When it comes to saving energy, everyone knows how important it is for your home to be properly insulated and few things offer such a quick return on the initial investment – or as good a long-term benefit – as effective loft or wall cavity insulation.
Over recent years a growing range of eco friendly options have joined traditional insulation materials allowing us to ensure that we can save money on our energy bills, without literally costing the earth.
Choosing Organic Materials
Organic materials are amongst the most eco friendly of the currently available forms of insulation and score heavily over many traditional and other “alternative” materials because of their low-embedded energy – the amount of energy required to make them in the first place.
For the environmentally aware energy saver, in addition to this inherently low carbon-footprint, their natural origins, biodegradability and claim to sustainability clearly give them an immediate appeal too. Most types come as “batts” – pads suitable for laying as loft insulation or as cavity insulation, especially between timbers before the inner dry-lining is fitted.
“Thermafleece” – sheep’s wool – is one of the most popular candidates and seemingly a long-term favourite of the TV property renovation shows. An excellent insulator, which is naturally fire retardant and very easy to install, its popularity is easy to understand. Fully biodegradable, it is particularly useful as cavity insulation in wooden framed buildings due to its natural ability to absorb water.
Staying firmly with the agricultural, straw – one of the oldest forms of insulation – is also finding favour with new generations of householders and DIY enthusiasts. Especially in rural areas where it is produced en mass, the benefits of its low embedded energy and low transport costs are particularly impressive and like wool it naturally offers good thermal insulation. However, it is prone to going mouldy and this makes it not suitable for all uses.
Two old-time crops – flax and hemp – which had become little seen over previous decades are also enjoying renewed interest as a result of their potential as natural insulation materials. Hemp shares many of the insulating properties of wool and is naturally resistant to insect damage. Flax – a type of linen – is very similar to hemp in its performance and use, but a little less dense.
Some of the flax and hemp offered for sale is imported, so the embedded energy cost is a little higher than it would have been had it been home grown, but never-the-less it still represents a significantly lower carbon footprint than many other forms of insulation, so they remain worthy candidates for your insulation requirements.
Cellulose is another popular choice, which is typically made from recycled newspaper fibres which were otherwise destined to be land-filled – making its eco-credentials pretty clear. During the production process the cellulose is treated with fungicide to stop it going mouldy and inorganic salts to improve its fire-retardant performance.
How Do They Compare?
There are many ways to compare insulation materials, but one of the most straightforward is to look at their “K value” – or thermal conductivity. This is usually given in Watts per metre per degree C – written W/m.k – and is the measure of how much heat energy travels through a one metre thickness of material for every one degree of temperature difference between the “inside” and the “outside.”
Insulation materials should not conduct heat well – that’s how they work – so the lower the number, the better a material is at insulating. Traditional materials such as fibreglass or mineral wool commonly used in lofts or cavity insulation, for example, have a typical K value of 0.033 W/m.k – 0.040 W/m.k and as the list below shows, eco friendly insulation compares very favourably.
- Wool 0.037 W/m.k – 0.040 W/m.k
- Flax 0.038 W/m.k – 0.040
- Hemp 0.039 W/m.k – 0.043 W/m.k
- Cellulose 0.038 W/m.k – 0.040 W/m.k
According to the Energy Saving Trust, about a half of the heat lost from a typical home disappears through the walls and loft and the savings they estimate you can make with good insulation are staggering – cavity insulation offering an average saving of £120, for example.
Proper loft insulation could slash your annual bills too – by £155 – while from an environmental point of view, if every UK household topped up their existing loft insulation to the recommended 270mm, the cumulative saving would be a staggering £560 million. Making those sorts of savings using today’s eco friendly insulating materials offers a real win-win situation, all ways round!