For home that aims to blur the line between indoor and outdoor living, large glass windows and folding glass walls create an easy-to-use solution that looks good and helps let the sunshine in.
Windows are our portals for natural light, temperature, fresh air flow and views. There are choices to be made regarding size, orientation, opening type and direction, frame material, glass type and treatment, number of glazing layers, and quality of seals. It is vital to understand each element, and to design and use appropriately to maximize the benefits and minimize the disadvantages.
We have considered what qualities are needed for each living space and from each window. We have also considered how all the windows work together as a whole house system. And, as always, we made responsible choices with all components in regard to their life cycle – from womb to tomb.
Ordinary windows can represent a major source of unwanted heat gain in summer and significant heat loss in winter. Frames and seals can be ill-fitting and allow draughts. Inappropriate orientation of glazing can make the indoor environment uncomfortable in terms of light, temperature, air flow and views.
Many products on the market have high embodied energy, and green house gas (GHG) issues in some materials e.g. aluminium, glass from overseas (issues of manufacture and transport miles). Laminated glass often ends up in land fill as it is harder to recycle. There can be biodiversity issues (destruction of, or an erosion of habitat and/or biodiversity values) if ‘Bad Wood’ is used in framing.
Choices for ecokit
Windows and doors will be manufactured in Victoria. The standard will be double glazing with frames manufactured from FSC certified Australian timber.
Timber Treatment: Quantam Aquaoil, E Colour – E0 Poly Clear or Hymes UVEX Timber Primer. All are high performing products, rated zero VOC and manufactured in Australia.
Glass: Viridian Glass, energy tech or Sol tech ‘Smart Glass’ all made in Australia.
Summary of Research & Choices
Compared to PVCu, non-verified timber, and aluminium, FSC-certified timber has the most positive outcomes in terms of production of greenhouse gases, ozone-depleting chemicals, health (products or emissions during production or use that directly impact on human health) and biodiversity (destruction or an erosion of habitat and/or biodiversity values, e.g. threatened species or species loss).
Energy efficient windows will make your home more comfortable, dramatically reduce your energy costs and help to create a brighter, cleaner, healthier environment.
To enable the selection of high performance in different areas of Australia, WERS (Window Energy Rating Scheme www.wers.net) has split the country into three main areas that each require different window properties to achieve the best results.
Cooling Climate Zones
The priority in a cooling climate is to keep unwanted heat out of the home. In order of decreasing importance, unwanted heat gain takes three forms; radiant heat gain, conducted heat gain and infiltration of hot outside air.
In a cooling climate (tropical, subtropical or hot arid), coloured red on the map, the best results are obtained from windows that limit solar heat gain on all orientations (low solar heat gain coefficient). Although the first two climates are frequently humid while the last one is not, they can all subject the home to the risk of overheating at any time of the year. Good insulation (a low U-value) is also beneficial, especially if the home is air-conditioned.
Mixed Climate Zones
The priority in a mixed climate is to keep heat out of the home, except during a relatively mild winter season, when ‘free’ solar heat gain and retention of warmth in the house become important. Heat gain or loss takes three forms; radiant heat transfer, conductive heat transfer and heat transfer via air infiltration. Ideally, mixed climates call for strong solar control on east and west windows, but deliberate use of free sunlight admitted by northerly windows. This means different glazing solutions.
In a mixed climate (temperate), coloured green on the WERS climate map, the best results are obtained from windows that insulate well (low U-value), admit plenty of free solar energy (high solar heat gain coefficient) on the north during cooler months, but limit solar heat gain from the east and west (low solar heat gain coefficient). Ideally, northerly windows should be protected by correctly sized eaves. This will provide protection from summertime heat and glare while still allowing sun penetration in winter.
Heating Climate Zones
The priority in a heating climate is to retain heat in the home and maximise the use of ‘free’ solar energy in winter. Heat transfer takes three forms; radiant heat transfer, conducted heat transfer and heat transfer by infiltration of outside air.
In a heating climate (alpine and cool temperate), coloured blue on the map, the best results are obtained from windows that insulate well (low U-value) and admit plenty of free solar energy (high solar heat gain coefficient). In a cold region, large west-facing windows may contribute to short-term overheating in summer, but glazing with a low solar heat gain coefficient must be used with caution on the west because of the energy penalty it causes over the rest of the year.
Passive Solar Heating
If you’ve watched a dog or cat bask in the warmth of a sun rays, you’ve seen passive solar heating in action. For centuries people have taken advantage of the sun’s radiant heat. Homes constructed of stone were built to capture the sun’s rays, retaining it for the evening hours. Stone and tile floors exposed to sunlight perform in a similar manner.
Passive solar design and heating differs from active solar heating systems. Passive solar efforts utilize windows, walls, flooring and other non-mechanical or non-electrical devices to gather and distribute solar energy in the form of heat in the winter, and to reject heat in the summer. Heat rejection in the summer is accomplished through planned landscaping, large eaves and window treatments. Heat is not the only benefit in passive solar design; lighting can be greatly enhanced through proper planning, resulting in lower electricity use.
Windows play a major role in passive solar design and ventilation strategies that can make a home more comfortable, and contribute to heating and cooling that doesn’t cost a dime.