Part L (2006) requires certain attributes to be entered for constructions in addition to the data required for other thermal calculations. This data is entered in the constructions database program APcdb. The additional attributes (broken down by construction category, and including attributes required for Part L1 (dwellings)) are:
Glazing
Display window?
Tick this box if the window is a display window. Such windows are exempt from certain L2 (2006) requirements.
Glazing type (dwellings only)
The SAP procedure which features in Part L1 has its own classification system for glazing types. Glazing types used in L1 SAP analyses must have the appropriate glazing type set.
% sky blocked (dwellings only)
The Part L1 SAP procedure requires the degree of overshading to be specified for each window. Select an appropriate option from the list. In accordance with the SAP method, rooflights are automatically set to ‘< 20% Very little’.
Frame material (Part L (2002) only)
Select a frame material from the drop-down list. This determines the required glazing/door U-values for Part L1 and Part L2 (2002).
Doors
Door type
Select from the following types:
a) personnel door
b) vehicle access or similar large door
c) wall or roof element that is not to be treated as a door for the purposes of Part L
d) smoke vent
e) high usage entrance doors
Doors of types b, d and e form special categories in Part L. Type c is provided to allow door drawing facilities in ModelIT to be used to create wall or roof elements.
Ground floors
Ground floor U-values can be calculated using a floor area / perimeter method.
Floor area - Enter the ground floor area
Exposed floor perimeter - Enter the exposed floor perimeter
External wall thickness - Enter the wall thickness of the external wall that bounds the floor perimeter.
Ground conductivity - Enter the conductivity of the ground below the ground floor
All construction categories
Thermal bridging coefficient
Part L2 (2006) requires an allowance to be made for non-repeating thermal bridging. In the <VE> implementation this is handled via a coefficient expressing this component of heat loss as a multiple of element area. This can be thought of as an addition to element U-value. The default value of 0.035 W/m2K represents a typical value for office spaces built to the standards of the Robust construction details defined in IP 17/01[4].
In the notional building, thermal bridging coefficients are set to standard values laid down in the NCM methodology document.
