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Our extensive industry experience means that we hold a lot of valuable knowledge and we would like to share this knowledge with you.

Here you will find blog posts from the SIDERISE team including articles written by our technical experts. Find out more about our products and what’s going on in the industry for acoustic, fire and thermal insulation.

Chris Mort, Technical Officer at Siderise, believes that despite being a life safety issue the juncture between the supporting structure and external façade is quite often wrongly specified, or completely misunderstood.

Chris Mort, Technical Officer at Siderise, believes that despite being a life safety issue the juncture between the supporting structure and external façade is quite often wrongly specified, or completely misunderstood. This has become even more of an issue with CE Marking in place.

The ‘Construction Products Regulation’ (CPR) came into force on the 1st July which in effect makes it mandatory for construction products to be CE Marked prior to sale on the market, however this only applies to products with a ‘Harmonised Product Standard’ (hEN).

Curtain Walling external facades are covered by hEN13830 and therefore the final product being sold or installed must be CE Marked. Direct responsibility for this rests with the manufacturer or fabricator, with supporting Initial Type Testing (ITT) carried out by system suppliers.

Whilst there is ITT data available for all extruded aluminium elements, glazing, fixings etc., there is one critical element of ‘Life Safety’ that tends to be overlooked when estimating and designing a project. This element is the linear gap seal juncture between the compartment floor and the curtain wall where a suitable ‘Passive Fire Protection Product’ (PFPP) is required.

Lack of hEN’s

With PFPP constructions being ‘Life Safety materials’, albeit they come in a variety of forms, one would have reasonably expected these products to be amongst the first to be CE Marked. However, the reality is that there is currently no hEN that covers them. Consequently there is no formal route for CE Marking. A further reality is that the publication of any relevant hEN is also a number of years away due to the complexity of products and testing requirements.

Alternative Route to CE

PFPP companies can obtain a voluntary CE Mark by using the European Technical Approval (ETA) route and following a European Technical Approval Guidance (ETAG). For the linear gap seal at edge of the slab for Curtain Walling there is ETAG 026 Part 3. This document gives a prescriptive route to the correct test standard for this type of linear gap seal. Curtain Walling is covered by EN1364 Part 3 & 4. Part 3 is for full Curtain Wall screens typically 4.2m x 4.2m and is normally a test for ‘Fire Rated’ systems, whilst part 4 is a test of the ‘Linear Gap Seal’ and Curtain Walling which would occur at floor slab locations. Part 4 tests ‘Fire Rated’ and ‘NON Fire Rated’ systems.

Curtain Walling Designer / Fabricator

How does this affect you, with the majority of Curtain Wall systems being ‘NON Fire Rated’?

The hEN13830 for Curtain Walling section 4.10 ‘Fire Propagation’ calls for fire resistance to accord to EN13501-2 the ‘Fire Classification of Construction Products and Building’. The fire test standards for various construction products, and PFPP products that are installed into other elements of construction, fall within this classification. For Curtain Walling section 7.5.3 Classification of Curtain Walling states “Curtain Walls shall be tested in accordance with EN1364-3. Parts of Curtain Wall shall be tested in accordance with EN 1364-4” which is replicated in ETAG026-3.

Section 6 of the Curtain Wall hEN13830 however, allows for ‘No Performance Determined’ and only considers fire propagation from inside to outside, outside to inside and in both directions. It does not call for the inside to inside requirement, which is where the linear gap seal is required for life safety, as detailed in ETAG026-3.

Although it is apparent that there is no mandatory requirement for the Curtain Wall in conjunction with the Linear Gap Seal to be CE Marked, it is correct test procedure for all Curtain Wall Linear Gap Seals to be tested to EN1364 Part 4. This supersedes the BS476 requirement, which is now accepted as a minimum within the UK only.

Fire and Façade Consultants in the UK are starting to require compliance with the EN1364-4 test. This is a sign of change within the market that has been influenced by the CE Mark requirements for Curtain Walling.

The ETAG026-3 is part of the current work in Europe to produce a hEN for Passive Fire Protection Products. It is expected that this will be published within the next 2 years at which point the CE Marking of such products will be mandatory.

Siderise Position

Chris has been part of a research and development team at Siderise that has considered all of these requirements and has successfully tested a ‘NON Fire Rated’ Aluminium Curtain Wall to EN1364-4 with 210 minutes insulation and integrity on the full system, using the Siderise CW-FS180 linear gap seal and Siderise CW-FB protection system for the Curtain Wall. The team is currently engaged in further testing to EN1364-3.

Chris said that Siderise are interested in forming partnerships with façade companies that want to test their ‘NON Fire Rated’ and ‘Fire Rated’ systems. Contact facades@siderise.com for further information.

Laquisha
17 January 2015

What a joy to find such clear thinking. Thanks for posting!

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Graham Laws, Business Development Officer - "Acoustics is widely recognised as a complex and demanding subject. For Motoryacht engine rooms in particular, understanding the relevant acoustic issues can be extremely challenging".

Acoustics is widely recognised as a complex and demanding subject. For Marine craft engine rooms in particular, understanding the relevant acoustic issues can be extremely challenging.

An important objective for the boat builder is to achieve a condition where engine noise is controlled to the point where it does not become obtrusive within the recreation or accommodation areas of the boat. The ideal target is inaudibility.

The problem is that, as engines become more powerful, the noise they create increases. This results in ever increasing levels of noise pollution for the occupants and for anyone else in the near vicinity.

The drive for increased speed and power means the boat designer is always looking to reduce weight in the boat. Unfortunately, losing weight from the shell and dividing structures reduces the ability of these elements to stop noise. The surface mass of these structures is of primary importance in containing noise within the engine room and away from sensitive areas.

It is a simple fact that a marine engine is always going to create a high level of noise. The boat builder can do little to about this. However, measures can be taken to significantly reduce the level of noise escaping from the engine room. Of course an important issue for the builder is - what level of cost is associated with these corrective actions? In order to answer this question a basic understanding of the important principles and acoustic treatments is necessary - then a value engineering exercise can be undertaken.

Vibration Isolation

Firstly ensure correctly specified anti-vibration mountings are employed for the engine, generator/s and other vibrating equipment. Where possible, flexible connectors and isolated drive couplings should be incorporated.

Sound Insulation

Ensure that the enclosing structures forming the engine room / housing are free of gaps or apertures. The importance of these potential 'leakage' paths cannot be over emphasised. A single small hole can dramatically reduce the acoustic effectiveness of a bulkhead. A large aperture can almost entirely eliminate its sound reducing capability. If through air movement is required, then employ the minimum number of apertures for the purpose and design them in such away as to allow an air passage whilst attenuating noise. The techniques for doing this include: forcing the air through 2 or more bends; passing the air down a long thin duct lined with sound absorbing foam (or better containing foam splitters); or the use of proprietary products such as silencers or acoustic louvres. 

Once sound leakage has been addressed, it follows that noise break-out from the engine room must now arise from sound transmission through the enclosing structures (bulkheads, decks, etc.). To obtain further improvements it is necessary to apply treatments to these elements to improve their Sound Reduction Index (ability to reduce sound transmission). For lightweight structures this would normally consist of adding further mass in the form of a flexible 'spaced layer barrier' material. The term 'spaced' means that the heavy layer component is held away from the original substrate by means of an integral resilient isolation layer. The resultant twin wall system gives an improved performance over direct application of the barrier to the background surface. The thickness of the isolation layer is important. The greater the thickness the more substantial is the improvement.

A further advantage of some flexible limp high-mass barriers is that they substantially lessen the effect of 'Coincidence Dip'. This is a phenomenon associated with rigid sheet materials whereby at a certain frequency range there is a pronounced dip in their Sound Reduction Index (sound can pass through more easily at these frequencies).

Sound Absorption

Significant improvements in sound break-out from an engine room can be obtained by lining the internal surfaces of the room with a sound absorbent material. This has the effect of reducing the Sound Pressure Level within the engine room. In consequence sound levels outside will drop by a corresponding degree. The reduction in the internal SPL arises as a result of suppressing the 'reflected sound field' (noise that has bounced off one or more internal surfaces of the room).

The level of improvement obtained by absorption treatments is dependent on two factors. Firstly, what proportion of the internal surface area of the room is to be treated (the greater the proportion the better the results). Secondly, the ability of the material to absorb sound, referred to as the material's 'Sound Absorption Coefficient'.

The Sound Absorption Coefficient is effected not only by the nature of the material but also by its thickness. Thicker absorbent materials generally have improved performance, particularly in the low-frequency range.

Significant care should be exercised in selecting the right sound absorption material.

Sound absorbent materials invariably have an open cellular structure. Consequently, they tend to be relatively susceptible to damage, cannot easily be cleaned and can absorb liquids such as fuel or oil. These shortcomings are normally overcome by using a material with an applied facing. Unfortunately, the wrong selection of facing can substantially reduce the materials Sound Absorption Coefficient in the frequency range of interest.

Additionally, there is an increasing requirement for the material to have a high level of fire resistance. Also, light reflection characteristics, aesthetic qualities and ease of installation should also be carefully evaluated.

Damping / anti-drumming

Structures formed from rigid materials can be excited by vibration or airborne sound into acting as sound radiating surfaces. The direct application of specially formulated thin anti-drumming materials can substantially reduce these additional noise sources. Also, many of the flexible acoustic barriers and composite materials offer useful dampening properties.

The Composite Solution

One extremely practical and cost effective solution to the applied treatments previously described is a multi-function composite material. These products are specially formulated to provide the three important acoustic characteristics, plus the necessary practical properties from a single lining material.

A typical composite specification would comprise: a fire resistant foam base isolation layer, a limp heavy layer barrier, a fire resistant foam sound absorption layer and a wipeable oil and fuel resistant facing.

There are a number of different protective/decorative facings now available. Most of these will to some extent impair the Sound Absorption Coefficient of the sound absorbent foam (particularly in the higher frequencies). However, some specially developed facings can actually enhance sound absorption (particularly in the more problematic low and mid-frequency ranges associated with marine engines).

With so many factors to consider it is hardly surprising that many boat builders fail to adhere to the following checklist for optimised noise control:

  1. Employ effective engine anti-vibration mountings & associated isolation measures.
  2. Fully enclose the engine room if possible. Seal all possible sound leakage points. Incorporate sound attenuated air movement apertures.
  3. Improve the sound reduction performance of lightweight engine room structures using flexible spaced barriers. Use the thickest practical isolation layer thickness.
  4. Apply sound absorption linings to as many of the engine room surfaces as possible. Select a material employing an applied facing enhancing sound absorption in the frequency range of the greatest interest.

A Systematic Approach

There are two key questions first to be asked:

  • How much of a noise problem do I have?
  • Do I need to meet a specified noise level or do I just want the boat to be as quiet as possible to improve its commercial appeal?

The answers to these questions whilst not substantially influencing the approach will obviously alter the level and cost of the acoustic treatment finally undertaken.

The normal step by step assessment process can be divided into two main areas:

Basic Design Concepts

All too often many acoustic problems arise simply through inadequacies at the initial design stage. A comprehensive list of all potential areas to assess is not practical here but the following specific tips may prove of assistance.

As previously highlighted specify adequate anti-vibration measures for the engine, generator, etc. Remember that any connecting rigid pipes should ideally incorporate flexible connectors as these also represent potential routes for vibration transfer.

Consider air movement points into the engine room at any early stage. Provide sufficient room to provide sound attenuating measures such as extended lined ducts or silencers.

Review carefully the design of the dividing structures forming the engine room. Frequently these comprise a single sheet material attached to stiffeners. Consider the possibility of converting these to partition type elements i.e. twin sheet materials with an intervening airspace. Use a sound absorbing infill material in the void (there are now some very low weight materials for this purpose). Remember a partition construction will always outperform a single sheet solution of the same total mass.

Consider door / hatch positioning, their construction and incorporate an effective gasket / sealing system.

Allow sufficient room to permit the application of sound absorbent or composite linings to the internal surfaces of the engine room.

Remedial / material solutions

Assuming that all possible enhancements associated with initial design have been investigated, further improvements would now arise from the use of specialist acoustic materials. This is equally the case for instances where changes to the basic design are not possible (such as a refurbishment project).

Engine rooms / housings can be broadly categorised into the following types. The material approach for each would generally be different.

1. Those having a high sound leakage potential i.e. the enclosing structure has open apertures that cannot practically be sealed or closed.

2. No leakage potential i.e. a fully sealed enclosure (would normally therefore include sound attenuated air vents). 

The above groups can be further sub-divided into 2 types:

  •  Those without a neighbouring 'sound sensitive area'.
  •  Those with a dividing structure immediately adjoining a 'sound sensitive area'. The typical material approach associated with the above 4 possibilities is as follows:

1/A. Generally, sound absorption treatments only are employed. This is because noise break-out is predominantly arising from 'leakage' from apertures. There is in consequence little to be gained from the use of barrier or barrier composite products. However, if there is any suspicion that any of the enclosing elements may be 'drumming or panting' (normally this would occur with lightweight rigid materials), then utilising materials with dampening properties would be prudent. These might be either a multi-function absorption / barrier composite or an absorption / dampening layer composite.

 1/B. As 1/A except that the particular enclosing element/s directly adjoining the sensitive area (bulkhead, deck, etc.) should be treated with a multi-function absorption / barrier composite.

2/A. The use of multi-function absorption / barrier composites will generally show significant improvements in this type of enclosure. Their use may be either general or cost restricted to enclosing elements of weaker acoustic performance (normally the lightest constructions).

2/B. As 2/A except that the particular dividing element directly adjoining the sensitive area should be treated with a multi-function absorption / barrier composite having a high SRI improvement potential.

Material Selection

The process of selecting the optimum material/s may be simplified by the use of material profile charts. These profiles provide a quick means of visually assessing and comparing materials with reference to a range of specific characteristics. We provide materials profile charts against the following set of performance variables:

Sound Absorption: At Low, mid and high frequencies

SRI improvement: Ability of the material to improve the SRI (Sound Reduction Index) of lightweight sheet substrates such as thin metal, plywood or GRP. The exact increase will change dependent on the particular substrate. The value is based on the average improvement for 0.7mm steel and 12mm plywood.

Dampening: As for SRI improvement, dampening performance is greatly effected by the substrate material. The result is consequently an assessed guide value for a typical range of common marine substrate materials.

Fire Resistance.

Ease of Installation: An assessed value based on the requirement to use a separate adhesive and / or mechanical fixings. Self-adhesive backed products will record a high value.

 Please see our Motoryacht Noise Control Solutions

SIDERISE has the technical ability and experience to find the optimum noise control solution whatever your project requirements.

Aggy
17 January 2015

Finding this post. It's just a big piece of luck for me.

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