Here is a link to
download a trial copy of HVAC-Calc Residential 4.0. This is a program that runs on the PC and will calculate the heat loss (or gain) for a house.
They also have a commercial version, but the residential is more suited to homes.
This is a timed version, but the time that they allow is very generous.
It is a great way to try various "renovations" and calculate how much they will reduce heat loss.
* * *
And here is another
free heat loss program, in the form of a spreadsheet, from Canada, called RetScreen.
I have seen plenty of interest in RetScreen from lots of professional people. With some going so far as expanding the usefulness of the program and making their version available also.
I have seen discussions on this site (EcoRenovator) about making spreadsheets, but if they are being posted, I have missed the posts.
At any rate, RetScreen is an impressive contribution to a world running short of energy, and it is wonderful to see what a generous nation can do.
Best regards,
-AC_Hacker