Here at Transsolar we call ourselves climate engineers for a lot of reasons, but one of the main reasons is because we like to look and see how the outdoor climate affects the indoor climate of a building. While we understand it very well (it is our job, after all), it’s difficult to explain many concepts of building physics quickly and easily—which is why Transsolar New York has started working on a tool that won’t just tell you. It will show you, using Sankey diagrams, how energy enters and leaves a space, and affects the temperature.
Sankey diagram displaying solar radiation entering a building at the moment of highest solar radiation
Sankey animation showing how heat flows through a room and into the air over a 24 hour period
These Sankey diagrams allow us to see the proportion of how much energy is hitting the façade, how much energy is being radiated into the walls, how much energy is being convected into the air, and how much heating or cooling is actually needed to maintain an acceptable indoor air temperature. The animation is the first example we’ve ever seen of a Sankey diagram that represents the dynamic, ever-changing relationship of heat flows in a building with time.
In the end, we’re hoping that this tool will give high resolution animations that are fully customizable, allowing us to input different climates, gains, facades, ventilation methods, heating/cooling methods, and many other things. This way, we could compare different designs and show this energy flow to architects and design teams so they can better understand the building physics behind design considerations.
Of course, there are plenty of things to learn from this very basic design above on how to reduce a building’s energy emissions while still maintaining a comfortable indoor climate. The above animation represents a single New York City office with a south facing façade, on one of the first days of autumn, and even from this we can see some key design concepts
1) Exterior shading is extremely important – Our general rule is, once the heat is in a building, it’s in. Exterior shading reduces the amount of solar radiation that hits a façade by up to 80%, which can significantly reduce cooling. Operable or scheduled exterior shading is even better, as then you can allow more heat into the building during the winter, reducing heating costs.
2) Reduce your artificial lighting – For 10 hours a day, over half of the heat that is being convected into the air comes directly from internal gains. One of the only internal gains that designers have direct control over is the lighting. By decreasing the amount of artificial lighting (by either increasing daylight or switching to a more open floor plan), the amount of heat the lights convect into the air can be significantly reduced, and cooling loads would not be as high.
3) Walls absorb heat – You can see the internal energy of the walls change significantly through the day—increasing due to solar radiation in the day time, and decreasing due to higher convection at nighttime. Keeping that in mind…
4) A lot of solar energy goes into the floor – moreso than any other surface. Also, the floor absorbs a lot more of that energy than is directly convected. Finding a way to remove that absorbed heat before it gets convected (through a radiant system, perhaps) would reduce the amount of air conditioning necessary.
We’ll keep you updated on this tool as it develops.