Passive House: an economic and environmental solution to building
Anyone that owns an old house knows that while they are charming and full of character, they are notoriously inefficient. I love my old bungalow, but it is nearly impossible to keep at a consistent temperature or save on energy costs. Despite being a solid structure that has lasted 100 years without major failures, there was no need to keep it sealed for efficiency. All summer long the windows would have been open because air conditioning was not available.
One hundred years later we have progressed through many innovations in building development. Construction methods and materials changed, we retrofitted houses with air conditioning, then moved to an integrated furnace and air conditioner system, moving away from radiators. Home owners have installed solar panels on roofs to reduce electricity costs, invested in spray foam insulation to reduce the heat transfer through exterior walls, and added insulated window glass. While all these have made steps towards a more efficient house in both energy and cost savings, the passive house standards have taken it to the next level.
Most people have likely heard the term LEED (Leadership in Energy and Environmental Design) with the three levels of achievement: gold, silver, and bronze. The problem with a building achieving LEED status is they can obtain points for features that are not related to the buildings efficiency such as installing bike racks. The addition of bike racks encourages alternative forms of transportation which reduces greenhouse gas emissions, but the building itself is not contributing to lower emissions. The new standard for better building design emerging today is Passive House, a standard for energy efficiency in a building, reducing its ecological footprint, resulting in ultra-low energy buildings that require little energy for space heating or cooling.
The Whole Foods development in downtown Minneapolis that achieved a LEED Silver rating (image courtesy of oakwood.com)
Passive house is not a new concept (it started decades ago in Europe), but the use in large multifamily housing projects in the U.S. is giving it more recognition. In 2009 there were less than 25 Passive House projects, but by 2016 there were almost 350 in development. Despite the increased construction costs (typically the cost is less than 10 percent more than a standard development), developers are choosing Passive House because of the long term savings. The Portland Housing Authority opened a 45 unit project that is expected to cost $10 per month for heating and cooling.
The idea behind Passive House (image courtesy of egreengroup.com)
The way these cost savings are achieved is through proper exterior wall insulation, sealing the building to avoid any air infiltration (unfortunately this means no operable windows), triple-pane windows (most homes, especially older homes have single pane windows), and high-efficiency heat-recovery ventilators to supply each room with fresh air.
It is surprising to me that the Passive House standards have primarily been applied to residential construction and not commercial or institutional buildings. Government buildings using Passive House standards could greatly reduce annual costs to heat and cool the buildings, helping to reduce operating costs in the budget. Not only does it helped to reduce costs, but the Passive House standards would help government agencies lead the way in reducing greenhouse gas emissions.
The Passive House standards have been used around the world for years. The east coast has jumped on board with these standards, and the rest of the States are starting to look towards this program for building development. I feel these standards can offer both an economic and environmental solution to our need for more housing. Even in Minneapolis we are seeing the first project proposing to use Passive House standards. It will be interesting to see how the building fares and whether it is the first of many Passive House buildings in the city.
