## Site Analysis Metrics

Site analysis is an important tool for building designers to help guide the form and orientation of their designs to take optimum advantage of whatever amenity and resources are availabe. As the design develops, site analysis becomes even more important as a means of demonstrating compliance with building codes and meeting the energy efficiency and sustainability criteria set by clients and/or regulatory bodies. As with most building performance analysis though, there is no single metric that will solve all your design problems. Instead, you typically have to compare multiple metrics on each design iteration and try to make the best set of compromises for both your building and the impacts it will have on those that surround it. The aim of this article is to outline the range of site analysis metrics that can be computed and to loosely group them based on their input requirements.

## Solar Position

The position of the Sun in the sky varies continually throughout the day and also changes signficantly over the course of a year. It is also very location-dependant, so it is critical that you know the latitude and longitude of your development site before you begin any calculations. Despite our fundamental physical understanding of solar position as a result of experiencing it every day, calculating it at any specific date and time is by no means a trivial exercise. The tilted rotation of the Earth and its elliptical orbit around the Sun add significant complexity to the equations required. Add the fact that one day isn't actually the time required for a full rotation of the Earth around its axis and that 365 days isn't actually the time required for a full orbit around the Sun, and we're in for some real fun and games.

## Sky Distribution

This article discusses the processes involved in determining the luminous distribution of daylight and solar radiation over the skydome in order to accurately account for the effects of shading and reflections in and around a building site. It looks at the mathematical models used and their implementation, as well as some of the issues associated with aggregating multiple skies over longer periods.

## Significant Latitudes

This article discusses a range of latitude lines on the Earth's surface that have some solar significance. Latitude refers to one of the angular components that define a geographic location, more specifically to imaginary lines that run around the Earth parallel to the line of the Equator and vary from -90° at the South Pole to 90° at the North Pole, passing through 0° at the Equator. As the Earth's axis is tilted relative to the Sun, the amount of available solar radiation varies throughout the year giving us the four seasons. This seasonal variation is marked by solar-related minima and maxima that occur at particular latitudes.

## Significant Days of the Year

This article discusses those days within the year that have some solar significance. Known as Solstices and Equinoxes, these days are defined by the cyclical nature of available solar radiation and mark the changing of the seasons. Understanding seasonal variations in temperature, daylight and solar radiation throughout the year is an important part of the building design process.

## Significant Times of Day

Over the course of any 24 hour day, the world transitions from the darkness of night to the brightness of day, and then back again. As the Sun arcs its way through the sky during that process, it crosses a number of thresholds and reaches certain maxima that have long influenced man's activities, even today. This article discusses those particular times of day that have some solar significance, which include different stages of twilight, sunrise and sunset, as well as local and solar noon.

## Dynamic Daylight Simulation

This article presents the methodology used in the initial versions of the web-based dynamic daylight simulation tools and compares the results with those from Radiance using the exact same model. It is intended as a detailed supplement to a research paper with a similar title submitted to the PLEA 2017 Conference in Edinburgh, providing additional explanatory material, information and results to support the arguments made in the original paper.

## Solar Availability in Cities

Analysing solar and daylight availability in dense urban environment is quite a complex process and depends on dynamic overshadowing inter-relationships between buildings and other site obstructions. Accurately quantifying the effects of shading and overshadowing is key to the prediction of building performance metrics such as solar gains, daylight access and thermal behaviour, as well as the potential benefits of photovoltaics and other renewable energy sources. Not to mention increasingly stringent legislation on solar-access and rights-to-light. All this means that the use simulation tools to predict these complex effects are becoming increasingly necessary, as is the ability to visualise and convey this information obviously and effectively. The first part of this article deals with the means of mapping solar radiation and other metrics on buildings surfaces, whilst the second deals with calculating the full spatial variation in solar availability over the entire un-built volume of a site using an analysis grid.

## Comparing Solar Position Data

I have had a couple of occasions recently where I needed to directly compare different solar position algorithms, as well as predicted versus recorded position data. This sounds pretty simple, but there are actually some interesting little quirks where even datasets that are so close as to be virtually identical will still throw up spuriously large differences in individual values. I thought these might be worth documenting and discussing.

## ECOTECT and the Average Energy Year

When you perform solar and thermal calculations in Ecotect, it does not do these for any specific year, but rather a standard 'average' energy year. This is true of nearly all thermal and energy analysis tools. Even the weather files used for solar and energy analysis are usually averaged to better represent long-term conditions. This article explains the basic assumptions behind the 'average' energy year and why this approach is more appropriate than using any particular year.

## Introducing Scripts in ECOTECT

Scripts have been available in ECOTECT from very early on in its development and are probably one of its most under-utilised features. Anyone can write and run a script in ECOTECT and they can be used to add new functionality, automate complex tasks, initialise or standardise a model to your firm's requirements, generate summary data, export to another application, etc. Pretty well anything you can imagine. This article is a brief description of what a script is and what it contains.

## Behaviour of Light

Understanding the behaviour of light within materials and spaces is a key skill for any competent architect or building designer. Without this knowledge, a huge amount of the amenity available from natural light and solar control is at risk of being under-utilised or worse, seriously compromised. The concepts themselves, though many, are relatively straightforward. However, once you understand them, you will very likely use them everyday in your design work and specification writing.

## Are Highly Efficient Buildings Sustainable?

Many recent regulations and energy codes focus almost exclusively on energy efficiency during the operational life of a building. In our struggle to adapt to these changes and still appear 'modern', architects and designers are increasingly looking to energy-intensive materials and high-tech solutions, often ignoring many of the wider impacts of their projects. This article questions the true sustainability of these kinds of buildings and suggests that there are better ways to achieve the efficiencies we need.

## Fitting a Spatial Analysis Grid

Many people have questioned why the analysis grid produced by the 'Auto-Fit Grid' function in Ecotect leaves a gap around the edges of a room rather than covering the full extents of its floor area. There is a very good reason for this and, as it touches on some more general analysis concepts, is deserving of some detailed explanation.

## Averaging Solar Radiation

For the most part, the mathematics of solar radiation is pretty straightforward. However, there are a couple of situations that are less intuitive than they first appear. This is definitely true in the calculation of average hourly incident solar radiation (insolation).