I really hate this co-insurance clause. I believe the insurance company should decline coverage and not write the policy. It is VERY unfair to a policy owner (who does not have the information to understand how the value of a home should be determined) to write a policy they know is under-insured. They will NEVER declare a home a total loss as they know the cistern and other parts of the home will survive almost anything.. In my case I questioned the insurer how the under-insurance clause worked and was told by E-Mail that usually if the "value" of the home was within 80% of the sum insured , the under-insurance clause would not apply. I have that in writing and the adjuster is still questioning if this is in effect.