In full-scale improvements. It may make just as much sense to upgrade a home system (with an improved one) as to repair it or incur ever-more-frequent and expensive maintenance for an inefficient, obsolete or dying system. For a DIY project, it is also useful to establish limits on how much time and money you’re willing to invest before deciding a repair (or list of repairs) is overwhelming and discouraging, and less likely to ever be completed.
