How External Wall Insulation Prevents Overheating in London Flats
- LXM Building Services
- Jul 3
- 5 min read
Updated: 5 hours ago
A Summer Retrofit Guide by LXM Building Services
As summer temperatures in London continue to rise, many flat owners are facing an uncomfortable reality: their homes are becoming unliveable during hot spells. Urban flats, particularly those in older or poorly insulated buildings, absorb and retain heat throughout the day, causing internal temperatures to soar.
The good news? External wall insulation prevents overheating, and LXM Building Services has the expertise to install it efficiently as part of a dedicated summer retrofit London flats package.
Request a quote – Call 020 335 54797 or email info@lxm-london.com
Why Overheating Is a Serious Issue in London Flats
External wall insulation prevents overheating, which has become one of the most pressing retrofit challenges in London. According to government data, nearly 20% of homes in the capital experience uncomfortably high temperatures during the summer months. For flats, especially those on top floors or with poor ventilation, the risk of overheating is even greater.
Several factors contribute to this:
High solar gain through unshaded walls and windows
Lack of insulation or thermal breaks in wall construction
Inadequate cross-ventilation
Urban heat island effect in dense boroughs like Camden, Ealing and Westminster
These conditions not only affect comfort but can also impact health, productivity, and even tenancy conditions for landlords. External wall insulation offers a strategic solution to mitigate this issue while delivering long-term energy savings and improving building performance.
How External Wall Insulation prevents Overheating
At first glance, insulation is associated with keeping properties warm in winter. But high-performance insulation, when correctly applied, also helps regulate internal temperatures during summer. Here’s how external wall insulation prevents overheating in practice:
1. Slows Heat Transfer
EWI acts as a thermal barrier, reducing the rate at which external heat penetrates through solid or poorly insulated walls. This means that even when outdoor temperatures peak, your flat remains cooler inside.
2. Enhances Thermal Mass Efficiency
With insulation installed externally, the building’s inner thermal mass (such as brick or concrete) is allowed to absorb and regulate internal temperatures more evenly. This stabilises indoor climates and minimises rapid fluctuations.
3. Limits Night-Time Heat Retention
Uninsulated walls release absorbed heat during the night, contributing to stuffy conditions even after the sun sets. EWI slows down this release, making your flat cooler and more restful overnight.
4. Compatible with Passive Cooling Strategies
EWI complements other passive cooling techniques such as external shading, reflective glazing and mechanical ventilation, helping you create a holistic overheating prevention system.
In short, summer retrofit London flats projects that include EWI not only address winter inefficiencies but also drastically improve summer comfort levels.
A Case Study: External Insulation in a West London Flat
A recent case study external insulation project in Ealing highlights just how transformative EWI can be for overheating. Our client, the owner of a top-floor Victorian flat, reported indoor summer temperatures frequently exceeding 30°C, even with windows open.
LXM’s team completed an external wall insulation installation using breathable mineral wool and silicone render. Within days, internal temperatures dropped by an average of 4°C. The client noted better sleep quality, improved indoor air conditions, and a marked reduction in the need for fans or air conditioning.
The entire retrofit was completed in under a week, with minimal disruption to residents or neighbours.
Why Choose LXM for Your Summer Retrofit in London?
LXM Building Services has grown from a reputable commercial contractor into a highly sought-after provider of domestic insulation and refurbishment services across the capital. Our tailored summer retrofit package offers homeowners and landlords a stress-free, high-quality route to comfort and energy efficiency.
What Sets Us Apart:
Decades of Combined Experience: Our background in complex commercial builds means we understand deadlines, building physics, and detailed planning inside out.
Quality Without Compromise: We use only high-grade breathable insulation materials like mineral wool, and work with premium render systems that are both durable and attractive.
Fully Certified & Insured: LXM is accredited by CHAS, Gas Safe, Constructionline, and NICEIC, giving you peace of mind that our work is safe, legal, and professionally executed.
Clear Communication and Honest Pricing: From your initial quote to final inspection, our team keeps you informed and in control.
London-Wide Local Knowledge: Whether you live in Notting Hill, Barnet, Camden or Chelsea, we understand the local planning landscape, building types, and resident expectations.
External Wall Insulation: A Step-by-Step Guide
Initial Site Survey We assess your flat’s thermal performance and overheating risk, and determine suitability for EWI.
Planning and Retrofit Design We tailor our solution to meet PAS 2035 standards and local authority requirements.
Insulation Board Installation Mineral wool or other breathable panels are fixed to external walls, ensuring thermal continuity.
Mesh Reinforcement and Basecoat A fibreglass mesh is applied to prevent cracking, followed by a high-performance basecoat.
Topcoat and Finishing Render Choose from coloured silicone or mineral renders designed for durability and weather resistance.
Final Inspection and Aftercare
We complete detailed checks, hand over documentation, and remain available for post-install support.
Are There Grants or Funding Options Available?
Yes, particularly if your flat qualifies under PAS 2035 retrofit schemes or local authority funding streams. LXM can help you:
Apply for insulation grant UK programmes
Navigate government insulation funding for 2025
Access external insulation grants London boroughs are offering
We offer a grant support service as part of our summer retrofit package, ensuring you maximise the benefits available to you.
Contact us to check your eligibility
These accreditations give our clients peace of mind—knowing that every project is delivered by qualified professionals who care about doing things properly.
Take Control of Overheating Today
With temperatures climbing and London’s building stock under increasing pressure, now is the time to consider an insulation retrofit. Whether you live in a converted Victorian flat or a post-war estate block, external wall insulation overheating solutions from LXM Building Services can help you stay cool, comfortable and energy-efficient.
Contact our expert team today to schedule your survey and receive a no-obligation quote.
FAQs: External Insulation and Overheating
1. Does external wall insulation help reduce indoor heat in summer?
Yes. EWI creates a thermal envelope that slows heat transfer, helping to keep your home cooler during hot spells and preventing night-time heat retention.
2. How long does external insulation take to install?
It depends on the size of your property, but many flat retrofits can be completed within 3 to 5 working days, often with one-day scaffolding setups.
3. Can EWI be used on blocks of flats?
Yes. We regularly retrofit single flats and entire façades, subject to planning and freeholder approval. LXM handles both partial and full EWI installations.
4. Is mineral wool safe for external insulation?
Absolutely. Mineral wool is a non-combustible, breathable and environmentally-friendly material suitable for residential façades, including high-rise flats.
5. What does external wall insulation cost in London?
Costs vary based on building type, access, and materials. On average, prices range from £90 to £150 per square metre. LXM provides transparent quotes with no hidden extras.
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