A few weeks ago, I went to a brownstone in Harlem that was being totally gut renovated. I went specifically to see the blower door test which helps determine the air tightness of the construction.
What was interesting was that the contractor took great care in using recycled materials in most aspects of the renovation. Other than electric, plumbing and insulation the materials used were not new. Any material that had nothing to do with the airtightness and energy factor of the brownstone was used. I was amazed and impressed.
The hardwood floors were deconstructed from a church and reinstalled in this project. Some sheetrock, bathroom fixtures and other materials were brought in from elsewhere. What impressed me was the metal staircase that was reinstalled in this four level brownstone.
At the end, the blower door test was a success. There were 2 or 3 holes that were discovered in the basement which would be sealed.