Draft. These pages were imported from the ARC Technical Criteria document (16 April 2026) and have not yet been reviewed in this format. Several thresholds are still being settled and are flagged on the pages concerned.

Step 1 and Step 2

Step 1 is a naturally ventilated building that can be retrofitted over time; Step 2 is fully mechanically conditioned but still able to run on natural ventilation.

Step 1 means constructing or refurbishing to create a naturally ventilated building that can be incrementally retrofitted over time to incorporate mechanical systems for cooling. The building operates in natural ventilation mode, but if retrofitted with mechanical systems, becomes a ‘multi-mode’ building over time.

Step 2 means constructing or retrofitting to create a fully mechanically conditioned , but ‘multimode’ building i.e. one that can also operate effectively in natural ventilation mode.

Step 1 requires designing and constructing a robust, physically and technologically simple building that relies for effective performance on:

• passive design features such as appropriate building orientation; solar shading; exterior facing materials with high reflectivity; hot air-shedding from rooms and roof spaces via carefully placed openings in the building fabric ; optimising cross ventilation and airspeed for enhanced cooling of occupants; providing consistent ventilation for occupants; appropriate use of thermal mass suitable for each climate
• relatively simple, low-carbon and affordable technologies, including energy-efficient electric fans for additional cooling of occupants
• comprehensive, insect protection measures such as mosquito mesh screens and nets

Step 1 requires a building design to have considered the most likely future improvements that people will make to that building in order to improve its performance over time, a typical example includes room by room addition of air-conditioning.

Step 1 designs should be future-proofed so as to anticipate how this may be achieved most effectively (performance), most cost-effectively (reducing the amount of associated building work required to make the changes), most energy-efficiently (to keep air-conditioning energy use, carbon-emissions, and running costs as low as possible), and also to facilitate adequate background ventilation of rooms when air-conditioning is running.

The design should make it straightforward for occupants who later retrofit air-conditioning to move easily between having the air-conditioning running efficiently and reverting to cooling the building using natural ventilation only, when conditions allow. Future addition of air-conditioning should not ‘lock out’ the ability to effectively operate the building in electricity-free, natural ventilation mode.

A well-designed Step 1 building provides a straightforward, practical pathway for people to make improvements over time - adding mechanical cooling, dehumidification and ventilation, solar and battery backup, as the climate changes and heatwaves become more extreme.

A Step 1 building can change over time into a Step 2 building i.e. the end stage of a process that may take several years to complete. In some cases, there may be adequate budget and a good reason for designing and constructing the building to a Step 2 specification straight away. Examples of a Step 2 strategy include working to the ARC standard, the international Passivhaus Standard, or with particularly careful attention to best ‘cool building’ practices, to the less comprehensive EDGE buildings standard.

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Source: ARC Technical Criteria - 107
Pattern · confidence medium · Imported 2026-09-12, not yet reviewed · next review 2026-12-12
Tags: untagged
Citation key: steps-1-and-2