Green scheme

Design Advice provides the services of an environmental architect or engineer for a day. But although a real-life expert might be good value for money as a one-off, the consultant who visits you may have designed only a handful of low-energy schemes. The software program, however, includes the details and experience gained from dozens of projects, and can be used for calculations on new buildings whenever you need it.

The program, called Design Tools for the Choice of Natural Ventilation, is intended to promote low-energy, natural ventilation strategies in preference to mechanical air-conditioning. The CD format software runs on Windows 95, Windows 98 or Windows NT, and has two elements: a database of 150 real buildings, and a calculation program that allows design parameters to be input and performance data and costs to be generated. The case studies include fully air-conditioned and part air-conditioned buildings, as well as buildings that use displacement ventilation and natural ventilation.

Each building is shown in great detail. Data presented includes plan dimensions, U-values, window specifications, lighting specifications, predicted and measured temperatures and running costs, energy consumption (broken down into constituents such as fans, cooling and heating), and the type of ventilation used.

Three assessment methods

Clients, architects, engineers and other consultants can use the program to check whether their buildings are suitable for low-energy ventilation in one of three ways. The first is through a simple analysis of the database. Once basic requirements such as floor area, floor width and cost per square metre have been input, the program searches the database looking for case studies that match the requirements.

Users can then browse the selection generated by the search, gaining ideas of what can and cannot be achieved. In most cases, the database will produce examples of buildings that use a variety of ventilation strategies, so variations in performance between, say, displacement ventilation and full air-conditioning can be compared.

The program can also assess the potential for natural ventilation through a series of questions and answers known as a "decision tree". Based on a model developed by the Chartered Institute of Building Services Engineers, the program asks a series of questions about the building being assessed. For instance, it asks what kind of heat gains are likely, how wide the building is (important when considering how much artificial lighting is needed), how high local air pollution levels are, whether the building needs tight temperature control and whether humidification is required.

As with the first method, a selection of close matches from the database is garnered, allowing comparisons to be made.

The third element of the program allows a rough model of a building to be created and its performance assessed. From previous analyses of the database, users get an idea of what type of ventilation system they want to try – for instance, displacement ventilation. The user can choose a generic model using displacement ventilation from a menu. A screen appears that is split into three. To the left are graphs depicting benchmark capital and running costs for displacement ventilated buildings. In the middle is a panel showing the performance of the buildings, including temperature, noise, natural daylight and air quality. The right-hand panel of the split screen shows a basic plan and elevation of the building, for which the designer controls the parameters.

The dimensions of the plan and elevation of the building can be altered, and the effects of these changes fed into the performance calculations shown in the middle panel. This allows users to see how increasing the size of windows, for example, increases the amount of natural daylight, but also increases temperatures.

Detailed data input

The level of information that can be fed into the calculations is sophisticated. It includes: