Seal Heating & Cooling Air Ducts With Mastic & Save Energy. Leaking air ducts can be found in attics, crawlspaces, basements, garages, closets, ceilings & walls. Sealing all joints & seams with RCD Mastics will reduce wasted energy, lower monthly energy bills, reduce carbon emissions, and improve indoor air quality & comfort. Seal those areas highlighted in blue with Mastic.
