How well insulated are British homes?

The operational running costs of UK homes contribute to an astounding 34% of the country’s emissions. This highlights serious inefficiencies in the way we use energy to support our housing stock.

In recent years, the focus has been on developing strict regulations to ensure new homes meet certain energy efficiency standards. These policies and regulations have been successful in what concerns the growth of the ‘energy efficiency appliances market’. Houses built after 2010, using new technologies, are highly efficient.  

Old buildings v Innovation

Another complex part of our built environment remains trapped in a dangerous and energy intensive limbo. A big portion of the UK’s housing stock consist of old and often poorly constructed buildings - especially in terms of thermal regulation.

Studies show that all houses built before 1990 and 75% of those built before 2010 are inefficient, mostly because of poor insulation. An astonishing number of houses are far from meeting current energy efficiency standards which poses a tremendous strain on the decarbonization process of the built environment.

Efforts have been made in recent times to drive innovation in old buildings. In 2012 a scheme called the Green Deal was put in place to promote the installation of insulation and of more efficient appliances ranging from heating and cooling systems to water boilers and more. The scheme’s structure was badly thought out however, and even after efforts to reform it in 2014, the Deal’s success rate did not come close to what was expected and needed.

Attempts made by the government to drive change by incentivizing efficiency within the home - through the addition of insulation, optimization of hot water handling and so on - have been unsuccessful. The Green Deal expected 14 million households to participate and in the end only 1,746 did.

One of the main reasons this is especially worrying is that four out of five homes that will be inhabited by 2050 have already been built, meaning that around 25 million homes will need refurbishing to meet energy standards by 2050. *

The truth about Spray Foam and Fibreglass…

Spray Foam and Fibreglass are currently among the most popular materials for insulating finished houses. This is due to the ease with which they can be installed. And although efficient in insulating buildings, they have downsides.

Firstly, they have low breathability. This is an important factor when looking at carbon assessments. Poor breathability can lead to damage to the building fabric due to dampness and humidity, thus creating the need for material substitution and additional manutention. When retrofitting a relatively old building, adding non-breathable materials can alter the moisture equilibrium of the fabric leading to serious damage.

Furthermore, they are energy intensive to produce and hard to dispose of or recycle. Fiberglass, as other widely used insulation materials such as mineral wool, is also dangerous to handle.  

Exactly how important is energy efficiency within the sector in the long run?

The assumption that swapping one type of insulation for a more efficient one is necessarily going to positively impact the overall emissions needs to be carefully considered. The new material might be energy intensive to produce, it might be hard to dispose of at the end of its life, or major renovations may be needed to install the insulation or optimize the building.

The same applies to buildings that are being designed. If in order to achieve maximum energy efficiency, a designer decides to use pollutant foam insulants and ends up significantly increasing the embodied carbon footprint of the building, it may not be ecologically worth it.

It is therefore important to consider more natural and less polluting alternatives. These kinds of products are becoming more available, and as demand increases, they will keep improving in technical terms and affordability. In fact, even though the products that constitute state of the art natural insulants are valid and accessible alternatives, they may not yet be as high performing or as cheap as polyurethane foam, for example.

Natural alternatives

One natural, low impact material is sheep wool. This natural animal fiber offers numerous advantages such as low flammability and moisture regulating properties. However, a problem related to the use of sheep wool is that it is prone to moth infestation and must be treated with non-natural materials. Thermafleece, the leading UK producer of sustainable and natural insulation, also adds a 25% of recycled plastic to sheep wool to provide a durable and effective insulation material, while Irish company SheepWool Insulation produces 100% pure wool rolls.

Another natural fiber is cellulose, generally made from recycled newspapers. It is particularly good at adding insulation to finished houses as, in its loose fill form, it can be blown into lofts, cavity walls or floors avoiding the need for disruptive installation processes. Other advantages of cellulose, like sheep wool, include high breathability and, with the addition of a mineral fire retardant, low flammability. Furthermore it boasts good acoustic insulation.

In addition to cellulose, plant fibers are used as insulation in the form of wood fiber insulation boards, such as those produced by German company Steico. Cork, either loose fill or in board form, produced by Secil, and hemp fiber insulation which is produced by many companies including Thermafleece.

Some ongoing research concerns less traditional materials such as Biohm’s mycelium-based insulant. The mycelium is grown on special farms starting with other industries’ organic waste products. It’s then harvested to form boards of insulant organic material with astonishing properties - fire resistance, acoustic insulation and durability. It is also easy to dispose of these when the building reaches the end of its operative life.

Good practice

In addition to the above-mentioned natural materials, some valid alternatives are products with a high percentage of recycled content. For example, Thermafleece produces insulation from recycled PET bottles and guarantees that only 5% of the plastic contained in the final product is virgin.

Equally important is that the installation is done in a way that makes reusability possible. This is particularly true with loft insulation: in case of reroofing, insulation will need to be substituted. Fiber insulation is the most prone to reusage as it doesn’t deteriorate or lose its insulative capacity over time. It can only potentially be affected by dust deposits or loss of anti-flammable materials - especially for what concerns cellulose insulation.  

Good insulation is paramount. Most importantly, a building’s footprint must be assessed over its entire life span thus considering the impact the materials that make up its fabric have both in the cradle and the grave.

*UK Green Building Council (report)


PaperCrete - Build with Rise

Types of Insulation - Renewable Energy Hub

Passive Solar Home Design - US Gov

Energy Efficiency in Old Buildings - SPAB

What are the benefits of Natural Insulation? - Energuide

UK must insulate 25 million Buildings - BBC