Passive House Design: Understanding the Basics
Introduction to Passive House
A Passive House (PH) is a building that tactfully uses building orientation, thermal massing, passive heating/cooling, and daylighting to greatly reduce its energy needs. Though the name suggests that most certified Passive House projects are residential, a Passive House does not necessarily mean the building must be a “house” per se. Passive House Certification is available for most building types, including commercial, educational and multi-family projects and is increasing in popularity each year.
In fact, many project teams that are looking to increase the energy efficiency of a building will incorporate passive building techniques into their early design strategies, regardless if PH certification is a goal. Early on, most PH projects did have a distinct “box” look, many passive homes now maintain a similar style to typical homes, while considerably outperforming them in energy savings.
But what makes a passive house passive? The most vital design aspect is air tightness! Here are the passive design strategies utilized by both certified passive buildings and other high-performing buildings:
Air Tightness –Passive House certification and passive building design require an airtight building envelope, which limits uncontrolled leaking and allows for a level of ACH (air changes per hour) for healthy indoor air quality.
Building Orientation – Orienting the building and living spaces in an ideal alignment with the sun will drive the energy use of the building. The latitude, the angle of the sun as it hits the building, and the building’s massing can greatly impact how interior temperatures are maintained.
Building Massing – The size, shape and material of a building can have a huge impact on how energy is transferred, stored, and held within the space. Creating a specific mass or shape of the building can either minimize or maximize energy conservation measures. Depending on the climate and design, proper orientation and massing alone can help to maintain a constant indoor temperature with little need for additional heating and cooling.
Passive Heating –When the building is properly aligned with the sun, solar radiation can be used as the first heating source for the building. As the sun’s energy heats up the space through windows (on the south side in the northern hemisphere), massing and structure can capture and hold this energy and warm the space without mechanical systems.
Passive Cooling – Natural ventilation, air-cooling, and shading can greatly reduce the need for mechanical cooling. Opening windows on cool nights can not only help to reduce interior temperatures but also brings in fresh air directly to the living space. The use of evaporative and geothermal cooling strategies can also help to keep the building comfortable. Solar shading can be used in addition to other passive cooling techniques to minimize solar radiation and glare throughout the summer.
Lighting/Daylighting – Unless there is too much direct sunlight causing glare, most people typically prefer natural light to artificial light. Proper placement of windows and orientation of the building can maximize the building’s ability to capture natural light and minimize the need for artificial light.
Design Program –With proper layout of the rooms, spaces that are used most often can take advantage of daylighting, passive heating/cooling, massing and orientation. Typically living rooms, kitchens, and other gathering spaces are better placed in areas with desirable views and/or the south side of the building to take advantage of passive strategies directly. Bathrooms, mechanical rooms, laundry etc. can be put on the northern side where there is typically less light.
Passive House Institute US’s Building Standard provides an approachable solution to reducing energy and costs while maintaining comfort. Now, more than ever, the building community needs a program like PH as we push towards zero energy and zero carbon solutions.