Apart from the obvious benefits of a warmer home, lower energy bills and going green, getting a home retrofit will ensure that you get the best solution for your home.
You will get an upgrade plan for your whole house, ensuring solutions that compliment each other, rather than a piecemeal approach where you could end up with installations that work against each other and cause problems in the long run.
Best of all, you only have to deal with one contractor and the whole job will be done.