If you’re designing a completely new home or even extensively refurbishing, make the most of free sustainable resources by using solar energy to heat your home – it’s probably the most cost-effective heating method you can use. Jonathan Belsey, whose eco-home was featured on Channel Four’s Grand Designs spoke about the experience at 2011’s Grand Designs Live show: “The house uses solar design which means it stays warm in the cold weather and in the summer the concrete walls keeps the house cool. It was minus 13 one day this winter and we were warm as toast,” he said.
So what is passive solar heating?
Simply put, passive solar heating is the process of using warmth from the sun to heat your property – just imagine being sat in a greenhouse in the summer and you get the idea. The main aim is to capture and store sunlight in building materials which can later be released when you need it. The process is deemed ‘passive’ because it doesn’t use any mechanical or electrical devices – this makes it simple, cheap and easy to maintain.
How does passive solar heating work?
Passive solar heating works in the following ways:
- The building is orientated towards the sun within 30 degrees of south to get the most sunlight throughout the day.
- Large south-facing windows are used to let in adequate amounts of sunlight; they must be at least 15% of the room’s floor area in size to work effectively.
- Rooms that need more heat and light should be placed on the south side of the building, whereas less-used rooms can sit on the shaded north side.
- An open plan design allows sunlight to penetrate more of the property.
- Building materials should be chosen which can absorb or transmit solar energy for heating such as concrete, which absorbs sun in the daytime and releases it at night when it’s colder. Materials with a good thermal mass include concrete, brick, stone, metal and glass.
When designing your building there are three passive solar heating approaches you can take:
- Direct gain – in this system the thermal mass areas like the walls and floors absorb sunlight shining in through the windows. Floors may be
dark coloured stone and walls made of thick concrete for example, to store heat. These areas then act as a heat distribution system at night when it’s cooler, giving off their stored heat.
- Indirect gain – a thermal mass, such as a wall is placed between the sun and the living space, heat is transferred from this wall through
conduction into the living area. A wall can either be placed immediately behind south facing glass with vents to transmit heated air into the property or a container of water placed on a flat roof with glazing on top – the heated water warms the room below. You will need a strong roof with good drainage and insulation for roof pond systems to work.
- Isolated gain – the solar collector is separated from the rest of the house; for instance as a separate sunroom or conservatory. The heat generated in these rooms through direct or indirect gain is passed into the house through the walls or vents.
Passive solar cooling
Passive solar energy can also be used to cool your property in the following ways:
- Lots of large windows can be opened to ventilate the house.
- Thermal chimneys funnel rising hot air out of the building, drawing in cooler air to replace it– this circulation of air cools the room.
- Shading can be employed, for instance through planting deciduous trees to shade windows in summer and expose them in winter. Canopies can also be used to shade your property.
- Wing walls accelerate natural ventilation through pressure differences.
- Installing shutters can help cool the property.
- It can be used to heat and cool your property.
- Passive solar heating will save you money on mechanical heating and ventilation.
- Using a passive heating system will cut your household carbon emissions.
- A natural heating and cooling system can appeal to potential homebuyers.
- Passive solar heating will keep your home at a comfortable temperature.
- Large amounts of glazing in passive solar building designs lets in natural light, which can save on electricity bills and make your home more attractive.
- Passive solar heating systems have no moving parts so require no maintenance.
- It’s easier to incorporate passive solar heating into new buildings, but it can still be retrofitted depending on characteristics of the area and property.
How much does it cost?
When incorporated into a new build, the cost of solar passive heating doesn’t differ much from building a standard property. However, materials which absorb sunlight such as stone or brick may be slightly more expensive than other options; but they can also look nicer. Ask your architect about incorporating passive solar heating into your home design.