Three types of air conditioners:
The central air conditioner comprises a fan, a compressor and a cooling coil, all of which are housed in a module outside the home. Central air conditioning uses a duct system to distribute cooled air forced from the heating system. It is the most expensive and longest-lasting (more than 15 years) air-conditioning system, providing uniform fresh-air circulation throughout the home. If you don't have forced-air heating, you can turn your attention to a mini- or multi-split air-conditioning system. These systems include a wall-mounted outdoor compressor and a condenser supplying up to three air diffusers. If well maintained, split-system air conditioners can last up to 10 years. If you only have one or two rooms to cool, or if you expect to move any time soon, a room air conditioner – a window unit, a built-in wall unit or a mobile unit you can move from one room to another – may be your best option. A room air conditioner can be expected to keep you cool for at least five years.

Reversible mode
Some central air conditioners and mini- or multi-split systems feature a heat pump and are therefore reversible. By drawing heat from outdoors and pumping it into your home, a reversible air conditioner can also serve as a heating system – but only as a backup in the spring and the fall. At temperatures lower than 7oC, it no longer provides the performance you need!

Seasonal energy efficiency ratio (SEER)
To purchase an energy-efficient air conditioner, look for a unit with a minimum SEER ratio of 12. Better yet, opt for an Energy Star model, which consumes at least 20 percent less energy than a conventional unit. And while heat pumps are not eligible for the Energy Star program, Inverter technology – in contrast to conventional reversible air-conditioning systems – gives you the option of varying compressor speeds based on the ambient temperature in your home.

Where a conventional air conditioner stops when the desired temperature is reached, this technology lets the user reduce compressor speed to a minimum. The result? The unit operates on a continuous basis but at a carefully regulated speed – with no costly peak consumption periods.

Some air conditioners are equipped with dual compressors: Approximately 40 percent of the energy is consumed by a smaller compressor, and the primary compressor consumes the remaining 60 percent. When the desired temperature is reached, the primary compressor shuts down and the secondary compressor takes over with its lower consumption ratio. Consumers therefore spend less on energy than they would with a conventional machine, which always operates at 100-percent capacity.

Power
Always an important consideration: Too much power and your air conditioner may not run for long enough to dehumidify the air; not enough power and you'll never reach the optimal comfort zone. As a general guideline, a 5,000 BTU air conditioner is designed to cool a room measuring 14 square metres.

Noise
Not so long ago, central air conditioners emitted some 80 decibels (dB); today's models come in at 60 dB and 75 dB. And although the compressor – the source of the noise – is outside the home, experts advise owners to mitigate the noise by creating a “barrier” of conifers. Other systems – mini- or multisplit units or room air conditioners – emit 35 dB to 45 dB. If you use a room air conditioner, more specifically a window unit, and the window frame is unstable, it's likely to make more noise.

Air quality
Since the refrigerant R-410A (Puron) was introduced in Quebec in early 2006, more and more manufacturers are using it instead of CFC, a refrigerant fluid whose harmful effects on the environment are well documented. In fact, as of 2010, Canadian manufacturers will be obliged to comply with a total ban on CFC use. Already, some air-conditioning units circulate negative ions meant to purify the ambient air, while others have carbon filters to eliminate odours. As we now know, refrigerant fluids are not totally harmless to the environment.

Room air conditioners continue to use CFCs – hence the importance of never dumping an old air conditioner in a landfill. Rather, find out where the nearest municipal waste-recovery site is located, or consult the Yellow PagesTM under “recycling.”

Design
Air conditioners have become more attractive in recent years. With a rounder shape and cleaner lines, today's models do a better job of blending with furnishings. And while white is still popular, we're now seeing blues, metallic greys and even natural wood! A manufacturer of mini- and multi-split models recently went so far as to create an air diffuser behind the front panel – and for a touch of elegance, these models also allow users to frame the front panel with a photograph or a painting! Manufacturers have also worked hard on the appearance of outdoor modules in a bid to harmonize them with landscape design.

Maintenance
It is important to clean the air filters on a regular basis and remove any leaves or debris stuck in the condenser. Where necessary, the drainage system should also be unblocked. Some models feature automatic filter cleaning, but in general consumers are advised to consult a specialist for the overall maintenance of their air-conditioning system: every two years for mini-split and multisplit units and every three years for central air-conditioning systems.

Price and warranty
Central air-conditioning systems range from $4,000 to $6,000, and mini- and multi-split systems ring in at roughly $3,000. If you're able to find something considerably cheaper – usually imported – you can be sure that the quality will match the price. For room air conditioners, count on spending at least $300 for a good-quality window unit and up to $800 for a built-in system; mobile air conditioners retail at roughly $1,000. Most central air-conditioning systems come with a 10-yearwarranty on parts (including the compressor) and five years on labour. Mini- and multi-split units generally include a five-year warranty on parts and labour, while warranties for room air conditioners cover even shorter periods.

About dehumidifiers
Itchy skin, irritated airways, non-stop colds...the list of ills linked to high humidity goes on. If that isn't enough, ambient humidity, with time, can lead to chronic allergies, damage your belongings and even cause your wood to rot! If you notice condensation build up on your windows, or if your basement is never comfortable, chances are the humidity in your home is too high and something needs to be done about it.

First, check the ambient humidity using a mechanical or electronic hydrometer. (The first is often available for under $10 and is accurate within 5 percent; the second is that much more precise and sells for approximately $30.)

According to Health Canada, household humidity should hover between 30 and 50 percent – a humidity level of 40 percent or less is recommended for asthma sufferers. A base level of 40 percent also helps to avoid the spread of dust mites, which irritate the respiratory airways and proliferate where humidity is high.

When you reach the shopping stage, be sure to take into account the dehumidifier's water extraction capacity, which varies between seven and 24 litres a day depending on the area covered. According to the Office of Energy Efficiency, a daily extraction capacity of at least eight litres is required for a humid room spanning 93 square metres. The extraction capacity of most humidifiers is certified by the Association of Home Appliance Manufacturers (AHAM) in the United States. Check the packaging to make sure that the model you've chosen meets this quality standard.

Check the unit's energy efficiency ratio (EEF): This will give you a good idea of its annual operating cost. To meet the requirements of the international Energy Star program, the unit's EEF must be at least 1.2 (meaning that it extracts a minimum of 1.2 litres per day).

The majority of dehumidifiers reach their optimal efficiency when the ambient temperature is approximately 27oC and the humidity level is 60 percent. But some units function just as well at cooler temperatures – which can be useful if, for example, the temperature in your basement never exceeds 15oC. Other points to consider: Does the dehumidifier have overflow protection? A washable dust filter? A removable tank? An outdoor drain connection? Units with an electronic control panel are preferable, as they are easier to adjust. And don't forget to run the machine to test it for noise!

Dehumidifiers range from $200 to $400. The Canada Mortgage and Housing Corporation recommends that a dehumidifier be purchased in the spring, when retailers have sales. Of course, make sure to carefully read the warranty, which can vary considerably from one manufacturer to the next. And bear in mind that these auxiliary machines can't perform miracles. In other words, you can take other steps to reduce humidity: Dry your clothes on the line and your wood outdoors; use a fan when you take a shower and a range hood when you cook – since they force humid air out of the house.