Though it was first introduced forty years ago as an ecological ethos, passive house design strategies are the basis of most of the world’s regional architectural expression prior to the 1900s and bears massive potential for the future of buildings in its abilities to simplify quality construction and save money. This article offers a brief overview of the passive house movement and offers some valuable points as to why this field deserves greater consideration for your next construction project.
From the Regional to the Universal; From the Efficient to the Excess
Born from later twentieth-century initiative to maximize the energy efficiency of the modern living space, passive houses were proposed in response to both rising energy costs and the increasing development of energy-inefficient housing over the course of the twentieth century.
For much of human history, domestic architecture was defined by the region in which it was built. In antiquity, for example, there was the Roman insula, or apartment block, that incorporated a central open courtyard to promote airflow during the dusty, dry days of a Mediterranean summer. In the nineteenth century, even low-income housing applied design thought to mitigate the sweltering humidity of the season by using lofty ceilings and shotgun orientation. These living spaces were designed with the regional climate in mind and thus were configured to maximize efficiency. These distinctions began to disappear in the twentieth century, though, with the introduction of air conditioning. This new cooling technology meant that architecture could become more universal, but what it also prompted was a downturn in domestic energy efficiency.
Enter the Passive House
This consumption trend reached a climax in the 1970s, when energy costs were skyrocketing and homes were increasingly sprawling for a number of reasons as designs became more ubiquitous due to standardized aesthetics and wide-spread use of air conditioning. This dangerous trend urged architect to consider new ways to make the modern home an efficient space. As early landmarks in this push toward efficiency began to appear – Eugene Leger’s “Leger House” of 1977, built using the principles of superinsulation, is a prime example – the roots of the passive house movement began to grow. Though only a handful of passive houses were built around the globe by 2000, the movement was gaining momentum.
Less Energy Costs = More Savings
The beauty of passive house design is in its energy savings. By boosting air tightness with calibrated ventilation and adjusting the size of heating and cooling supply, passive houses can reduce the demand for heating and cooling and can have the potential to reduce energy costs by 75%. This of course means less energy spent, but it also means less money spent too.
Let’s consider a basic equation to illustrate this point: most people in the Dallas-Fort Worth area pay roughly $0.11 per Kilowatt hours of electricity. The Department of Energy estimates that the average Texas house uses a little more than one Kilowatt hour of energy per home square foot, then a family living in a 1500 square foot home might spend approximately $170 per month on their electricity bill. That is $61,200 over a 30 year mortgage (without factoring in an increase in electricity).
If you could cut that bill by 75%, you can estimate the long-term savings to be about $46,000 over this 30 year period. So the challenge is to know what additional investment it takes to lower your energy bills by that much. Historical data shows that basic passive house upgrades can cost about 10% or less in construction when appropriately designed. So, in the current DFW market a basic 1500 square foot house that costs around $300,000 will require an additional $30,000 more. The payback on this conservative scenario would be around 22 years. As electricity rates increase, alternative construction methods and strategic appraisals are factored in, this payback starts to quickly decrease. There is also a financial security measure one should evaluate when preparing for an investment project, i.e. lowering bills, preparing for retirement, or sadly, the next recession. Taking steps to minimize lifecycle costs and implement performance-oriented construction can help give a homeowner more control over their property in any type of economy.
The Growing Popularity of the Passive House
In recent years, legislators have even begun to realize these benefits and have started to promote the concept of the passive house across the country. In Pennsylvania, financial incentives for passive house construction have been awarded to over 30% of its affordable housing tax credits applicants despite other allowable lower-entry standards such as Energy Star and the Department of Energy’s(DOE) Zero Energy Ready programs. In Texas, the impotence for this level of efficiency is in its early stages, with only 92 high-performance homes including passive house and other energy standards. The annual Humid Climate Conference and the DFW Solar Tour are two local examples of the growing availability in educational tools and advancing research dedicated to warm southern climates that has traditionally come from modified data based around northeastern cold climate research. As this regional knowledge base grows, passive house strategies in Texas will become more prevalent in both the market and in legislation.
My practice has been committed to passive house building science and incorporating these strategies to strengthen our equity within the built environment. Look for future blog posts that look more closely at the specifics of passive house design and the statistics and numbers that further bolster the possibilities of the movement.