Sustainable school buildings - how to reduce the risks

Sustainability is a key driver in the design, construction, and choice of power and heating services for new independent school buildings. Many new buildings are designed to have a life span of 60 years. Is that a sustainable solution when there are buildings built from traditional materials e.g. brick, stone, slate and tile, still in everyday use that are over 100 years old, and many 200 years old?

 

As insurers, we recognise the need to improve energy efficiency and reduce the carbon footprint of building stock, and we have witnessed numerous innovative construction techniques and the emergence of green energy systems over the last couple of decades. The development of these new methods of construction and energy systems has brought new challenges in respect of fire risk, resilience to the effects of water and safety. In this article, you will find some common issues that have arisen, their associated risks and the steps you can take to reduce the risk to your school buildings.

The selection of structural timber framing for new buildings, be it a light timber frame, glued laminated timber (Glulam) or cross-laminated timber (CLT) has seen significant growth in the education sector. Its popularity has risen due to it being a naturally sustainable material and for its carbon capture properties on the basis a living tree absorbs carbon, when it is harvested for construction the carbon is trapped within the timber for its lifetime reducing carbon emission.

 

The construction industry maintains that structural timber frames are as safe as conventional masonry buildings, however, a number of large fires have raised concerns regarding the speed and spread of fire when the frame is ignited, particularly if used in conjunction with foam-based insulation materials. Fires have tracked inside a building's wall cavity making it difficult for Fire and Rescue Services to trace and tackle the fire.

 

In respect of cross-laminated timber and glued laminated timber framing, it is often said they do not burn, that they only char on the outside, similar to a solid oak beam for instance. However, there is a difference, a solid oak beam is just that, whereas laminated timber is layers of timber bonded together. Research by Edinburgh University¹ highlighted that the integrity of the bonding agent holding the laminated timber together in a fire is a key aspect of the reliability of the fire performance.

 

From an insurer’s perspective, we have concerns about the fire performance of a timber structure. Where you have selected a timber framed building, protecting the frame from the effects of fire is essential. The selection of non-combustible materials to clad, line and insulate the building at the design stage can improve fire resilience. Where the building is already built, take simple measures to protect the frame such as regularly inspecting the cladding and lining surfaces for damage and service penetrations where the frame could be exposed. Where there is damage, it should be fixed promptly by either repair or sealing using fire-stopping, intumescent material with the same level of fire resistance as the cladding or lining.

 

 

Another common risk with timber framing is the susceptibility to the effects of water both through an accidental escape of water and when fire-fighting water is applied to a building. When exposed to water timber can swell and may not dry back to the designed installation parameter resulting in the structural timber needing replacement.

 

Escape of water losses are increasing due to a combination of factors, such as poor installation, use of compression joints, ageing and pipework that is hard to access, and demands for more washing and toilet facilities, particularly in boarding accommodation.

 

Not much can be done when the building is on fire and fire-fighting water is applied, however, you can take measures to mitigate against the effects of accidental escape of water. Having plans of your buildings and the location of stopcocks, and training staff on where they are and how to isolate water can significantly reduce loss. We once saw a substantial escape of water loss in a school, exacerbated by staff taking an hour to find the stopcock and isolate the supply. You can find printable stopcock labels in the documents section at the bottom of this page.

 

Water leak detection devices can also greatly reduce the amount of damage caused by escaping water. Some devices use linear detection whilst others monitor flow rates in pipework and can link to isolation valves, alarms and building management systems.

To achieve thermal integrity and energy efficiency, today’s modern school buildings are heavily insulated. There is a broad choice of insulation materials ranging from natural materials such as hemp, wool and straw to foam based products such as polystyrene, polyurethane, polyisocyanurate and phenolic foams, through to materials made from spun molten rock such as mineral wool or recycled glass such as cellular glass.

 

Selection of the insulation material has typically been focused on thermal performance and cost with foam based materials being the most popular. The fire performance and toxicity of the material when exposed to fire, are often overlooked.

 

Natural materials such as hemp, wool and straw and foam based insulation products are all classified as combustible materials and used in conjunction with timber framing, or combustible cladding systems can have serious consequences for a building's ability to withstand the effects of fire. Studies such as Fire Toxicity by Anna Stec & Richard Hull Lancashire UCLAN, have also highlighted that foam based insulation materials can give off high levels of hydrogen cyanide and carbon monoxide when involved in fire.

 

Research² by the Fire Protection Association has revealed legitimate paths for gas flow between building systems and occupied spaces that could have lethal consequences.

The selection of building materials and in particular insulation materials therefore needs careful consideration and should not just be based on cost.

 

From an insurer’s perspective, non-combustible materials such as mineral wool or cellular glass are preferable. Where combustible insulation is already present, similar measures to those described in mitigating fire risks to timber framing can be adopted.

 

 

These are just some of the challenges a sustainable building can present. We encourage involving your insurer at the planning stage for any new school building or sustainability project. That way, you can work together to mitigate risks at the planning stage to achieve a modern sustainable building.

 

¹Structural response of fire-exposed cross-laminated timber beams under sustained loads, Sean A. Lineham, Daniel Thomson, Alastair I. Bartlett, Luke A. Bisby, Rory M. Hadden

²Occupant toxicity threat from rain screen cladding systems, Dr Jim Glockling