Embodied energy of insulating materials

Credit to: ENERGY + International

© ENERGY + International

The author of this article is the young architect Razvan Enescu. We met him at the symposium ” Nearly Zero Energy Building Design” that took place in October, 2012 in Bucharest, Romania. We were very impressed with Mr. Enescu’s study in depth of embodied energy of insulating materials. Many of these materials contain high levels of embodied energy and their use does not lead to logical and environmental solutions. We are excited that architect Razvan Enescu has accepted our invitation to share his research and knowledge especially for the readers and followers of Energy +.

I will begin this article with two questions, what is the purpose of efficient buildings? And the second one, it is worth gaining efficiency at any cost? The answer for the first question can be simple: the reduction of energy consumption. The second question has also only one answer, but this answer can have many nuances. The market can offer a balance, economically speaking, between cost, energy price and energetic efficiency. But, unfortunately, the answer obtained from the market isn’t always the best answer available, and it can be inconvenient in the energetic consumption balance.

Everybody knows that every industry available today consumes an amount of energy, so the insulating material embodies energy used in their manufacturing process. This article will analyze only the embodied energy of thermal insulation materials, and the effect of this energy in general energetic performance. The aspects as fire resistance, the necessity of special trained workers, the resistance in time or the costs, won’t be analyzed. These advantages or disadvantages along with the quantity of embodied energy could be arguments when choosing a thermal insulation.

The production technologies, raw materials, the length of transportation routes can make the difference between the materials according to their sustainability and eco-friendly character. There are many studies reflecting the quantity of energy embodied in construction materials, but in few cases the architects or engineers are aware of these studies. The embodied energy represents the amount of energy necessary to extract the raw material, the transportation to the factory, the energy consumed by that industry and the transportation to construction site (sometimes the chain is longer considering the transport to warehouses, markets, or other commercial buildings). This data can fluctuate from region to region, considering the industrial, energetic and transportation strategies and models, but general conclusions can be drawn.

An exact study involves data from manufacturer, knowledge of manufacturing and raw material extraction processes, the transportation routes and the means of transportation. The use of materials obtained from renewable sources, produced in energy efficient industries, short transportation routes, are path to obtain low embodied values. Recycled materials have good performance in all these chapters so thermal insulation like cellulosic insolation have good performance.


Material density

[kg/cubic m]

Material embodied energy [MJ/Kg]

Material embodied energy [kWh/Kg]

Total embodied energy per cubic m

Cellulosic insulation
AAC (Autoclaved Aerated Concrete)
Mineral wool
Steel for construction
This table shows the quantity of embodied energy in some important and very used construction materials. As we’ve argued before, the thermal insulations obtained from recycled materials, embodies the least energy (cellulosic thermal insulation), and classic thermal insulation materials like EPS (expanded polystyrene) and mineral wool embodies larger quantities of energy caused by the energetic process of manufacturing. Another important aspect is that the mineral wool has better thermal qualities and less than half the embodied energy of EPS, widely used thanks to its low price (embodied energy per cubic meter).  In this table we have shown also the embodied energy of steel and wood, not only for comparison with insolation materials, these representing options when constructing light structures.

To easily compare the performance of insolating materials according the embodied energy, the next chart will show the amount of energy embodied in materials necessary to raise thermal resistance (R-value, in sqm.K/W) with one unit considering an area of one square meter of opaque envelope, without the influence of thermal bridges. Again the recycled materials perform better, and the use of massive masonry to raise thermal resistance is not energy efficient(in this case AAC who has over 130 kWh/sqm, but also can be applied to clay blocks or other types of masonry). Of course this conclusion doesn’t apply when the purpose of masonry is structural or to raise the thermal mass of building.

Passive Houses, and nZEBs (nearly zero energy buildings), need an intensive study of insulating materials, caused by their high efficiency.

These buildings have thicker insulations, so the impact of an poor performing insulation material can be higher than in case of classic buildings. A classic efficient building, with a good, but not state of the art insulation, can have between 2 and 5 kWh/sqm.year of embodied energy. This means that for an energy consumption of 70-80 kWh/sqm.year, the influence is less than 5%, so we could say acceptable considering that the user’s habits could lead to a greater error.  In case of PH or nZEB, the problems start to appear when choosing a system like EIFS (exterior insolation finishing system), ICF (insulated concrete formwork) or other systems based on high embodied energy quantity materials (EPS is one of the worst case scenarios). For low U-value, under 0.15 W/sqm.K (a thermal resistance over 6.7 sqm.K/W), and an yearly energy consumption with heating of 10 kWh/sqm, a thermal insulation made from extruded polystyrene can have 14.75 kWh/sqm.year embodied energy (accepting a variation of 30%, and a 30 year lifetime period of insulating system), this means a raise of 150% of energy consumed by this building. Other types of insulations with similar properties perform better, the mineral wool can have only 60% influence, and cellulose can be negligible. This analysis has considered an optimal insulation without thermal bridges, and the other materials used in insulation system were also neglected.


35 cm
30 cm


30 cm


Embodied energy per sqm (considering a 200 sqm building)


The impact of embodied energy considering a 30 years period representing the building insulation lifetime


The purpose of this study is to underline the importance of a careful energy study, including at least the embodied energy of thermal insulation materials (a study for the entire building could be also useful, including structural materials or even finishes), because neglecting these features while raising the efficiency with low costs, there is a risk to transfer the energy consumption from the building itself to the industry manufacturing insulation materials. This is a risk concerning all efficient buildings (PHs, nZEBs, NZEBs, etc.), and the people involved in design and construction must be aware of this. The highly efficient buildings will be mandatory in less than a decade from now on according to European Union Directive 2010/31/EU, and the transfer of energy from building consumption to embodied energy isn’t a logical and sustainable solution.             

arch. Razvan ENESCU

In this study, the quantity of embodied energy was obtained from a study regarding the energy consumption of construction materials industry, made by University of Bath, from UK. The data used refers only to quantities of energy embodied in materials, the study regarding thermal properties, energy efficiency, etc. is made exclusively by the author of this article. In this study we can consider that the pattern of British industry, raw material sources and transportation paths can apply to any EU state, considering a variation of 40%.

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