Polystyrene is a synthetic aromatic polymer made from the monomer styrene. Polystyrene can be solid or foamed. Expanded polystyrene (EPS) is a rigid and tough, closed-cell foam. It is usually white and made of pre-expanded polystyrene beads. Polystyrene is one of the most widely used plastics, the scale of its production being several billion kilograms per year.
Polystyrene foams are produced using blowing agents that form bubbles and expand the foam. In expanded polystyrene, these are usually hydrocarbons such as pentane
Extruded polystyrene (XPS)
Extruded polystyrene foam (XPS) consists of closed cells, offers improved surface roughness and higher stiffness and reduced thermal conductivity. It is slightly denser and therefore slightly stronger than EPS.
Water vapour diffusion resistance (μ) of XPS is very low - making it suitable for application in wetter environments.
Phenolic foam
Phenolic foam insulation is made from a resole resin in the presence of an acid catalyst, blowing agents (such as pentane) and surfactants.
Polyisocyanurate/ Polyurethane foam (PIR/PUR)
Polyurethane (PUR and PU) is a polymer composed of organic units joined by carbamate (urethane) links. Polyurethane can be made in a variety of densities and hardnesses by varying the isocyanate, polyol or additives.
Polyisocyanurate, also referred to as PIR, is a thermoset plastic typically produced as a foam and used as rigid thermal insulation. Its chemistry is similar to polyurethane (PUR) except that the proportion of methylene diphenyl diisocyanate (MDI) is higher and a polyester-derived polyol is used in the reaction instead of a polyether polyol. Catalysts and additives used in PIR formulations also differ from those used in PUR.
Glass mineral wool
Made from molten glass, usually with 20% to 30% recycled industrial waste and post-consumer content. The material is formed from fibres of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties. The density of the material can be varied through pressure and binder content.
Rock mineral wool
Rock (Stone) mineral wool is a furnace product of molten rock at a temperature of about 1600 °C, through which a stream of air or steam is blown. More advanced production techniques are based on spinning molten rock in high-speed spinning heads somewhat like the process used to produce candy floss. The final product is a mass of fine, intertwined fibres with a typical diameter of 2 to 6 micrometers. Mineral wool may contain a binder, often a Ter-polymer, and an oil to reduce dusting
Cellular glass
Largely manufactured from recycled glass (e.g. windscreens) and mineral base materials such as sand and without the use of binding agents. The ingredients are melted into molten glass, which is cooled and crushed into a fine powder. The powdered glass is poured into molds and heated (below the melting point) in a "sintering" process that causes the particles to adhere to one another. Next, a small amount of finely ground carbon-black is added and the material is heated in a "cellulation" process. Here, the carbon reacts with oxygen, creating carbon dioxide, which creates the insulating bubbles in the (material). CO2 accounts for more than 99% of the gas in the cellular spaces.
Wool
Wool insulation is made from sheep wool fibres that are either mechanically held together or bonded using between 5% and 15% recycled polyester adhesive to form insulating batts and rolls. Sheep are no longer farmed primarily for their wool; however, they need to be clipped annually to protect the health of the animal. The wool used to manufacture insulation is the wool discarded as waste by other industries due to its colour or grade
Cellulose
Cellulose insulation is a material made from recycled newspaper. The paper is shredded and inorganic salts, such as boric acid, are added for resistance to fire, mould, insects and vermin. The insulation is installed either blown or damp-sprayed depending on application.
Wood fibre
The success of wood fibre insulation derives from an attractive environmental profile combined with a whole bag of functions including rigid insulation, sheathing and sarking for timber frames, roofs and flooring as well as flexible insulation for studs and rafters.
Wood of course is renewable, it sequesters carbon during its growth and product production is relatively free from pollution. The insulation value of wood fibre boards is not as dimensionally efficient as some of the orthodox petro-chemical materials - but it's no slouch either - typically coming in with a 'k value' range of between 0.038-0.043 W/mK depending on format.
Hemp
Hemp fibres are produced from hemp straw of the hemp plant. Most hemp is imported, but an increasing amount of home-grown crop is becoming available. Hemp grows up to a height of nearly 4 metres within a period of 100-120 days. Because the plants shade the soil, no chemical protection or toxic additives are required for hemp cultivation. The product is composed of, usually, 85% hemp fibre with the ballance made up of polyester binding and 3-5% soda added for fire proofing.
Straw
Straw is an agricultural by-product, the dry stalks of cereal plants, after the grain and chaff have been removed. Straw makes up about half of the yield of cereal crops such asbarley, oats, rice, rye and wheat.
External wall insulation often referred as EWI or K-Rend, is a compact multilayer insulation system fixed to an existing wall. It is made from many layers, including a base coat, reinforced mesh and finishing coat designed to improve home energy efficiency and repel water, keeping masonry delightfully dry. External wall insulation is one of three potential ways to insulate the walls of your home, the other options being cavity wall insulation and internal insulation. The effect of external insulation is to warm the wall by separating from cold temperature. It has been proven by German specialists that in order to improve the insulating properties of the building, insulation must be fitted on the exterior of the walls. By doing so the dew point is simply moved away from the wall.
The installation process involves fixing a layer of insulation material to the external walls of a property, and covering it with reinforcement and a special render in a range of decorative finishes. As with stone walls, the external insulation can be glued and then mechanically fixed to the wall. This method is often required for insulating walls on solid wall properties where there's no option for cavity wall insulation. The external insulation cost is usually higher than internal wall insulation. On top of that, there will be a cost involved in erecting scaffolding and removing all of the pipes that are fixed to the masonry wall. External wall insulation may be expensive but it is effective. Even with the higher cost, the advantages external insulation offers over internal mean that it is difficult to disregard. However, EWI and render systems take a fair amount of work to install, and essential to the process is having good tools for the job. It will also change the external appearance of the house. In most cases that will mean gaining planning permission before undertaking the work, so you do need to check with local authority from the outset. Under Building Regulations, if 25% or more of a wall is to be insulated externally, it is typically necessary to bring the entire wall up to current standards. The thermal performance of the insulated wall must have a U-value of no more than 0.30W/m²K. When it comes to using external wall insulation to insulate a solid wall, you'll be looking at the following U-value figures:
External insulation will add physically thickness to the wall, most evident at the reveals and eaves. You will have to extend your existing window sill using either uPVC or Aluminium window sill extender. In addition, it is usually impractical to return the insulation into the window and door reveals. There are thin insulation options, like 10mm white or grey polystyrene that can be used on a reveal to help overcome this challenge. On other hand, installing EWI doesn’t disrupt things inside your property in the way that internal insulation would, so you can easily live in the house during the work. You can expect some noise while walls are being prepared and the insulation is fixed. But disruption should be minimal. EWI can also help to improve weatherproofing and sound resistance. For instance, Rockwool DD sound slab has been specifically developed for use in external wall insulation systems where a higher density slab is required. The structure of the fibres in Rockwool Sound Slab make them ideal for use as a sound absorber. Rockwool Sound Slab works in two distinct ways to reduce noise, either by impeding the transmission of sound through an element of the structure, or by absorption of sound at the surface. Noise absorption is expressed as a factor between 0 and 1.0. Adding external wall insulation is also a good opportunity to update the appearance of your home. You could make it look pretty much identical to how it was previously or make some improvements to boost your house appearance, possibly even increasing its value. External wall insulation is an invisible part of your home that you won’t be able to see once in place. That is why it is often called fit-and-forget solution.
EWI INSTALLATION
The first step before beginning the EWI installation process is to do a render test. This will identify whether your existing render is strong enough to support the particular insulation. Second step would be removing an existing pipework from the building so the installation process can begin. On this stage you should also fit a protective layer over your windows, which will prevent them from being damaged during the installation process. External wall insulation does not normally reach the ground but instead begins a few inches above. Once you’ve decided on the height, this is where the aluminium start track or base track, will be installed. Starter tracks should be installed against a flat surface, with any gaps filled with expanding foam, plastic trims, or silicone sealant, however it would be preferred to dub out the wall locally to ensure full contact with the wall and rear up stand of the trim. Trims are usually set 150mm above ground level to reduce the effects of ‘splash back’ of rainwater, dirt and other contaminants, however it is advised that DPCs should not be bridged.
Once the starter track has been installed, the application of the insulation boards onto the wall can begin. Boards should be laid in a staggered pattern, and should be staggered at the edges of buildings so that they form a toothed finish. Generally boards should be cut in an L shape around the corners of openings, and small cuts of boards should not be allowed. It would be best practice to limit cuts to a minimum of 200mm. Gaps in boards should be limited, and should be filled with expanding foam. Boards should be level so that the basecoat and decorative finish are installed on a flat true surface. Leveling of boards can be undertaken with adhesive renders or dubbing out renders, and should be assessed at contract stage and allowed for within the contract costs. Adhesive renders should be applied to the rear of the board, and should follow either a dot and dab method, with renders to the board edges, or a fully applied adhesive using a serrated trowel. As well as the adhesive, mechanical fixings are also used to secure the insulation boards. Around 8-10 fixings are hammered in per square metre, to ensure the insulation boards will not get blown off or fall off during periods of bad weather. Next step would be to add corner beds to the corner surfaces. Corner beads and stop beads are a great way to ensure the insulation remains secure and tight around windows and doors. Once the boards and beading have all been installed, two layers of render with strengthening properties are applied, with a fibreglass mesh sitting between the two layers of render. Meshes should overlap by a minimum of 100mm at all edges and should overlap with integral meshes on the corner beads and starter track clips. Check with the system supplier as laps can reduce to 75mm if agreed. Stress patches should be installed to all corners at openings and should be sized by the system designer. Base coat application should only be carried out when the weather is fine and free from rain. It is recommended to carry out a daily check on the weather forecast, for a minimum of 48 hours prior to the proposed application of system designers. Polypropylene or glass fibre meshes should be installed into the wet basecoat, using the back of a steel trowel and pushed in, so that they sit in the top third. Meshes should be continuous, and should have a minimum 100mm (10cm) lap with the adjacent mesh. Any meshes that are integral to beads and trims should also allow for 100mm (10cm) lapping. This ensures strength and continuity of the basecoat. A second basecoat is then applied, and there should be no visual sign of the mesh once this is applied. Once the basecoat has been applied, it should be left to cure in its appropriate state to receive the priming paint and then final finish i.e. suitably scarified in the case of thick coat finishes or sponged for fine textures. The final coat of render can now be applied. This render is the last coating in the installation process, meaning that it is important to choose the exact colour and texture you like, as it will be in view on the outside of the building.
EWI SYSTEM COMPONENTS
INSULATION LAYER
This is the main insulation normally made of either expanding polystyrene or mineral wool. Technologies such as phenolic resin insulation are also available. All of these materials are used to prevent heat escaping through walls. The insulation forms the main thermal layer as well as being the background for applying the basecoat and finishes to. Boards are fixed either directly with adhesive, with mechanical anchors, or a combination of both.
The spider diagrams below are an extract from a recent multi-criteria comparison of insulation materials carried out for EUMEPS (European Manufacturers of EPS). These are taken from the External Wall Insulation comparison and shows EPS having the lowest overall environmental impact.
Picture credit:sundolitt.com/en/Environment/
FIXINGS
Fixings are specified to suit the existing substrate, the height and shape of the building, its location and elevation, and proximity to other buildings. Fixings should be specified by the system designer, and calculations made to check the pull-out value of the specified fixings. All mechanical anchor suppliers will provide printed literature with characteristic pull-out values and these can be used to specify the fixings, however best practice would be to check the site pull-out value and carry out wind and fixing analysis calculations based on these findings against localised conditions. This is the approved method to ensure the correct fixings and quantity are used.
PRIMER
The primer helps waterproof the EWI system and act as a barrier to moisture passing from the outside in. Some primers also have inherent insulation properties adding to the overall efficiency of the system.
GLASS FIBRE MESH
This part is used to hold the basecoat in place whilst it dries. Another layer of primer is then applied over the top of it.
BASECOAT/ BOARD ADHESIVE
Adhesive provides the perfect base for fixing all types of external insulation boards. The adhesive is waterproof, frost proof and vapour permeable, ensuring that your EWI system remains stable and structurally sound for years to come. Adhesive renders should be applied to the rear of the board, and should follow either a dot and dab method, with renders to the board edges, or a fully applied adhesive using a serrated trowel.
RENDER FINISH
This is the final layer of EWI and has a decorative function, enhancing the look of your home. There are various different renders available. Silicone Render is a flagship silicone-based thin coat render. Renowned for being long lasting and aesthetically pleasing, this render is the classic choice for homeowners and businesses alike. With hydrophobic properties, the Silicone Render has self-cleaning capabilities and also increased resistance to biological growth. It’s a customer favourite because once it’s installed it requires minimal upkeep and continues to look fantastic.
Silicone Silicate Render is the most popular hybrid silicone render, offering great performance and great value. Silicone Silicate is fantastically versatile, providing the key benefits of a thin coat render with the added boost of self-cleaning and breathability that the silicone technology provides. Silicone Silicate is perfect for a standard classic finish that will maintain its brilliance in the long term.
Acrylic Render is the best value render. It is impact resistant and is most well known when it comes to coloured render as it retains the colour pigment even after extended exposure to UV. Acrylic Render achieves a vibrant, stand out finish.
Fischer DIPK 8/20-40 Render Only Fixing (boxed in 200's) is a drive anchor consisting of a white fixing sleeve with an integrated plate and a glass-fibre reinforced plastic nail used in render-only EWI systems.
Render Only Fixings Fischer DIPK 8 are suitable for a wide range of building materials..
100mm Hardened Wood Screw KMH-60 (box of 100) is a quick and easy to install timber screw with a countersunk head suitable for use on wood, chipboard, plywood, sterling board and MDF board substrates.
KMH-60 Screws are typically used in conjunction with fixing discs to anchor insulation to wood s..
