These two factors, along with the tenants' thermostat setting probably account for most of the variance.The other thing to look at from a weatherization perspective, beyond insulation, doors and windows, is looking for air leaks from penetrations of the top plates by wiring and plumbing, outlets, soffits, plumbing and chimney chases, etc.  

I embrace hard work, the knocks, the kicks, and the lessons with open arms.Thanks for your welcome.

So embrace, the fear, let it lead you to success not analysis paralysis. 

Your letters most likely will not penetrate the owners, especially having them clicking on a we buy house website.  

There is one that stands out over and above the rest...I wrote the following article as my first BiggerPockets Blog post -- to this day, I believe it's the most important advice I have ever (or ever will) be able to provide to other investors/entrepreneurs:http://www.biggerpockets.com/renewsblog/2010/02/10/controlling-your-real-estate-deals-manage-catastrophe/Ignore it at your own peril...or embrace it and find that everything in your business becomes less frustrating, more productive and more in-control...

I just called a mold removal company and they said they could penetrate walls to treat mold.

Embrace your "competition" and I think you'll find that it is to your benefit.

Embrace it...

You will step up your Real Estate game if you stop fighting technology and begin to embrace it.

I am going to perform a miracle and embrace the pink tile and make it look intentional.