Design is important because it is powerful
In a recent article I looked at 5 reasons why building design is more important than ever, and considered how we can leverage high performance building design techniques to create truly great buildings. We will soon publish a case study on a 100,000 sq. ft. New York residential project which powerfully illustrates how good design can dramatically improve building performance. In this article, I’ll share a sneak peak of the results, but first, let’s take a look at a new technology which helps us achieve high performance buildings.
The most cost effective approach to high-performance design is to equip designers with right the tools – and in particular architects working at the early stages of design. One of such tool is the Sefaira for SketchUp – Real Time Analysis plugin from Sefaira which gives immediate feedback directly inside the design software while the architect develops their concept design. Whenever a building designer changes their model, Real Time Analysis provides a full, dynamic energy analysis in seconds. It uses a powerful cloud platform to crunch the numbers needed for rigorous energy calculations. This means that design options can rapidly and effectively be explored for their impact to overall building performance.
Looking at a New York Residential project
Our sample case is a New York residential project. The goal of the analysis was to find the design strategies that would provide the biggest benefit over minimum requirements. In this case our benchmark is ASHRAE 90.1-2010, although ASHRAE 90.1-2013 is becoming more common as the go-to guidance code.
Strategy #1: Siting and massing
This collection of strategies allow us to explore the impact of different building aspect ratios and placements on the project site. In this instance we evaluated 3 different massing options – a tall tower, a square block and a rectangular block. The baseline already met code, but by selecting the optimal siting and massing (a square block, in this instance) we achieved results with the following improvements over the code baseline:
Energy use – 23% improvement
Peak heating capacity – 37% reduction
Peak cooling capacity – 37% reduction
Strategy #2: Exploring glazing ratios
We explored ratios from 30% to 80% over a number of iterations and we saw the best performing option delivering energy use performance that was 29% better than the worst performing, with 32% lower peak heating and 50% lower peak cooling requirements.
Strategy #3: Creating powerful shading strategies
Designing good shading on the building reduced energy use and peak cooling requirements by a further 16%.
Strategy #4: Thermal Mass
We evaluated various thermal mass options such as a medium thermal mass option (based on a steel frame with concrete topping slabs) and a high thermal mass which was a more thermally dense concrete construction. Due to the significant temperature swings in New York the high thermal mass option can reduce peak heating requirements by 7% and peak cooling by 9%, further reducing the capital we have to invest in HVAC systems.
Summing the Benefits of Strategies #1 to 4
Because buildings are integrated systems, the total benefit of multiple strategies is not directly equal to the sum of the parts. Every time we pursue one design strategy, the effectiveness of all other design strategies is affected.
Only by evaluating the strategies together can we correctly assess their combined benefit (this type of rapid, aggregate analysis is one of the powerful features of Sefaira).
When we combine the 4 strategies described above, we achieve a 43% improvement over baseline, even before analysing envelope improvements such as insulation and high performance glazing. Next, let’s look at what happens when we add in further envelope improvements.
Bonus Strategy: Envelope Improvements
Even in a well-designed building, high performance building materials and construction techniques can easily yield more than 10% of additional reduction to annual energy use. By making the right envelope specifications such as air tightness, insulation and glazing properties, peak heating in particular can be further reduced — in this instance a further 49% below the annual energy use of the already optimised building.
Putting it all together
High performance building design is design at its very best – design that simultaneously offers many opportunities and constraints, and which can be explored and improved only through countless iterations as the designer goes through the many possibilities. In this instance, combining all the strategies have a 49% improvement to overall energy use, a 77% reduction in the peak heating requirement and a 75% reduction in the peak cooling requirement, compared to the worst option that meets code. As a next step we could now fit sophisticated systems and renewable technologies, which might further improve building performance.
Using high performance design to deliver more for less
Buildings are costly, expensive to design, and in particular expensive to construct. Here is the good news: We can use high performance design techniques to create fundamentally better buildings while reducing the capital required to build these, thereby breaking the historical trade-off between “high sustainability” and “high cost”. We can create buildings that cost less to build, less to run, deliver a better experience for their users and are more sustainable for all of us. How so? Well, by designing buildings smartly – as illustrated by the case above – we can reduce e.g. peak heating and cooling loads, which means that we can deliver the required thermal comfort to a building using smaller systems.
In this case our design strategies reduced peak cooling and peak heating loads by 75% and 77% respectively, and the savings from this run into several million dollars on a project of this size. And this is just the beginning. Smaller systems mean lower capital cost, lower energy use and an overall much smaller Total Cost of Ownership over the life of the building (when factoring e.g. system maintenance and replacement costs into the equation).
Not all buildings are created equal
It is important to note that not all locations and use types will produce these types of results. For example, benefits will be smaller for buildings that are dominated by internal loads, but even here the impact of daylight, glare etc. is important. That is one of the reasons why it is so important to integrate analysis (including daylighting) directly into the design process. Only by integrating design and analysis using high performance design techniques (and software such as Sefaira) can we understand design performance well enough to make the right decisions.