Category Archives: Sound Proofing

Acoustic and Fire Design

Fire and Acoustic Isolation

Having recently come across a best practice guide for Electrical installations and their effect on the fire performance of buildings I have decided to change  the approach to the fire/acoustic isolation between rooms. I will now install Rockwool flexi 50mm in the 100mm partition walls and Rockwool flexi 100mm in the 140mm partition walls .

Electrics before insulation
Partition before Insulation with Wiring
Rockwool
Partition wall with Rockwool installed

From an acoustic perspective I was advised that it is better to install the Rockwool in the centre of the partitions rather than touching one or other side of the plasterboard as this limits the sound transfer.

The Electrical Safety Council best practice guide deals with Electrical installations and their impact on the fire performance of Domestic premises at this link when one is building a home. A summary is as follows but the full document is worth reading for any self builder.

  • Fire containment in the event of a fire
  • The need to prevent fire from passing through holes in all elements whether solid or lightweight is addressed.
  • Electrical Equipment is identified that has a direct and significant influence on the fire performance of an element.
  • Partial Penetrations –those that reduce the fire performance of part of the wall/ceiling or floor.
    Full Penetrations-such as ducts and fans that go through both elements of a wall/ceiling/floor.

 

Internal Partitions and Soundproofing

Partitions

The internal partitions were recently installed.

Passsive House
Passive House Build

Solutions now need to be planned to minimise noise between some of the rooms. The effort one puts into this needs to be balanced with the fact that there will be a 10mm gap under the doors for the air to circulate when using heat recovery.  I might install a supply and extract outlet in the important rooms in order to minimise noise. How much noise will travel in these ducts is for another day.

Proposed Method

All the air gaps (wall to floor gaps, sockets, switches and service cavity) around the partitions need to be filled.

I will fill the ceiling and wall gaps of the service cavity with rockwool (see below).Perimiter Insulation

The method to reduce the noise I am considering for the walls is a product that uses a dampening material between two sheets of plasterboard. One of these products is Green glue and the other is Quietglue pro.  The solution appears to perform very well and I feel it is the simplest method. I plan to take  extra measures between the study and living room such as including rigid insulation (Rockwool RWA45 but I note the insulation costs €37 in Ireland and £13 in England (more research required) .

The performance values used to measure the sound proofing in America is called STC (Sound Transmission Class) and is measured in decibels (dB) against 16 different frequencies. If the sound level was 80dB in one room and the measured sound level in the other room had a  STC of 37dB the sound reduction would have a figure of STC 43.

STC only calculates the dB levels down to a frequency of 125 Hz. One needs to be aware that low frequency sound can exist from drums , traffic and an additional solution may be required.

The performance test data of the Green Glue can be found here

If one was to use one layer of green glue with an extra sheet of plasterboard one would achieve a STC value of 43 for a 4 inch wooden stud wall with 24 inch centres.

If one was to use 4 inch block this would achieve a STC of 44.

Filling a standard 4 inch wooden stud wall (with 16 inch stud spacings) with fibreglass and using plasterboard on each side achieves a STC of around 39. If one increased the stud spacing to 24 inches and filled it with insulation then the STC value would be 46.

If one was to leave out the insulation on a standard wooden stud wall one would achieve a STC value of 34.

A good source of information on sound proofing is at USG (Gypsum)

Robust Airtightness

In locations where the partitions meet the airtight membrane I am using Solitex Plus (see below -blue material). If one used only the airtight membrane it can easily be damaged.

Passive house
Solitex Plus