Since high-efficiency buildings often need only limited heating and cooling, it can be possible to combine that function with the ventilation of an ERV into a single unit. While most of these “magic box” systems are larger than the furnaces they replace, because they incorporate several functions, the total footprint required for all mechanical systems is smaller than what would be required for all of the functions if provided by separate pieces of equipment.
Several of the units are not carried by distributors in the United States. These “magic boxes” are better suited for European conditions (with milder winters) than they are for those in North America. Holladay outlines the reasons for this, noting that the costs of these units are generally higher than the cost of individual pieces of equipment. Some manufacturers point out that the faster installation time for only a single piece of equipment helps offset the higher cost. However, unless space is at an absolute premium, in most cases it is probably better to use separate pieces of equipment.