Skip to content


Repository files navigation

Thermal Bridging & Derating (TBD)

An OpenStudio Measure that first autodetects major thermal bridges (like balconies, parapets and corners) in an OpenStudio model (.osm), and then derates outside-facing, opaque surface constructions (walls, roofs and exposed floors). It interacts with the OpenStudio SDK and relies on AutomaticMagic's Topolys gem, as well as rd2's OSut gem.

Guide & Downloads

Building professionals and energy modellers are encouraged to first consult the online Guide - it provides an overview of the underlying theory, references, suggested OpenStudio workflows, etc. Users can download the latest TBD version directly from the Guide itself, or under releases, or via NREL's BCL (search for "bridging" or "rd2"). Questions can be posted on UnmetHours - a very useful online resource for OpenStudio users. TBD is also available as a Ruby gem - add:

gem "tbd", git: "", branch: "master"

... in a v2.1 bundled Measure development environment "Gemfile" (or preferably as a gemspec dependency), and then run:

bundle install (or 'bundle update')

New Features

Bugs or new feature requests for TBD should be submitted here, while those more closely linked to Topolys or OSut should be submitted here or here, respectively.


The installation and testing instructions in this section are for developers interested in exploring/tweaking a cloned/forked version of the source code. In an effort to lighten TBD as a Ruby gem, only the most basic tests are deployed in this repository. More detailed tests are housed in a dedicated TBD testing repo.

TBD is systematically tested against updated OpenStudio versions (since v3.0.0). The following instructions refer to OpenStudio v3.6.1 (requiring Ruby v2.7.2), strictly as an example. Adapt the instructions for more recent versions - see OpenStudio's compatibility matrix.

Windows Installation

Either install Ruby using the RubyInstaller for Ruby 2.7.2 (x64), or preferably under WSL2. Run the following steps if going down the RubyInstaller route. From the command line, check that the ruby installation returns the correct Ruby version:

ruby -v

Install bundler, if not already installed:

bundler -v
gem install bundler -v 2.1

Install the OpenStudio SDK 3.6.1, or the OpenStudio Application 1.6.0.

Create a new file C:\Ruby27-x64\lib\ruby\site_ruby\openstudio.rb (path may be different depending on the environment), and edit it so it points to your new OpenStudio installation:

require 'C:\openstudio-3.6.1\Ruby\openstudio.rb'

Verify your OpenStudio and Ruby configuration:

ruby -e "require 'openstudio'" -e "puts"

MacOS Installation

MacOS already comes with Ruby, but likely not the right Ruby version for the desired OpenStudio measure development environment. Instructions here show how to install Ruby v2.7.2 alongside MacOS's own Ruby version. Although no longer officially supported, instructions for an OpenStudio v2.9.1 setup is described here.

From a Terminal, install Homebrew - nice for package distribution and management. Using Homebrew, install rbenv (which allows users to manage multiple Ruby versions) and finally Ruby:

brew install rbenv
rbenv init
rbenv install 2.7.2

Install bundler (if not already installed), great for managing Ruby gems and dependencies:

bundler -v
gem install bundler -v 2.1

In the Terminal, check the Ruby version:

ruby -v

... should still report the current Ruby version used by MacOS. To ensure the right version is used for developing OpenStudio Measures, instruct rbenv to switch Ruby version locally within a user’s chosen directory (e.g. "sandbox361"):

mkdir ~/Documents/sandbox361
cd ~/Documents/sandbox361
rbenv local 2.7.2
ruby -v

… should report the desired local Ruby version, to be used by default for anything under the "sandbox361" directory tree. To ensure both Ruby versions are operational and safe, run the following checkup twice - once from a user’s home (or ~/), then from within e.g. "sandbox361":

cd ~/
ruby -ropen-uri -e 'eval"").read'
cd ~/Documents/sandbox361
ruby -ropen-uri -e 'eval"").read'

If successful, one should get a Hooray! from both Ruby versions confirming valid communication with Rubygems.

Install the OpenStudio SDK 3.6.1, or the OpenStudio Application 1.6.0.

Create a new file ~/.rbenv/versions/2.7.2/lib/ruby/site_ruby/openstudio.rb (path may be different depending on the environment), and edit it so it points to your new OpenStudio installation:

require '/Applications/OpenStudio-3.6.1/Ruby/openstudio.rb'

Verify your local OpenStudio and Ruby configuration:

cd ~/Documents/sandbox361
ruby -e "require 'openstudio'" -e "puts"

Clone TBD

Once done with either the Windows or MacOS setup, install the latest version of git (e.g. through Homebrew), then git clone the TBD repo, e.g. under "sandbox361". Run the basic tests below to ensure the measure operates as expected.

Complete list of test commands

Run the following (basic) tests from TBD's root repository:

bundle update (or 'bundle install')
bundle exec rake libraries
bundle exec rake

Run tests using Docker - optional

Install Docker.

Pull the OpenStudio v3.6.1 Docker image:

docker pull nrel/openstudio:3.6.1

In the root repository:

docker run --name test --rm -d -t -v ${PWD}:/work -w /work nrel/openstudio:3.6.1
docker exec -t test bundle update
docker exec -t test bundle exec rake
docker kill test


Merci aux gouvernements du Québec et du Canada (CNRC, CanmetÉNERGIE).

Thanks to the Quebec and Canadian governments