so that the built package go into a subdir of your BUILDRESULT directory, just put that in your .pbuilderrc :

#
# hack so that build result is in $(package)_$(version) dir
#

pkg_version=`dpkg-parsechangelog | sed -n 's/^Version: //p'`
pkg_source=`dpkg-parsechangelog | sed -n 's/^Source: //p'`
BUILDRESULT="/home/madcoder/debian/results/${pkg_source}_${pkg_version}"
mkdir -p $BUILDRESULT