Souad,
I believe that there is a way of opening a 2d dwg as a
background image in SketchUp so that you can then trace
over it more quickly than if you were to start from
nothing. Still, each time that I have encountered this
issue I have found that it takes juat about the same
amount of time if fight with and correct an automatic
import or if you start from nothing.
Here are a few tips that might help.
1. use as few thermal zones as possible on each floor.
Often you can group together rooms that face a certain
direction (i.e. have a particular sun exposure) into a
single thermal zone.
2. model the plenum between floors as its own zone;
this makes it much easier to deal with the zone
adjacencies from one floor to the next.
3. rely heavily on the line drawing tool. Draw the
perimeter of each thermal zone's floor then draw
vertical lines for the corners then connect their tops.
I have run into a lot of frustrations with the extrude
tool.
4. where possible avoid copying and pasting zones. It
is nearly as fast to draw another floor perimeter and
walls. When I try copying and pasting I sometimes have
trouble with SketchUp selecting things that aren't part
of the zone that I am trying to copy.
5. do all the walls floor by floor first and then add
windows after you have all the walls completed.
6. import the *.idf into TRNBuild and check adjacencies
early and often. I don't usually do more than 3 or 4
zones before I save the *.idf, import it into TRNBuild,
check it and then increase the version number in the
name of my *.idf file. When you run into import errors I
find it is often easier just to start over and redraw a
few zones than it is to figure out where the error is.
7. this one is rather specific but if you are drawing
opaque doors (i.e. walls contained within another wall)
make a vertical line between the middle of the door
lintel and the ceiling. This will break the containing
wall into two walls and while that adds another surface
for Type56 to deal with I have found that it avoids a
lot of wall area calculation issues and errors in the
*.idf file.
best,
David