ROUGH DESIGN CRITERIA FOR HEAT LOSS CALCULATION

 

For more in debt analysis of U valves.

Best Overall Guide

http://www.microgenerationcertification.org/admin/documents/U-Values%20from%20Domestic%20Heating%20Design%20Guide%20v1.0.pdf

For walls; cavity, solid, insulated, materials and debts;

http://www.combustionresearch.com/Infra-Spec/infra-spec/uvalue.html

Windows, Glazed and materials, debts of glass;

http://www.gsecg.com/residential-secondary-glazing-thermal-insulation-glazing-types-u-values

Another useful resource (also good for windows and others) 

http://www.scotland.gov.uk/Resource/Doc/217736/0088291.pdfA