Increasing the size of the window will on hand increase the passive solar gains but also increase heat losses as the glazing is not as good an insulator as the wall. The simulation will indicate whether overall we get a benefit from having a larger window.

We changed the area of the window from 7.5 m2 to 13.5 m2, meaning that we have a size increase of 80%. The basic ventilation from the outside remains at 0.03 ac/h for both the bedroom and the ling room-kitchen zones with the ventilation rate between the adjacent zones remaining at 8 ac/h.

As a result, we obtained an increase of the passive solar gains from 4002.2 kWh to 6108 kWh (52.6% augmentation).

The heating demand dropped to 940.6 kWh from the original value of 1519.2 kWh. In other words we have a reduction of 38.1%.

It is important to note that this can only be achieved by using glazing with excellent insulating properties in order to avoid having heat losses which would eliminate the benefit of the additional passive solar gains.

Simulation 4: Use of shading & natural ventilation after having increased the size of the south facing window

One problem however is that after the increase in the size of the south facing window, the cooling demand becomes significantly larger because of the increased passive solar gains. It is -1057.9 kWh.

The increased cooling demand is mainly concentrated in the summer period while the heating demand occurs mostly during winter. We could approximate the shading effect through a 30% decrease of the new glazing area during the summer months in order to return to a lower yearly passive solar gain of 5625 kWh. The natural ventilation is the following one:

Introducing an insulation layer in the floor structure was considered very important in order to avoid heat dissipated to the ground (winter period temperatures stay close to zero).

The new modified U-Value has been altered from 2.825 W/m2K to 1.510 W/m2K.

This simulation proves the advantage of improving the floor's U-Value. As a result the heating demand was further reduced to a value of 525.2 kWh (65% decrease of the base case).

Simulation 6: Use of shading & natural ventilation after having improved floor U-Value & max indoor Temperature levels increased to 27°C.

However the summer cooling load augmented significantly with the insulated floor to a value of -1522.8 kWh. This was dealt with by increasing natural ventilation (the same values as in simulation 4) through the north side window and setting cooling control to an acceptable max temperature level of 27°C. Utilising again a reduced south window (30% reduction as before) size for the summer period we managed to diminish the cooling demand to -2.0kWh.

Conclusion:

The results upon the heating demand reduction in Glasgow are presented in the following graph::

Case study 2