While energy efficient homes are gaining in popularity, many homeowners still wonder what they actually entail. Expert in the creation of high-performing, energy-efficient homes, Andy Mitchell, Managing Director at 21°, demystifies the concept. Good planning means you can secure the benefits and the best features that make these properties low energy, comfortable, healthy and sustainable.

Through practical elements like airtightness, thermal insulation, and efficient ventilation, Andy explains how energy-efficient homes are far more accessible than many people realise.

Core components of an energy-efficient home

An energy-efficient home comprises three main pillars – minimal air leakage, effective ventilation, and a thermally-efficient core building shell (wall, roof, floor, windows, and doors) and connections between them. All of these elements must work together in synergy for optimal results.

In fact, these ‘optimal results’ provide a level of health and comfort that often far exceed what most people have experienced. It’s therefore essential these components are carefully considered as a whole system, rather than being viewed in silo, to guarantee their overall effectiveness.

For example, installing thermally-efficient windows and doors is not enough to foster a comfortable indoor temperature if there is uncontrolled air movement throughout the house.


Airtightness is crucial in preventing uncontrolled air leakage, which can lead to energy loss and increased heating costs. Airtightness is often overlooked, yet accounts for approximately 30-40% of a home’s heat loss. An airtight home helps to maintain a stable indoor temperature and improves energy efficiency.

From tapes and membranes to advanced sealing solutions, airtightness products are essential for creating a well-sealed building envelope.

These solutions should also extend to products such as windows and doors – where not only the frame is well-sealed to the building, but the opening element has gaskets that ensure an airtight seal when shut. Class 4 (BS EN 12207) is the best grade of airtightness for windows and doors These products prevent air leakage which can typically account for as much as a third of a home’s heat loss.


Effective ventilation is essential for maintaining indoor air quality and comfort while also being energy-efficient. Although making our homes airtight is key to improving efficiency, some air changes are still required to stop the moisture buildup. If this is not done correctly it can lead to mould and dust mite issues, as well as the accumulation of other toxic gases such as VOCs.

Mechanical ventilation with heat recovery (MVHR) systems are engineered to provide continuous fresh air while recovering heat from exhaust air, maintaining a comfortable indoor environment and alleviating the need for additional heating, further reducing energy consumption.

MVHR systems provide optimal ventilation, ensuring properties remain fresh and healthy – without compromising on energy efficiency.

For example, in addition to providing triple-glazed windows and doors, we designed and supplied the MVHR system in a new build Passivhaus home project, utilising a Zehnder ComfoAir Q MVHR unit with rigid steel ducting.

For this project 21° worked with oak frame specialists, Oakwrights (also a NaCSBA member), to develop an MVHR system that would work alongside the encapsulation system. The client cited the quality of the products and the precise installation as being “crucial for the airtightness of the project, ultimately contributing to the Passivhaus certification”.

Thermal efficiency

The thermal efficiency of the building elements is integral to overall energy efficiency, reducing the need for artificial heating and cooling by maintaining a consistent indoor temperature. High-quality insulation materials and solutions ensure every part of the home, from walls and the roof to floors and the foundation, is well-insulated.

High-performance doors and triple-glazed windows are also an essential factor in a properly insulated property, as they’re designed to minimise heat transfer and ensure warm air stays in during the winter and out during the summer. Windows and doors should also contribute to the overall airtightness of the home, furthering energy efficiency.

A whole house retrofit in Cambridgeshire springs to mind in highlighting the role of windows and doors as part of wider thermal performance considerations. Here, our client chose inward opening windows, a lift and slide door, a fold-aside door, and two entrance doors (styles PA2 and GR1) from the GBS78 triple glazed timber range. The result was a comfortable, sustainable home that came as near as possible to Passivhaus standards.

Achieving exceptional energy efficiency with integrated solutions

At 21°, we believe that energy-efficient homes are not just for the eco-conscious few, but for everyone. By combining high-performance products with the right specifications and integration, homeowners can achieve remarkable energy savings, improved comfort, and a healthier living environment. Whether building a new property or retrofitting an existing one, solutions are available to meet the highest standards of energy efficiency and sustainability.

Energy-efficient homes are characterised by airtightness, thermally efficient building elements, and efficient ventilation, all working together to create a comfortable, healthy, and sustainable living space.

Through advanced construction techniques and technologies, energy-efficient homes are becoming more practical and accessible to all. As an industry leader, we are committed to advancing the knowledge and application of these solutions, helping to build a more sustainable future for all.


NaCSBA member SIP Build UK has scooped a prestigious award in the brand new Making Better Homes Awards, run by national builders’ merchant Jewson. The awards recognise those creating energy-efficient, safe, and comfortable homes across the UK. SIP Build UK’s commitment to sustainability ensured SIP Build UK won in the Best Building Fabric category for its self build, Munoz House.

For the winning project SIP Build UK was commissioned to create a highly insulated and airtight envelope using Structural Insulated Panels (SIPs) for a self build in Colchester. The panels minimise heat transfer and energy loss through walls, providing excellent thermal performance.

The judging panel was impressed by the use of modern methods and fabric-first approach. Judge Matthew Handley said: “This high energy efficiency build is a great example of how SIPs can add value. The fabric-first method and renewables have delivered a wonderful living space.”

Ian Still, SIP Build UK National Sales Director said: “It’s fantastic to win Jewson’s Building Better Homes Award. Working closely with the homeowner from the start helped ensure this dream Passive Haus Certified SIP home was a success. Seeing the family now enjoying the benefits of their thermally efficient SIPs home makes this project even more special.

“We are immensely proud of this project, as it shows the perfect balance between energy efficiency and aesthetics. We entered the awards to showcase our dedication to quality, efficiency and sustainability in construction. This award is not just an achievement, but a responsibility to keep providing excellent sustainable solutions.”

About SIP Build UK

SIP Build UK is a highly accredited award-winning SIP company that designs, manufactures & installs SIP superstructures. We work nationwide to exact standards and take great pride in delivering our customers fabulous homes and buildings.

Words: Duncan Hayes

Self builders interested in creating a sustainable home won’t want to miss the Passivhaus Open Days from 28-30 June. Organised by the Passivhaus Trust, the event sees homes nationwide welcoming visitors to find out more about Passivhaus.

This annual event sees owners of Passivhaus buildings around the world opening their doors to visitors to educate and inspire others about the benefits of Passivhaus design.

The Passivhaus Open Days are a unique opportunity for self-builders and professionals to find out more about how the designs work, from principles to the lived-experience and how this translates to running costs. Meeting and talking to the owners or professionals involved offers useful insight and inspiration.

Projects listed to date include new build homes and retrofit refurbishments, including a Victorian church in Northumberland, and more projects will be added over the coming weeks.

Booking for the event is essential as space is limited – find out more and book on the Passivhaus Trust website.

The Passivhaus Trust is a membership organisation bringing together expertise and professionals involved in the construction sector working to promote the adoption of Passivhaus in the UK.

Buildings contribute to 35% of total global energy consumption, and Passivhaus embraces a range of proven solutions to optimise new and existing buildings to create better energy efficiency for heating and cooling to create more comfortable living conditions.


NaCSBA member Air Craft Southern has added the innovative Heliomotion system to its suite of heating, cooling and solar solutions. Ideal for any self builder interested in improving sustainability, Heliomotion is a solar power plant for residential and commercial use, that moves to track the position of the sun, thereby maximising efficiency.


Easily installed by DIYers, once in place the configuration follows the sun in two-axes, which means the solar panels can deliver between 30-60% more energy annually, in comparison to a conventional roof-mounted system.

It uses GPS to calculate the sun’s location from its position to maximise the energy produced from solar power. This can be used to power the home, or stored in batteries for later use.


Not every roof is suitable for solar, and Heliomotion is a great solution for those with sufficient outdoor space for this clever alternative to solar generation. 

Produced by Bee Solar Tech, tracking systems can increase productivity, meaning that you can secure the same energy output with few panels than a fixed system. Heliomotion won Best Sustainable Technology or Product category in the 2022 Build It Awards

NaCSBA member Beattie Passive is running a pair of free Passive Haus training events in October to support anyone considering adopting a passive methodology for their new build or retrofit project. One event is curated with self builders in mind and the other is designed to support professionals working in the sector.

Offsite modular specialist Beattie Passive, a member of the Passivhaus Trust, the Association for Environment Conscious Building (AECB) and the Good Homes Alliance, is holding the Passivhaus events at its offsite factory in Norwich.

The sessions offer attendees an insight into the principles of Passivhaus and how the standard can be applied to deliver energy efficient, net zero homes.

The sessions also include a guided tour of Beattie Passive’s 100,000 sq ft housebuilding factory.


Wednesday 11th October, 10am-12pm, Beattie Passive’s factory at Unit 1, Carrow Works, Norwich, NR1 2DD

This event has been specifically designed for self-builders that are interested in the energy and carbon-saving benefits of Passivhaus.

Attendance is free, but space is strictly limited, so register early to avoid disappointment.


Beattie Passive also has a second event for professionals interested in learning more about passive approaches to building:


17th of October, 10am-12pm, at Beattie Passive’s factory at Unit 1, Carrow Works, Norwich, NR1 2DD

This session is designed for local authorities, housing providers, policy makers, architects, builders, developers, and anyone else with an interest in building new net zero homes to Passivhaus standard (or retrofitting their existing housing stock to EnerPHit standard).


Ron Beattie, founder and managing director of Beattie Passive, said: “These events are part of our mission to promote sustainable building practices. Passivhaus has become synonymous with energy efficiency, and for good reason – a Passivhaus needs as little as 10% of the energy required by a conventional UK home – but we shouldn’t overlook the other benefits, such as thermal comfort, noise reduction and air quality.”

“Passivhaus is a panacea for many of the challenges facing the housebuilding sector – it can put an end to fuel poverty, raise living standards and eliminate damp and mould. At our net zero event, we’ll be paying particular attention to the environmental benefits of Passivhaus, and the role the standard plays in the delivery of net zero homes and retrofit projects.”

The Building Performance Network (BPN) has published three free modules to support a range of stakeholders, including self builders, to help them get sustainability right. The guides are designed to support stakeholders to understand the gap between planned energy performance and the actual reality of living in the home.

At NaCSBA we know self builders often become semi-professional in the level of knowledge they develop as they pursue their own build. As such, while these guides won’t be relevant for all, there will be many self builders researching sustainability who will find them insightful as they work to create an energy home that performs as well as promised.

What is Building Performance Evaluation (BPE)?

BPE refers to the performance of a home and its systems. Understanding  around this area can be complicated, drawing on various data sources, but is necessary to support the emergence of more homes better able to reduce their carbon footprint.

The Building Performance Evaluation modules:

The guides , the first three of five, will support your understanding of what it’s like living in buildings where sustainability has been factored in, in comparison to their predicted performance. This in turn will help you when it comes to making decisions about fabric and systems for your own build, helping you to cut through the greenwash.

The new guides are available at the BPN’s Resource Hub, which is sponsored by Ecology Building Society, and are designed to be entry level for those who are new to BPE and want to understand how to avoid building inefficient homes.


Mechanical Ventilation and Heat Recovery (MVHR) systems are a big ticket item that work very well in a self and custom build. This is because they can be designed in at the very earliest stages of your project, to work in conjunction with your building’s fabric.

But what do you need to understand about MVHR to ensure that it’s the right choice for you? NaCSBA member Airflow shared some of its experience with the Self Build Portal, to help you decide if investing in MVHR is the right choice for you.


Our changing climate means that homes in the UK need to not only provide heating requirements but also need to stand up to extreme heat for prolonged periods of time. 

MVHR offers your the opportunity to control your internal environment, especially when combined with a fabric-first approach to building. This is because it needs an airtight building envelope to work efficiently, so how you build is as important as the MVHR system itself. 

Efficient energy usage

The heat recovery element of MVHR is an extremely energy efficient process, as no heat is lost, so reducing demand. Conversely, in Summer, many systems bypass this exchange process, to bring cool fresh air in from outside and allowing internal heat to be expelled. Be sure to ask when specifying if your system has an automatic bypass, or partial bypass for Spring and Autumn. 

Used well this allows some degree of cooling, especially as the MVHR system will remove humid air, which can in itself make you feel warmer. Removing excess humidity is also important to reduce mould build up. 


Airflow MVHR function image

How does MVHR work?

Heat recovery captures and retains heat that would otherwise be lost as it leaves the building. MVHR removes the heat from stale air as it is extracted from the building. This is passed through a heat exchanger that transfers the heat from the outgoing air to fresh air entering the building. Incoming air is filtered to remove impurities, such as allergens, heated and then distributed around the building.

This requires good levels of airtightness in your build envelope to prevent air leakage, as well as ducting and the actual unit where the exchange takes place. MVHR does away with stand alone extraction systems, such as hob and bathrooms extractors. 

Air conditioning or MVHR?

In regards to cooling Airflow has some useful insight on comparing the two systems. 

Primarily, air conditioning will cool more powerfully, but it does this by recirculating the stale air that is already in the room. 

Whereas air conditioning is reliant on a unit per room, with associated running costs and local noise, MVHR is a whole house system. This means there is one piece of plant, in the loft or plant room, and ducts in individual rooms, rather than entire units. 

As well as fresher air and a quieter system, this can result in lower energy usage, but check if this translates into lower running costs. 

MVHR is better at maintaining a constant temperature using fresh air, but is more reliant on external air temperatures to secure this. Therefore regulating the temperature early in the day will result in a cooler building. 

A more powerful MVHR system can move larger volumes of air which can help with cooling, so again, speak to your specifier about your expectations for the system.

When to find out more

MVHR needs to considered early on in your plans, and needs to work in harmony with your build model. If you are considering it speak to system manufacturers/installers and do your research in advance.

This can be from neutral sources, such as magazines, as well as supplier websites (although be aware they are promoting MVHR). The Passivhaus Trust and Green Building Store are also good sources of information, and the NSBRC runs several courses on heat and energy. 

If you decide it is for you, ensure that your architect and package manufacturer are planning for it from the get go, and that any follow on trades are aware of the need for airtightness. This needs a ‘fabric first’, whole house approach, and this might affect window orientation and shading and solar gain. For example, trickle vents on windows should be avoided, as they will reduce the airtightness. 

Images: Airflow

Member update – find other members offering MVHR in the Directory

When planning a project self builders should adopt a fabric first approach to the construction. Zero carbon homes are at the top of the government agenda, and combined with the energy crisis it’s never been so relevant to build with energy efficient materials.

Fabric first refers to the building fabric that creates the envelope of your built home, including the materials used to create the frames, structure and insulation, and specifically in relation to heat retention.

Choosing high performance materials, such as Structural Insulated Panels (‘SIPs’) means you are building with energy efficiency from the start. All other decision, such as heating and cooling systems, start from this fabric first approach.

A fabric first approach should consider:

  • High-quality insulation
  • Increased air-tightness
  • Thermal bridging issues
  • Solar gain and
  • Natural ventilation for cooling

Specialists SIPS@Clays, which designs, fabricates and installs the Kingspan TEK® SIPs Building System, shared their insight with the Self Build Portal as to how this approach can make all the difference to the final home, with the example of building with SIPs

Ian Clay of SIPS@Clays explains that as one of the most sustainable methods of construction available, the popularity of SIPs is soaring for environmentally conscious self builders.

These high performance panels are made up of sandwiches of boards bonded together with insulation, with different configurations and thicknesses available for different applications and performance.

The structure can be finished to look like a conventional build, clad in timber, brick slips or render, depending on the customer’s design (as shown in this SIPS@Clay home, clad in sheet metal and burnt larch teamed with render).

The advantage of SIPs is that, because they are structural, they can be used to build the floors, walls and roof. Plus, they have the the added benefit of not needing roof trusses, which maximises usable loft space. 


“There are so many benefits of building with SIPs including speed of build, increased living space, flexibility of design, predictable build programme and exceptional versatility. However, amongst the most important are the thermal efficiencies, low energy living and green construction credentials the system provides. This is why SIPs lend themselves so well to the fabric first approach.

“The ‘built in’ thermal properties of SIPs and reduced thermal bridging, the low U-values and the increased airtightness that the system offers, can reduce the amount of energy used to heat or cool a room by up to 50%.

“In most cases it removes the need for additional technologies or conventional heating entirely, relying on the natural efficiency of the fabric of the building. Of course, additional sources of heating or cooling can be included if desired.”

“Add into this, the off-site manufacturing, minimal waste and low environmental impact, SIPs are the perfect construction solution for all self-build projects, including those being built to achieve Passivhaus accreditation.

So, if you’re at the start of your self-build journey and want to build a low or zero carbon home, ensure you adopt a ‘fabric first’ approach from the outset.

Member update: SIPS@Clays

For more on the Fabric First approach, check out Homebuilding & Renovating magazine and Build It magazine’s features on the subject. Or visit out Build Methods section. 

New research from The Eco Experts finds that solar panels have moved from an eyesore to an asset in people’s perceptions. The research will be welcomed by self builders debating the merits of solar and their visual impact on potential future resale value.

NaCSBA knows that self builders stay in their projects for far longer than average home owners, but eventually move on, often due to personal circumstances, such as downsizing, or to embark on another self build project. So it is reassuring to know that eco-measures that individual’s invest in could well add curb appeal to a project when the time comes to sell.

The Eco Experts’ National Homes Energy Survey found that over two thirds of people (69%) in the UK would be ‘likely’ or ‘very likely’ to buy a property if it had a solar panel array. This figure is is up from 65% figure from 2022, possibly reflecting a changing mindset as a result of the ongoing energy crisis.

Undoubtedly, the energy crisis has many people reassessing green and micro-renewable technology, and considering the costs in terms of including them in their own project, both in terms of installation and payback. 

The US online property portal Zillow reported that, in the USA, installing solar panels on your property could increase its value by around 4.1%. This fact could help self builders make the decision of whether or not to invest in such technology.

Self builders have traditionally been the pioneers for new products in these markets, with many of the leading suppliers working with owners of one-off projects that pave the way for uptake by the wider housing market. 

Charlie Clissitt, Editor of theecoexperts.co.uk commented: “It’s magnificent to see solar panels swing from neighbourhood eyesore to a property desirable. The energy crisis has had a big part to play in this, but solar panels have also come a long way aesthetically.”

Find suppliers for your project.

Anyone debating whether to self build or retrofit an existing building to improve energy efficiency will be interested to read that new research has found that ‘greening’ up an existing building requires a far larger investment than previously thought.

The University of Nottingham findings show that retrofitting your home to the highest levels of energy efficiency costs significantly more than the government’s expected average £30,000, with a typical home costing around £68,000.

The research has created a retrofitting roadmap for the decarbonisation of the city’s housing stock, which reflects a major national issue, as 80% of the buildings that will form our future housing stock have already been built. Many of these date from before the 1990s, when Building Regulations had comparatively low targets for energy efficiency.

The Government put up £350,000 to support the “Nottingham Carbon Neutral Housing: Cost vs Carbon Retrofit Roadmap” retrofitting project to address the fact that 22% of our greenhouse gas emissions come from residential buildings, according to the London Energy Transformation Initiative.

Professor Lucelia Rodrigues, project lead and Professor of Sustainable and Resilient Cities at the University of Nottingham said that, “for most homes, it is both more cost- and carbon-effective to first improve the building’s fabric before electrifying heating.”

This fabric-first approach is an essential tenet for all self builds as well, as the effectiveness of any energy efficiency measures or micro-generation is dependent on this principle.

Register for Nottingham Retrofit Roadmap Guidance, once published


Image credit: Image by MVOprp from Pixabay