Tips for Retrofitting to Passive House Standards: A Case Study from Thoughtful Balance

Thoughtful Balance, a sustainable architecture and design firm, renovated and retrofitted a former YMCA into the 84-unit McKeesport Downtown Housing – the first retrofit of this scale to be designed to meet Passive House Standards anywhere in the U.S! The 65,ooo-square-foot building was in rough condition, with aging systems and a 40-amp electric service that powered the entire building. The renovation was planned to have new lighting, air conditioning, and make-up air and ventilation systems, plus other amenities. The team at Thoughtful Balance used an integrated design process and teased out issues that were important to the owner, to the people maintaining the building, and to the residents themselves.

Below, Thoughtful Balance shares some of its experiences during the retrofitting process, offers insightful utility data from McKeesport Downtown Housing, and suggests some tips to consider regarding energy savings in retrofits.

Despite not passing the air tightness test, we anticipated a positive outcome for energy savings. Even with the new real air-tightness numbers, we hit the energy use targets – we were at 2 ACH (air changes per hour) @ 50 pascals instead of our target of 1 ACH @ 50 pascals for a Passive House retrofit. We wanted to understand the effect this had on energy costs. What does 1 ACH extra air leakage really mean?

Our blower door testing process was complicated. The building was partially occupied throughout construction, so we were able to test a few individual units but that wasn’t helpful in predicting whole building air-tightness. Later, the building was filled with residents and we were unable to verify that all windows were closed and latched. We suspected that our test results were inaccurate, but re-testing would have been disruptive to the residents and owner, so we had to live with the results.

The image below shows Michael standing in front of the project with a card that is orange and blue. The amount shown in blue is the amount of air leakage for the building allowed by Passive House. The amount shown in orange is the amount by which we missed that target. Now, imagine putting that area in orange in a paper shredder, toss it around the building, and find the tiny leaks all over the 65,000 square-foot building. The area shown in blue points out how rigorous the Passive House standard is for air-tightness and how much every little bit matters!


Energy Savings at MDH

So, if we saved 67% of the energy at MDH, our utility bills were 67% lower, right? Well, not exactly. We installed a geo-thermal system that supplied pre-heating and cooling to heat pumps and we had three large energy recovery ventilators that replaced the gas boiler in the basement. So, we replaced our gas equipment with electric, except for our hot-water system. Thus, the reduction in cost was 28%. Why?


The cost of gas per MMbtu is $16.35, but the cost of electric per MMbtu is $27.65 – we paid a penalty by switching to electric. Traditionally, gas and electric prices had been similar, until 2005 when gas prices dropped, then they began to parallel each other, and then again became divergent in 2010. Electric, at this moment, is almost twice as much as gas. This doesn’t appear to be a trend that will continue, so to suggest that all buildings should have gas equipment to save money is a long-term potential fix for a short-term problem.

By using all electric equipment, we have allowed the possibility of adding PV/solar and switching to renewables when it becomes feasible for us to do so. If we use gas equipment, our opportunities for powering our buildings with PV/solar have largely been eliminated for the 50-year lifespan of our building. We are helping our clients to participate in a near-zero-energy future when we install electric equipment.

Issues to Consider When Predicting Energy Savings in Retrofits

It is important to consider what clients are asking to accomplish when embarking on a deep energy retrofit in order to product energy savings in buildings. In general, whole-building retrofits are done approximately every 50 years. Clients usually have multiple goals for retrofits. Owners want to update their buildings, but they also want to improve their function as well. Maybe this means adding a community room with a kitchen, improving the lighting, adding an elevator, adding automatic entrance doors, or air conditioning, computer rooms, dishwashers, garbage disposals, laundry facilities, or TV and data ports to each unit. In addition, the code may require fresh-air systems, upgraded electrical service entrances, and life safety systems – all things that require more energy.

At MDH, there were no cooking facilities on-site, so the client wanted to add a microwave and mini-fridge in each unit, as well as a place to prepare hot food and clean up. Additionally, we added single-user restrooms as well as showers in the cold-weather shelter.

Some building owners want to add space in the form of additions or making a more efficient use of space that exists. Perhaps the owner wants to implement changes that have the potential to lower energy consumption as well. For example, reducing the unit count of studios and converting to one-bedrooms or combining units to lower density are ways that energy might be reduced. But, typically, the desires for the new building increase the energy consumption for the new project. Making these changes part of the discussion and the prediction for the future energy profile of the building are important as the increase in energy consumption can be significant.

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