With heating bills rising and winter quickly setting in, considering how you warm your home is crucial. Locking heat in will increase your comfort without cranking up the central heating, and the best way to prevent heat transfer is with insulation. 

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Typically, our houses have internal insulation panels underneath the plaster. However, especially in old homes, it is not always possible to upgrade or install these panels. When this is the case, we can employ external wall insulation instead. Here&#;s a breakdown of the advantages and disadvantages of external wall insulation.

What is External Wall Insulation?

As opposed to internal insulation panels, external wall insulation is attached to the outside of a building. Panels of polystyrene (EPS), mineral wool or wood fibres are installed and finished with rendering layered over the top.

Why Should I Install External Wall Insulation?

External wall insulation has many benefits. However, primarily, we install it for the tea-cosy effect, hugging your home and adding an extra layer of protection to trap heat inside. 

Advantages Of External Wall Insulation

Installing external wall insulation has several benefits, not just keeping heat inside your home. Here are the helpful advantages: 

Reduced Energy Bills

The main advantage of external wall insulation is locking heat into your home to reduce your reliance on central heating. Especially with the current cost of living crisis, those savings make a huge difference.

Increased Comfort

Drafts are never comfortable; no one wants to be cold in their home. Choosing external insulation combats heat transfer and keeps you warm.

Doesn&#;t Reduce Space

The main alternative to external wall insulation is internal insulation. However, this option can reduce the overall floor plan of your rooms. External wall insulation has the same energy-saving effect without this size reduction.

Increased Durability

The extra layer of rendering over the insulation protects your home from harsh weather conditions, strengthening your external walls. 

Sound Resistance

When you insulate your home to keep in the heat, you also keep in sound, increasing your privacy. Plus, it reduces sound entering your home from the outside.

Disadvantages Of External Wall Insulation

There are some key downsides to external wall insulation that you should consider. With the right installation and rendering company, some of them can be avoided.  

Can Encourage Damp

Depending on how permeable your walls are, external insulation can cause damp and impact respiratory conditions such as asthma.

Permeable walls allow moisture to pass through. Therefore, this moisture can move out of your home and evaporate away. However, impermeable walls trap moisture and have other ventilation systems to remove it.

The problems arise when permeable walls are insulated with impermeable insulation panels. As they don&#;t have other ventilation means, moisture is trapped inside, causing damp walls or insulation. 

These hazards are avoidable. Choose a responsible rending company that will create thorough plans to implement new ventilation. 

It May Require Planning Permission

When you change the appearance of your home, you need planning permission from your local council. Whilst some external wall insulation falls under the permitted development plans, other cases require approval. No matter your situation, it is always best to consult your local authority before installing anything.

Problems Around Windows and Sills

Window and door frames cause external insulation issues. If you do not insulate them, you&#;ll create cool bridges that channel warmth away from your home. These temperature differentials encourage condensation and dampness. Alternatively, if your frames are narrow, they are difficult to insulate.

It&#;s best to go with thinner insulation around these areas to cater to their small size.

Expensive

Price will always be a critical consideration when insulating your home, and unfortunately, the benefits of external wall insulation come at a larger cost. To insulate a typical three-bedroom semi-detached house, you will likely pay between £5,000 and £9,000. If you want to insulate a larger detached house, it will cost between £8,000 and £15,000.

So Can External Wall Insulation Cause Damp?

External wall insulation can potentially cause damp issues. Moisture can enter walls from external sources like rain and internal sources such as cooking, laundry, and breathing. The choice between impermeable and breathable walls before cavity walls affected moisture penetration.

Cavity walls act as moisture barriers, allowing rainwater to evaporate due to air movement. Modern non-permeable insulation materials protect against rain but not internal moisture, necessitating improved ventilation. The dew point, where moisture in the air condenses into water, changes as air moves through the wall. Properly installed external insulation shifts the dew point outward, reducing the risk of internal condensation and damp. However, the dew point can end up within the insulation, which is addressed by a vapour barrier in most external insulation systems. Verify this with your supplier for effective moisture management.

Building Regulations and Planning Permission

In the UK, significant building changes require planning permission from local councils. However, external wall insulation is categorised as &#;permitted development&#;. 

Class A of the government&#;s &#;Permitted development For Householders: Technical Guidance&#; states:

The installation of solid wall insulation constitutes an improvement rather than an enlargement or extension to the house and is not caught by the provisions of (e), (f), (g), (h) and (j).

Therefore, you should not need planning permission to install external wall insulation. Despite this legislation, it is always good practice to contact your local authority for further clarification, or you risk having to remove your insulation and revert your home to its original state, costing you thousands. 

It is also important to remember that conversation areas and listed properties are subject to further development protections. One of the most common usages of external wall insulation is insulating old homes. These homes are often listed due to their age. So, again, you must check with your council before making any changes.

Common Complications

When you spend thousands on your insulation, you should be aware of the potential complications. However, there is no reason to fear. An expert installation and rendering company will work with you and avoid these risks.

Damp

• As we&#;ve already discussed, external wall insulation can trap moisture and condensation, leading to mould growth and damp.

Damage

• If installed incorrectly, the insulation can damage your property. 

Fire Hazards

• Adding insulation to your home can complicate your fire escape route. A reputable company will consider your fire doors and exits in their installation plan to avoid any blockages. 

Thermal Bridging

• A thermal bridge is simply an area of your building where large amounts of heat are lost. Look for spaces around windows and doors and factor them into your installation plan, as these openings and frames are often problem areas. 

Reveals, Sills and Eaves

• The added thickness of external wall insulation is most obvious at the eaves; they often aren&#;t wide enough for the added material. You should choose thin insulation, around 10-20mm, to work with these space restrictions and prevent heat loss in difficult areas.

External Wall Insulation For Different Types Of Walls

You can construct a wall with varying building materials. The most common is brick, but solid stone walls are also popular. When installing insulation, you should understand your walls&#; construction and permeability to achieve the best results.

Solid Stone Walls

Solid stone walls have a misleading name as they actually have a rubble-filled cavity between two stone skins. They tend to be breathable, letting air and moisture pass through them, so it&#;s best to choose a breathable type of insulation and then cover it with a lime render.

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Brick Walls

Brick walls vary in permeability, but they generally aren&#;t breathable. That means that most forms of rigid insulation will work well on brick walls. They can be attached with fittings and then covered with render.

How External Wall Insulation Affects U Values

A U value measures the rate of heat transfer through a material. A high U value indicates that heat transfers easily, meaning lower U values save money on our heating bills. A 255mm thick solid brick wall has a U value in the region of 1.20W/m2, and a 450mm thick stone wall is around the same. A cavity brick wall has a U value of 1.5W/m2.

External wall insulation lowers these U values to:

• 0.31W/m2 with 100mm of EPS insulation
• 0.30W/m2 with 70mm of rigid foam insulation
• 0.30W/m2 with 110mm of mineral wool, wood fibre or hemp batts insulation

Our Rendering Services

Now that you understand the advantages and disadvantages of external wall insulation, you can decide whether to install it in your home. If you install it, you cannot leave it open to the elements. Doing so will place the insulation at risk and affect your home&#;s aesthetic. That&#;s why at AB Drylining, we offer expert rendering services to cover it.

Our rendering lasts for 25 years, meaning that we can not only improve the aesthetic of your home but also provide long-lasting structural protection. To find out about our services and discuss your requirements with a specialist, contact our team today.

FAQ

How much impact can external wall insulation have?

External wall insulation can lower the U value of your walls from 1.20W/m2 or 1.50W/m2 to 0.30W/m2, preventing heat transfers from your home. 

What is the best external wall insulation?

Polystyrene EPS insulation has the best insulator properties and is cheaper than other alternatives.

Can external wall insulation cause damp?

Yes, damp can form if external wall insulation prevents moisture from escaping through permeable walls. To combat this issue, you should also install extra ventilation to remove the moisture.

Should you put external wall insulation on a cavity wall?

Cavity walls typically have existing internal insulation. Though you could install external insulation on the wall, it would be ineffective.

Can external wall insulation impact your health?

If external wall insulation is installed on permeable walls without implementing additional ventilation, it can trap moisture and cause damp. This dampness exacerbates respiratory conditions like asthma. 

How long will external wall insulation last?

Due to its weatherproof rendering, external wall insulation can last for decades without any issues.

Do I need planning permission?

According to the UK government&#;s advice, you don&#;t need planning permission to install external wall insulation unless your building is listed or in a conservation area. However, you should always contact your local council and check before construction to avoid having to revert your home to its original condition.

Are external wall insulation panels ugly?

The external wall insulation panels are an ugly addition to your home, but they are covered by rendering for an aesthetic protective coating.

Are you thinking about insulating the walls of your home and asking yourself, "External vs Internal Wall Insulation: What&#;s the Best Choice for Your UK Home?" Effective wall insulation is key to reducing heat loss, lowering energy bills, and decreasing your carbon footprint. With both external and internal wall insulation offering distinct advantages, it can be challenging to decide which option is right for you.

One of our clients, who owns a charming solid wall property in the heart of London, faced a similar dilemma. They wanted to retain the historical character of their home while ensuring it was warm and energy-efficient. After weighing their options, they found the perfect solution that balanced both aesthetics and functionality.

In this article, we'll explore the advantages and drawbacks of each type, focusing on solid wall insulation, to help you make an informed decision for a warmer, more energy-efficient home. Dive in to discover how you can best insulate your solid wall property and enjoy the comfort and savings that come with it.

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What Is Wall Insulation?

Wall insulation involves adding an extra layer of material to your property's walls to help retain heat within your home. It offers numerous benefits and plays a crucial role in creating a comfortable living environment by regulating indoor temperatures and reducing heat transfer. Wall insulation contributes to noise reduction, ensuring peaceful interiors, and lowers the carbon footprint by reducing the energy required for heating and cooling. Depending on the type of walls you have, insulation can be added internally, externally, or within the wall cavity itself.

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What Are The Different Types of Walls in the UK? 

Understanding the type of walls in your home is essential for selecting the most effective insulation method. Here&#;s a breakdown of the two most common types of walls in the UK:

Solid Walls

Solid walls are predominantly found in homes built before . These walls consist of either a single or double layer of brick or stone, with no cavity in between.

Insulation Options for Solid Walls: Internal and External Insulation. 

Cavity Walls

Cavity walls are commonly found in homes constructed after . These walls feature an outer and an inner layer with a gap (cavity) in between.

Insulation Options for Cavity Walls: Cavity Wall Insulation.

External vs Internal Wall Insulation: What&#;s the Best Choice for Your UK Home?

Internal Wall Insulation for Solid Walls 

Internal wall insulation involves adding insulation to the interior walls of your home. This method is used when external wall insulation is not possible. It can be done by fitting insulation panels directly onto the walls and covering them with plasterboard or constructing a stud wall filled with insulating material. 

Advantages of Internal Wall Insulation

• Cost-Effective: Generally more affordable than external insulation.
• Soundproofing: Enhances the soundproofing of your property, making it quieter inside.
• Preserves Exterior Appearance: Ideal for properties in Conservation Areas that need to maintain their original look.

Disadvantages of Internal Wall Insulation

• Disruption: The installation process can be quite disruptive, involving the removal and reattachment of fixtures.
• Reduced Room Size: Reduces the size of your rooms.
• No External Waterproofing: Does not provide an additional waterproof layer around your home.
• Damp Risks: Poor installation can lead to damp issues. Existing damp problems must be resolved before installation.

External Wall Insulation for Solid Walls

External Wall Insulation (EWI) involves attaching insulation to the exterior of your home. This process includes applying two layers: an insulating layer and an outer layer made from either mineral or synthetic render. In the UK, the most common materials used for EWI are expanded polystyrene (EPS), mineral wool, and phenolic foam. EPS is lightweight, affordable, and offers good thermal performance, while mineral wool is fire-resistant and provides excellent acoustic insulation. Phenolic foam, known for its great thermal performance, is ideal for spaces where thickness is limited. 

Advantages of External Wall Insulation

• Minimal Disruption: Since EWI is installed on the exterior, it does not disrupt the household or reduce the size of your rooms.
• Crack and Gap Filling: EWI helps fill in cracks and gaps in the outer walls, reducing drafts and improving energy efficiency.
• Condensation and Damp Reduction: By insulating externally, EWI can reduce inner wall condensation and dampness issues.
• Enhanced Weatherproofing and Sound Resistance: EWI improves the weatherproofing and sound resistance of your property.
• Increased Lifespan of Walls: Protects the brickwork, increasing the lifespan of your walls.
• Aesthetic Improvement: The facade of your building can be enhanced with a finish of your choice, boosting its curb appeal.

Disadvantages of External Wall Insulation

• Change in Appearance: EWI will alter the exterior appearance of your property and may require planning permission, making it unsuitable for period and listed properties.
• Potential for Cold Bridges: If gaps around windows and doors are not properly sealed, this could create 'cold bridges' where the insulation is compromised.
• Unsuitable for Structurally Unsound Walls: EWI is not recommended for properties with outer walls that are structurally unsound and cannot be repaired.
• Higher Initial Cost: EWI requires a larger upfront investment.

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Investing in insulation is a wise decision to enhance your home's energy efficiency, save on energy bills, and reduce your carbon footprint. Both internal and external wall insulation are effective methods to improve a home's thermal performance. When choosing the right insulation for your home, consider factors such as the age of your property, location, cost of the installation, R-value, and environmental impact.

The advantages of External Wall Insulation generally surpass those of Internal Wall Insulation. EWI offers a lower risk of thermal bridging, minimises the chance of damp issues, and avoids disruptions to your household during installation. It also preserves your internal floor space, making it a highly efficient option for many homeowners.

Ensuring professional installation is essential to maximise the effectiveness of any insulation method you choose.

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For expert advice tailored to your home's specific needs, PD Rendering is here to assist. With over 15 years of experience in professional rendering and insulation services, we ensure your property receives the best care. Start your journey toward a more energy-efficient and comfortable home with us today.

For more information, please visit External Wall Insulation Phenolic Board.