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what are the best insulation materials?

posted by Gordon Glass on 01 December 2007

tags: insulation ,

insulation materials

This article takes a look at a range of different insulation materials which are available to the DIY enthusiast or self-build house builder.

Please download the PDF page right for tables comparing the relative thermal effectiveness, cost and environmental friendliness of these materials.

insulation materials

Aerogel

Cork

Cotton

Flax

Foam (10mm)

Foil Quilt

Glass Wool

Hemp

Mineral Wool

Paper

Perlite Beads

Polystyrene

Sheep’s Wool

Straw

Wood

Note: If you are taking advantage of UK government, energy supplier or council insulation grants, the choice of material will be limited to mineral wool (or exceptionally, polystyrene beads for cavity walls where access is difficult). If you already have 150mm loft insulation, buying cheap loft insulation from a DIY store and topping it up yourself is a good option (remember to wear a mask, gloves and protective clothing). However, if you have 60mm or less of loft insulation, it will almost certainly be cheaper (and less hassle) to take advantage of grants and get the job done by a professional installer. Cocoon can tell you the likely cost of going this route.

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aerogel  

Just 20mm of this super-insulant achieves better U values than other insulating materials. It is now available bonded to plasterboard (Spacetherm). Although relatively expensive , it might be an attractive solution for inside the external  walls of solid wall properties, particularly where a reduction in floor space would be an issue. It is also now being used by NEA to provide external wall insulation on park homes. Sandwiched within lightweight PVC panels, it becomes a highly effective solution for these otherwise hard to heat homes.

The manufacture of aerogel involves silica solution, ethanol, aqueous ammonia and a process called supercritical drying which requires the venting of ethanol.

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cork

Mostly used for floors and flat roofs, cork keeps its shape when trodden on and has excellent sound proofing and insulating qualities. It comes from the outer bark of older cork oak trees found around the Mediterranean. It is lightweight, soft and buoyant, and contains suberin, a natural wax which makes it impermeable to liquid and naturally resistant to rot, fire and termites. Production is sustainable when properly managed. The outer bark can be stripped every 8 - 14 years, after which it regrows. Large sections of bark can be punched (for bottle corks) or ground, compressed and baked, to make floor or wall tiles.

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cotton

Cotton mill scraps/recycled cotton is mixed with a bulking fibre such as hemp and a thermoplastic binder like polyester. It is delivered in slabs or rolls. Sometimes borate is added for pest and combustion control. It is non-allergenic and is able to absorb and release moisture. Its 'breathable' construction is good for general comfort and it provides superb sound insulation. Brands include Isonat which offers a product composed of 42.5% recycled cotton, 42.5% hemp and 15% polyester matting.

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flax

This insulation uses the fibres of the flax plant's stem. It has temperature and moisture regulating qualities, being able to absorb moisture in high humidity and release it again when humidity is low. It is made in Germany, Finland & France and potato starch can be used to bind the material making it 100% natural. It is delivered in slabs and can be handled without gloves. Brands include Isovlas.

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foam

Dense latex foam with a fibre glass face is available for internal DIY wall insulation (eg. Sempatap 10mm foam). It is can be bought in rolls and glued to the wall rather like wallpaper, before being painted over. This is not to be confused with Urea Formaldehyde Foam - a very different product piped into cavity walls in the 1970s - which emits formadehyde whilst drying. This product has fallen from use in the UK and should now only considered in exceptional circumstances where it can help hold crumbling brickwork together. See 'Polystyrene' for solid foam insulation.

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glass wool

To make glass wool, recycled glass and sand is superheated and spun into fibres. This is an efficient insulator except when wet. Some undesirable emissions are involved in its manufacture and it causes irritation when handled and releases toxic smoke if burned. Brands include Knauf DIY Loft Insulation or Space Blanket (0.035U)

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foil quilt

Foil quilt is relatively new. It is a sealed quilt of multiple layers of tough aluminium foil sandwiching layers of pliable foam. It is delivered in rolls 38mm thick which can be cut with scissors and are safe to handle. It is intended for use in the roof rafters, so promises to be suitable for loft conversions and new homes.

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hemp

Hemp is provided in rolls or slabs. It's manufacture is 100% pollutant free. It can be grown without pesticides and is naturally resistant to bugs and mould. Sodium bicarbonate is added to act as a fire retardant. It has good sound damping, insulation and moisture regulating qualities. Brands include Thermo Hemp. It is now also available as a thermally efficient building block material in the form of Hemcrete.

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mineral wool

Two types of mineral wool are widely used: 1) slag wool and 2) rock wool. Slag wool uses the waste produced by iron ore blast furnaces - over 75% waste mixed with 25% basalt. Rock wool uses natural rocks. Rocks & limestone are heated in a 1500C furnace and the liquid stone is spun into fibres and blown with gas to make them finer. 80% of global mineral wool is slag wool. It is an efficient insulator but causes irritation if handled. In the UK, most energy supplier subsidised loft and cavity wall insulation is mineral wool. Cavity wall insulation generally means mineral wool fibre blown into the cavity through a hose. Brands include Rockwool.

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paper

Cellulose loft insulation is a fluffy material made of finely shredded recycled newspaper. With added fire retardant and biocidal additives, it is non-toxic, not attractive to vermin, doesn't rot, and requires little energy to produce. Issues may arise if it gets soaked - it could release printing ink smells or loses it fire retardant qualities. It is safe to handle and can be spread between and above loft joists without any negative effects on PVC covered electrical wiring. Paper can also be made into board form with the addition of recycled jute sacking. It may be treated with borax for resistance to fire and rot. Brands include Excel Warmcel and Homatherm board.

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perlite beads

Perlite is a volcanic glass which expands to 7-16 times its original size when heated to 900C. It ends up as lightweight white beads suitable for use in wall cavities. Perlite contains countless tiny air cells that account for its thermal insulation value and light weight. It can be poured into wall cavities from above during house construction and has the advantage of easily finding its way into nooks and crannies, providing excellent cover thoughout the wall.

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polystyrene

Expanded polystyrene is the only rigid foam block not made with CFCs (chlorofluorocarbons) or HCFCs (hydrochloro-fluorocarbons) - both of which destroy the ozone layer. Usefully, when a building is dismantled, the block can be removed and reused or crumbled into bits and remolded. Styrofoam board is suitable for use between roof rafters. Polystyrene beads are suitable for cavity walls where access for machinery is difficult. Beads are easily recovered and can be melted down and reformed. They are resistant to moisture, rot and compression. PVC plastics used to cover wiring can be degraded by long time contact with polystyrene. Pentane gas is emitted during its production (contributes to smog) and toxic fumes are released if it is burned. Brands include Kingspan Kooltherm K7, Xtratherm Estra Performance.

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sheeps wool

Sheeps wool comes in slabs made of fleece offcuts. It copes with moisture due to natural microbial action and can absorb 40% of its dry weight in moisture, thus offering exceptional condensation control. It is good for summer coolness too as it reduces peak temperature by 7% compared to other forms of insulation. Unscoured fleece can be used to line walls (Add quassi chips to deter moths). It will be good for the life of the building as it keeps a tight fit. On the flipside, the methane (greenhouse gas) produced by sheep might be a consideration if sheep were bred solely for this purpose (not likely anytime soon). Brands include ThermaFleece which comes in thicknesses of 50/75/100mm.

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straw

Straw is inexpensive. Bales, panels or slabs can be used as partitions or linings for external wall and roof insulation or for the roofing itself (eg. thatched roof) - or indeed for the walls themselves (straw bale construction). Straw usefully reduces the need for timber and other more costly materials. Precautions to prevent insect and moisture intrusion need to be taken. Staw produces its own resin which binds it together under compression. It can be compressed into large panels 3m x 1.5m x 120mm, of the type which were used on European buildings in early 1900s. It is 100% natural but will be susceptible to decay if untreated.

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wood

Wood shavings have been used for loft insulation in the USA since the 50s. Sawdust can be blown into wall cavities (Finland) where it can also be sucked out and reused when buildings are dismantled. It is important to keep heat generating wiring away from chippings due to the fire risk. Mixing it with limestone will keep vermin away. Boards can be made from compressed waste from wood mills and provide solid wall, loft or floor insulation.

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  • Notes for editors
    • This article was produced by United Sustainable Energy Agency (USEA). This organisation was created by the merger of Milton Keynes Energy Agency & Thames Valley Energy Centre in May 2008. Contact: Gordon Glass, Marketing Co-ordinator. To email USEA staff, please use firstname.lastname@usea.org.uk

    • The information contained within this article is correct to the best of our knowledge. USEA cannot in any way be held legally responsible for any advice given or any work carried out as a result of this information.

    • USEA works in partnership with local authorities throughout Bucks, Berks, Beds, Herts, Oxon, Hants and the Isle of Wight. USEA was recently awarded a new contract with the Energy Saving Trust to operate an Energy Saving Trust advice centre for the South East. The centre provides impartial energy saving advice to the residents of Bucks, Berks, Oxon, Hants and the Isle of Wight. USEA also offers a free insulation price comparison service called Cocoon.

    • Cocoon is a free, independent, comparison service established since 2003. It is being promoted by local authorities across Buckinghamshire, Bedfordshire, Berkshire and Oxfordshire and is now available in Hampshire. The service offers callers at least two estimates from reputable professional insulation installers, including any council, government or energy supplier grants or discounts for which you may be eligible. 

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    Cocoon is operated by United Sustainable Energy Agency - a not for profit company. Registered in England No. 3553525.