Save big with passive technologies

Reducing energy use during the design and construction phase of a new building is almost always easier than retrofitting the building afterwards. There are many techniques that can be used to reduce the amount of energy a building needs. Using efficient systems like LED lighting and heat pumps are obvious.

However, the building architecture itself can be designed to save energy, both without management of control systems (passive technologies), and with controls (active technologies).

Architectural and advanced mechanical systems that should be considered during building design include such things as: building orientation, insulation, thermal mass and other radiant barriers, windows, window frames, air conditioning economization, directly controlled humidification/dehumidification, and heat recovery from wastewater.

That seems like a lot of technologies. It’s hard to find construction professionals who are familiar with all of them. Fortunately, an organization exists to help people involved in new construction projects to learn from the experiences of those who have designed particularly efficient buildings before.

The Passive House Institute (Passivhaus) was founded in Germany in the late 1980s, to explore and promote the design of buildings for optimal energy use. Passivhaus offers significant resources to people who want to prioritize energy efficiency, thermal comfort and indoor air quality through a combination of passive design strategies and advanced active technologies.

Passivhaus buildings typically consume up to 90% less energy for heating and cooling compared to conventional buildings. This reduces the size of the electric infrastructure needed to serve them, and ongoing operating costs. Designs using Passivhaus principles simultaneously achieve lower costs, lower energy use and improved occupant comfort through the use of systems like:

Exceptionally high levels of insulation, to minimize heat loss and heat gain through the building envelope.

Airtight construction, to prevent unintended air leakage, ensuring thermal comfort and reducing energy demand, accompanied by…

…Mechanical ventilation with heat recovery (MVHR), to ensure a good supply of fresh filtered air while recovering heat from outgoing stale air. Airtight construction with MVHR helps to reduce energy use while still maintaining indoor air quality.

Meticulous architectural detailing to eliminate thermal bridging, ensuring uniform temperatures throughout the building envelope. For instance, a Passivhaus window frame will be designed so that the frame itself has insulation value, rather than providing a thermal conduction path that negates some of the effect of insulation.

Triple-glazed windows with low-emissivity coatings are standard in Passivhaus buildings, maximizing natural light while minimizing heat loss.

Some Passivhaus technologies are free, e.g., building orientation for optimal heat management and use of daylight instead of artificial light. Others are slightly more expensive than standard systems (e.g., triple-glazed windows rather than double-glazed), but can be installed economically during first construction or a scheduled retrofit. Others (e.g., superinsulation, or heat recovery from wastewater streams – your bath and laundry water are still hot, and some of that heat can be redirected into your water heater’s storage tank) cost money up front but save significant energy in the long run.

Occupant surveys and monitoring data indicate high levels of thermal comfort in Passivhaus buildings, which have stable indoor temperatures and minimal temperature variations. Continuous mechanical ventilation ensures a constant supply of fresh air, reducing the concentration of indoor pollutants and allergens.

If you’re involved in new construction, encourage your architect to use Passivhaus concepts. For further information, see www.passivehouse.com.