Comparison of home ventilation solutions matrix

Secure trickle vents Opening windows Positive pressure systems (HRV, DVS etc) Balanced pressure systems (with heat exchangers)

Controls condensation

Utilises cross-flow ventilation to replace damp air with outside air which has a lower total humidity than inside air and roof space air.

Uses cross-flow ventilation to replace damp air with drier outside air

Uses a fan and ducting in the ceiling space to force roof space air into the home, displacing damp air through external openings. Controls condensation as long as the roof space air has a lower total humidity than the inside air (not always the case)

Yes. Uses outside air which has a lower total humidity than inside air or roof space air.
Minimses heat loss Yes. Does this by providing a small, but effective opening size. Cooler outside air is quickly brought up to inside temperatures Controlling unwanted heat loss is difficult with opening windows. Even slightly open windows result in over-ventilation and excessive heat loss in the winter Relies on the natural thermal properties of the roof space since the input air comes directly from the roof cavity. This air is often colder than outside during winter periods Yes. All incoming air is preheated to some degree by the outgoing air.
Recovers heat No No Strictly speaking "no". Positive pressure systems simply force roof space air into the home. During warm periods this air is warmer than inside. During cold periods it's colder than inside. Some times it's even colder than the outside air. So while the roof space generates a large amount of "free heat" over the course of the year, it doesn't store the heat, so it's not usually there when you want it. Yes. The warm but damp inside air is passed through a heat exchanger where the heat is partially transferred to the cooler incoming air, but the moisture is not. This means that, for example, the heat from steamy bathroom air can be used to pre-heat the fresh air coming in.
Provides cooling in summer Minimal. The vent openings are not generally sufficient for significantly cooling a home down on hot summer days. Yes. This is still the easiest method for controlling heat buildup in a home, although it's not a secure solution Standard installations do not cool in the summer. In fact, the uninsulated roof space can get very hot during the summer, causing the system to either shut down, or pump hot air into the home. Summer kits can be added, which simply bypass the roof space. In combination with a heat pump / air conditioning unit, it can make the air conditioner more efficient by passing the cooler inside air through the heat exchanger to pre-cool the warmer incoming air. This only works if the inside air can be kept cooler than outside.
Security Totally secure. System is glazed in to the window system. No. Even with double tongue latches or security stays, a window left ajar is an invitation to burglars Totally secure. As the input is through the roof space. Totally secure. Input and output is generally through the roof
Insect proof Yes. Most secure trickle vents have an insect mesh which prevents all insects from getting inside No. Flies, mosquitos and other pests can and do get in through an open window. Yes Yes
Cost Low - Generally $1,000 for a 3 bedroom home. Can also be used to cost-effectively ventilate smaller buildings for a per vent price. Free Medium to high. The total cost depends on the number of outlets and the system used, but costs generally start at about $2,000, and are typically more like $3,000 - $4,000 High. Again, the cost will depend on the size and type of system, but prices generally start from around $4,000 - $5,000
Ongoing running costs & maintenance None. Trickle vents are maintenance free (apart from the occasional wipe down), normally guaranteed for the lifetime of the window, and they cost nothing to 'run' None Filter changes every 1 - 2 years. These can be in the range of $300 - $400 per change. Although you can DIY if you want to save some money. Power consumption. The fans are quite low wattage, but there is a cost to your power bill. Maintenance. The systems may need repairs and maintenance. Warranty periods vary, but the system may need to replaced after 10 years or earlier. Similar to Positive pressure systems although the systems have 2 fans, so the running costs may be marginally higher

1 comment:

kelly said...

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A good ventilation system for your roof will have an air intake hose along with an exhaust hose.
Thumbs up!
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