Page 97 - Build 161

Quiz
1. Which of the following statements is true? a. All noise control work must have a
building consent.
b. The performance requirements for
sound insulation are set out in clause
G6 of the Building Code.
c. All building work must have a building
consent and comply with the Building Code.
2. For sound insulation, which are typically weak elements in an external wall assembly? a. A window or door opening.
b. A hot-point/light switch/power socket. c. A re collar.
d. All of the above.
3. Can you interchange building products
speci ed as part of a wall assembly system? a. Yes, there are no real issues.
b. Sometimes, but it depends if it is an
Table 1
external or internal wall. It is not recom- mended, but the product must meet the Building Code to the same extent as the substituted product in all respects.
c. No, changing any part of a building system is not generally permitted by manufacturers and may void any appli- cable warranties.
Table 1: Wall assembly construction to reduce sound transmission
WALL ASSEMBLY SOUND TRANSMISSION TO WHAT TO CONSIDER CONSIDER
Bridging inter-tenancy walls
Airborne noise
Internal sound insulation
Sound transmission by bridging occurs when a solid object connects two objects that otherwise would not have touched, for example, in double stud or staggered stud wall constructions. This often occurs for inter- tenancy walls at the façade or at junction details, reducing the sound insulation of the inter-tenancy wall. Solution: Prevent bridging by removing the bridging element or using a vibration isolation layer like rubber or a exible sealant around the bridging element. The exact solution depends on the project.
Windows and openings
Airborne noise
External sound insulation
Windows and openings are weak points for sound insulation. Generally, windows with thicker glazing and bigger air gaps between panes have better sound insulation.
Solution: Double glazing is slightly better than single glazing for sound insulation. However, it is not always better for low-frequency noise such as planes and some tra c. If low-frequency noise sources are expected, get advice from an expert.
Studs at 400 mm centres
Airborne noise
External sound insulation
Studs at 400 mm centres make linings too rigid at certain frequencies, reducing sound insulation performance. Solution: If sound insulation performance is a priority, avoid installing or detailing studs at 400 mm centres as there is no cost-e ective solution to insulate the sound in this situation.
Lack of ' u '
Airborne noise
Internal and external sound insulation
Flu helps to absorb noise. Flu is typically wool, breglass or polyester insulation installed in wall or roof cavities or between oors. A meaningful increase in the sound insulation of a building element typically needs a minimum density of u of 9.8 kg/m3. Generally, R1.8 thermal insulation will do the job.
Solution: There is little bene t from greater-density u , although increasing the R-value will improve thermal performance. Adding internal linings to walls, ceiling or both is more e ective.
Cladding systems with polystyrene and sandwich panels have limited sound insulation performance. The best solution is to add mass to the construction.
Sarking
Airborne noise
External sound insulation
Sarking improves sound insulation.
Solution: If you value sound insulation and your building has sarking in the walls, roof or ceilings, try to keep it. However, be wary of potential bridging.
Gaps
Airborne noise
External and internal sound insulation
If a torch can be shone through a gap, noise will travel through it. Solution: When sound insulation is a priority, try to avoid gaps.
Glues and sealants
Impact and airborne noise
External and internal sound insulation
Glues and sealants for sound-insulating elements often need to remain exible throughout their life to prevent noise transmission.
Solution: Stick with what has been speci ed and check if you have concerns. Changing glues or sealants to a non- exible option or one that hardens over time can signi cantly reduce overall sound insulation performance.
Penetrations
Airborne noise
Internal and external sound insulation
Penetrations are made by items such as re collars, fans and socket outlets and can bridge inter-tenancy constructions or provide holes in the wall assembly.
Solution: Stagger socket outlets on either side of studs to prevent a weak point in sound insulation. Avoid having a socket on both sides of the wall in one cavity space, for example.
For better overall sound insulation performance, install re collars and fans above ceilings that already have improved sound insulation. Fan ducting can also be sound insulating.
Build 161 — August/September 2017 — 95
Answers
1.b 2.a 3.c