Frequently Asked Questions about our natural insulations, this page contains answers to commonly-asked questions about our products.


Continuously rising energy prices are forcing society to make serious considerations towards long term home improvements. During the past decade, energy prices have risen by almost 30% and are set to increase by up to an additional 50% before 2030.

Insulating a building is the first step towards reducing energy consumption, improving thermal efficiency and cutting energy costs. By insulating the loft space of a typical house this can reduce energy bills by 25%.

Why should I choose natural fibre insulations over mineral wool?
Natural fibre insulations can offer a number of unique benefits in addition to being an excellent thermal insulator. These benefits include:
  • Moisture control
  • Absorption of noxious gases
  • Improved breathability
  • Durability
  • Sustainable
  • Biodegradable
What is the difference between Black Mountain natural insulations and other brands?
Black Mountain maximises the amount of natural fibre in the product – using up to 95%. This is higher than many competing products that use plastic fillers to reduce manufacturing costs. Black Mountain is the only company in the UK with its own dedicated factory, which ensures that we have excellent quality control measures. We also have short lead times and the ability to produce bespoke sizes on request.
What are the lead times on your products?
Black Mountain can normally deliver within 48 hours of ordering if required. However, standard shipping is generally 3-4 working days within the UK and for overseas orders, please allow 5-7 working days.
Where can I buy your products?
Black Mountain insulations are available throughout the UK, Europe and the USA. We have a number of stockists and retailers nationwide. Please contact us for further information about your nearest stockist Tel (UK): +44(0)1745 361911


I have heard that there were some issues with the moth resistance of some sheep wool insulation?
We understand the treatment used by a competitor during the period 2001 - 2005, although well meaning, was not totally effective. To reassure you, this method was never used by other European manufacturers, including Black Mountain. Our wool is thoroughly washed before it arrives at our factory and is treated to protect against moths for the life of the product and perform to the same standard as modern carpets and other textiles. Black Mountain has never had a complaint regarding product quality, including moth infestation – a record that we are proud to maintain.
What is the thermal performance of natural insulations in comparison to mineral wool?
Natural insulations have an excellent thermal resistance and comparatively achieve the same conductivity with approximately 10% less material required.
How do natural insulations buffer moisture?
Natural fibre insulations can absorb a significant amount of its weight in moisture without any deterioration in thermal performance. Natural fibres are able to buffer moisture by absorbing water molecules into the core of the fibre and storing them until moisture levels in the external environment decline. Hence they can help prevent the onset of condensation. Comparatively, man-made mineral fibre insulations are far less capable of managing condensation. Subsequently, exposure to even a small level of moisture can dramatically impact thermal performance. My son suffers from asthma how can you assure me that natural insulations really improve indoor air quality? Reducing spikes in condensation helps to reduce the probability of a building developing damp problems and mould growth. Wool fibres are also unique in their ability to permanently absorb and break down a range of harmful volatile organic compounds emitted from some commonly used building products. The amino acids in wool react and create a bond with these harmful compounds and prevent them from being re-released back into the internal environment.


I have a century-old home - what product would you recommend?
Natural fibre insulations are excellent for use in traditional and period properties for a number of reasons. Older properties will not necessarily measure to standard dimensions and it is common to find a varying range of joist or rafter widths within the same property. Black Mountain products are incredibly versatile and easy to cut and shape as required. For larger projects, bespoke products are an alternative solution to an unconventional building. Elevated moisture levels are a common occurrence in traditional buildings. Black Mountain natural insulations absorb excess internal humidity to protect against damp and mould without damaging the often delicate fabrics of the building.
Can I use black mountain insulations to insulate my floor?
If the floor is timber then yes – if there is a crawl space or cellar below the floor ensure that wire mesh, breathable membrane or plastic netting is put in place to hold the insulation in place. To install from above simply remove floor boards or panels and use a breathable membrane or netting to create a trough for the insulation.
Should I leave a ventilation gap when insulating a loft space?
When insulating loft space it is important to assess where the insulation is required. For attic conversions, insulating the rafters may require a semi-rigid insulation to prevent slumping. However, sheep wool insulation can be stapled to the rafters to maintain its original position. It is important to be aware when insulating a warm loft, the type of roofing felt present; ‘breathable membrane’ and older bitumen based ‘non-breathable membrane’. The key difference between a breathable membrane and the older bitumen membrane is the 50mm ventilation gap required for non-breathable membranes.
How would you install insulation into an unused loft?
In order to avoid energy escaping into unused loft space, it is recommended that insulation is applied between the joists on the floor of the loft. The first layer of insulation should fit snugly between the joists to avoid gaps from occurring. Additional layers should be fitted at 90-degree angles to the previous layer to avoid thermal bridging through the joists. Rolls are particularly easy to install between joists and can save a significant amount of time to apply.
Are natural insulations suitable for cavity walls?
It is not recommended to install natural insulation into brick and block cavity due to the possibility of running water from driven rain. For this situation, we would recommend an inert material.
Can I use natural insulations on the inside of a solid stone wall?
A solid stone or brick wall may be susceptible to damp or driven rain. It is recommended that a stud wall is constructed with a ventilation gap between the solid wall and the stud partition.
Should I remove any insulation already present?
Black Mountain Insulation can be placed over any existing material unless it is badly damaged or covered in debris. Some man-made insulation materials can be time consuming and unpleasant to remove and we would, therefore, advise against doing so unless it is necessary.
What thickness should I use to insulate?
Please refer to our individual product data sheets available on our website.


What sizes are Black Mountain products available in?
We manufacture a range of natural insulation products with various thicknesses and widths and lengths. Please see our individual product data sheets on our website. However if you cannot find what you are looking for please contact us to discuss your special requirements.
How long should I allow for the insulation to reach full thickness after installation?
Black Mountain compress pack their products to lower costs and ‘carbon miles’ – however both wool and hemp fibres are very resilient. Within 72 hours Black Mountain insulations will regain their original thickness.
How long will natural insulations last for?
Natural fibres have an incredible resilience and durability that enables them to maintain their thermal performance throughout the life span of a typical building.
Why does the colour of sheep wool insulation change in different batches?
The colour of sheep wool insulation varies occasionally depending on the breed of sheep and type of wool available at the time. All wool will perform to the same technical standard despite any alteration in colour.
Can I use the off cut pieces of insulation?
Off cuts are ideal for ensuring that all corner spaces are covered and no gaps are present to maximise thermal performance.
How easy are natural insulations to cut and shape to size?
Black Mountain sheep wool insulation is incredibly easy to tear accurately across the width of the roll or the batt, to cut down the length compress between planks of wood and use a sharp knife or a pair of material scissors. It is often easier to tear more pieces of material across the width to fill a narrow gap rather than cut a total length.
Does your sheep wool insulation have a distinctive smell?
Black Mountain sheep wool insulation is similar to the smell you get when installing a new carpet. Most customers do not notice a smell at all but where it is noticeable, the smell will usually pass within 3 days and is not unpleasant.


Why is black mountain NatuWool more sustainable compared some man-made products?
The wool used in NatuWool insulation is coloured wool that is not required by other industries such as the textile industry and would have otherwise been disposed of. The energy used in our factory is very low - 90% lower than some man-made products. Whilst the product will last many years if properly maintained, disposed at the end of its life allows it to biodegrade rather than occupying scarce landfill resource.
Can I buy products that fail to meet your quality standards at a discounted price?
We reprocess all rejected product internally hence we don’t have any scrap products to dispose of. We do believe this is fundamental to the achievement of truly sustainable products.
What is carbon sequestration I have read about concerning natural products?
As plants grow they absorb carbon dioxide and then emit the oxygen molecule and lock up the carbon molecule in the cell structure of the plant. This is also true for the wool fibre which locks two kg of carbon dioxide per one kg of wool. The carbon dioxide is locked up for the life of the product, whereas man-made are emitters of carbon dioxide in their production with no ability to lock up carbon dioxide. Many manufacturers only refer to the energy saved during the life of the product and state this is far greater than the energy used in the manufacture. However true sustainable products are low carbon in their manufacture and also have sequestered carbon dioxide.

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