Last week, two interesting reports were published analysing how regulations can better support ‘sustainable’ material use. Very esteemed colleagues, united in a Dutch ‘Gideons tribe’ to make the buildings sector move faster, have been working on this. 
I can agree in general with the contents and analyses ( to adapt and improve current regulations like the mandatory MPG: building materials performance) , but as often, the conclusions or proposals could be formulated much sharper.. The climate situation, as well as the raw materials situation, requires us to steer very sharply, and it will be impossible to keep all demands and wishes in view. Moreover, it is not possible to accommodate everything and everyone, its impossible to maintain a level playing field. That is: the playing field can remain the same, and everyone can continue to participate, but the playing rules will have to change. The basis for the reports , the actual Dutch governmental policy, provides the clue : “The policy goals and ambitions are high: by 2030, CO2 emissions must be reduced by 55% and primary raw material consumption must be halved ”
That determines the specific rules of the game. As follows:
First : when we talk about new construction it is about the CO2 emissions at delivery (“Module A”) Its in the report ( that is, as the embodied energy or embodied CO2 or CO2-eq of the 1st order) and advised as : “must be visible, and communicated”. But that is not enough: there must be a hard requirement attached to it, to avoid discussion about the playing rules, and let me make the first move: Every new building should be CO2 neutral, immediately from the start of delivery.
Because the Carbon budget is limited in absolute sense and is fully needed to adapt existing buildings. There is de facto no CO2 budget for new buildings!
More practically: The new building may have some (low) CO2 impact upon completion, but it must in any case be 0-CO2 by 2030, otherwise it will be at the expense of that 55% target (if there are still net CO2 emissions by 2030 from new construction, that would mean that much more has to be reduced by or in the existing building…). So within 8 years a surplus of renewable energy generated on or at building in the order of the energy invested (embodied). This is also the requirement that we are going to use in a student project next fall, (albeit not in terms of CO2 but in terms of energy: zero energy in 2030 in operational and embodied terms). This requirement leads to less high-rise building, and more biobased building, as previous projects showed (where the same requirement was still for 2050…). And yes, not everything is possible anymore, that the consequence. Same playing field, only different outcome. ( and this would not even compensate all initial impact, but would be a flying start)
Iet’s call this first requirement for CO2 and building materials: MNB 1, Material Neutral Building 1: 0-CO2 by 2030
Secondly, we have a material problem, now already recognized and documented by the government, by the requirement to use 50% less new material by 2030.  Many groups are busy studying how this ‘circular building’, as it is called, should be measured.
Again, you can’t make everyone and everything happy, and a hard target must be set. Let me propose a hard requirement for this: a requirement (MNB 2) for the amount of materials by weight that may be used per m2. Which will be set at a maximum of 550 kg per m2, of new material. If you know that an average new house weighs between 1000-1100 kg per m2 (depending of course on the type, as detached, or apartment, or otherwise) then 550 kg is the 50% reduction as required by politics. No need to make this more complicated. And If more is needed, then it should only be provided by recycled and or reused material and or products.
Sounds Strange? Just look at how we have set one of the energy requirements for new buildings In the Netherlands: : expressed in kWh/ m2! That is exactly of the same order as a kg/m2 requirement.  Which is not meant to say that calculating per m2 floor normalized is the best way to regulate things. It still does not limit m2’s, and might even lead to more m2 to lower the average. But its a good start… ( more about this some other time).
With these two indicators and ambition requirements, we are heading in the right direction regarding materials. There are many other issues, packed in all kinds of evaluation methods, which are also interesting but currently not normative. These two are. And let’s not take 10 years to find out…
As a form of reference, see this house design just launched as new concept by one of the larger Building companies in NL, Ballast Nedam. The first 8 are under construction. It is called ‘Nature house’, based on a concept by Strotec, prefrbricated straw -wood elements. Its 95 % biobased , and very low weight.
1 Reports ( in dutch) to be found at : https://www.gideonstribe.nl/verhalen/code-rood-voor-de-wereld
 material transition: http://www.ronaldrovers.com/from-energy-transition-via-materials-transition-to-welfare-transition/
 kg person per kg house: http://www.ronaldrovers.com/kg-house-per-kg-person-material-need-per-function/