DOE-2 Reference Manual Version 2.1 - DOE2.com

slightly more computer time. In the following cases use of the CustomWeighting Factors is suggested:Notes:• Buildings with thermostat set-back and/or set-up• All passive solar buildings (only direct-gain systems can currentlybe modeled)• Masonry buildings• Heavy construction buildings• Any building in which it is necessary to define the distribution ofthe solar radiation within the building• Buildings located in sunny locations with large amounts of solarenergy entering the spaces.1. When using Custom Weighting Factors, specify all EXTERIOR-WALLs,INTERIOR-WALLs, and UNDERGROUND-FLOORs with "delayed-" or dynamic-typeconstructions. If a surface is of the "quick-" or steady-state-typeconstruction, its thermal mass will not be accounted for in the CustomWeighting Factors (CWF) calculation.---Because the response-factorcalculation for delayed surfaces is expensive, users are advised to uselibrary walls as much as possible, that is, specify wall LAYERS from theDOE-2 Library (BDLLIB).2. Input all of the bounding surfaces of a space. This includes interiorwalls, floors, and ceilings across which there is negligible heattransfer. Such surfaces contribute to the radiation balance that isperformed in calculating the CWFs. Also, interior surfaces, particularlyfloors, often contribute substantially to the space thermal mass:3. Use the full area of underground walls and floors, not just the perimeterarea (that is, an area equal in length to the perimeter and one footwide). This is especially important for slab-on-grade structures wheremost of the thermal mass could well be in the slab. To avoidunrealistically high heat transfer to the ground when the full slab areais used, the keyword U-EFFECTIVE in the UNDERGROUND-FLOOR instructionshould. be used. It works as follows: if the UNDERGROUND-FLOOR isdescribed as delayed (as it should be for CWFs) and if U-EFFECTIVEisinput, then the response factors for this surface will be used in the CWFcalculation, but the heat transfer (Q) in LOADS will be calculated aswhereQ = (U-EFFECTIVE) * AT * (TG - TR),AT = total slab areaTG = ground temperatureTR = LOADS-calculated space temperature.II 1.144 (Revised 5/81)