as a system / device grows old , the amount of energy will used by the system / device will increase & energy is used for heating a building by a heating system ->  as a heating system grows old, the amount of energy used by that heating system will increase  as a heating system grows old, the amount of energy used by that heating system will increase & old is the opposite of new ->  if a heating system is newer then the amount of energy used by that heating system will decrease  something positive is desirable & using less of a resource has a positive impact on the resource ->  using less of a resource has a desirable impact on the resource  using less of a resource has a desirable impact on the resource & an impact is a kind of result ->  using less of a resource is a kind of desirable result for that resource  using less of a resource is a kind of desirable result for that resource & to use less of something means decreasing the use of something ->  decreasing the use of a resource is a kind of desirable result for that resource  decreasing the use of a resource is a kind of desirable result for that resource & energy is a kind of resource ->  decreasing the use of energy is a kind of desirable result for an energy resource  if a heating system is newer then the amount of energy used by that heating system will decrease & decreasing the use of energy is a kind of desirable result for an energy resource & a heating system is a kind of energy resource -> a desirable result of a new heating system is decreasing the amount of energy used