Despite the increasing world population, energy resources are limited causing the inefficient energy use to turn into a big problem; hence, the efficient use of energy has become important. The concept of thermal insulation has emerged in order to prevent energy losses in winter, unwanted energy gains in summer and make the comfort of living spaces more stable. Thermal insulation systems provide energy and money savings and pave the way for people to live and work in a healthier and more comfortable environment. In addition to thermal insulation, fire insulation increases the confidence of the building.
Thermal insulation prevents the loss or unwanted gains of heat energy and balances the ambient temperature. Temperature is a scalar quantity that rises with the increase of molecular activity in an object and is considered an energy level. It is expressed in temperature units such as degrees celcius (°C), degrees kelvin (°K). Heat is a type of energy and is expressed in units of energy such as joules and calories. The energy flow from the high temperature energy level to the low temperature energy level is called heat flow. The heat encounters a resistance during this flow, depending on the thermal conductivity coefficient and thickness of the materials between the spaces. In the most general sense, thermal insulation is a resistance that reduces heat transfer. While designing in terms of comfort, the thermal differences between summer-winter, day-night should be taken into consideration according to the location of the building or the purpose of use.
Heat is transferred in three ways as conduction, convection, and radiation. Heat conduction is the heat transfer that occurs in solid objects flowing from high temperature through low temperature. Heat convection is a type of heat transfer that takes place between a solid surface and a fluid. This transfer is done by means of streams in the fluid; therefore, it happens in liquids and gases, but not in solids. Heat radiation is the radiation or transfer of energy in the form of electromagnetic waves or particles. In addition, all the elements that cause radioactive materials to emit rays such as alpha, beta, gamma or any electromagnetic beam emitted in space is also called radiation.
The European Standards for thermal insulation materials were translated by The Turkish Standards Institution and published as Turkish Standards. These standards describe the properties that thermal insulation materials should have, along with material testing, marking and labeling procedures. In addition to product standards, there are Turkish Standards for calculation and analysis procedures used in insulation calculations.
The reference standard for the applications of thermal insulation in Turkey is TS 825 " Thermal insulation requirements in buildings". The materials to be used in thermal insulation must provide a certain "thermal conductivity coefficient" (U value). According to ISO and CEN standards, materials with a thermal conductivity coefficient of less than 0.065 W/m2K are accepted as thermal insulation materials, while larger ones are accepted as building materials. In TS 825 standard, Turkey was divided into 4 regions and assigned different coefficients of thermal conductivity designated for use in insulation calculations. These coefficients are in 4 different forms as wall, ceiling, floor and window according to the locations of the insulation.
Masonry or mudbricks used in traditional buildings had insulating properties as they were used in the form of thick walls, but today this is not possible, so low thermal conductivity and lightweight construction materials are used.
The important features in the selection of thermal insulation material are as follows:
- Thermal conductivity coefficient (should be low.)
- Water vapor diffusion resistance coefficient (must allow vapor passage at a certain rate.)
- Fire standard (in terms of fire safety, the ignition of the material, its emission of flame, heat, smoke and toxicity should be examined, materials suitable for the class specified in the regulation should be selected.)
- Toxicity (natural materials are more advantageous in this respect.)
- Water absorption by volume (water absorption value should be low since the higher this value, the higher the thermal conductivity coefficient.)
The external impacts which the building is exposed change depending on the geography, climatic conditions, the function of the building and the users. Many items in homes are flammable. Since the oxygen required for a fire is present in the air, flammable materials that reach the ignition temperature may cause loss of life and property if fire insulation is not applied.
Most of the casualties in fires in buildings are caused by the toxic gases released during the burning. For this reason, it is important to place smoke barriers, escape corridors, fire-resistant thermal insulation and facade materials in buildings.
Building and insulation materials are divided into 7 fire reaction classes in EN 13501-1 "Fire classification of construction products and building elements-Part 1: Classification using test data from reaction to fire tests." as follows:
- A1: Material that does not contribute to fire in any way.
- A2: Material with extremely limited contribution to fire.
- B: Material contributing to fire in a very limited extent.
- C: Material contributing to fire in limited extent.
- D: Material that contributes moderately to fire.
- E: Material that contributes a lot to fire.
- F: Material that burns easily.
Heat insulation materials and fire classes commonly used in buildings can be listed as follows:
- Glass wool (MW) - Fire class A.
- Rock wool (MW) - Fire class A.
- Wood wool (WW) - Fire class B.
- Expanded cork board (ECB) - Fire class E.
- Cotton board - Fire class A.
- Cellulosic board - Fire class A.
- Perlite (EPB) - Fire class A.
- Aerated concrete - Fire class A.
- Pumice block - Fire class A.
- Polyurethane foam (PUR) - Fire class D, E or F.
- Polyisocyanurate sheet (PIR) - Fire class B.
- Phenol foam (PF) - Fire class B or C.
- Glass foam (CG) - Fire class A.
- Expanded polystyrene rigid foam (EPS) - Fire class D or E.
- Extruded rigid polystyrene foam (XPS) - Fire class D or E.
- Polyvinylchloride foam (PVC) - Fire class B.
In addition to the above classification, materials are classified in "s" categories according to smoke gas emissions during combustion and "d" categories according to flame droplets as follows:
- s1: The amount and velocity of smoke emission are too weak or not present.
- s2: The amount and velocity of smoke emission are moderate.
- s3: The amount and velocity of smoke emission are high.
- d0: Material that does not form flame droplets or particles.
- d1: Material that creates less flame droplets or particles which quickly extinguish.
- d2: Material that creates a lot of flame droplets or particles which do not extinguish quickly.
In the European Commission numbered 2000/367/EC, building materials are divided into 3 classes according to the resistance they show against fire as follows:
- R: Load bearing capacity - Ability of the material to maintain its mechanical properties and load bearing capacity during fire.
- E: Integrity - Ability of the material not to let smoke or other gases through during fire.
- I: Insulation - Ability of the material not to transfer heat to the non-fire (cold) side of the material.
The resistance of the materials against fire is expressed with the performance times in minutes as 15, 20, 30, 60, 90, 120, 180, 240 or 360 after the lettering such as R, RE, REI. A material with 143 minutes of load carrying capacity, 95 minutes of integrity and 54 minutes of insulation performance against fire is defined as R120 / RE90 / REI30.
In addition to material classification, passive and active measures are taken for fire protection in buildings. In the most general terms, passive measures are the measures that aim to slow the spread of fire, limit the fire, and allow people in the building to evacuate the building safely. Active measures, on the other hand, are active actions such as warning the people in the building during the fire, extinguishing the fire, collecting and removing the formed toxic gases.
In terms of facades, "Regulation on Protection of Buildings from Fire" was published by The Turkish Council of Ministers in the official newspaper which states the following:
- Exterior facade materials should be made of (at least) hardly combustible materials (A2, s1, d0) in buildings with a height of more than 28.50m, and (at least) hardly flammable (C, s3, d2) materials in other buildings.
- In buildings with a height of less than 28.50 m with an external facade of hardly flammable material or system (at least C, s3, d2), a distance of 1.5 m above the natural or leveled ground level should be covered with non-combustible material, the building height should be over 6.50 m. In buildings with excessive amounts of windows and similar spaces, the side edges of the windows and similar spaces should be at least 15 cm wide and the upper edge should be at least 30 cm wide, and fire barriers should be created with non-combustible material.
- The thermal insulation material should be fixed to the building element mechanically so that it does not fall during the fire.
- In order to prevent the flames from passing from one floor to another, at least 100 cm height of fire-resistant facade claddings should be formed vertically between the unprotected spaces such as windows of the two floors or sprinkler heads should be placed at a distance of 1.5 meters at maximum 2 meters in the interior of the facade and protected by a sprinkler system.
- When the thermal insulation system created using thermal insulation material, heat insulation adhesive, dowel, plaster mesh, plaster and other similar equipment, the system must be certified by an accredited laboratory within the scope of the relevant standards.
- The intersections of facade elements and floors that do not have spaces where flames can pass should be insulated with ensuring enough duration of fire resistance of the slab in a way that prevents flames from jumping to neighboring floors.
- Facade and insulation materials used in buildings with open joints or ventilated curtain wall systems should be at least hardly combustible (A2, s1, d0).
The Grenfell Tower disaster in the UK in the recent past can be given as an example regarding the importance of fire insulation. On the facade of the tower, which was renewed in 2015, aluminum sandwich panel with polyethylene (PE) core, and polyisocyanurate (PIR) boards were used as thermal insulation material. The fire that started in the kitchen of a room on the 4th floor of the 24-storey tower in June 2017 spread to the facade of the building, and in a short time it progressed on the whole facade, causing 72 deaths. In addition to the fire classes of PE and PIR materials not being A, PIR sheet releases toxic hydrogen cyanide gas when it burns. This disaster is a painful proof of the necessity of paying attention to the above-listed features in the selection of thermal insulation and facade cladding materials.