The sun's energy can be harnessed to keep your home warm and dry.
By combining good design with effective insulation, you can collect and store the sun's energy to provide your home with warmth day and night, throughout the year. Using the sun to heat your home (passive heating) can slash your heating costs, reduce condensation and dampness, and make your home healthier and more comfortable.
Passive heating can be incorporated into new homes, renovations or existing homes of all types. In some homes, passive heating will maintain stable temperatures year-round without any need for supplementary heating. Others may need additional heating in winter - this supplementary heating will be far more effective in a home that uses passive heating principles.
As well as benefiting you, passive heating is by far the most environmentally friendly way to heat your home. Other forms of heating such as gas and electricity generate greenhouse gases and other harmful emissions when produced by burning fossil fuels.
Is passive heating right for me?
Using the sun to heat your home combined with good insulation is suitable for any type of home, on any site, in any location. Stand-alone houses, apartments, townhouses and rented homes can all benefit.
Costs and benefits
The most important element in capturing the sun's warmth is good design. It doesn't have to cost more, for example, to make sure your main windows face the sun or, if your site allows, to use an insulated concrete floor for thermal mass to retain heat instead of a timber one.
There may be some costs involved in passive heating - for example, for additional insulation or double glazing. These will pay for themselves over time because less energy will be needed to heat your home resulting in lower power bills.
In general, if you incorporate passive heating principles in the planning stage, construction costs shouldn't be significantly greater than those for a conventional home.
When you're budgeting for passive heating, the highest priority should be additional insulation above the Building Code minimum requirements.
When should you think about passive heating?
Planning a home or renovation
Passive heating principles can influence every aspect of the design of your home. Ideally, you'll start thinking about it before you've bought a property or started planning your home or renovation. Passive heating should be considered alongside passive cooling and ventilation.
In your existing home
Passive heating can be improved in an existing home without making major alterations. The most obvious way to achieve this is by installing extra insulation in your ceilings, walls and floors. You can also reduce heat loss by double glazing your windows, replacing poorly-performing windows and sealing up draughts.
With passive heating, the first step is getting the sun's warmth into your home. To make the most of the sun, the main living areas of your home (or any rooms you use a lot) need to face north. You will need to plan your windows so that the majority of your glazing faces north and east to catch the sun. You can use also conservatories and trombe walls to catch the suns heat.
Once you've got the sun's warmth into your home, you need to keep it there for as long as possible. Heat escapes by passing through the ceiling, walls, floor and windows. To keep warmth in, you'll need to block off its escape routes: insulate, take steps to reduce heat loss through windows (with sealing, double glazing and thermal-lined curtains) and block off draughts.
Insulation in your home is essential for effective passive heating. It:
- keeps heat in on cold days
- prevents too much heat from getting in on hot days
- reduces condensation and dampness - cold air holds less moisture so it will condensate on windows and walls.
Insulation is one of the best investments you can make to improve the quality of home life. No matter where you live and what type of home you have, the ongoing benefits of good insulation will far outweigh the costs.
There are legal minimum requirements for insulation in new homes and renovations - it's worth exceeding these requirements to get a warmer, more comfortable home.
See Insulation for more.
If your home is well insulated, the biggest source of heat loss will be through glass (i.e. windows, skylights and glass doors). You can reduce this by:
- using close-fitting heavy drapes with pelmets
- using double glazing and/or low-emittance glass
- using timber, PVC or thermally-separated aluminium window frames
- designing larger windows on the northern and eastern sides, and smaller windows on the cooler western and southern sides of the house
- locating windows so that eaves provide shade in summer, but let sun into the house in winter.
Draughts are caused by air moving from a warm area to a cold area, creating a breeze. They contribute to heat loss. Typically, draughts can come from:
- gaps between frames and walls during construction
- gaps around badly fitting windows and doors
- inability to shut off heated areas
- chimneys and flues.
Stopping draughts is one of the simplest and most cost-effective steps toward conserving heat.
See Draught stopping for more information.
To prevent heat loss:
- locate rooms that are used least such as garages, bathrooms and laundries to the south - they'll provide a buffer, preventing heat loss in living areas
- use 'air locks' at external entrances to your home, to keep cold draughts out - entryways, laundries and attached garages can all function as air locks
- design door swings so they will blow closed if left open in strong winds or consider using door closers on external doors.
The shape of your home can also influence heat loss. For example, a multi-level home will be easier to keep warm because it has less roof surface through which to lose heat. The top strey will also be warmer because heat rised up through the house.
You can store the sun's warmth by using materials with high thermal mass (materials that are good at absorbing and storing heat). These materials are usually heavy - such as concrete and brick - and are used in floors or walls.
Used properly - the right amount in the right place, with proper insulation - will ensure they absorb heat during the day and radiate it out as the temperature drops in the afternoon or evening.
See Thermal mass for heating and cooling for more detail.
Achieving the right balance
It's vital to get all aspects of passive heating working together. If you consider only one aspect, you risk not making the most of the sun's warmth and your home not being as comfortable as it could be. For example, if you install large windows on the north wall of your home but don't think about how to store or conserve heat, you might find you're hot during the day and then cold when the temperature drops sharply after the sun goes down.
If you do nothing else, at least make sure your ceiling and walls are properly insulated - you'll get a more comfortable home and lower power bills.
From Smarter Homes
- Draughts stopping
- Using thermal mass for hearting and cooling
- Thermal mass
- Understanding your site
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From other sites
The Energywise website has a web page on designing for the sun. And you can download the Energy Efficiency and Conservation Authority publication Design for the Sun, which provides comprehensive and conceptual information and guidance for designing energy-efficient and passive solar houses in New Zealand.
Designing Comfortable Homes is a guide to energy-efficient design using glass, thermal mass and insulation, produced by EECA and the Cement and Concrete Association of New Zealand (CCANZ). The booklet can be downloaded for free from the Energywise website.
The former Waitakere City Council website has sustainable home guidelines which include Design for the Sun, a guide to the principles of passive solar design.
The Australian Your Home website has a comprehensive section on passive design, both cooling and heating.
The Design Navigator website has a solar design FAQ with information on the basics of solar design.
Visit the Ecobob website for case studies of other homes which use passive solar design.