Construction and glazing model Option

Construction and glazing

The Construction and glazing model option controls the way construction templates are loaded on the construction model data tab. When the option is set to Pre-design you can load construction templates using the Insulation and Thermal mass slider controls. When set to General, templates are loaded by selection from a list in the usual way.

Floor/slab/ceiling representation

You can choose to model floors, ceilings and flat roofs each having a single construction or by combining separate constructions for floor, slab and ceiling. The options are:

1-Combined - all wall, floor and roof constructions are defined using a series of single constructions without the complication of understanding how layers are combined. This can be easier to understand for new users and requires less input model data. You may also find it easier to use this option when assessing your building for compliance with energy codes because by default the combined constructions used have exactly the maximum U-values allowed by the local code. See the Combined Constructions section for more details.

With Combined constructions, the volume of the floor constructions can be included or excluded from the zone air volume used in calculations by making the appropriate setting under Zone volume calculations. By default the volume of floor constructions is ignored in the calculation of zone volume, i.e. for a single zone rectangular box block the zone volume is:

Zone volume = Block height x (Block width - wall thickness) x (Block depth - wall thickness).

When the floor constructions are to be subtracted from the zone volume then the volume of the floors are calculated by multiplying the construction Thickness by the surface area.

The 3 options (shown in the screenshot above) are:

Internal floor constructions not subtracted from zone volume - selected by default, this option allows you to include/exclude the volume of the internal floors from the zone volume. Clear this option if you wish internal floor constructions to be subtracted from zone volume.

External floor constructions not subtracted from zone volume - selected by default, this option allows you to include/exclude the volume of the external floors from the zone volume. Clear this option if you wish external floor constructions to be subtracted from zone volume.

Ground floor construction is below ground and is not subtracted from zone volume - selected by default, this option allows you to include/exclude the volume of the ground floors from the zone volume. Clear this option if you wish ground floor constructions to be considered as being within the zone and subtracted from zone volume. Keep option selected if the ground construction is to be modelled as being below ground level and not subtracted from the zone volume.

For more information on the effect of these options and also some limitations see the Model Geometry Example section.

2-Separate - internal floors are defined in model data by selecting constructions for floor, slab and ceiling with air gaps. Likewise flat roofs are defined by separately defining the ceiling and roof details etc. This approach can be more economical in the number of different construction components required, but requires more input model data and more careful planning. When using this option you must first familiarise yourself with the meaning on the data as described in the Separate Constructions section. Choosing this option configures constructions in the same way as DesignBuilder version 1.2 and earlier.

With Separate constructions, the volume of the floor constructions + floor void and ceiling constructions + ceiling void can be included or excluded from the zone air volume by making the appropriate setting under Zone volume calculations.

IMPORTANT NOTE: New users are advised not to use the Separate construction option. This is because it can be confusing trying to understand how constructions are built up with this option, especially if you do not check EnergyPlus idf data.

Note: the zone air volume referred to above is for calculating air flow rates for natural ventilation, mechanical ventilation and for infiltration.