, L Aeq Classroom Standing seam No RAM Standing seam 2 layer RAM 18 dB reverberant sound pressure levels, L Aeq Gymnasium 12 dB 19 dB A – weighted acoustic values Profiled metal cladding 21 dB32 dB 22 dB34 dB n/a Standing seam 2 layer RAM
What does this represent ? 10dB reduction in acoustic terms is very significant. It will approximately halve the loudness….. A further 10dB reduction will halve the loudness again, and so on ……
Play -10 dB Stop -20 dB -30 dB -3 dB -6 dB -9 dB P lay – represents PIR composite cladding Reduce by ……… 10dB – profiled metal cladding 20dB – Standing seam + 2 layer RAM 5 30dB – Standing seam + 3 layer RAM 5 Acoustic demonstration
Summary of testing The use of Rockwool within metal roof constructions significantly improves acoustic performance with respect to impact noise from rain …but is this not a well known fact ? You have seen and heard for yourself! …
How does Rockwool offer this improvement? acoustic absorption When used within metal lightweight roof constructions the fibrous structure of Rockwool insulation provides very effective sound absorption.
How does Rockwool offer this improvement ? acoustic isolation When in direct contact with metal cladding, Rockwool insulation offers acoustic damping. Rockwool Acoustic Membrane in direct contact with metal cladding provides enhanced acoustic damping which will significantly enhance acoustic performance..
How does Rockwool offer this improvement? Mass Rockwool Acoustic Membrane 5 offers an effective mass layer. Two layers of this product are equivalent in mass to a sheet of acoustic plasterboard. The addition of a mass layer to a lightweight roof construction will improve acoustic performance.