How to Retrofit a London Home to the EnerPHit Standard

How EnerPHit retrofit principles are shaping London's low-carbon future

London is a city stitched together with brick, slate, and ambition. From Victorian terraces to Edwardian semis, its residential fabric tells a story of expansion, craftsmanship, and domestic life. But behind those charming façades lies a hard truth: most of these homes leak energy, cost a fortune to heat, and struggle to offer the comfort we expect in the 21st century.

And yet, tearing them down isn’t the answer.

At RISE Design Studio, we see a different path forward—one rooted in care, craft, and carbon consciousness. It’s a design philosophy that begins with what’s already here. And it finds its full expression in the EnerPHit retrofit.

EnerPHit is more than a standard. It’s a statement—that even the oldest homes can meet tomorrow’s environmental challenges, without losing their soul.

Low-energy extension to a Victorian home in London, designed to EnerPHit with triple glazing, natural materials and airtight detailing.

Why Now Matters

We’re standing at a crossroads. The homes we refurbish today will carry us through to 2050 and beyond. And given the UK’s commitment to net-zero carbon emissions by mid-century, we have a narrow window to make meaningful change.

The uncomfortable truth? Most older homes in London were built at a time when coal was cheap and climate change wasn’t on the radar. They’re typically 2 to 3 times less thermally efficient than a modern home built to current regulations. That inefficiency doesn’t just affect bills and comfort—it directly undermines our collective ability to meet climate targets.

So when we retrofit a Victorian house today, we’re not just making it warmer. We’re giving it new purpose. A new lease of life. A future that aligns with the planet’s.

☉ These are no longer just family homes. They are climate solutions in brick and timber.

A Whole-House Approach

Unlike piecemeal energy upgrades, EnerPHit retrofit is a holistic strategy—treating the building as a complete ecosystem.

Think of a Passive House retrofit like a well-sealed thermos: stable, comfortable, and low-energy. Every element—walls, windows, ventilation, heating—works together in harmony. There are no weak links. No heat escaping through forgotten cracks.

To achieve this, five key principles guide the transformation:

• Super-insulated envelope: From walls and roofs to subfloors, insulation reduces heat loss dramatically. We often use natural materials like wood fibre, which offer high performance without compromising breathability.

• Airtight construction: Drafts are one of the biggest culprits in heat loss. An EnerPHit home seals out cold air and moisture while keeping warmth in.

• High-performance glazing: Triple-glazed windows, carefully detailed and often FSC-certified timber framed, preserve the building’s character while delivering modern comfort.

• Mechanical Ventilation with Heat Recovery (MVHR): These smart systems remove stale air and introduce fresh, filtered air while recovering up to 90% of the heat.

• Thermal bridge elimination: Even a small gap in insulation can cause condensation, discomfort, or structural problems. Detailing here is critical.

☉ In short, it’s not about fixing one thing. It’s about rethinking everything—with care, precision, and purpose.

Refurbishment Without Compromise

There’s a misconception that performance upgrades mean sacrificing character. We disagree. If anything, the process of EnerPHit retrofit offers a rare opportunity: to enhance heritage through innovation.

Take a typical London terrace. The sash windows, the brick arches, the lime plaster—all elements we respect. We don’t wipe them out. We reinterpret them.

For instance, at a recent North London retrofit, we retained the solid brick structure but added a breathable insulation layer finished with natural lime plaster. This allowed the wall to regulate moisture naturally, improving thermal mass and air quality, without damaging the original fabric.

Inside, the MVHR system was hidden within floor voids and joinery, maintaining a clean, minimal aesthetic. Outside, the windows were replaced with bespoke triple-glazed units designed to mirror the original detailing—delivering comfort without compromising the building’s story.

☉ A retrofit should be felt in how the home performs, not in what it loses.

The Role of Data and Design

Every EnerPHit retrofit starts with forensics. Before we draw a single line, we test and measure—thermally image walls, assess condensation risk, analyse air quality, survey materials.

From there, we model various performance scenarios using specialist software to simulate how heat, moisture, and air will behave once the upgrades are complete. But it’s not just numbers. We also consider the daily rhythms of life: how the sun moves through the rooms, where heat is needed, where cooling is most important.

This deep, integrated analysis leads to better decisions—ones that are specific to your home, not lifted from a checklist.

Step-by-Step Progress

Budget, time, and logistics don’t always allow for a one-time, full-scale retrofit. And that’s okay. The EnerPHit Retrofit Plan enables phased improvements—while still working toward certification.

→ Can’t afford to replace the sash windows this year? No problem. You can focus on airtightness and insulation first, then come back to glazing later.

We work with clients to sequence their retrofit journey intelligently—mapping out short-term wins and long-term goals. It’s a marathon, not a sprint. But with the right plan, each stage builds on the last, unlocking comfort and efficiency as you go.

☉ Sustainability isn’t just in the outcome. It’s in the process.

Renewable Technologies: The Final Layer

Once the home’s envelope is performing at its best, we look at how to cover the remaining energy demand through renewables.

Our go-to strategy often includes air source heat pumps (ASHPs)—devices that absorb heat from the outside air (even in winter) and use it to heat water or underfloor systems. When combined with solar panels or battery storage, they offer a route to near net-zero operation.

But it’s the synergy between passive measures and active systems that makes the biggest difference. Heating systems work best when the building doesn’t need much heat in the first place.

Case Study: A Home Reborn

In one of our current projects, a late-Edwardian home in West London is being reconfigured with EnerPHit at the heart of the design. The owners loved the original proportions and detailing but were tired of the cold winters, rising energy bills, and summer overheating.

Our brief: retrofit without losing character. The solution? A blend of high-performance upgrades and visual restraint.

We introduced breathable wall build-ups using wood fibre insulation, lined the roof with vapour-open membranes, upgraded every window to triple-glazed units, and concealed an MVHR system throughout the home’s floor voids and eaves.

Now, the house runs quietly. Efficiently. And most importantly—comfortably. It’s a home that feels rooted in the past, while confidently facing the future.

A Wider Impact

At RISE, we don’t believe in throwaway architecture. Every building we work on should leave a legacy—not just for its occupants, but for the planet.

That’s why we push for EnerPHit retrofits wherever possible. They offer one of the most impactful ways to reduce carbon emissions, preserve architectural character, and create truly comfortable homes.

Our role as architects is not just to design for aesthetics or profit. It’s to create buildings that serve people—and the planet—for the long term. It’s to be stewards of the built environment. To retrofit not just homes, but systems. Ideas. Expectations.

Building Forward

Retrofitting London’s housing stock to EnerPHit standard isn’t just a technical goal. It’s a cultural shift. One that moves us toward healthier homes, lower bills, and lighter footprints.

It requires a mindset that values patience, precision, and purpose.

At RISE Design Studio, this is the work that excites us. It’s architecture that matters. It’s design that performs. And it’s a future that starts with the buildings we already have.

→ Curious how EnerPHit principles could transform your home?
Let’s talk about a low-energy future rooted in heritage and driven by design.

RISE Design Studio

Designing places that do more—with less.
☉ Low energy, high integrity. Always.

Building for a low-energy future

At RISE, we believe that EnerPHit isn’t just about ticking sustainability boxes. It’s about reimagining what old homes can become—beautifully designed, radically efficient, and deeply comfortable.

It’s about preserving the past while building forward.
Creating homes that feel good to live in—and do good for the planet.
That quietly push boundaries. That invite in the future.

Thinking about retrofitting your home to EnerPHit standard?
Let’s explore how your home could rise to the challenge—and set a new benchmark in low-energy living.

→ Email us at architects@risedesignstudio.co.uk
→ Or call the studio on 020 3947 5886

RISE Design Studio Architects, Interior Designers + Sustainability Experts

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