From ZEB to ZEEB : 0-embodied energy buildings 2/2

In principle, its impossible to create a 0-embodied energy house, energy will always be needed. However, in the present time 0-embodied energy it is understandable as 0-fossil embodied energy, exa house exclusively based on renewable energy. 0-embodied energy, if that is fossil-related, is actually 0-embodied CO2. But then , CO2 is of course not embodied, but “emitted”. So more accurate is actually 0-emitted CO2 house.

As a unit of measurement, this again has the advantage that it can also be positive, in terms of calculation , if more CO2 is committed than invested. And that is possible through, for example, biobased materials, such as building in wood.
Note that this applies to CO2 emissions related to materials, the embodied energy (EE). Simce there is of course also (possibly) CO2 emissions of operational energy (OE). Somewhat confusing perhaps, but we must try to keep things pure. If OE is included, then a house as a whole can be ‘climate neutral’: no emissions of CO2 as a result of material plus energy investments. But here I focus on the material side, and the 0-CO2 emission home.

A low embodied energy house, or low CO2 emissions, is one thing, as described in the previous article, but to get to 0 still requires some serious attention. Which can be summarized in 3 approaches:
1 reduction of impact through design and material alternatives
2 production (of the house) with very low embodied energy (CO2 emission) materials, actually renewable material and energy, from on or around the building site, with the use of labor energy
3 products made as 0-embodied energy products by industry, in combination with sustainable transport.

First of all: if there is an alternative with lower embodied energy, that’s of course preferable. Take window frames, for instance for which about three materials are common: aluminum, PVC and wood. The embodied energy figures per kilogram of material already give an indication: for example for aluminum and wood that is around 230 MJ / kg. and around the 5 to 10 MJ/kg. But the right comparison is, of course, per function: various studies are devoted to this, with more or less the same results: A frame of 1.2 m2 with double glazing made of aluminum, PVC or wood comes out at respectively 5978 MJ, 2657 MJ, and 738 MJ, [1]. a factor of 8 difference. Perhaps even  a frame-less solution is also possible for windows in the future, but that depends on how innovative the building world will be.

For various elements of a house it can be difficult to find a low or 0-EE alternative. In that case we can look for alternative solutions in stead of products: As in a case study where there was no alternative product for such things as steel door hinges. So the solution is to avoid them all together: instead of hinged doors, use sliding doors. Another such component is the foundation. , for which reinforced concrete is the usual solution. Often already 30% of the impact,( especially if the house was already designed from low embodied energy materials): But that is at the same time part of the solution: because a biobased house weighs much less, up to half of a usual house (about 500 kg / m2 floor compared to 1000 for the average Dutch dwelling) This makes it possible to base the house on point loads, ie on six or eight columns, free from the ground, which only requires a very limited investment in foundation material: in this case study it was 6 second-hand ‘stelcon’ plates. If the ‘shoe’ can also be made of fiber-reinforced biobased material, the impact of the foundation will be very low. Incidentally, in this case the house was so light that an extra anchor was needed to withstand the wind load.

Using material from the construction site itself is a very common option in the rest of the world, such as working with clay and bamboo for example. The majority of people live in such houses (source), but in the Netherlands this might be more difficult, mainly at least because of the social and cultural demands of the people. Moreover, this requires a lot of land, and since we live in the third or fourth most densely populated country in the world, land is scarce. Even though , the earth houses like in Olst in the Netherlands , may come close (someone already calculated earth houses ?). [2]

More obvious, in our over-regulated society, is that the industry has to become very innovative, and produce 0-embodied energy products. After all, that is two birds with one stone: the industry has to switch to renewable energy anyhow, and if all products are supplied with 0-embodied energy, then the problem in building a house is solved as well. What is embodied energy for construction , is actually 0-operational energy for the production sector: They have to produce with renewable energy, and thus make their process 0-energy. There are already some companies that implement this more or less. We will however not see this in embodied energy calculations because these are usually based on the industry’s average, and on the basis of primary energy. These companies are therefore at a disadvantage with the current approaches, despite being at the forefront.
Moreover, installations are still a tricky one. These are almost all and nearly always made of metals. It is striking that for these devices virtually no figures are known with regard to embodied energy. There is a big lack of transparency there. And it is clear that the number of installations (- components) is increasing more and more. Transport, which is also part of embodied energy, is left out of consideration here .

This is of course only a brief exploration of the role of embodied energy, or better 0-CO2 emissions, but this topic will play an increasingly important role in the coming years, not least because of EU policy, which focuses strongly on materials. And that will change the building practice. Biobased building, building with renewed materials, is then inevitable. Even if the non-renewed material industry (metals and minerals) would want to produce everything with renewable energy, it would cost a huge (material and energy) investment in wind turbines and solar panels. So its smarter to build directly with renewed materials for which the embodied energy is already much lower, with as a result, a much lower demand for wind turbines and solar panels in the energy supply.

Nevertheless, a kind of protocol to deal with embodied energy for buildings is needed, [3], as I also already advocated a few times , in the form of a EEPC , a Embodied energy performance coefficient , net to a EPC, a (operational) energy performance coefficient. [4]

There is howvere already a low embodied energy trend visible, in the form of construction with renewed materials, in the “axis of biobased countries “, such as Austria, Germany and Sweden (Scandinavia). They made a lot progress in this field, and have even started a battle for the highest wooden building (with the note that this is not the desired development, high-rise has in general a higher impact per m2 floor than low-rise). Meanwhile, outside that ‘axis’, attention is also starting to increase, With for instance England and Canada entering the “ competition. [5]

It was about time, after 150 years of experimenting since the industrial revolution, with all sorts of materials but without a clear direction, finally we will see some common understanding and direction towards a sustainable architectural language and materialization: on the basis of the embodied energy / 0-CO2 emission criterion.

There is one other important criterion that should be mentioned: The lifetime: The embodied impact at the start is important, of course, but the longer a building (or product) lasts, the lower that impact becomes per year of function service : A building that lasts 100 years instead of 50 has only half of the embodied energy, or CO2 emissions, averaged over the years. So in addition to low or zero-embodied energy at the start, lifespan is also an important element. ( also in maintaining existing buildings)
With attention for embodied energy we are getting in the right direction, but are not there yet: it still requires material to build , and thus causing exhaustion and land seizure. In other words: we also have to work towards a 0-material home. …. But I’ll keep that for another occasion …

[1] M Asif, T Muneer and J Kubie Sustainability analysis of window frames, Building Serv Eng Res Technol 2005; 26; 71, DOI: 10.1191/0143624405bt118tn


[3] Dixit, M. et all, Need for an embodied energy measurement protocol for buildings: A review paper , Renewable and Sustainable Energy Reviews 16 (2012) 3730–3743

see also the IEA annex 57 and 72 references in the previous article)


[5] (mind that this is no a full wood construction, it still has concrete cores)

Author: ronald rovers