This depends on which part of the property you are talking about.
To make a property genuinely energy-efficient, all aspects need to work together. There would be little effect, for example, if you insulated all the walls but left the roof/loft uninsulated, as all the heat within the property would simply escape via this route, effectively making the wall insulation partially ineffective. This also applies to windows and doors etc. Here at Westville, we can offer advice on the type, method, and product most suitable for your property.