typical value, heat transfer through building assembly.
Heat conductance of building wall. Use 0.088 for R-13 insulated house wall.
Heat conductance of building floor. Use 0.047 for R-13 insulated house raised floor.
Heat conductance of building ceiling. Use 0.031 for R30 insulated ceiling including attic and roof.
Heat conductance of building roof. Use 0.031 for R30 insulated roof including attic and ceiling.
Heat conductance of window glass. Use 0.65 for dual pane window.
Heat resistance of building wall. Use 11.3 for R-13 insulated house wall.
Heat resistance of building floor. Use 21.4 for R-13 insulated house raised floor.
Heat resistance of building ceiling. Use 32.5 for R30 insulated ceiling including attic and roof.
Heat resistance of building roof. Use 32.5 for R30 insulated roof including attic and ceiling.
Heat resistance of window glass. Use 1.54 for dual pane window.
These include inside and outside air films, typical construction, and effect of framing members.
Conductance U-value is in btu / (hr* square foot * degreeF). More insulation gives lower conductance. Less insulation gives higher conductance.
Resistance R-value is in (hr * square foot * degree F) / btu. More insulation gives higher resistance. Less insulation gives lower resistance.
If estimating window glass, you can start with 14% of walls are window glass.
Solar - winter. The contribution of solar heat is ignored for the sizing of winter heating equipment. It is most likely the greatest need for winter heat will occur at a time when the sun is not out.
Solar - summer. Estimate 60 btu/hr/ square foot enters every window on average during the daylight hours. (Although there are about 450 btu/hr per square foot of sunlight, this amount is not entering every window simultaneously, and there are many other reasons to calculate with the lower rate. For discussion, see solar through windows.) This estimate assumes even distribution of windows around all sides of the building, some overhangs, some window tinting, and curtains that are left open. For other or non-average window conditions, a better solar estimate may be necessary.
Other related starting values. A gas furnace has 78% AFUE efficiency (heat out delivered / heat in fuel burned). An air conditioner or heat pump has 10 SEER or EER (btu/hr/w). The heating part of a heat pump achieves 6.6 btu/hr/w heating season HSPF.
The above values are (mostly, not the solar) from the California Energy Commission model of most new houses built in the Sacramento Valley in 1992. Of course your building and every building is different. However sometimes it is handy to have some starting values to get a quick calculation, or as starting values to estimate your values.