When we talk about energy efficiency in buildings We usually refer to the set of procedures that lead to the I build consume less energyBut the crux of the matter is determining how far it is possible or reasonable to go.
State regulations inspired by the Energy Efficiency Directive usually take as a reference what is called “optimal cost”, which is that the investment costs are acceptable in relation to the economic benefits that the energy entails. lower energy consumption (optimization).
Note: You can consult the application of the «optimal cost» methodology in EU countries from HERE in English.
Although the economic viability, is it is not the only criterion possible and could try to reduce the energy consumption of the building until it is practically nil or that the environmental impact resulting from the construction and operation of the building is minimal (minimization).
It is evident that according to the different criteria adopted as a reference, the levels of ambition in obtaining energy efficiency will also be different.
In this article we will try to evaluate for a given building, what is the level of ambition provided by these different criteria and we will show that the most commonly used, which is energy optimization, leads precisely to being the least ambitious and we would do well in do not consider it as the preferred criterion.
It is considered for this case, a multi-family building between houses composed of ground floor + 4 floors with a total of 16 houses with a conditioned area of 1282 m2 (only the houses are considered conditioned)
The following image shows the building considered:
BUILDING CHARACTERISTICS:
The first step consists of evaluating the amount of final energy consumed by the heating and cooling systems, including the associated consumptions of the fluid circulators.
In both cases, it can be seen that within the insulation levels considered in the study (between 0 and 22 cm) consumption is decreasing as the availability of insulation increases, and, therefore, it will always be positive to increase the insulation if desired. minimize energy consumption.
It is called “Total cost” to the sum of the costs derived from the investment in insulation and the operating costs of the building.
The results are reproduced below:
It is evident that, in this case, there is a value that provides a minimum total cost and that lower or higher insulation levels lead to an increase in cost.
It is also appreciated that the higher levels of insulation represent negligible total cost increases. While lower insulation levels, they provide considerable cost increases.
What is commonly referred to as the "optimal level" of insulation, is actually the "minimum level" below which we should never be in order not to include significant cost overruns.
To evaluate the environmental impact due to the incorporation of the insulation, the Environmental Declarations of the Products (DAP / EPD) introduced in the building have been taken and the greenhouse effect (GWP) of each case has been considered throughout the life cycle.
Let's remember that we have an extensive article on how to calculate the environmental impact of a building and what programs, also written by Josep Sole.
In a similar way to how final energy consumption has been translated into operating cost, the greenhouse effect potential has been evaluated based on the type of fuel used. The results are summarized in the following graphs.
As with energy consumption, in this case, the total environmental impact throughout the entire life cycle is reduced by increasing the level of insulation without finding, at least within the environment studied, a limit value that cause an increase in the environmental impact of the building.
Consequently, contrary to what some claim, the amount of insulation to be installed in the building should in no case be limited for environmental reasons.
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