EcoRenovator - excellent article on winter heating conservation

I agree, it's explained in a very simple and understandable way.
One thing that caught my attention, though, was this:

Quote:

Say you live in San Francisco, where the average winter temperature (day averaged with night) is a moderate 50 degrees Fahrenheit. If I keep my house at 50, I will need to add absolutely no heat to it to keep warm. If you keep your house at 70, you will need some heat, and if someone between us likes 60 degrees, she will use exactly half of the amount of heat you use.

So halving the temperature difference should also halve the heat loss? This would imply that heat loss through a medium is a linear function of temp difference, while I had the notion that the function is exponential, ie twice the temp difference will cause more than twice the heat loss.
Of course, this is splitting hairs. Overall the article is quite good:thumbup:

EDIT: Here's what I found on Wikipedia:

Quote:

Convective heating or cooling in some circumstances may be described by Newton's law of cooling: "The rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings." However, by definition, the validity of Newton's law of cooling requires that the rate of heat loss from convection be a linear function of ("proportional to") the temperature difference that drives heat transfer, and in convective cooling this is sometimes not the case. In general, convection is not linearly dependent on temperature gradients, and in some cases is strongly nonlinear. In these cases, Newton's law does not apply.