Retrofits for energy efficiency must accelerate to meet zero carbon deadline districtPH tool enables detailed modelling at city and nation scale

17 August 2022 by Jason Quinn

Imagine: being able to model an entire city’s energy use—or the whole country!—just like you can a single building in PHPP. This is what districtPH does. Bland name for an exciting tool that enables extremely significant outcomes. The model shows how global changes to the building stock impact energy usage and thus carbon emissions over long time spans. It’s been used in Germany to model at a neighbourhood and district level. The analysis takes into account grids for electricity and heat, renewable energies, electrified transport and public consumers.

Just like in PHPP, you can easily test the impact of different choices, individually and how they work together. For example: what if roof insulation in all new homes is increased to R6.6? The districtPH model would detail the energy saving across the country and account not just for the homeowner’s energy cost savings but also the reduction in demand on the New Zealand electrical grid. Expanding electricity generation has a huge capital price tag, so being able to model changes to building efficiency has big implications. And it goes without saying we need this data to make informed decisions about how we get to net zero carbon emissions.

Time and funding is needed, but I want my team to build a districtPH model for all of New Zealand. That’s not quite as wildly ambitious as it sounds—a districtPH model for all of Germany has already been developed by Dr Jurgen Schnieders, the COO at the Passive House Institute. 

The startling conclusion of his analysis is that step-by-step EnerPHit retrofits are not sufficient. It would work eventually to meet the Paris climate goals but not in the necessary timeline. To meet the 2050 carbon target, Germany needs to use the EnerPHit accelerated curve—see graphs below. This means all replacements are EnerPHit step-by-step but refurbishment occurs sooner than the economic optimum and requires significantly more investment

The base EnerPHit approach only upgrades components once they are at the end of their lifespan so the cost premium for extra performance is small. Jurgen estimates the extra cost at only 10% (in Germany) in this scenario.

The net cost of EnerPHit upgrades, taking into account the savings on energy use, is less than business as usual. Not changing is the most expensive option for Germany.

Here’s a watchable 18-minute presentation by Jurgen on ​​the impact of implementing energy efficient buildings and the subsequent mitigating effects on climate change. We include the summary of his presentation below.

Moderate improvements come with a big cost that is often overlooked. There’s a performance gap between the moderate improvement and the best possible solution that would hit the EnerPHit standard and that gap means more carbon emissions. We “lock in” that higher level of emissions when we settle for modest upgrades. For more on this important concept of lock-in, see Dr Diana Ürge-Vorsatz’s work. I summarised the concept in this post, Zero-energy building sector vital to addressing climate change. Diana was also the lead author of this technical paper I discussed here: Toward net-zero building: put this paper on your reading list.

As Jurgen points out in his presentation: “Current building standard[s] will leave us with a building stock that is not suitable for our climate goals… Act now but act wisely. If you refurbish, do it right – [refurbish to] EnerPHit levels”

Climate Architects Network’s summary of Jurgen’s presentation can be found here and is published below for easy reference.

“Let’s act now! The moment a building is modified or new buildings are constructed, let’s use the most efficient technologies and materials available. In this way, we will achieve a gradual improvement in the quality of the building stock.

  1. The main goal is to achieve a state where buildings do not negatively affect the climate and its protection. The way to achieve this is a climate-neutral building stock. This needs to start now, especially with buildings with long lifetimes (e.g. public buildings). 
  2. According to the Paris Agreement, we only have about 10-20 years to achieve climate-neutral buildings. 
  3. The Passivhaus Institute is working on how to achieve these goals technically, economically and socially. Therefore, they have created a model of all buildings in Germany (their energy needs for heating, hot water and electricity) and based on this they have modelled different scenarios for achieving a neutral building stock. 
  4. The current legislative constraints (in Germany) are very light and even in 50 years buildings will not meet these criteria. With the use of quality materials (at a level suitable for passive houses) and components in gradual renovations while constructing new buildings in passive standard, about 80% of the energy will be achieved in 50 years. In combination with renewable energy sources, neutrality can thus be achieved by 2050. 
  5. Continuing to build and renovate buildings at the current quality will not allow the targets to be achieved and is also the most expensive way to go given rising energy prices.”

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