As part of the acoustic design reviews we carry out we always look for value engineering opportunities. We can often save our clients a significant amount of money by ensuring that materials are only specified where required.
Please see below 10 common value engineering opportunities in the design of new residential developments:
1) Acoustic resilient layers in addition to EPS insulation in concrete floors:
|Where floors are constructed from precast or in situ concrete slabs, an EPS thermal layer under a floating screed will normally provide the required impact sound insulation. A dedicated acoustic resilient layer is therefore not normally required.
2) Extra acoustic insulation in walls or floors:
|As a general rule, it is not worth adding more than 25mm of mineral wool into a wall or floor cavity that is smaller than 100mm and more than 50mm of mineral wool in a cavity that is more than 100mm. The additional benefit of thicker insulation is marginal and therefore generally not cost affective.
3) Acoustic insulation in internal walls:
|Insulation is not necessary within internal walls within dwellings provided that you have room to use a 70mm stud. The following wall construction is compliant with Building Regulations Part E requirements and is often much easier/quicker/cheaper to install onsite that a thinner wall containing acoustic insulation:
4) Reverberation control in common areas:
|Building Regulations Part E requires that reverberation control is provided in communal areas (corridors etc). However, reverberation control is only strictly required in communal areas that provide <strongdirect access to dwellings. Communal areas that do not contain apartment front doors do not need to be treated. This generally means that reverberation control is not required in entrance lobbies or stairwells.</strong
5) Attenuators in MVHR systems:
|Attenuators are often over-specified in MVHR or MEV systems. As a general rule it is not necessary to include attenuators in ducting between MEV/MVHR units and external supply inlets and discharge outlets. If attenuators are required between the MEV/MVHR units and habitable rooms it may be more cost effective to upgrade the MEV/MVHR units to quieter models (see below) rather than use the attenuators. Some attenuators also only offer poor sound attenuation and therefore are not cost effective.
6) Acoustic resilient layers in hotels or student accommodation:
|Carpet can be used to control impact sound within hotels or student accommodation because the building operators will have control of floor finishes. Therefore, a dedicated acoustic resilient layer may not be required.
7) ‘Acoustic’ products:
|We sometimes come across ‘acoustic’ products that claim to have special ‘acoustic’ properties. Often the benefit of these materials is marginal at best. Sometimes the claims are simply wrong. If in doubt contact Cass Allen for an impartial view.
So what do you do with all those cost savings? Well, there are some areas where we generally recommend spending that little bit extra. The following items are normally recommended to improve the development and may save money in the long-term by preventing noise-related complaints from future occupants:
8) Independent wall liners to lift shafts, stairwells and bin stores:
|Lifts tend to be well isolated these days however complaints regarding structure-borne lift noise do sometimes occur. We therefore generally recommend installing independent wall liners to any walls separating habitable rooms from lift shafts. Independent wall liners minimise the likelihood of complaints and subsequent expensive investigations and remedial works. We also recommend independent wall liners to bin stores and stairwells where regular impacts on the separating walls may also occur.
9) Over-sized MVHR units:
|Noise levels generated by MVHR units can vary considerably when moving the same quantity of air. A smaller MVHR unit will have to spin faster and work harder than a larger unit and this leads to more turbulence and higher levels of noise. A doubling of fan speed results in a ~16 dBA increase in noise. It is therefore often worth spending a bit of extra money on larger MVHR units that can comfortably achieve required airflow rates. This is particularly cost effective if it means that attenuators or acoustic duct lagging are not required or if it prevent future complaints from residents.
10) Anti-vibration mounts for pipework in plant rooms:
|Pipework in plant rooms is often hung directly from the slab above. Structure-borne noise from the pipework can be audible in the rooms above and consequently provoke complaints from affected residents. Where residents are located above plant rooms, we recommend installing the pipework on anti-vibration mounts/hangers to minimise the likelihood of complaints and/or subsequent expensive investigations and remedial works.
We hope you find the above examples useful. Please get in touch if you would like to discuss any of the above examples or if you would like us to review any of your projects in more detail.