There is an ever-growing demand within the construction industry for building materials that are both sustainable and cost-effective. Propelled by legislation forging the UK’s path to net-zero emissions by 2050, and the very real threat of irreversible climate change, the industry is being forced to closely consider the materials they use.
Further, ESG factors (environmental, social and governance) in business now matter greatly and there is increasing pressure on companies to become more responsible and transparent about their environmental impact.
Concrete has ruled the roost as the most popular building material in the UK for several years. However, legislative changes, coupled with an increasing amount of education surrounding the construction industry’s impact on the environment means that traditional timber-framed construction is gaining popularity once again.
There is still significant uncertainty over what level of sustainable bio-energy could be available to the UK when we reach 2050, and part of the answer to this will be influenced by the level of timber construction at the time.
CURRENT BARRIERS
According to the UK Housing: Fit for the future? report by the Climate Change Committee, there are several barriers surrounding timber construction. These include a lack of skills in the use of timber materials in construction, and the sheer amount of forward-planning that is needed to create a robust supply chain to facilitate the needs of the UK’s timber construction industry. Additionally, wood burns, and we also know fire is a devastating force. Its effects have been seen far too often for the impact of fire to be ignored. Fire safety is one reason why, in the past, timber has not been considered a realistic alternative to concrete or steel.
However, proper engineering design, correct material choice and effective installation, coupled with a robust inspection regime, ensure that timber constructions can be as fire-safe as concrete and steel options. Furthermore, while it is a combustible material, timber can provide the necessary two-hour window required for fire protection due to its slow rate of charring.
Safety can be further enhanced if you use timber that has been treated with a specialist fire retardant, which will provide the material with an invisible shield to help protect against fire.
Flame retardant products are made from materials that are chemically treated to be slow-burning or self-extinguishing when exposed to an open flame.
These products can be made from any material, but these materials must be treated with special formulations/additives to qualify as a flame retardant and delay the effects of being exposed to open flame.
There are five categories of flame retardants. Our technology group here at Zeroignition has thoroughly investigated each one to see how well it performs both in terms of fire safety and ecologically.
1. Halogenated flame retardants: Commonly used in the electronics, construction products, textiles and coatings industries. Here, bromines are used because when heated the bromine atoms essentially quench the chemical reactions occurring within the flame. This quenching can prevent the burning process from initiating, or slow it such that other measures can be taken to extinguish the fire.
One major issue with this type of flame retardant is they are becoming increasingly restricted for addition to materials because of safety concerns.
Conventional halogenated flame retardants are suspected of being harmful to health and the environment. Non-harmful replacements are therefore called for in most countries and other countries ban these types of fire retardants.
This is the one category that industry should completely move away from, as the release of chemicals in a fire can be very toxic and detrimental to the health of individuals.
2. Inorganic flame retardants: Found in paints, adhesives, wires and cables, and fabric coatings. A variety of inorganic compounds are used, but the most common are hydrated aluminium and magnesium oxide, and they are often combined with the other fire retardant classes. Inorganic fire retardants slow down the process of decomposition and release of flammable gases.
Because these inorganic flame retardants need to be combined with other types of flame retardants, such as halogenated fire retardants, they can cause environmental and health issues.
3. Nitrogen flame retardants: Melamine based products are the most commonly used type of nitrogen flame retardants. When melamine is in the condensed phase the molecular structures transform into cross-linked structures. This transformation promotes the formation of char, which blocks the oxygen supply to feed the flame.
The main common advantages of nitrogen flame retardants are their low toxicity; their solid-state; and, in case of fire, the absence of dioxin and halogen acids as well as their low evolution of smoke.
Since high quantities of these types of flame retardants are added to give the required fire retardant performance, these additional levels change many of the characteristics of the material protected and thus are not the optimum flame retardant for many applications.
4. Intumescent coatings: When exposed to the heat from a fire, these coatings expand significantly to create a fire-resistant and insulating layer on the material surface. That layer protects the material from high temperatures, which can prevent or slow structural damage by deformation from the heat.
The effectiveness of intumescent flame retardants is due to the foamed char formed on the surface of the material that is exposed to a fire. The char acts as a physical barrier against heat transfer to the surface of the combustible material. Char formation lowers the rate of temperature increase of the surface beneath the char.
These types of flame retardants are developed for specific applications that provide fire retardancy but offer no room temperature thermal protection or insulating properties. Again, these types of flame retardants have specific applications where they may be desirable but they are not universally applicable.
5. Phosphorus flame retardants: Science proves this is the most environmentally friendly category and forms the basis of Zeroignition’s product portfolio of fire retardant additives. Phosphorus flame retardants both chemically bond to materials and are also physically incorporated as an additive. A char is formed when the phosphorous compound is heated, thereby inhibiting the formation of combustible gas and inhibiting the pyrolysis process (the process of chemically decomposing organic materials at elevated temperatures in the absence of oxygen).
What is particularly interesting about the formation of char is it hinders the release of combustible gasses while also forming a thermally protective layer that shields the protected material from the heat of the flame.
These flame retardants are considered environmentally friendly and are great at promoting a char formation when exposed to a flame source. They also generate far less smoke compared to all other fire retardant categories. Innovation of products using this retardant is coming, and it’s only a matter of time before they reach the open market.
INNOVATION IS IMMINENT
As we edge ever closer to that 2050 netzero target, manufacturers and specifiers are likely to favour companies who can help them become more environmentally friendly. Solid wood, capable of being properly fire protected, would be more widely used as a result.
To achieve this, the industry is crying out for an effective non-toxic fire retardant that stops the wood from burning and therefore reduces damage to the environment. With this in place, the use of natural building materials, such as wood would be promoted and encouraged.
The hard work has begun, people are listening and they’re looking for ways to adapt and change their building techniques. This is encouraging. Now the innovation must cut through, and this is where we, at Zeroignition find ourselves at the forefront.
