ERV - Energy Recovery Ventilator
ERVs are simple, and inexpensive fan boxes that constantly supplies fresh air from the exterior, run the fresh air through a filter, while simultaneously exhausting the stale air from the interior and recovering the energy via a simple energy-exchange core on the way out. The ERV is the lungs of the building. It provides a building with fresh, filtered air 100% of the time with minimal energy loss.
Building code requires that new homes meet a minimum threshold of 5 Air Changes per Hour (ACH) in the Denver, CO climate zone. This means that the conditioned air that you pay a hefty price to heat (or cool) was allowed to leave your house up to 5 times per hour! Naturally, because this requirement has been so liberal, most builders never concerned themselves with this and relied on the typical plywood sheathing, building wrap and interior wall board to achieve this “air tightness” threshold.
Recently, due in part to a global movement towards energy efficiency, that requirement became more stringent and is now at 3 ACH. This means that builders can no longer rely on the simple fact that they are putting up 4 walls and a roof to meet the air leakage requirements and must be more careful with how the building envelope gets detailed and constructed.
Because the air leakage requirement had been so forgiving, a generally accepted notion that “buildings breathe through their skin” was accepted. This is a mistake and leads to issues such as moisture/condensation build up through the walls which creates mold, excessive loss of heat/cooling leading to high costs of energy bills, and to put it simply, poorly functioning and unhealthy buildings.
The 3 ACH requirement forces builders to pay more attention to how they construct buildings and is a large step towards alleviating a lot of these issues, but is still quite a way from ideal, or even efficient. In a perfect world, buildings would leak ZERO ACH and breathe through their lungs, and not through their skin (walls) like a salamander… To date, the best building standard that we have been able to come up with is the Passive House Standard, which requires a 0.9 ACH. This level of air tightness significantly reduces air leakage, drastically increased energy efficiency but requires a building breathing mechanism like an ERV. This is because minimal air gets lost through the walls and humans need fresh air!
At BONSAI we strive to exceed code requirements with every one of our builds and are always looking for the latest and greatest in building science and technology to improve the energy efficiency and most importantly, the health of our clients.
