Tips & FAQ
What does the ‘K’ value or Thermal Conductivity mean?
‘K’ is the ability of a material to allow heat to pass through it. The lower the ‘K’ value the less heat will pass through the material.
What is the K Value or Thermal Conductivity of Thermafleece?
Thermafleece has a K value of 0.039W/m.K.
What does ‘R’ value or Thermal Resistance mean?
‘R’ is the ability of a material to prevent heat passing through it and is dependent on the ‘K’ value and the thickness of the material. The higher the ‘R’ value, the less heat can pass through the material.
What does ‘U’ value mean – how is it calculated?
The ‘U’ value is the thermal transmittance of a material. This is the amount of heat that will be lost per square metre at a given temperature difference between inside and outside a building. It is calculated as 1/R value. For example, if you insulated your house to a ‘U’ value of 0.5 and the temperature inside is 20C and outside is 10C then energy will be lost at a rate of 5 watts per square metre of ceiling.
Does Thermafleece meet Building Regulations?
Yes, Thermafleece has British Board of Agrément (BBA) for three applications, meaning that it totally complies with Building Regulations, in between joists in ventilated and unventilated lofts; under pitched roofs and between rafters for tiled or slated pitched roofs, as well as timber frame wall applications between studding with a weather resistant cladding, and a ventilated and drained cavity. You can get more advice on how to meet Building Regulations by telephoning our Technical line on 0844 800 9953.
How does the thermal performance of Thermafleece compare to other insulation?
Very well: the low thermal conductivity of Thermafleece is comparable to other forms of fibrous insulation and performs within a range of 0.005 W/Mk. Thermafleece is approximately 10% more thermally efficient than glass fibre insulation, which means in a loft you would need a depth of 250mm to comply with current Building Regulations as opposed to 275mm glass fibre compliance.
What are ‘Centres’
The ‘centre’ is the precise measurement between the structural timbers where the insulation is to be placed. You take your centre measurement by measuring from the centre of one timber to the centre of the next timber and not the gap in between the timbers. If the insulation is either 400 or 600 mm wide the actual gap where the insulation is laid will be smaller than 400 or 600 mm.
What sizes are available?
Each pack contains a cubic metre of insulation and the pack dimensions are approximately 1200 mm x 1200 mm x 800 mm high: the weight of each pack is 25kgs.
| Batt Dimensions | Batts Per Pack | Square Metre per Pack | |
| 50 x 400 x 1200 | 42 | 20.16 | |
| 50 x 600 x 1200 | 28 | 20.16 | |
| 75 x 400 x 1200 | 27 | 12.96 | |
| 75 x 600 x 1200 | 18 | 12.96 | |
| 100 x 400 x 1200 | 21 | 10.08 | |
| 100 x 600 x 1200 | 14 | 10.08 | |
What thickness of Thermafleece should I use?
This will depend on where the insulation is to be fitted and the desired U value that you need to achieve for the property.
If you are upgrading your loft, basically the more insulation you can put in the better, but whatever you can put in will help significantly – as a guide a 250 mm thickness will achieve current Building Regulations. For further advice and to calculate U values, please ring our Technical Help Line on 0844 800 9953.
Where can I buy Thermafleece?
Second Nature UK work with a network of merchants who supply our products throughout the UK. Details of your nearest supplier can be found on our Where to Buy page or by ringing us on 017684 86285.
Where do we get prices?
Prices are available by telephoning our merchants on the Where to Buy page or telephoning us on 017684 86285.
Is Thermafleece readily available?
We have a very efficient network of stockists and merchants and where possible we will try and deliver Thermafleece to you within a week.
Can you lay Thermafleece on top of the existing insulation in my loft?
Yes, that’s not a problem.
Does Thermafleece smell?
Because the wool in Thermafleece does not undergo any further chemical processing such as dyeing, the odour arising from Thermafleece may be slightly more pronounced than other wool materials such as clothing. It is also very important to remember that Thermafleece is made from a natural breathable material.
With this in mind, when Thermafleece is delivered or stored in a newly plastered environment it has the ability to absorb the excess moisture present within the building. This can result in a slight odour from the wool. Once the Thermafleece is installed within the application and building is complete, any odour present will diminish as the insulation balances with the environment within the building.
Is Thermafleece 100% pure wool?
Thermafleece contains 85% pure wool from British hill sheep. The remaining 15% comprises a polyester lofting agent of which 50% is recycled. Our wool is also treated with borax to protect the insulation against moth attack.
Why does Thermafleece need a synthetic lofting agent?
A lofting agent is required to ensure that the insulation maintains its shape and entraps air throughout its service life. There are no natural materials available that can do this, so we use a lofting agent composed of polyester. Every effort has been taken to ensure that the virgin polyester content of the product is kept to a minimum. Thermafleece contains 7.5% recycled polyester and 7.5% virgin polyester.
If Thermafleece aids breathing will this affect the air tightness of my building?
Air tightness and breathability are two separate issues. Air tightness concentrates on mass seepage of air through the building fabric which is a visual measurement that can be taken under pressure, for instance a draught through a letter box. Breathability is looking at the building fabric’s ability to adsorb and desorb water vapour. A ‘breathing’ house can aid a healthy living environment but the amount of vapour that the building will breathe cannot be measured on the same scale as air tightness. Therefore airtight buildings can still be breathable.
Is Thermafleece susceptible to moth attack?
No. Thermafleece is treated with borax, a natural mineral capable of controlling the development of many insects and fungi that can cause damage to materials. Although Borax is able to prevent moth development within the Thermafleece, the insulation is completely safe to handle and generates no harmful substances.
What about sheep dip?
Sheep are clipped in the Summer when the residues of sheep dip are at their minimum levels within the fleece. Any subsequent traces of sheep dip are removed during the washing process along with the lanolin, dirt and debris from the fleece.
I am a Farmer: can we sell our fleeces direct to you?
No, unfortunately Second Nature UK is not able to purchase wool direct from the farmer. The British Wool Marketing Board was established in 1950 as one of several Agricultural Marketing Boards to buy and market at auction the Wool Clip for the United Kingdom and we have to comply with these regulations.
Can Thermafleece burn?
When exposed to fire, wool self extinguishes and naturally melts away from the flame source. Thermafleece is also treated with a natural fireproofing agent, Borax that improves its fire resistance and complies with British Standard BS 5803-4 with regard to flammability and resistance to smouldering. Thermafleece has a higher fire resistance than both cellulose and cellular plastic insulation.
How is Thermafleece affected by changes to the Building Regulations introduced in April 2006?
The new Building Regulations introduced in April 2006 require different amounts of insulation depending on the type of construction. For advice on how to meet the Regulations for various types of construction please ring our Technical Help Line on 0844 800 9953.
Can you get grants for Thermafleece?
Grants vary greatly from area to area. The best way to find out about grants in your area is to contact your local energy advice centre. They can be contacted on 0800 512 012.
Does Thermafleece have a COSHH data sheet?
Thermafleece is not a controlled substance under the COSHH regulations. However, we have prepared a Material Safety Data Sheet which is available on request.
How much more expensive is it than conventional insulation?
The price of other insulation varies greatly so it is difficult to make an exact comparison. However, the price difference has narrowed as the energy costs in producing conventional insulation have increased. Thermafleece, along with most natural insulations, tends to be more highly priced than the mainstream, but do bring significant attributes to your home.
What unique properties does Thermafleece have?
Unique properties and characteristics include:
• Thermafleece is hygroscopic and can adsorb and desorb water vapour without affecting thermal efficiency. It is therefore ideal for use in roofs, and timber-framed walls that are designed to allow water vapour to migrate through the building structure.
• Thermafleece is ideal for use in suspended floors or timber framed wall applications since it can provide acoustic insulation in addition to improving thermal performance.
• Wool generates heat when it adsorbs moisture from the air. This heat energy is known as the heat of sorption and accounts for the warmth felt by wearers of woolly jumpers in winter conditions. Wool can adsorb 40% of its dry weight in moisture, producing 960 kilojoules of heat energy for every kilogram of dry wool. This helps prevent interstitial condensation in construction cavities by maintaining the temperature above the dew point in damp conditions.
Can Thermafleece actively control temperature?
Yes. Because of its ability to adsorb and release water vapour, wool insulation can help to keep buildings cool in summer and warm in winter. When the outside temperature increases and begins to heat the wool, it releases moisture. This moisture release has a cooling effect on the fibre, which reduces the flow of heat to the inside of the building, reducing peak temperatures by up to 7°C compared to buildings in which synthetic insulation is installed. In the winter, the adsorption of moisture by wool insulation can increase peak temperatures by up to 4°C when compared to buildings in which synthetic insulation is installed.
How easy is Thermafleece to install?
Thermafleece is very easy to install and does not require skilled labour.
• Thermafleece is harmless and can be installed without gloves or protective clothing. It is not irritating to the skin, eyes or respiratory tract and causes no discomfort to site workers during installation. Any fibres that reach the living space will not be hazardous to the health of occupants. We do however recommend that you wear a mask in an enclosed dusty area, such as a loft.
• Even though Thermafleece is a tough and durable product it can be cut to size, or alternatively 'torn' apart using your hands.
How do I cut Thermafleece?
Thermafleece can be cut using a straight edge and a Stanley Knife or simply torn apart.
We suggest sandwiching the fleece between two solid pieces of straight edged board. Overhang the fleece where you want to cut keeping the two board edges exactly above each other. Compress the fleece as much as possible either by kneeling on the top board or clamping the boards together. Use a sharp scalloped edge knife and keeping the blade firm and square against both board edges, cut using a sawing action. Trim any fine remaining fibres with large scissors or shears.
Diagrams are available on our Thermafleece Applications page or see our Thermafleece Movie.
Can Thermafleece be used in a brick and block cavity building?
No, Thermafleece is not suitable for this application because the breathability of the product is impaired because of the density of the bricks and blocks and our production module of 1200 mm length is not compatible with the brick or block tie spacings which are 450 centres.
If Thermafleece gets damp will it slump, sag or cause my timber to rot?
No, the density is higher than most quilt insulants, therefore it is more rigid and will not slump. Wool fibres are coarse and therefore stronger than man-made fibres: the ability to transfer moisture when the system warms ensures no danger of rotting by retained water.
Does Thermafleece cause allergies?
There is no evidence to suggest that wool can cause allergies. Individuals who are sensitive to wool may be affected by close or prolonged contact with the product. The human body has been associated with sheep/wool for over 10,000 years, and in this respect it can be viewed as the most natural choice for insulation on the market.
Is Thermafleece susceptible to rodent attack?
• Mice infestations in domestic properties are common although generally consist of small numbers. Mice usually stay within a small territorial range (less than 6 metres) centred on a food source.
• Due to the low tolerance threshold for rats and mice in UK domestic properties it is unlikely they will be given the chance to cause much damage to wool insulation.
• Rodents will use any available materials to build nests, including paper, wood shavings and natural or synthetic textiles. Research has shown that rodent proofing has little effect, as they will still gnaw through materials avoiding the bad taste repellents.
Can Thermafleece be installed around recessed lights?
Insulation of any type should not be laid directly over the lights since most recessed lights are designed to have airflow around them. An air gap is necessary to prevent over-heating of the fittings. This is true for all types of insulation. Some recessed lights have heat shields so insulation can be laid around the fitting. It is advisable to check which type of recessed fitting you have before laying insulation. It is advisable to check with a qualified electrical engineer regarding your type of light fitting.
Why should I be concerned about indoor air pollution?
Indoor air pollutants can cause health effects ranging from respiratory irritation to cancer. They have been linked to sick building syndrome and can have a significant impact on quality of life.
How can I minimise the level of indoor air pollution?
Reducing sources of pollutants and ensuring a supply of fresh air are critical. The use of pollutant reducing building materials such as Thermafleece will have an impact on indoor pollutant levels.
How does Thermafleece reduce formaldehyde levels?
The protein building blocks in the wool fibres react in a complex and permanent way with formaldehyde molecules. The reaction is very rapid and cannot be reversed even at high temperatures.
How long will Thermafleece adsorb formaldehyde?
Under typical conditions, tests have shown that the wool in Thermafleece will adsorb formaldehyde for at least 30 years.
How can formaldehyde move through a solid surface?
Formaldehyde moves through a building in the same way as water vapour. Most people are familiar with the fact that moisture can move easily between walls. This is because many solid materials used in building are porous. This may not be visible to the naked eye but at a molecular level many gases can move through solid surfaces. Formaldehyde can also be generated from materials within wall, floor or ceiling cavities and move outward into living spaces.
How long will Thermafleece last?
Thermafleece will last the lifetime of the building in which it is installed.
Can Thermafleece be recycled?
Yes, Thermafleece could be recycled back into insulation or bedding.
Is Thermafleece biodegradeable?
Yes, Thermafleece will biodegrade and can be composted.
I have some offcuts what do you suggest?
Because Thermafleece is so safe, you could use any off cuts for all sorts of things! Here are a few suggestions; pet beds, pet carrier liners, cushions, hanging basket liners, plant and tree protection, welly liners!
What are the VAT rules for Thermafleece?
The Vat rules allow for reduced rate or zero rated VAT on Thermafleece in certain types of renovation or construction project. The VAT rules are also extremely complicated and so the following is for general guidance only and you should ask your local VAT office to give you specific advice on your project. In the majority of cases an Installer would have to be satisfied that their customer was eligible for either reduced rate or zero rated VAT and invoice accordingly. This does not affect Second Nature UK Ltd's requirement to charge VAT to the installer. People who buy their own materials for DIY installation are usually liable for VAT in full, even though they appear to meet the criteria for reduced rate or zero rated VAT. Zero rate VAT could apply to: Sales outside the EC; Sales within the EC where an EC VAT import number is provided; Installation in protected buildings (includes listed); Installation for disabled people; Installation during construction of a new dwelling. Reduced rate VAT (currently 5%) could apply to: Installation in buildings used by Charities for non-business use; Charities providing accommodation for disabled people may be eligible for zero rating; Installation in village halls.
Is there anything we have forgotten??
If you have any suggestions or advice you would like to add to our Tips and FAQ page please don't hesitate to contact us.