There is a new product in the ventilation field that promises to simplify the construction and renovation of zero energy homes. Automatic ventilation is an essential element of a super-tight home. Heat recovery ventilators (HRVs) have filled the need for decades. And yet, they remain a major obstacle to high-performance construction. The reasons are many.. To begin, you need to find a good, central location for a bulky box that is readily accessible for maintenance. Most homes require long duct runs for stale, outgoing air and fresh, incoming air. Those ducts should be located within the thermal envelope, and finding a sensible route is often difficult. Finally, installed costs generally start at $3,000, while the value of the energy savings may be worth the cost only in colder climates. Despite the challenges, HRVs are standard equipment in virtually all high-performance homes and some apartments.
Now there is another way to keep indoor air fresh and dry in high-performance homes. Lunos, has developed a “decentralized” heat recovery ventilation system that delivers whole-house ventilation with no ducts. The system is based on two 6⅜- inch tubes mounted through the exterior walls. Each tube contains a fan and a ceramic heat recovery element that temporarily stores heat. When warm air flows from the heated space to the outside, the ceramic element captures more than 80% of that heat. Here’s the unique part of the system: after just 70 seconds, the fan reverses to pull fresh air from outside. As the cooler, outside air passes through the warm ceramic element, it picks up heat and enters the living space at more than 80% efficiency. The Lunos e2 comprises a pair of tubes with fans connected to the same wall-mounted controller. One fan blows fresh air in while the other blows indoor air back out. Working in tandem, the Lunos e2 will supply about 22 cubic feet per minute (cfm) of continuous ventilation.
Two other models are also available. The Lunos Nexxt is the highest capacity model that provides up to 53 cfm of fresh air ventilation. The Lunos eGo has two fans in a single tube and is intended for use in in single room or bathroom. It moves 12 cfm of air in heat recovery mode or 22 cfm in exhaust-only mode.
The best applications of Lunos products may be for apartments, small single-family homes or isolated areas in larger homes where running ductwork is impractical. They are especially well suited to renovations on the path to zero, and they can simplify construction in larger homes where running ductwork is impractical. As of this writing, Lunos Nexxt is priced at $1,595.75, uninstalled. The e2 runs $1,055.00 and eGo is $795.00. The amount of air flow provided by each unit is relatively low, ranging from 12 to 53 cfm, so some applications will require more than one unit to provide adequate ventilation. For example, one builder found that two e2 units worked well for a 1,700 sf home he was building. But for larger homes requiring multiple units, this decentralized system may end up be just as expensive as the traditional ducted HRV.