Both the energy use of the whole buildings and of single classrooms have been simulated separately in order to evaluate general consumptions and local discomfort conditions.

At building scale total consummations for cubic meter was calculated for the school models and divided into:

— heating consumption to maintain comfort conditions inside the building;

— cooling consumption to maintain comfort conditions inside the building;

— lighting consumption for the period when no natural lighting is available and areas with

low daylight.

At room scale: classrooms with critical interior conditions have been selected and analysed; for each classroom the following parameters have been evaluated:

— average internal temperature;

— sensation temperature trend over a two weeks period (based on typical temperature of the four seasons);

— daily temperature variation (At).

Strategies of interventions

The strategies of interventions for the schools, can be divided into three categories:

— energy gains control (internal or solar gains);

— structural cooling;

— sensible cooling.

For these categories several strategies of interventions have been proposed; for each strategy a table that describes: technology, dimensions and physical parameters has been proposed.

Energy gains control

Reduction of thermal gains through the envelope:

— roof insulation;

— facade insulation by ventilate facade;

— replacement of the windows.

Solar control trough:

— shading of the windows;

— shading of the fagades.

Reduction of internal gains:

— increase of daylight using sun ducts and light shelves applied to the windows;

— improving energy efficiency of lighting fixtures.

Structural cooling by active night ventilation

Improving night ventilation, it is possible to reduce energy consumption in summer, when the outside temperature is low then the inside, the outside air is faced in the building.

Sensible cooling by direct cross ventilation of the classroom

As known, to have a sensible cooling it is necessary to have air temperature below skin temperature (33°C). In Mediterranean countries this effect can be better achieved using low speed fan especially when the outside air temperature becomes to hot for direct ventilation.

figure: 3 Example of a shading device for a window 150 cm high facing south

figure: 4 Daylighting distribution before and after sun ducts installation

Guidelines

The guidelines are intended as a support for the planner during the selection of the retrofit interventions. For every intervention the effect on energy consumption and comfort conditions can be visualised. On the other hand it is possible to plan the interventions with the best energy efficiency and pay back.

A short description of the effects of some interventions are reported:

Roof insulation

The analysis shows that the roof insulation produces the largest energy saving in every school building with low dependence on orientation and building technologies:

Improving roof insulation energy saving of about 40% can be achieved.

This percentage can be improved shading the roof using tents or pergolas (summer cooling reduction)

Windows shading

The cooling consumption can be significantly reduced using shading systems to protect transparent surfaces.

For every type of window and orientation, the effect of some shading devices is reported together with the description of the technological solutions (figure3).

Shading the windows the reduction of energy consumption changes significantly according to orientation. In the model A (prefabricated panels dimension 60×240 cm) for example, we had the following results:

building with north-south axis 19% energy saving;

building with east-west axis 22% energy saving;

building with northeast-suthwest axis 30% energy saving.

Shading the windows both energy consumption can be reduced and thermal comfort improved due to the reduction of direct solar radiation near the window.

Fagades insulation

Ventilated fagades reduce the cooling consumptions of approx. 20%. This construction is quite easy to build and the solution is highly recommended for school buildings without or with poor insulation into vertical panels.

Windows replacement

The effect of old windows in bad conditions is very important but cannot be easily modelled by simulation software. In our experience this problem is normally under estimated.

Windows replacement is necessary in all rooms facing north and when plastic sheets have been used for the orientations the effect of windows replacement has be evaluating.

The global effect of all the interventions leads to a 60% of energy saving in all the simulated buildings.

SHAPE * MERGEFORMAT

CATANIA

north surface: 46 mq windows surface: 28 mq suth surface: 37 mq suth windows: 36 plan: 653 mq roof: 653 mq

Total comsuption

SOLUTION 5

ROOF INSULATION

WINDOWS SHADING

WINDOWS REPLACEMENT

FACADE INSULATION

Vblume: 2220 me plan: 653 mq ovest surface: 124mq ovest windows: 31 mq east surface: 93 mq east windows:62 mq

17,55 KWh/rrS

4,46 KWh/m3

і і building before retrofit і і building after retrofit

7,94 KWh/m3

5,15 KWh/m3

Heating KWh/m3

GO

MODEL

heathg Cooling lighting

figure: 5 example of a table proposed for each solution. The graphic compare the comparison the energy consumptions (total, heating, cooling and lighting) of the building before the retrofit with the energy consumption after the retrofit.

The icons describes the physical proprieties of every surface (wall, floor, window, etc).