To stop heat loss through walls the walls should be properly insulated and you should seal any gaps and drafts with some weatherstripping and or caulk.
If your walls don't contain insulation it can cause a lot of heat loss out of the walls and if the walls are not properly insulated it can also lead to heat loss through the walls.
Insulation is key to keeping heat in and preventing the heat being lost through the walls and ceilings.
Insulate any walls, floors, lofts and ceilings if possible to create a good thermal barrier and keep heat in where it should be.
You can also use external solid wall insulation options to minimize the amount of heat that escapes out through the walls.
If your wall has no insulation you can also drill holes in the exterior of the wall and use a machine to pump the insulation into the walls between the studs.
Windows lose more heat than walls.
Windows and especially single pane windows are poor insulators when compared to walls which are properly insulated.
A significant portion of heat in the home or building is lost through the windows.
With a properly insulated home you'll lose more heat through windows instead of your walls.
However if your walls are not properly insulated or not insulated at all then you can also lose lots of heat through the walls as well.
In older homes they sometimes don't have any insulation in the walls, especially if the house was built 100 years ago.
You can drill holes on the exterior of the walls between the studs and force insulation through the hole into the walls with a machine.
Double pane windows or other insulated windows lose less heat than single pane windows.
Upgrading your windows can help to keep your home warmer in winter and cooler in summer and help lower your energy bills as well.
Single pane or single glazed windows lose around 10 to 20 times as much heat as the same area of a wall that is properly insulated.
Storm windows or double glazed sealed windows will reduce the heat loss by almost half.