Lighting heat gains to return air

NECB-2017 Article 8.4.4.5.(4)

In accordance with Article 8.4.4.5.(4) the proportion of heat gain from lighting going directly to return shall be modelled as being identical in the reference building to that of the proposed building.

The user can create a system or may edit a system prototype for the proposed model; thus the proposed system may / may not have a return plenum.

The reference model uses a prototype system defined by the building type (table 8.4.4.7.-A); systems 1 & 8 do not have return air plenums.

When the reference model is created the automation applies Article 8.4.4.5.(4) as follows:

If the proposed system DOES NOT have a return air plenum set the:

- Proposed internal lighting convective gains to return air plenum to 0%

- Reference internal lighting convective gains to return air plenum to a default % based on system … system 1 = 0%, Systems 2 to 7 = 45%;

If the proposed system DOES have a return air plenum:

- If the reference system type has a return air plenum (systems 2-7) set the reference internal lighting convective gains to return air plenum to be the same as the proposed system;

- If the reference system type does not have a return air plenum (system 1) set the reference internal lighting convective gains to return air plenum to 0%.

The internal lighting convective gains to return air plenum default 45% value is based on a typical office luminaire; the user may edit this value however it should be documented.