Windows and doors are the points at which we open our homes to the outside world, both in terms of being the points of our own (and our guests’) entry and exit, but also in terms of letting light, warmth and air flow into our homes.
They are also the only “weak points” in the envelope of our homes. They should be robust and enough to shield us from the extremes of weather.
They should also keep any unwanted visitors (and I’m not talking about door-to-door salespeople) firmly on the outside.
Changing to suit the climate
In October 2007, parts of the Building Code focussing on energy efficiency were changed, effectively requiring houses to use about 30% less heating energy than before. In practice, this means that most new houses and additions to houses are required to have better insulation. Although architects, designers and builders have been aware of these changes for some time now, were you? How does this affect you if you’re building or renovating?
For starters, you may have noticed an increase in the number of advertisements for double-glazing, or even retro-fitting of double-glazing for existing homes. Double, or even triple-glazing has been standard for many years in Europe and the USA for a very good reason – it’s much more efficient. In New Zealand even modern, well insulated homes are still losing up to 50% of their heat because it escapes easily through single-glazed windows. Despite this, double-glazing is not mandatory under new H1 requirements. It’s more complicated than that.
The technical stuff
To demonstrate that a new house complies with the new requirements, an architect or designer must look at the total thermal envelope of the building. That includes roof, exterior walls, floors, and most windows and doors, taking into account all the insulation within them. He or she must total the R-values (the “R-value” measures how well a building material resists heat transfer, or in other words, how good an insulator it is) of all the materials that make up the envelope to figure out the Building Performance Index (BPI). The BPI of the house must meet the minimum level of performance required for that part of the country.
Here are some things to consider:
- Glass and aluminium, both common components of doors and windows in New Zealand, do not, by themselves, have very good R-values.
- The larger the window (or door), the more heat can potentially escape through it.
- The sun rises in the east and moves through our skies in a northern arc until it sets in the west. This means north-facing windows best capture light and warmth from the sun while south-facing windows will mostly let heat escape.
- Skylights are allowed, but must be calculated as part of the BPI. H1 encourages 1.2m2 or less of skylights by requiring architects and designers to use a more complicated type of calculation to prove compliance if the area is greater than 1.2m2.
- Solatube Daylighting Devices are a good solution here as they are Energy Rated with an insulation R value of 0.4 which is considered above that of triple glazing and much higher than standard skylights. They reduce the need for electrical lighting and provide an abundance of pure, clear, natural light – even for those interior spaces where natural light is rarely an option. Daylight from a Solatube can even be controlled with a dimmer.
Most of us want nice big windows that will let the sun in while letting us admire the view of the garden (or countryside, cityscape, beach and so on). Glass is a good conductor of heat, meaning heat escapes quickly through it. The larger the window, the quicker that process is. Air is not a good heat conductor. Double-glazing traps air (or gas) between two layers of glass, reducing the heat loss, meaning we can have our big windows and still stay warm in winter.
Windows are made up not just of glass but also joinery. A newer option to New Zealand as far as window joinery goes is that of uPVC frames. These have been popular with the efficiency-conscious in Europe for some time as uPVC is a very bad conductor of heat. Some window systems go beyond mere thermal efficiency. The main point of entry in over 60% of the burglaries in New Zealand is through an unsecured window. Multi-point locking technology is available to create some of the most secure windows around.
Over the last forty years, aluminium joinery has developed to become the most used window and door system in New Zealand for its strength and durability in New Zealand’s occasionally harsh environment. There are a wide range of options available to suit any house style or budget. Fairview say that price of the different systems available depends on their complexity and the size of the windows.
The Fairview, an extremely functional, competitively priced range. Evolution Series has a more modern look and clean internal finish at a slightly dearer price. Architectural Series is a high performance range which allows for over-height doors and windows and is slightly dearer again. Timberview combines the durability of aluminium on the outside and the warmth of real timber on the inside.
With the changes to the Building Code, Fairview has recognised the need for joinery that will help improve the thermal performance of the home. Thermacolour was introduced as a thermally efficient suite that minimises cold and condensation for about the same price as the Architectural Series. Thermacolour allows there to be one colour on the outside and another on the inside.
Did you know that roughly 60,000 burglaries and 10,000 counts of trespass occurred in New Zealand in 2008 according to Statistics NZ?
Do all you can to improve the security of your home and reduce the risk that you will be targeted by thieves. Install good quality locks – preferably deadlocks – on all entry and exit points in your house (both doors and windows) and get into the habit of using them at night, when you’re out and even if you’re at home but in the garden.
The New Zealand Police also recommend not leaving a door key hidden outside – burglars know all the places to look. If you tend to lose keys, or like to go out for a run or walk unencumbered, keypad locks for your main doors are available. Just enter your code and you’re in. Too many wrong code entries and an alarm will sound, deterring potential intruders. They give you the option to have different codes for different people, plus the ability to add and delete temporary codes if you have visitors or tradespeople coming and going, so you will never need to risk the security of your home by leaving keys out.
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Find out what you can do to be Life Cycle Costing savvy in the articles linked below.