The ‘Lock-In’ Concept and Passivhaus Construction
It’s better to save up your money for a deep-energy retrofit in a few years than it is to implement less comprehensive measures now
Alan Gibson (my GO Logic colleague) and I just returned from the 18th annual International Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. Conference in Aachen, Germany. This incredible three-day conference featured some of the superstars in the Passivhaus community as well as influential European policy makers, including Dr. Wolfgang Feist, founder of the Passivhaus Institut.
We witnessed a watershed moment in the adoption of the Passivhaus standard in European policy, and saw solid evidence of widescale, successful implementation of all types of Passivhaus projects across the globe. And I am happy to report that North America was well-represented. Our GO Logic presentation was one of several demonstrating Passivhaus market viability in North America.
Higher renovation standards yield increased energy savings
Of the many inspiring, interesting, and in some cases very geeky perspectives that we were exposed to, there is one that has really stuck in my mind that needs to be better understood in order for anyone — be they policy makers, lenders, or homeowners — to make sound decisions regarding investment in reduced building energy consumption. Dr. Diana Ürge-Vorsatz, director of the Center for Climate Change and Sustainable Energy Policies at Central European University, presented this new perspective using the catchphrase “lock in.”
When you look at the long-term impact of different levels of energy-efficiency in buildings across a 50-year span, taking an incremental approach to renovations — achieving, say, a 40% improvement in building performance — is actually a very poor strategy, Dr. Ürge-Vorsatz explained, as compared to waiting several years until a proper Passivhaus-level building shell can be implemented. How could that be?
Well, across a 50-year period, on a macro scale, a moderate, LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. -Gold-level energy retrofit will hold the greenhouse gas emissions from building energy use to only a 46% increase from today’s levels of CO2 in the atmosphere. This is not such a bad result. Consider what would happen if we do nothing to improve energy efficiency by the time the global population is 9 billion people. Building energy use will increase by 110%, with CO2 emissions increasing by 68%. Draw your own conclusions about what will happen next.
Meanwhile, a Passivhaus-level renovation approach will actually reduce energy use of buildings from today by 34%. That means the difference between doing a Passivhaus renovation over standard, incremental improvements is actually an 80% difference in CO2 levels over 50 years! The graph at the top of the page illustrates this concept.
Window replacement jobs are infrequent
In Dr. Ürge-Vorsatz’s words, the “lock in” effect is acknowledging that most buildings that undergo a moderately efficient renovation are not likely to be renovated again for another 50 years, given the financial strain on owners to recover the original renovation investment cost. In other words, you will not re-replace the windows in 10 years, even if you understand window specifications better then than you do now. Your replacement windows have “locked in” a moderate level of efficiency for the long term, and that decision will result in 80% more CO2 emissions than a Passivhaus renovation would have.
Conventional wisdom is that incrementally increasing the performance of buildings is the best approach. That concept needs to be revisited. “Locking in” with moderate improvements in energy performance has a massive negative outcome over the life of a building renovation — which is the margin we require at this stage to combat global warming. So if Passivhaus-level efficiency appears out of reach when building new or renovating — given that the policy, products, and financing required to make it happen are not yet in place — it is worth considering waiting a few years until they are available, for your own financial interest and for the health of the planet.
For more information on the “lock-in” concept, please visit the Global Buildings Performance Network.
Matthew O’Malia is an architect and principal at GO Logic in Belfast, Maine.
- Global Buildings Performance Network
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