paper igloo architecture and design

Making the layers work harder....

September 28, 2013

More on the topic of making the layers in the construction work harder....

As we are aiming for the Gold Standard in the Section 7 Sustainability of the Technical Standards we have to meet a higher acoustic performance rating for airborne sound transmission in our internal partition walls and the intermediate floor construction.

For a while, this was the only real issue that was making the achievement of this Standard problematic for our house, which is incredible really!

We need to achieve a design performance level for a minimum airborne sound insulation of 45 dB Rw, compared to the standard value of 43 dB Rw. (The levels are 'Rw' which means that they are a single number quantity (weighted) which characterises the airborne sound insulation of a building element from measurements undertaken in a laboratory, in accordance with BS EN ISO 717-1: 1997. This is required because there is too much flanking transmission on site from door openings for sound testing for airborne noise to be meaningful....)

Even thought the difference is only a 2 dB improvement, due to the decibel scale being logarithmic in intensity we have had some issues meeting the higher targets that we didn't anticipate. All of the manufacturer's that we spoke to who produce test certificates for products such as British Gypsum and Rockwool only release test data for the level of performance required by Section 5 Noise and nothing better.

So, when we were researching to find a wall board that could give us an improved acoustic performance, we came across Fermacell. Also a Category 1 strength racking board we can now substitute our previous typical stud partition build up of 9mm OSB plus a 15mm gypsum based wallboard for a single layer of Fermcell. Over the whole area of both sides of all of the internal walls in the house this will save us a considerable amount of labour. I have yet to do the absolute financial comparison of the two options, but a quick check indicates that it should be a saving overall.

The best part of all is that Fermacell is a board made from by-products of other industries and recycled materials. It is made from gypsum (a waste product from a nearby power station - a separate debate entirely but given that the gysum and the power station are there already, etc.!), cellulose fibres from recycled newspapers and magazines, and recycled water (all by-products created in the manufacturing process are fed back into the production process itself). The board is also recyclable and is intended to last the lifetime of the building. Definitely better environmental credentials than a combination of standard gypsum wallboard and OSB which was the alternative option....

To go over the final detail of this we are meeting the Fermcell rep who covers our area in Scotland on Friday the 4th so we will have more to report on this then!