ETTV: Time for Something New?
As part of the Singapore Green Building Week program, the International Green Building Conference 2016 provides us with an opportunity. An opportunity to show case interesting local and international projects and products, learn about the new Green Mark developments and importantly to meet the like-minded and set forth an improved plan to engage, design and construct better buildings.
Today, we are at a point of no return for climate change mitigation, so the subject of what comes next in the green building movement is increasingly being asked. With all meaningful scientific data pointing to our ongoing role warming the planet, it is clear to anyone willing to uncover a stone from the mountain of evidence that we need change now.
Change disconnected from our short-term, self-indulgent political landscapes, that will enable mitigation legislation and strategies and for the future. Without such vision, the design and construction industry may very well end up as one of the biggest missed opportunities of our lifetimes and one we will regret!
Answering the Call
Providing a submission for this year’s ‘Call for Presentation’, I have been given the opportunity to provide a Green View Tech Talk at the anchor trade platform, BEX Asia. After chewing through a few topics, I have decided to ask a somewhat rhetorical question for me: Are we ignoring true performance opportunities in Singapore?
Since 2004, Singaporean design teams have used guidelines to assess the thermal performance of the building envelope for the purpose of energy conservation. Known locally as Envelope Thermal Transfer Values (ETTV) with slight regional variations (tweaks to the underlying equations), this pre-Green Mark approach to design stood strong ground in the green building development years where simplification was key.
Today, with advances in façade design and our ability to model it to a greater level of accuracy, i believe our old friend ETTV is now a metric of the past. Much like the now widely defunct daylight factor, the ETTV underlying equations are prime for improvement to take into account much more than a simple area weighted value of opaque and transparent materials of the façade design.
For example, through today’s existing equation of using the centre of pane performance values of shading coefficients (SC) and U-values, we can get a feel for the performance of façades in the most rudimentary way. But can these in anyway be used to define a façade true performance given that the absolute omission of conductive elements (thermal bridging) of framing, shading and other details are ignored?
My presentation will aim to ask this question through a review of the equations and aim to deliver a case in point for a more realistic representation of a façade systems. Presenting a quick stead state calculation for a typical aluminium curtainwall frame detail under Singapore conditions, I will be illustrating the relative weakness of the frame from a thermal perspective, with massive heat flows under peak exterior conditions.