Last Updated: Aug 23, 2022
Whether you live, integrating passive solar design into new home construction or old home renovation should be one of the priorities for people interested in sustainable and energy-efficient dwellings. Why would we not use the energy continually provided to us by the largest source of energy found in our solar system: the sun?
More recently, however, the “Passivhaus,” popularized by Wolfgang Feist, utilizes several techniques to maximize homes' energy efficiency by placing importance on an airtight envelope, super-efficient windows, and conditioned air recovery systems.
The airtightness of homes built under Passivhaus standards can often lead to indoor air quality problems when the home is not properly ventilated. Passive houses often have problems with excessive humidity, which reduces indoor air quality and can lead to problems with mold. Paints, sealants, adhesives, and other commonly used building products that contain VOCs that off-gas accumulate rapidly in airtight homes leading to potentially toxic air quality. Thus, passive homes absolutely need a mechanical ventilation system provided by high-efficiency Heat Recovery Ventilators (HRV) and Energy Recovery Ventilators (ERV).
The main purpose and use of an HRV or ERV are to provide passive homes (and other improperly ventilated homes) with a ventilation system that takes away stale, humid air and delivers fresh air into the home. These ingenious mechanical devices have the ability to separate the different “types” of air in your home and thus bring in fresh air while also expelling the stale air that accumulates in your home along with the toxins, humidity, and other common indoor air pollutants.
During the winter, these devices can “capture” some of the warm air in your home, transfer that warm air into the fresh air it pulls from the outside, and thus recover the warm air that would have otherwise been lost. HRVs and ERVs can increase the heating efficiency of a home built under the Passivhaus standards.
An ERV also has the ability to utilize enthalpy transfer, which is a fancy way of saying that it allows for moisture transfer between the two different air streams utilized in the ventilation process. When outside humidity is high, this device reduces the amount of moisture that can enter your home.
When choosing between an HRV and an ERV for your passive home, the following guidelines are important to follow:
Zehnder America offers various HRVs and ERVs for different types of passive homes in differing climates. The Zehnder Novus 300 Ventilation Unit is one of the most efficient models in the world at 93% efficiency. If you don’t want to have a device that requires much maintenance, the automatic flow control on intake and exhaust streams allows you to let this device do the work for you.
Build Equinox's CERV uses a high-efficiency heat pump to exchange energy between incoming supply and outgoing exhaust air. Using the latest ECM fan technology, the CERV delivers fresh air efficiently and quietly. MERV 13 comes standard with the unit. The CERV accepts 10x20 size. A filter access panel allows for easy access to inspect and replace indoor and outdoor filters. A built-in 3.5" full-color capacitive touchscreen makes interaction with the CERV a pleasure.
Broan offers a wide range of ventilation products, including HRVs and ERVs. The HRV 250 TE is a unique HRV designed specifically for mid to large size homes. This HRV works great for frigid climates as it reportedly has a 66% heat recovery efficiency when the outside temperature is -13 degrees Fahrenheit. The 18 W electricity consumption also makes this an energy-efficient HRV option.
Renew Aire brings several different ERV models designed for both residential homes and commercial buildings. One of the top products offered by Renew Aire is the EV 130, which has an airflow range of 50-140 CFM. The EV 130 also comes with a low voltage circuit for controls.
Lifebreath is another company also offering a wide range of ERVs and HRVs. The aluminum core integrated into its products is so durable that the company offers a limited lifetime warranty on the products they manufacture. The 30 ERV offered by this company is one of the most compact ERVs on the market and is a great option for people looking to ventilate and maximize the efficiency of a passive home.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.