- Thermal envelope pictures, www.build.com.au "Building Envelopes, Draughts and Ventilation", and "How Does Insulation Work?". Retrieved 8:00 pm, Jan 20, 2019
- AirKrete picture banner, www.streamlinecompany.com Streamline Enterprises Inc., Lansing, Michigan, USA. Retrieved 8:10 pm, Jan 20, 2019
- Definitions of R-Value and U-Value from Wikipedia.org and from CRC Handbook of Mechanical Engineering 2nd Edition (2004), edited by Frank Kreith and D. Yogi Goswami, CRC Publishing, Boca Raton, Florida USA.
- U-Value and Effective R-Value diagrams - The Open University GB www.open.edu "Energy in Buildings", retrieved 8:00am Jan 21, 2019
- U-Value chart - The Ecomerchant, www.ecomerchant.co.uk. "U-Value for Dummies". Retrieved 10:20 am, Jan 21, 2019