Life-Cycle Assessment of StackHR

Alongside my experimental testing of the StackHR concept for my masters thesis, my buddy (and fellow postgraduate engineering student) Nikolaj Vendelbo and I have been working on a LCA study investigating the sustainability of the concept for quite a while now.

Today we presented our findings for our class on Sustainable Design and Production at Aarhus University, and apparently we must have done quite well as we got some great feedback from both of the professors attending the presentation.

For our study we investigated the sustainability of the StackHR concept through a comparative LCA where we benchmarked the proposed system against both traditional natural ventilation systems and State-of-the-Art mechanical ventilation systems featuring high efficiency heat recovery.
We did so by evaluating the total environmental impact of the systems in terms of greenhouse warming potential (as well as other relevant impact factors) over the full expected lifetime of a building. Doing so obviously requires a lot of assumptions (qualified guesswork) to be made, but even with the uncertainties that are inherent to this type of assessment, our findings were so significant that we can confidently conclude the following:

  • StackHR in its current form is a major improvement over traditional natural ventilation under Danish climate conditions.
  • StackHR in its current form does not come close to matching the performance of modern mechanical ventilation systems in terms of life cycle sustainability under Danish climate conditions.
  • It is unlikely that any practical and truly passive ventilation system can be designed that outperforms modern mechanical systems in terms of overall sustainability in cold climate locations.

These conclusions are largely attributed to a finding that embodied energy plays a minor role compared to operational energy use when it comes to environmental impacts of ventilation systems over the whole lifetime of a building.
Another key factor making modern mechanical ventilation the clear winner, is the fact that electricity will likely get significantly greener in the near future as renewables start dominating the energy mix. For delivered heating on the other hand, the transition to green alternatives will likely be much slower.
This therefore marks the end of the road for the passive StackHR system as a viable step towards a greener future.

During our work we did however find that the StackHR concept probably has the potential to beat all ventilation solutions currently available for high rise construction by making some slight alterations to the design. As these alterations include the addition of small low powered assisting fans, the StackHR system has gone from relying only on stack effect as the driving force, to technically becoming a hybrid ventilation system. For now I'm going to stick with the original name though.

I know it has been a while since my last post, so thank you for sticking with me. I will post our full report for the LCA analysis here as soon as we have it ready, so stay tuned!