One of the key tenets of a highly sustainable building is ventilation. We have begun diving into the detailing for several different projects regarding the heating, cooling, and ventilation systems, and the math keeps coming back to Energy Recovery Ventilators (ERVs).
An ERV provides continuous fresh air to a building or space, but transfers the heat energy from the conditioned, interior air that is being exhausted to the incoming fresh air being pulled from outside. The most basic system simply tempers the fresh air and the more advanced systems also transfer humidity and have other options included. They can be connected to a thermostat, or have ‘boost’ buttons installed that turn up the fan speed to exhaust more air than usual for a fixed amount of time. No matter the extras, they are integral to the temperature management of the interior spaces. By constantly providing that source of fresh air AND tempering it with existing heat energy or humidity control, an ERV system can help improve the interior comfort and drastically reduce the heating and cooling loads needed to temper your project.
We are currently installing a very small recovery ventilator for a basement studio renovation project. The Blauberg Vento ECO2 (link) simply connects though the wall with a grille on both the interior and exterior walls connected by a fan unit inside of a duct. It has it’s control system that can be programed for different speeds and air change goals. We’re intentionally bending the ductwork to prevent outside noise intrusion, but this is about as simple a setup as possible.
In other acoustically-sensitive studio projects, we’ve also specified and installed two different sizes of Soler & Palau ERVs. The TR90 (link) is going in a low-occupancy mastering suite, to quietly provide fresh air. And the TR300 (link) is installed in an intimate live performance space, silently helping to exhaust air from the crowd and keep the energy costs low. Both are extremely easy to install, but require ductwork and a dedicated space to install and house the units. These units require two grilles on the exterior of the building (one for intake and one for exhaust), separated by at least six feet to prevent cross contamination. The interior also receives two ducts (one for supply and one for return). Within a single room, we aim to keep these as far apart as possible to intentionally provide airflow to the entire room. They can be integrated into the heating or cooling system design, or function completely separately. These types of systems work great next to radiant heating or other systems that don’t involve forced air.
The Build Equinox CERV2 (link) is being installed as the whole house ventilation system in the Mt Airy Passive House. It has a supplemental heat pump (primarily for cooling and dehumidification during the late summer months). The electric heat pump works in conjunction with the ERV to manage the interior temperature and humidity, and is calculated to use over 90% less energy than a traditional furnace and air conditioner for a similar sized home. It connects to a typical smart thermostat to maintain a constant set of interior comfort parameters, and can be adjusted seasonally based on your specific environment. The unit connects similarly to the mid-sized systems above, but gets ducted throughout the house in a more traditional forced air design, but with much smaller duct requirements due to the constant airflow and minimal heating/cooling load requirements.
None of these systems work in isolation – they are designed and integrated into the whole building or renovation design. An ERV can be added entirely onto an existing building, also, simply to increase the health comfort of the occupants by providing a continuous source of fresh air without greatly affecting the heating and cooling loads. Many existing residential furnaces or air conditioners provide zero fresh air, and rely solely on windows or doors to bring in ventilation to a home. So we often recommend an ERV even on small additions or renovation projects.