Design

Summer design and overheating

How to avoid summer overheating

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Summer comfort is no longer an exclusive problem of Mediterranean region, but now affects also northern Europe. For this reason the topic is assuming big interest for the topic group. This problem is more perceived in the European social housing buildings, where often there aren’t cooling systems. Also for this reason the following considerations are based on some studies based on calculations without cooling systems, considering buildings located in the north of Italy, a place where summer period is warmer than in the rest of Europe and meanwhile winter period is cool. That’s why buildings in this area need have good performances in both periods.

The study of buildings behavior was done with dynamic simulation, that resulted to be an uncommon method in northern Europe. The software used are Energy Plus and Open Studio.

Two case studies where presented, each of them focusing on specific aspects.

Case study 1: multi-apartment building in Treviso

The first case study is a multi-apartment building in Treviso, built in the ‘70s, that was renewed to reduce thermal losses. Where compared: the baseline (building as it was before the renovation), the renovation project and some possible improvements (different insulation material, sun control, ventilation). The results show that both in the baseline and in the project the temperature is never in the comfort area, actually in the project scenario there is a little worsening.

All the supposed improvements give a little upgrade, but sun control and ventilation are strictly connected to the user behavior and not with the building design. If we use these three improvements together the summer comfort raises.

Case study 2: one floor building

The second case study is a one floor building with good winter performance. The focus of this study is the wall stratigraphy and the position of the insulating layer. In steady state calculation the U value doesn’t change with insulating layer position, but dynamic simulation shows the importance of layers position. The results show that an insulating layer on the inside face in addition to the external one can reduce the unmet hours (number of hours setpoint is not met). This positive effect decreases when the inside insulation has a greater thickness than the external one.

General results

According to the tow above mentioned case studies some general results can be outlined:

  • The sun control is a key topic, using external blind or shades.
  • Ventilation must be properly used.
  • Users have to be educated how to use sun control and ventilation in order to optimize them.
  • Insulation can worse the building’s summer behavior.
  • Is much better to split the insulation to improve summer comfort: the best combination for the cases above is 15 cm or more for outside insulation and 3 cm or less for inside insulation.
  • Also the very last internal layers matters.

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