Retrofitting houses: from object approach to a source approach 2/2

In the Netherlands most houses are heated by natural gas, but now we want to phase out that gas heating. Which of course is in principle easy: just close the tap, which is in the gas-fields in the North of the country. What would happen then, apart from a lot of squabbling?

Not so much I think: there will be no deaths, freezing days are something from the past, and the mild cold can easily be combated with extra clothes and extra blankets on the bed, a more active life, and if necessary retreat to a single small room where television, light and number of family members together generate enough heat to survive. This is how the ‘boomers’ grew up (the coal stove only was fired up when it was really freezing …). And there are many countries where that is still common habit: students from Peru, Nepal and China, for example, I learned from my time at Wageningen university, just sat in their rooms with their coats on, they were used to that at home. And I myself have also been working in parts of China, with the jacket on: there was not even a heating option in the rooms where we gave workshops.

Cooking might be problem of course (also on gas in NL) , except for the die-hard vegans. But with a loose induction plate that can be solved within a few days. Since we also have to move towards all-electric living, right?

This will not happen, of course, turning of the tap, but always good to have some ‘reference’ in mind when looking for solutions ….

But then what? In the first place, of course, not fleeing forward by introducing lots of technologies , which is putting the horse behind the carriage, moving energy impact to material impact (and therefore energy impact again).

The starting point must be: a CO2-neutral built environment, which then automatically includes natural gas-free houses. And CO2 neutral, includes CO2 neutral material deployment. And not even at building or neighborhood level, that must have a national effect, that is to say, stay within national cumulative CO2 budgets.

Step 1, as argued in the previous article, looking at existing housing stock, is to deflect the CO2 curve as quickly as possible with as little material as possible (calculated over the entire stock, not per property). This is possible with (for example) a rapid roll-out for all houses of heat pumps installed in hybrid mode with the gas heating, and all roofs fitted with of solar panels. By that time, a very big change has already been made, per dwelling, but in particular in the deflection of the cumulative stock curve, which gives room for further measures in the next years (other options, incidentally, welcome). It will also have little resistance in society.

Which gives time to take the following steps after a number of years (but of course the preparation of those steps does not have to wait, we have just gained some time for implementation).

This next sep first and for all should not be based on how to fulfill the original energy demand , but on the question of how we can reduce it. Regarding heating that is, as suggested in the intro, by reducing the heated area. As I call it creating Summer-Winter houses: for the few days left when it is really cold, and the Hybrid system changes to gas , the comfortably heated part is limited to the dining room or the kitchen diner. Living with the seasons, just as we should with food. How to achieve that, is still a challenge, and not my area of expertise, but we will find a way. Since making the whole house a Passive standard, with its enormous demand for materials, is of course weird, as if it were freezing all year round …

However, there is always a remaining heating demand. How to deal with that then in this second phase?

This requires a overall strategy, to make the final step towards 0-CO2 with regard to heating. Which should not start searching for individual and local solutions, but with an analysis at national level, and based on the potential of renewable energy systems in the Netherlands. Some 10 years ago I was involved in a long-term research project , called SREX : How could exergy approach be applied to regional space solutions. And actually the conclusion was simple: a certain area has a certain energetic (exergetic) potential, and that must be the starting point for deciding what are possible activities within such an area. As I described it in the conclusions at the time: “with an exergetic system optimization of an area it is not a question of energetically optimizing a given demand with the least loss of quality, but starting from the exergetic potential of the area and to deduce the maximum possible demand and functions “. [1]

In other words, what can the area deliver as a maximum , with an exergetically optimal approach – the maximum qualitative and continuous output. In this case, think of the Netherlands as a whole, the legally manageable and controllable area of energy flows. This leads to solutions that are optimal in terms of both energy and material use.

Lets call this a ‘source approach’, in contrast to the usual ‘object approach’. Thinking in these terms, its soon obvious that open surface water is exergetically the most interesting for ‘low-value’ space heating. The Netherlands has a lot of that , is densely populated  and many homes are close to surface waters. This can then be used for a low-temperature heat network. At the same time that is an option with a relatively low impact of the use of materials. Moreover, the knife cuts on several sides: the surface water in the Netherlands rises in temperature, which in turn has an adverse effect on ecosystems. Cooling that water to a limited extent improves the ecosystem (less chance of blue-green algae and botulism) and provides the basis for heating energy. A good example of this is a study: ‘Grip on the Maas’, which shows that cooling the river Maas water by 1 degrees can supply 1 million households with heat. [2] Since the Netherlands is very rich in surface water, the starting point is: All homes within a technically interesting distance are connected to surface water. In other words: no neighborhood or single house approach but a source-approach as a starting point. Which can go beyond municipality boundaries for instance.

Note: this will take time, so step 1 remains necessary to create that time, to have cum. CO2 curve to be deflected quickly.

By :technically interesting, I mean an energy and material optimization: such as with regard to minimize loss of heat for transport, but also including all housing measures, such as having to install yes or no a low temperature heating system. It may be that including these leads to a somewhat lower potential than, for example, the Grip on the Maas study.

In places where this option is not possible, alternatives will have to be sought, again based on their own potential sources within the area/country. Ideally, you then also use low-value sources for low-value demand. In other words, groundwater or shallow water layers. An option here is to use large-scale horizontal bottom heat exchangers, somewhere around minus 2 meters. Most existing houses do not have enough accessible surface, but that surface can be found under public areas, such as roads: Roads most likely will have to maintained or restructured once in say 30 years, and at that occasion a simple horizontal heat grid can be installed immediately under the road surface. Afterwards houses can be connected to this heat source. If the heat demand has already been limited, as described above, this might be sufficient. I did not calculate this in detail, this is a conceptual exploration, with a huge reduction in mind of demand, CO2, material, and high speed and feasibility. (financing is not included, its not interesting in times of crisis).

There are probably some special cases that require a separate local solution.

By the way, for other demands, like electricity the same approach should be followed: departing from source potential, with the lowest possible energy and material impact.

There is however another important issue to deal with: It might just be that cooling, not heating, becomes our biggest problem: there are hardly any frost days left here in the Netherlands, but heat days on the other side of the spectrum are all the more, and increasing. Which on one side makes all above steps the more important just to slow down the growth of heat days, especially those measures that can be implemented very quickly. But it looks like we won’t be able to avoid heating entirely. Therefor any strategy should also include a plan to deal with overheat-days. Firstly to prevent everyone from installing huge cooling installations, which will make the entire operation a farce anyway, because that will further increase the greenhouse effect. Secondly of course to get through those overheat days, with the lowest possible use of energy and material, and avoid new CO2 effects. Which in particular requires passive measures. Without launching a whole plan here, one can think of measures such as cooling through night-ventilation, adding window shutters, creating overhangs, reducing pavement around houses (including minimizing road surfaces at neighborhood level). And for new-build houses use biobased materials, with wooden cladding, with low heat absorption (Heat can also flow from the outside to the inside ….).

And maybe the most simplest and effective measure: To start by painting all existing stone houses in white.

Our task is to reduce CO2, and greatly reduce it and in the very short term, while preventing rebound effects. I am open for other or better suggestions as here presented, they are a first concept, It is however time that we started to think about it in that way and act on it.

[1] SREX report:

[2] Alliander en RWS: Grip op de maas. Zie oa :

Author: ronald rovers