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What is EnerPHit? Is it right for my home retrofit project?

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EnerPHit aims to achieve similar levels of energy efficiency as Passivhaus for retrofitted buildings. In this guide, I will provide you with a comprehensive overview of EnerPHit, its requirements, the benefits it offers, and the considerations you need to keep in mind if you are planning a retrofit project.

EnerPHit vs. Passivhaus

While Passivhaus standards are primarily applied to new builds, EnerPHit focuses on retrofitting existing properties. Retrofit refers to a form of renovation aimed at significantly reducing energy consumption and improving the thermal performance and comfort of a home. Unlike Passivhaus, which can start from a blank canvas, retrofitting involves working with existing buildings where many elements like geometry, orientation, and structural approach are already predetermined. Additionally, retrofit projects may have thermal bridges (or cold bridges) that are challenging to eliminate completely.

The EnerPHit standard acknowledges these challenges and sets slightly lower performance requirements compared to Passivhaus, considering the limitations of retrofitting existing buildings. To meet the EnerPHit standards, a space heating and cooling demand of 25 kWh/m2/year is required (compared to the Passivhaus standard of 15 kWh/m2/year). Airtightness performance should achieve 1.0 air changes per hour (compared to the Building Regulations for new homes, which require between 5 and 15 air changes per hour). While achieving these standards may use more energy than Passivhaus, it still represents a significant improvement over most existing homes and even new builds.

Douglas House, Kensal Rise, North West London. Douglas House includes MVHR, high levels of insulation and airtightness
Douglas House, Kensal Rise, North West London. Douglas House includes MVHR, high levels of insulation and Airtightness and Solar PVs

Guidelines and Design Considerations

EnerPHit provides a benchmark for renovators to work towards. Similar to Passivhaus, the Passivhaus Planning Package (PHPP) design tool is used when designing an EnerPHit scheme. This tool helps deliver more efficient buildings by considering factors like orientation and geometry at an early design stage. The PHPP enables informed decision-making regarding retrofit measures, cost implications, and energy considerations.

It’s important to note that retrofitting is not an easy task, and achieving the EnerPHit standard requires careful planning and execution. The thermal and airtightness strategies are likely to be more complex and challenging on site compared to new builds. Balancing the pros and cons of internal or external insulation is a critical consideration, as well as addressing potential moisture issues that may arise from changing the building fabric. Undertaking an EnerPHit retrofit demands a skilled and knowledgeable design team that can navigate these complexities.

Retrofit Measures and Certification Process

When carrying out an EnerPHit retrofit, several measures are required to meet the standard. These include:

  • High levels of insulation, either internal or external (with internal insulation requiring more attention to moisture risk)
  • High-performance triple-glazed windows and external doors
  • Careful window installation
  • Achieving an airtightness reading of 1.0, and
  • Implementing a Mechanical Ventilation with Heat Recovery (MVHR) system.

To receive EnerPHit certification, the process is similar to working towards Passivhaus certification. The project must be designed using the PHPP and certified by an accredited Passivhaus certifier. While the products used in the retrofit do not need to be Passivhaus certified, having certified products, especially for MVHR equipment, can be beneficial.

To make EnerPHit retrofits more accessible, the Passivhaus Institute has introduced the EnerPHit Retrofit Plan, a step-by-step certification process that allows payments for certification to be made in stages. This helps with funding for retrofit projects and provides a structured approach to achieving certification.

Herbert Paradise, Kensal Rise, North West London. Includes MVHR, ASHP, Airtightness, Solar PV and high levels of insulation
Herbert Paradise, Kensal Rise, North West London. Includes MVHR, ASHP, Airtightness, Solar PV and high levels of insulation

Cost Considerations

The cost of an EnerPHit retrofit can vary depending on the complexity of the existing building. As a general guideline, budgeting around £800-£1,000 per square meter for deep retrofit/EnerPHit, excluding VAT, is advisable. When considering specific components or systems, expect to pay around £10,000 for an MVHR unit installed in an average-sized house and approximately £400-£600 per square meter for windows and doors. However, the major costs lie in labor, as the installation of insulation and airtightness measures is time-consuming and requires meticulous attention to detail.

Insulation and Retrofit Challenges

One of the significant challenges faced by retrofitters is determining the optimal placement of insulation to improve the energy efficiency of existing houses. Regardless of where the insulation is placed, it is likely to create some issues. Internal wall insulation, for example, raises concerns about condensation and mold growth. When insulation is added to the inside of a wall, it can make the wall colder and disrupt the balance that previously allowed moisture to evaporate. This can lead to trapped moisture within the new wall assembly.

The Society for the Protection of Ancient Buildings (SPAB) has highlighted the issue of interstitial condensation and conducted research to better understand when and where it may occur. While specific recommendations may vary, the general advice is to avoid internal wall insulation in very exposed locations with porous external surfaces, as it can interfere with moisture management. This advice applies to buildings of any era, not just ancient ones.

Douglas House, Kensal Rise, North West London. Douglas House includes MVHR, high levels of insulation and Airtightness and Solar PVs
Douglas House, Kensal Rise, North West London. Douglas House includes MVHR, high levels of insulation and Airtightness and Solar PVs

Is EnerPHit Right for Your Home?

Considering an EnerPHit retrofit makes the most sense when you are already planning renovation or remodeling work on your house. If you are contemplating changes to your home to improve energy efficiency, EnerPHit offers a compelling opportunity. For instance, when replacing the roof or windows, it becomes easier to justify investing in high-performance materials that align with the EnerPHit standards.

While an extension project may not be the ideal time for a retrofit, it provides an excellent opportunity to create a long-term whole house plan that integrates the extension seamlessly and ensures compatibility with future retrofitting efforts. Planning for an EnerPHit retrofit from the beginning can help you achieve high levels of comfort and thermal performance in your home.

Light House, Clapham, South London. Light House includes MVHR, high levels of insulation and Airtightness and Solar PVs

Conclusion

EnerPHit represents the pinnacle of energy-efficient retrofitting, aiming to bring existing properties to levels of energy efficiency comparable to Passivhaus standards. While retrofitting poses unique challenges compared to new builds, the EnerPHit standard provides guidelines and benchmarks for achieving exceptional performance. With careful planning, skilled design teams, and a comprehensive understanding of the complexities involved, EnerPHit retrofit projects can transform existing properties into low energy and low embodied carbon homes.

By adhering to the principles of EnerPHit and working towards certification, you ensure rigorous quality assurance, airtightness performance, and adherence to the design objectives. While EnerPHit retrofit costs can vary depending on the complexity of the project and project location, the long-term benefits of improved energy efficiency, comfort, and reduced carbon emissions make it a worthwhile investment for homeowners looking to create sustainable living spaces.

So, if you’re considering renovating your home with the goal of achieving high levels of comfort and thermal performance, now is the time to plan for an EnerPHit retrofit. Embrace the challenge, work with knowledgeable professionals, and unlock the potential of your existing property to become an energy-efficient haven that aligns with your sustainability goals.

If you would like to talk through your project with the team, please do get in touch at mail@risedesignstudio.co.uk or give us a call on 020 3290 1003

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RISE Design Studio Architects company reg no: 08129708 VAT no: GB158316403 © RISE Design Studio. Trading since 2011.

RISE Design Studio stands with MPs calling for the government to reduce VAT on green home improvements

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RISE Design Studio, a small contemporary design-led architecture studio with 20 years of experience, is passionate about creating low-energy and low-embodied carbon designs. We believe in the power of sustainable architecture to combat climate change and create a better future for generations to come. That’s why we stand with MPs who are calling on the UK government to reduce VAT on green home improvements.

In an encouraging move, the UK government has announced its plan to scrap VAT on green home improvements for the next five years. Chancellor Rishi Sunak has expressed his intention to cut VAT to zero on solar panels, heat pumps, and insulation installed in British homes. While the details are yet to be clarified, including whether the VAT reduction covers installation or just materials and products, this initiative holds great potential. By making green home improvements more affordable, the reduced VAT will enable more people to enhance the energy efficiency of their homes.

Herbert Paradise, Kensal Rise, NW London. Undergoing complete transformation to become an exemplar of sustainable design for retrofitting a mid-terrace house.

The significance of this decision lies in the UK government’s legally binding commitment to reduce the country’s carbon emissions by 78% by 2035, compared to 1990 levels. This ambitious carbon reduction plan, the most progressive in the world, is a commendable step toward achieving Net Zero emissions by 2050. However, for this commitment to translate into tangible action, the government must implement measures that support and encourage green home improvements. Industry experts strongly urge the government to fulfil its promise by reducing VAT on such initiatives.

One crucial area that requires urgent attention is the high reliance on fossil fuels for heating UK homes. Astonishingly, over 90% of UK homes are heated using gas and oil, accounting for nearly 20% of the country’s carbon emissions. Surveys have shown that almost 80% of UK residents support renewable energy for electricity and heat. However, the adoption of renewable energy solutions has been slow, with only 36,000 heat pumps installed in the UK in 2020.

Red Brick House, Willesden, NW London. An extensive renovation and extension to a detached house following Passivhaus standards. The above image shows the heat pump installed at the back of the kitchen extension.
Red Brick House, Willesden, NW London. An extensive renovation and extension to a detached house following Passivhaus standards. The above image shows the heat pump installed at the back of the kitchen extension.

To meet the government’s ambitious target of achieving Net Zero by 2050, the Climate Change Committee (CCC), an independent government advisory group, recommends a significant increase in the number of heat pumps. The CCC suggests that by 2025, the UK should have 415,000 heat pumps installed annually. Although the government has committed to reaching 600,000 installations per year by 2028, this falls short of the CCC Pathway, which calls for 900,000 installations by 2028 and 1.1 million by 2030.

The high initial cost of energy-efficient home improvements remains a major barrier preventing many individuals from investing in these sustainable upgrades. By maintaining VAT at 20% on green home improvements, the government exacerbates this obstacle. It is crucial for the government to do more to reduce this financial barrier and ensure that greener heating options are accessible to all.

The Department for Business, Energy, and Industrial Strategy is preparing a new policy aimed at reducing carbon emissions from home heating in the UK, with an expected release later this week. However, according to The Guardian, ministers seem resistant to pressure from MPs, environmental experts, and the construction industry to reduce VAT on green home improvements.

It is worth noting that VAT on energy-saving improvements to existing homes increased from 5% to 20% in October 2019. At the time, HMRC cited EU tax laws as the reason for this increase. Now that the UK has left the EU, we are no longer bound by these tax laws. It is high time for the government to amend this policy and fulfill its promise to exercise control over taxes as a consequence of leaving the EU.

Interestingly, while new builds are not subject to VAT, green home improvements for existing homes are still taxed at the higher rate of 20%. This discrepancy seems illogical, as minimising the carbon footprint of existing homes is often the more sustainable option.

Regrettably, the government’s commitment to addressing the climate emergency has been marred by the withdrawal of support. In a puzzling move, the government terminated the Green Homes Grant initiative after just six months, offering little explanation. Under this scheme, homeowners could receive grants of up to £5,000 or £10,000 for energy-efficient home improvements. Consequently, the absence of this scheme leaves little government support or incentive for individuals seeking to reduce the carbon emissions of their homes. Additionally, the tax rate on burning fossil fuels for home heating remains at a mere 5%.

This lack of government support and the higher tax rate on green home improvements adds to the challenges faced by those considering transitioning from gas boilers to greener heating options like air source heat pumps. It is essential for the government to align its actions with its commitment to reducing the UK’s carbon emissions and ensuring affordable and accessible energy for all. By lowering the VAT on green home improvements, the government would demonstrate its genuine dedication to assisting individuals in making these crucial changes.

Herbert Paradise, Kensal Rise, NW London. House renovation and extension to meet EnerPHit standards, including no gas, ASHP, MVHR, additional insulation, airtightness and Solar PVs.
Herbert Paradise, Kensal Rise, NW London. House renovation and extension to meet EnerPHit standards, including no gas, ASHP, MVHR, additional insulation, airtightness and Solar PVs.

Furthermore, the government must prioritise helping people living in social and rented housing to lower their energy bills and reduce their carbon footprint. The government should ensure that policies enabling home improvements are not exclusive to homeowners but also extend to those living in social housing. The current provision of reduced VAT on energy-saving home improvements for specific benefits recipients falls short of addressing the needs of those on lower wages. Even for those who qualify for reduced VAT, affordability remains an obstacle for the majority.

NGOs such as Insulate Britain are calling on the government to implement policies that guarantee adequate insulation for all UK homes by 2030. They urge the government to prioritise insulation in social housing (including both council and housing authority-owned properties) by 2025. Without a comprehensive insulation policy, the risk of widening the poverty divide looms large, as individuals living in energy-inefficient homes face higher heating and electricity bills.

It is also worth noting that there is currently no direct incentive for private landlords to improve the carbon and energy efficiency of their properties. While tenants would benefit from lower energy bills and improved comfort, the increase in rental yield remains minimal. However, as awareness of the advantages of living in energy-efficient homes grows, this may change.

One effective approach to ensure action is for the government to enforce legal requirements regarding insulation and energy efficiency levels in homes. By doing so, the government would compel landlords to take steps toward creating a greener society. This approach would guarantee that no one is left behind on the path to sustainability.

Red Arches House, Kensal Rise. New Build House designed to Passivhaus standards

At RISE Design Studio, our mission is to collaborate with clients and improve their homes, reducing their properties’ carbon emissions, mitigating overheating issues, and enhancing energy efficiency. We possess extensive experience in designing with Passivhaus principles and can offer expert advice on low-energy home improvements. However, we believe that the government must do more to support everyone in making sustainable changes.

While reducing VAT on green home improvements is just one step in the right direction, it holds significant potential to create a greener and more sustainable world that is accessible and fair for all. Our commitment to sustainable architecture extends beyond our own projects, and we urge the government to take bold action in facilitating the transition to a low-carbon future.

To explore our portfolio of low-energy home improvements and learn more about RISE Design Studio’s work, click here. If you are interested in improving the energy efficiency of your home, feel free to contact us at 020 3290 1003. Together, let’s create a greener and more sustainable future.

If you would like to talk through your project with the team, please do get in touch at mail@risedesignstudio.co.uk or give us a call on 020 3290 1003

Contact us

RISE Design Studio Architects company reg no: 08129708 VAT no: GB158316403 © RISE Design Studio. Trading since 2011.