Energy Efficiency Buildings: Design Looking to the Past or to the Future
Sky Marketing presents a case study on energy efficiency in buildings… Is it better to design looking at the past or looking at the future? Energy Efficiency Buildings: Design Looking to the Past or to the Future, Design Looking to the Past or Looking to the Future.Energy Efficiency Buildings: Design Looking to the Past or to the Future
Design Looking to the Past or Looking to the Future
Buildings are currently designed or should be designed in order to optimize Energy Efficiency and meet the Near Zero Energy Buildings (NZEB) requirement.
To do this, regulations usually impose design limitations focused on reducing demand/energy consumption. For this purpose, dynamic regime multi-zone calculation tools are often used.
There are multiple tools for this purpose, but all of them have in common the use of a climate file with the hourly information of temperatures / solar radiation/wind / … to be able to carry out the calculations.
The climatic files are based on obtaining historical data from meteorological stations close to the location where the calculation is to be made, and then, the data from the nearby meteorological stations are adapted to the most realistic situation of the location.
Using historical climate files to carry out an energy evaluation of the building is “looking to the past” and assuming that the climate was stable, it would be suitable as a design basis for future buildings.
Unfortunately, it is more than proven that the global climate is changing substantially, and therefore the historical data of the past are not sufficiently
representative of the behavior of the climate in future years.
It is necessary to have future prospective climate files to be able to design current buildings “looking to the future”.
Obtain Perspective Climate Files of the Future
1.-Historical Climate Files
Historical climate files, either in EPW or TRY2 format, will be our starting point.
Historical climate files can be found on multiple web pages as an example, some of them are attached:
Via Energy Plus – One Building
The Intergovernmental Panel for the Protection of Climate Change (IPPC) has developed scenarios that make it possible to “predict” the future climate based on current data.
3.-Obtain Predictive Files of the Future
The University of Southampton has developed the CCWorldWeatherGen tool that allows transforming any historical.
The CCWorldWeatherGen tool is nothing more than an Excel spreadsheet that, feeding on historical data in new format and forecast scenarios of climate evolution prepared by IPPC, allows us to obtain predictive climate files for the future 2020 / 2050 / 2080.
Comparison of Climatic Files
Following the procedure described above, the climatic files of a location in Pakistan have been prepared for a 2020/2050/2080 horizon and will be compared with the data from the historical files commonly used by building designers.
The variables analyzed will be air temperature, diffuse solar radiation, and solar radiation in the normal direction.
ºC Historical 2020 2050 2080
T.min -1 -0.6 0.6 1.69
T.max 30.39 31.98 35.08 38.78
T.mean 15.72 16.59 17.95 19.69
A clear increase in both minimum and maximum or average temperatures can be seen.
Diffuse Solar Radiation
Via Josep Sole
W/m2 Historical 2020 2050 2080
R.Diff, max 569.83 482.75 483.25 485.58
R.Diff, mean 77.44 77.27 74.41 71.46
R.Diff accumulated 678410 676886 651804 626042
A slight decrease in accumulated and average diffuse solar radiation can be seen, while the maximum values decrease in a 2020 horizon and increase again in a 2050/2080 horizon.
Solar Radiation in the Normal Direction
Via Josep Sole
W/m2 Historical 2020 2050 2080
R.Diff, max 911.66 898.08 978.17 1059.16
R.Diff,mean 143.84 147.34 157.28 169.47
R.Diff, accumulated 1260017 1290758 1377814 1484540
There is a clear increase in the average and accumulated solar radiation, while the maximum value shows a slight setback in 2020 to increase again in 2050 / 2080.
From the analysis of the climatic files, it seems to be deduced that there will be a slight reduction in climatic severity in winter with an increase in climatic severity in summer; it also seems to be deduced that the cooling seasons will be longer than at present while the heating seasons will remain quite a bit Similar.
Remember that we also have the case study on energy efficiency in buildings in the face of insulation … Is the calculation of the “optimal cost” the most ambitious criterion?
Impact at the Building Level
Once verified that the climatic conditions will be different in the future from those we currently consider, the question arises… How will this affect the comfort of users?
We will consider a house within a block of flats as an example, and we will simulate it in the same construction and operational conditions for the different climates considered.
Via Josep Sole
We will analyze the operating temperature in free float (absence of air conditioning system) throughout the year.
Via Josep Sole
The graph shows how the free-floating operating temperatures tend to increase with the future evolution of the climatic scenarios, so the risk of lack of comfort due to excess heat becomes evident.
To obtain a unique numerical indicator, we can evaluate the number of degree hours in which the building is below 20ºC (cold sensation) or the number of hours in which it is above 26ºC (hot sensation) in each climatic scenario. ).
Historical 2020 2050 2080
GH < 20ºC (Cold) 7574 6230 3518 1596
GH > 26ºC (Heat) 8379 12405 19018 28527
It follows that the periods of discomfort due to heat will become longer and more intense while those of discomfort due to cold will remain fairly the same with a slight tendency to reduce intensity and duration.
⦁ “Future” climate data can easily be derived from available historical data
⦁ The usually established hypotheses of considering the refrigeration season between June and September should be questioned, and consequently, the hourly profiles of set temperatures, and hourly profiles for activation of sun protection or night ventilation should be adapted to the new situation so that the design of buildings is not done “looking to the past” but “looking to the future”
⦁ Similarly, those strategies aimed at reducing the lack of comfort due to heat, such as the best management of air transfer (infiltration + ventilation) or the solar collection surfaces (size and orientation of the holes) should be designed in accordance with future needs and not based on the criteria of the past.
⦁ We have not considered in this study the variations that will occur in the future related to social habits (greater occupation, teleworking, aging population,…) greater presence of equipment (automation, home automation,…), reduction of loads internal contributions provided by equipment and lighting due to the foreseeable technological evolution (led lighting,…) or a possible evolution of occupancy levels depending on the surface area of the dwellings (smaller dwellings)
⦁ We can conclude that the studies that are carried out to evaluate energy efficiency, whether regulatory or energy qualification, are anchored in the past instead of “looking to the future”
Do not forget to go through the article on whether high insulation in summer is useful for the residential sector.
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