Why Use Natural Insulation in Your New Build Home, Extension or Refurb project?
Sheeps wool - A fantastic sustainable and natural insulator
At Fen Studio, we believe that our homes should be as comfortable and sustainable as they are beautiful. One of the most effective ways to achieve this is by using natural insulation materials throughout your new-build, extension, or renovation. These materials are not only environmentally responsible — they also help regulate indoor temperature, manage moisture, and create healthier, more enjoyable spaces to live in. Here are our top reasons why natural insulation is the smart choice for any building project, big or small.
Natural insulaton examples.
Top row (left to right) - Sheeps-Wool, Wood-Fibre, Recycled Denim
Bottom row (left to right) - Cork, Straw, Hempcrete
1. Low Carbon and Sustainable
Natural insulation materials — such as sheep’s wool, wood fibre, hempcrete, cork and straw — are made from rapidly renewable resources that regenerate with minimal environmental impact. Unlike synthetic insulations, they require far less processing, produce significantly lower embodied carbon, and are biodegradable at the end of their lives.
Many of these materials also sequester carbon during their growth — meaning they actually help to offset emissions rather than add to them. This makes natural insulation a genuinely sustainable choice for any project focused on reducing environmental impact.
2. Keeping You Warm in Winter
Natural insulation materials don’t just help regulate summer heat — they also excel at keeping warmth in during the colder months. Products like sheep’s wool, wood fibre, hempcrete, and straw bale have excellent thermal resistance, meaning they trap heat inside your home, keeping it warm and comfortable with less reliance on heating systems.
Unlike some synthetic insulations that can create cold bridging or condensation issues, natural materials are vapour-open, helping your home to “breathe” without losing heat. This results in a more stable, cosy indoor climate, even in the depths of winter — and can lead to significant energy savings over time.
3. Keeping You Cool in Summer
Natural insulating materials such as wood fibre and sheep’s wool inherently have the added benefit of thermal mass — meaning they can absorb heat during the day and release it gradually when temperatures drop at night. This passive regulation helps to prevent sharp indoor temperature spikes, particularly in summer. Rather than letting your home heat up quickly in a hot spell, wood fibre slows the transfer of heat, keeping the interior cooler for longer and making the space more comfortable — even during a heatwave.
This doesn’t mean your house heats up at night though, as lower indoor and outdoor air temperatures, in combination with night-time ventilation (opening windows), allow the stored heat to be released and carried away.
In contrast, conventional synthetic insulation boards — such as Celotex (PIR) — have very high insulation values but virtually no thermal mass. This means while they reduce heat loss in winter, they don’t absorb or buffer internal heat gains in summer. As a result, they can actually contribute to overheating in well-sealed modern homes, where solar gain and internal heat build-up have nowhere to be stored, resulting in very hot and uncomfortable spaces — a common issue with modern housing using thin synthetic insulators.
For low-energy buildings aiming to stay cool in summer as well as warm in winter, natural materials like wood fibre provide a more balanced and comfortable indoor environment year-round.
4. Healthier Indoor Air Quality
Natural insulation materials are non-toxic, unlike their synthetic counterparts which have the potential to off-gas volatile organic compounds (VOCs), particularly when newly installed. These aren’t always detectable by smell, but can still contribute to poor indoor air quality and discomfort — especially for people with sensitivities. Natural insulators therefore only contribute positively to indoor air quality and introduce no harmful chemicals.
5. Moisture Management and Damp Prevention
One of the key advantages of natural insulation materials is their ability to manage moisture effectively. Materials like wood fibre and sheep’s wool are vapour-open, meaning they can absorb and release moisture without losing their insulating performance or breaking down over time.
In contrast, synthetic insulation boards such as PIR or EPS are vapour-closed — so if any moisture does get in (for example, from a leak or condensation), it can become trapped, leading to mould growth, material degradation, or even structural damage.
Natural insulations help buffer humidity, reduce condensation risk, and support a healthier building fabric — especially important in the UK’s damp climate. They’re particularly well-suited to breathable construction systems, where airtightness is paired with moisture permeability to the outside to create robust, comfortable homes and spaces.
6. Performance and Cost-Effectiveness
Although some renewable materials may have higher initial costs than cheaper synthetics, they often pay off in the long term. Construction using only rigid synthetic insulators has the potential to cause thermal bridging issues, due to unavoidable gaps between the insulation boards and building structure — especially in timber frame construction. This also means that the impressive U-values advertised by synthetic rigid insulators are rarely achieved in real-world scenarios, and can result in a leaky building fabric, causing energy loss, condensation issues, and ultimately damp.
Flexible insulation, like sheep’s wool or flexible wood fibre, on the other hand, ensures a snug fit between timber studs. Combined with an external rigid wood fibre board over the studs, this approach prevents thermal bridges — and can often outperform synthetic insulators in real-world conditions.
Their energy efficiency and low maintenance requirements can therefore save homeowners significant money over both the short and long term.
7. A More Natural, Calming Living Environment
Being surrounded by natural materials doesn’t just benefit the performance of your home — it can also have a profound effect on how it feels to live in a space made from them. There’s a comfort in knowing that the materials around you come from nature, not petrochemicals.
Natural materials are typically non-toxic, low-emission, and allow a space to breathe — helping to create a more grounded, healthy, and psychologically restful environment. Whether it’s the scent of timber, the softness of wool, or the warmth of natural surfaces, these materials can subtly improve how you experience your home every day.
8. Supporting Nature and Shaping a Better Industry
Choosing natural insulation materials like straw, hemp, or wool supports sustainable agriculture and rural economies, while also encouraging biodiversity through the cultivation of renewable crops. But it goes further than that — by specifying natural materials, you’re also making a statement about your values.
This kind of decision helps shift the wider construction industry towards healthier, more sustainable practices, promoting low-impact building and reconnecting architecture with the natural world.
Case Study: Hereford House - New Build Passive House
Hereward House - A Passive House in construction in Aldreth, Cambridgeshire
At Fen Studio, we don’t just talk about sustainability — we put it into practice. A prime example is our Hereford House Passive House project in Aldreth, Cambridgeshire, which is currently under construction. This bespoke new-build home is designed with natural materials at its core and features a suite of renewable energy systems, delivering a healthy, breathable building that also provides ultra-low energy living.
Flexible and rigid wood fibre insulation. (Flexible fitted inbetween the timber studs, and rigid fixed externally)
Pavaflex wood fibre inbetween wall studs at Herward House
The Vision:
Hereford House has been carefully designed to reflect the values of its eco-conscious owners — prioritising sustainability without compromising on style, comfort, or functionality. Every material has been chosen not just for its environmental performance, but for its visual quality and contribution to the overall design language of the home.
The architecture draws clear reference from the surrounding rural and agricultural setting, taking cues from traditional barn forms, pitched roofs, and robust, honest materials. The use of natural timber cladding and Greencoat steel roofing creates a palette that feels grounded and familiar — echoing the language of nearby farm buildings while delivering a crisp, contemporary interpretation.
This project stands as a strong example of how natural materials and thoughtful design can come together to create a home that is practical, durable, and deeply connected to its landscape.
Key Features of the Project:
Sustainably Sourced Timber and Steel Roofing
The structural frame and cladding are constructed from FSC-certified timber, chosen for its strength, beauty, and low environmental impact. The roof is finished in Greencoat steel, a durable, recyclable product made with Swedish steel and a bio-based coating derived from rapeseed oil — offering excellent longevity and reduced embodied carbon.
Wood Fibre Insulation
We’ve used a mix of flexible and rigid wood fibre insulation throughout the building envelope. As detailed above, It offers excellent thermal performance and breathability, helping to regulate heat and moisture and keep the home comfortable all year round.
Mechanical Ventilation with Heat Recovery (MVHR)
A whole-house MVHR system provides continuous fresh air while recovering heat from outgoing air. This improves indoor air quality and dramatically reduces heat loss — ideal for a well-sealed, low-energy home.
Ground Source Heat Pump
Heating and hot water are supplied by a highly efficient ground source heat pump, which extracts renewable energy from the earth and delivers it with minimal running costs and zero on-site emissions.
Photovoltaic (PV) Array
A PV system helps offset the home’s electrical demand, contributing to long-term energy savings and pushing the house towards net-zero operational carbon.
FAQs:
1. Are natural insulation materials harder to build with than traditional options?
Not at all — they just require a bit of know-how. Natural insulations like wood fibre, sheeps wool, and hempcrete often involve different installation techniques compared to conventional boards or rolls, especially when it comes to airtightness and breathability.
The good news is that most manufacturers now offer detailed guidance, and many suppliers provide training or resources for contractors. Once understood, these materials are straightforward to work with — and often much more pleasant to handle on site, with no harsh chemicals or itchy fibres to worry about.
2. Are natural insulation materials more expensive than traditional materials?
They can be slightly more expensive upfront — but that’s changing. As demand grows and more stockists begin to supply natural insulation, costs are becoming increasingly comparable to conventional options. While the price per m² may still be higher in some cases, natural insulations offer added value in terms of thermal comfort, breathability, and indoor air quality. Over time, they can lead to lower energy use and create a more comfortable, healthy home — making them a smart long-term investment.
3. How durable are natural insulation materials compared to conventional options?
Very durable — especially when correctly detailed and installed. Materials like wood fibre are resilient, long-lasting, and resistant to settling over time. Sheeps wool, when treated naturally (e.g. with borax), is also pest-resistant and fire-safe. Many natural materials can match or exceed the lifespan of their synthetic counterparts.
4. Can natural insulation materials be used in all types of buildings?
Yes — they’re incredibly versatile. Natural insulation can be used in everything from traditional renovations to modern new-builds and even Passivhaus-level performance. The key is to design with moisture and breathability in mind and to work with people who understand how these systems perform.
5. Are natural insulation materials suitable for the UK climate?
Absolutely. Natural insulations are ideal for the UK’s often damp and changeable weather. They’re vapour-open, helping buildings regulate moisture and reduce condensation risks. Their ability to buffer humidity and heat also makes them a smart choice for maintaining comfort year-round.
Want to know more, or would like to discuss a project?
If you’re inspired to explore renewable materials for your own new-build or renovation project, we’d love to help. Contact us to discuss how we can bring your vision to life while also prioritising sustainability, health and quality.