Can Thermafleece Keep my Home Warm?

Insulation, Membranes & Felts
Can Thermafleece Keep my Home Warm?

Thermafleece among other natural insulation is quickly rising in popularity, able to keep your home warm whilst also being friendly to the environment. 


The history of insulation is a long one, full of discovery and innovation. Whilst you could argue insulation goes back as far as the mud our ancestors would spread on the outside of their huts what we could consider ‘modern insulation’ only came into effect in the late 19th century.

Using asbestos builders protected homes from the heat loss that plagued us during the colder months. Being resistant to water, electricity and chemical damage it was seen as the perfect material for the job – this was, of course, before we discovered it was toxic to work with. Banned in the 1970s, asbestos gave way to the popularisation of cellulose insulation and then fibreglass, rockwall and the topic of conversation here, natural insulation.


Who are Thermafleece?

The UK’s first British Sheep’s Wool insulation manufacturer, Thermafleece has been warming up homes for over two decades. Now a leading brand of natural and sustainable solutions, Thermafleece have made great innovations including SupaSoft, insulation made from recycled plastic bottles.

Thermafleece’s commitment to sustainability comes through each and every product out of their doors as does their dedication to quality and performance. At its core, natural insulation is a solution meant to last, and with a Thermafleece label, you can rest assured it will. Maintaining its low heat conductivity properties across decades.

Why Use Natural Insulation?

It should be no surprise, given the discovery of asbestos’s danger and its subsequent banning that safety became the number one concern for its replacement. Whilst man-made materials still dominated much of the market in the coming years, growing environmental concerns made many visionaries look back at our history. 

They found that, when it came to keeping warm at least, the Romans, Greeks and Vikings had it right. Though they may not have realised it, using natural-forming materials remains one of the best ways to keep our planet cool. 

Unlike foils and boards, natural materials like cork or sheep’s wool have far lower embodied carbon, meaning fewer emissions in their manufacturing processes. Naturally forming in the first place, most of these materials can also be recycled or composted to save them from the landfill.

Natural vs Man Made Insulation: Thermal Performance

Direct comparison between Hemp and Sheep’s Wool to PIR Boards and the like is a bit tricky without bringing specific brands into the mix. So, let’s do that. Celotex, a staple of the insulation industry for years now offer a High Performing PIR Insulation with a thermal conductivity of 0.022 W/mK.

Thermal conductivity is a measure of a material's ability to conduct heat. In other words, how quickly or slowly heat moves through the material. W/mK stands for Watts per Meter Kelvin, sometimes known as the k-value. The lower this value, the slower the heat transfer and the better the insulation. Simple right?

We can compare this 0.022 W/mK then with Thermafleece’s flagship CosyWool which has a thermal conductivity of 0.039 W/mK. What does this tell us? Well, it means that the PIR boards are quite a bit better at preventing heat loss. Perhaps not the news you were looking for, but that isn’t the whole story.

Yes. In this specific case, manmade insulation outperforms natural, but this fails to take into account one key factor. Practical application. Buidling regulations in the UK are very clear about how well-performing your insulation should be and to do that, they don’t measure an individual material's k-value but rather the total heat transfer of all the materials – including your roof, timber and any pre-existing insulation. This is known as the u-value and can be met with Sheep’s wool just as easily as it could with boards and foils. 

Domestic New Builds, England (L1A). All thermal values W/m²k

What this means is that depending on your specific needs, natural insulation can be just as high performing in situ as anything man-made. What’s important is consulting with a professional to find out for sure. Which is exactly what the owners of the properties in the case studies below did.

To learn more about natural insulation, including the different types available to choose from, check out our detailed guide here.

Case Studies

Insulation Fit for a King

Place: Edinburgh Castle Palace Block

Insulation: Sheep’s wool insulation slabs

As you can imagine a castle is not a cheap place to heat. Not only are they known for being draughty, but the castle's age alone meant that it was haemorrhaging heat only on a daily basis to the tune of £400,000 a year. Clearly it needed a retrofit but boards and foils were simply not up to the job.

Again because of the age of the castle, the insulation used needed to be able to handle fluctuating humidity levels to avoid issues with dampness and condensation. Add to this that all the building's service areas ran through the loft, meaning that the insulation had to be non-toxic to the maintenance staff, and natural insulation become one of the only answers.

The next problem was the limited space available. The area being retrofitted was just below what was being used for offices, meaning the depth available was extremely limited. Able to handle the humidity, non-toxic and able to offer superb performance in limited space, Thermafleece was the obvious choice. 

And, as it turned out, the best one. Once all was said and done the palace block’s carbon footprint was cut by 18% with energy savings of around £110,000 every year since.

Reaching the Modern Standard

Place: St Albans Church, Acton Green

Insulation: NatraHemp

For most historical buildings, including St Albans Church, a lack of insulation makes them almost uninhabitable. To preserve these stunning buildings and keep their space ready for community use, proper insulation is key.

In the case of St Albans, this meant creating a cold roof to improve the u-value and using Thermafleece’s NatraHemp as a dual-action defence. Slowing heat transference whilst still allowing for air to move into the space above, ventilate the loft and prevent condensation.

Cold roofs are a type of construction that allows insulation to sit directly atop a plasterboard ceiling. This is opposed to a warm roof, where the insulation is installed between the roof’s rafters.

The church had stood derelict for 8 years prior to this and came close to being converted into a block of flats. By using natural insulation, it was able to be preserved. Remaining a communal space for dances, receptions, theatre rehearsals and, of course, worship.

Protecting Our History

Place: The Bodleian Library

Insulation: Sheep’s wool insulation slabs

A roof springing a leak is always a hassle. A hassle to find, a hassle to live with and, more often than not, a hassle to get fixed. However, very rarely will leaks in our homes run the risk of destroying century-old historical texts. 

It was precisely to avoid this that The Bodleian Library, home to over 8 million books and manuscripts, was recently re-roofed to keep it protected for another 150 years. Part of this project was fitting new insulation above the south wing which housed a principal reading room still used 400 years after it was opened in 1602.

Thermafleece was not only a phenomenal choice from a practical point of view – being breathable and high-performing – but also blended in well with the historic fabric of the building. This insulation now covers 500m² of roof, keeping scholars, students and guests comfortable whilst they peruse the books.

Breathable materials allow moisture to pass through them whilst stopping heat. This helps to avoid the moisture getting trapped which can lead to condensation and then damp and then rot – problems that older buildings are particularly susceptible to.

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