With energy prices rising and an increasing focus on the carbon footprint of our homes, many of us are looking for ways to insulate our houses in order to improve the energy efficency. While there are a wide variety of ways to insulate a house, external Wall insulating measures are becoming an increaingly popular option amongst homeowners, which is why our experts have put together their ultimate guide to insulating external walls, giving you all of the information you need all in one place.
What Is External Wall Insulation?
External wall insulation while traditionally has referred to a layer of insulating material added to the exterior side of a property, in recent years has been used to refer to any insulating measure that improves the energy efficency of a property from the outside. In order to understand external wall insulation, it is important to cover both internal and external insulating measures.
Internal Insulation
Cavity Wall Insulation
When we talk about wall insulation, the thing that often comes to mind is cavity wall insulation. Cavity walls are made of two layers of wall with a gap between them. Properties built after the 1920s are likely to have a cavity wall, while older properties generally have what is known as a solid wall, which is just one singular external wall. Cavity walls were designed to have a cavity wall to prevent the transfer of moisture from the external of a building into the internal wall. This is because exterior walls, whether they are stone, concrete, brick or render will absorb moisture, which in the case of a solid wall construction can then be absorbed into the property, causing damp and mould problems.
Cavity wall insulation is the process of injecting a foam into this cavity to help create an added level of insulation to the property to prevent heat loss. As the name would suggest is only applicable to properties with a cavity wall, meaning solid wall properties do not have the ability to insulate within the internal environment in the same way.
Aside from cavity wall insulation not being an option for some, it can also lead to a number of problems due to it removing the gap within the contruction of the property that was designed to keep the interior of a building dry. Cavity wall insulation has been widely linked with problems associated with damp. On properly fitted cavity wall insulation at the time of construction, the cavity has a small gap to allow rainwater to run down the wall instead of soaking the insulation. When retrofitted in properties with a cavity wall however, cavity wall insulation can be a real problem, as detailed by Building Research Establishment (BRE), a world leading, scientific research centre published their BRE Good Building Guide (44, Part 2).
“There can be an increased risk of rain penetration if a cavity is fully filled with insulation, i.e. moisture is able to transfer from the outer to the inner leaves resulting in areas of dampness on internal finishes. Rainwater, under certain driving rain conditions, can penetrate the outer leaf of masonry leading to wetting of the cavity insulation, a reduced thermal performance and damage to internal finishes.”
In short, poorly fitted insulation can create a bridge for moisture to absorb from the external side of the property into the cavity wall insulation, soaking the material. This can then allow the moisture to soak into the internal side of the cavity, causing internal damp. Other problems cavity wall insulation can cause include causing 'cold spots' due to the insulation falling to the bottom of the cavity and preventing the property from 'breathing', causing a build-up of moisture within the property. These have all contibuted to cavity wall insulation being extracted from thousands of properties due to the problems it can cause when not properly fitted.
Internal Wall Insulation
Internal wall insulation involves applying insulating boards to the internal wall of a property, instead of in a cavity wall. The benefit of this is that this can be applied to cavity wall and solid wall properties, as there does not need to be a cavity to apply the boards. While an option for all properties, adding thick insulation to interior walls can reduce the floor space of a property, can be invasive and if there are any problems caused by penetrating damp through the external wall of the property, this insulation can become easily saturated with moisture.
Thermal Insulating Paint
Thermal insulating paint, such as ProTHERM, are a new form of insulating measure in recent years. They absorb heat and become charged much like a battery, allowing them to hold heat 113% longer than standard emulsion. Not only does this heat prevent the formation of condensation, but also allows this heat to be released back into the room rather than being lost through the external wall of the property. While insulating paint does not provide the same level of insulation as other measures, it is an easy, non-invasive form measure that anyone can take at home.
External Insulation
Problems with cavity wall insulation and inability to add cavity wall insulation to solid wall properties means that in many cases, insulating measures for the outside of the property are desired by many.
There are two forms of insulating measures that can be taken on the outside of a property; external wall insulation and exterior waterproofing treatments.
External Wall Insulation
Much in the same way as interior wall insulation, external wall insulation is applied to the outside wall of a property. External wall insulation is made up of numerous layers of insulating material that is fixed to the masonry. The material used can vary, but is often contains a layer of render or cladding with insulating boards made of cork, wood or wool.
Some external wall insulation products are designed to not absorb water, but can also have low breathability, causing them to trap water vapour within the property. Other forms are designed with higher levels of breathability for this reason, helping to insulate the house while also preventing a build-up of moisture.
Exterior Waterproofing Treatments
The final form of insulating measure that can be applied to properties is an exterior waterproofing treatment such as a waterproof masonry paint or a masonry cream.
Damp content of just 5% can lower the insulating properties of a material by 50%, plus with 35% of heat being lost through the external walls of our homes, by keeping the walls dry you help to improve the thermal efficency of a property.
While other forms of insulation can lead to damp problems when they become saturated, these waterproofing treatments prevent this saturation, meaning they can also be successfully used in combination with other forms of insulation to prevent damp problems, aside from keeping the external wall dry & warm.
The crucial element of applying any waterproofing treatment to exterior walls is breathability. Traditional masonry paints and brick sealers have low breathability, meaning they can cause damp problems. In the same way that some insulation can prevent the building from naturally breathing, water vapour will build-up over-time if a low breathability coating is applied to the property.
Emperor Masorny Paint and Emperor Masonry Creme were developed in order to not only prevent water from entering the external wall of a property but also ensure that the building can naturally breathe and release water vapour. They contain the latest nano-technology that lines the pores of exterior walls without sealing these pores, meaning water in the form of rain is too large to pass through the nano-technology, while water vapour can freely pass through. This means that while water is completely repelled by the super hydrophobic (ultra water-repellent) surface that is created, water vapour is not trapped.
In independent testing, the treatments were found to keep a masonry wall up to 6°C warmer on average compared to an untreated wall. This meant they passed the EAD 040083-00-0404 - External thermal insulation composite Quality Standard, demosntrating their insulating properties. Following this testing, they were also verified by the Energy Saving Trust.
Emperor Masonry Paint is a coloured masonry paint that can be applied to any previously painted surface, or bare surfaces that have been sutiably primed. Emperor Masonry Creme on the other hand is a completely invisible treatment for bare brickwork and masonry, that is applied much like a moisturiser. Once applied to the brickwork, it absorbs and chemically bonds to the brickwork, providing the material with waterproofing properties rather than creating a waterproof film on the surface.
