Heating, Cooling and Ventilating Homes Naturally
A passively designed home incorporates design principles to reduce the need for mechanical heating or cooling. This includes maximising cooling air movement, shading, glazing and insulating to exclude entry from the summer sun. In winter, the building should trap and store heat from the sun and minimise heat loss to the external environment. Passively venting the house and the use of natural materials in the home will help to improve the quality of air in the home.
PASSIVE SOLAR HEATING
Design for passive solar heating is about taking advantage of natural heat sources to heat the home. This can be achieved by:
- Orientation of daytime living areas and appropriate sized glazing to the north;
- Location of materials with high thermal mass, where it is exposed to direct solar radiation to absorb heat; and
- Insulation of walls, ceilings and floors and draught sealing around doors, windows and extraction fans.
Floor plan zoning, based on heating needs for the occupants:
- Living areas and the kitchen located towards the north;
- Bedrooms located along the east or south façade; and
- Utility and service areas (e.g. bathrooms and garages) should not be located on the northern façade or orientated where they can block the passage of cooling breezes.
If mechanical heating is required, consider the use of: infrared panels; solar slab heating; solar heating; heat recovery ventilation systems; or efficient reverse cycle airconditioners. Heating systems should be placed adjacent to thermal mass walls and away from windows and passageways.
Passive cooling maximises the efficiency of the building envelope by minimising heat gain from the external environment and facilitating heat loss. This can be achieved by:
- Orientation of adequate sized windows to cooling breezes to maximise ventilation;
- Reduce internal air path barriers to increase natural ventilation;
- Install ceiling fans to assist in air circulation;
- Avoid extensive glazing on east and west facing facades to minimise heat gain;
- Where glazing is located on these facades, effective shading should be employed;
- Adequate levels of insulation to at least the minimum recommended for your climate zone;
- Appropriate use of thermal mass determined by the daily temperature changes in your region;
- Use light coloured roofs and walls to reflect solar radiation.
In certain climate zones, mechanical cooling maybe required. Where necessary energy efficient air-conditioners should be installed in rooms that:
- Minimise external air infiltration;
- Contain high levels of insulation;
- Have energy efficient glazing;
- Are located in cooler zones of the house i.e. rooms with lowest exposure to external temperature influences;
- Employ air-locks to doors that are commonly used; and
- Use airtight construction detailing, particularly at wall/ceiling and wall/floor junctions and around doors and windows.
PASSIVE VENTILATION THROUGH MANUALLY OR AUTOMATED SYSTEMS
Air quality can be improved by ventilating the house. If too little fresh air enters a home, pollutants can accumulate to levels that can impose health and comfort problems on the occupants.
Contributors to indoor air pollution include:
- Use of synthetic building materials, or high emissions from a few materials finishes and furnishings which release volatile organic compounds;
- Use of pesticides and household cleaners; and
- Biological sources such as insects, mould, and other fungi.
Factors to consider:
- Emissions – some materials will emit more pollutants than others.
- Toxicity – the potential harm a compound can occur immediately or over time.
- Quantity – Low emissions from large quantities of materials, or high emissions from a few materials can result in high total amounts of chemicals emitted.
- Proximity – The location of the material compared to occupants.
Some systems to employ to enhance indoor air quality include:
- Provide adequate cross-flow ventilation to allow fresh air to move through each room;
- Install ceiling fans to assist in air movement;
- Install extractor fans in rooms without natural ventilation e.g. bathrooms, kitchens etc.
- Employ measures to avoid dampness to minimise the growth of mould and fungi such as insulated walls, controllable vents and double glazed windows;
- Select mechanical fixing methods for floor coverings;
- Select natural untreated floor coverings eg linoleum, cork and natural fibres;
- Externally flue all gas stoves and heaters to allow pollutants to escape;
- Follow correct installation and maintenance procedures for chimneys and flues;
- Ensure that where internal access from garages exist that these are well sealed from the house and the garage has appropriate ventilation measures installed;
- Install only low-NOx heaters and avoid using them in confined spaces;
- Install an automated or manually operated ventilation system to enhance internal air movement;
- Select low or no emission paint and varnish finishes for cabinetry and flooring;
- Select low emission products for internal timber work;
- Select commonly used indoor plants to absorb emissions and if pesticides are used ensure this is undertaken outside; and
- Install an air filter where homes are located on a main road or in an industrial area.