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Solar Roof Ventilation Guide – Which Ventilator is Right for Me?

Roof ventilation is a saturated market, with everything from whirlybirds to tiled vents offering better roof ventilation. There are even active-powered options, such as solar roof ventilators and powered roof fans.

With all these whirlybirds and solar roof ventilators, trying to navigate this market can be tricky.

You might even find yourself wondering ‘What do I buy?’ with all these different, yet similar options.

What should I look for in solar roof ventilators?

It’s tempting to settle with the cheapest option. A reliable solar-powered roof ventilator can cost upwards of $500.00. There are still many options to choose from that price range. Here are the key factors to consider when you’re looking for a home ventilation solution.

Brand ReputationSolar Whiz RAF1400 Solar Roof Ventilator

A good first base to start with is going through reviews. Good service and reliable sales can give you an indication of whether a company’s roof ventilator is right for you. Look out for:

  1. Legacy: Has a company been around for a while? In some cases, they may be veterans of the roof ventilation industry.
  2. Prevalence: Do they have lots of positive reviews? This means satisfied customers.
  3. Transparency: Is it easy and accessible to find technical specifications and information? Some companies make information difficult to locate. The main thing to look out for is real airflow rating—more on that later.
  4. Technical knowledge: Do the company representatives understand what is required and why in order to achieve optimal ventilation in your home? This includes user accessories (ceiling and eave vents) to ensure enough replacement air is available for the roof ventilator to operate effectively.

Warranty

Make sure the warranty policy suits your needs. You don’t want to get caught off-guard if a roof ventilator needs maintenance or replacement in the middle of a stinking hot summer. Solar Whiz offers 10 years on our PV panels and 2 years on other components.

Anything less, and you’re selling yourself short.

Real Airflow Rating (RAF)

It’s all too easy to buy wholesale roof ventilators from overseas and slap on whatever airflow rating you want on a ventilator. There are ventilators that are said to produce 3,000 to 4,000m3/h (cubic metres of air per hour, AKA cbm/h) without having tested the units at all.

It is worth noting that all roof ventilators installed under typical roofing conditions will extract less air than their airflow capacity, due to restrictions in the replacement air supply. Replacement air enters the roof space via openings such as gaps in corrugations or between tiles, eave vents or ceiling vents. The resistance created by these entry points will determine how many air changes you get and, therefore, how close you can get to the temperature of the replacement air.

When we refer to real airflow at Solar Whiz, we mean the volume of air that the roof ventilator can move with unrestricted air supply.

What to ask: Is this the airflow rating of the fan itself, or the complete unit?

Solar Whiz measures the airflow of our units with the fan cap installed. This reduces the airflow reading, but it provides you with an accurate extraction capacity, instead of what the units move theoretically.

This is also why Solar Whiz does not base its recommendations on roof space volume. Instead, we use guidelines based on square meters and we always assess the availability of replacement air.

Accessories to Roof Ventilation

With all this in mind, one last consideration is accessories that can come with the product. Here are some options that Solar Whiz offers:

  1. Eave vents: Replacement air is critical for achieving the cooling results you need. A roof ventilator will struggle to work if there’s nowhere for it to draw in cooler, fresher replacement air or if there is insufficient replacement air intake.
  2. Ceiling vents: If you don’t have eaves or would like to extract heat directly from specific rooms, using ceiling vents to supply replacement air is a great option.
  3. Thermostats (adjustable OR fixed temperature): A thermostat gives you control over when a unit operates. Your Solar Whiz will automatically start ventilating when the air in your roof space exceeds a certain temperature and stop running when it dips below that temperature. Our fixed temperature thermostat is set to 30°C, while the adjustable temperature option can be set anywhere between 10°C and 30°C.
  4. Constant current module: This simple addition allows a Solar Whiz to top up from mains electricity if solar irradiation is insufficient for the unit to perform at optimal speed, such as in low-light or no-light conditions The constant current module allows you to continue to ventilate as long as required regardless of solar conditions. Paired with a thermostat, this ensures your unit stops running when it isn’t needed.

What is the right solution for me?

When you’re sourcing quotes for roof ventilation, it’s important to know what you’re looking for. That obviously depends on how much you’re willing to spend to get the desired results, but also very much on the physical layout of your house and roof.

Depending on the size and shape of your house and what else is in the roof cavity—partitions, dividers, ducting—your roof space may need more than one unit.

House Size

An important factor should be your house size. Some roof ventilator units provide minimal airflow that won’t have any significant impact on larger roof spaces.

Solar Whiz offers four distinct residential units and two commercial models. Each provides a different level of airflow, making it suitable to extract heat in homes and spaces of different sizes. In some scenarios, you may need more than just one unit in order to extract the necessary volumes of air.

Shape of Roof Space

The shape of some houses can make it impractical or impossible to ventilate the whole roof space with one unit. In these cases, using two or more units can help to prevent heat from building up in the parts of your roof space that would not be ventilated successfully by a single unit. Keep this in mind if your house is not a simple square or rectangular shape.

Separate Roof Spaces

If your home has separate roof spaces, or if your roof space has partitions or dividers inside, we can set you up with a tailored solution to meet your ventilation needs.

Gable Mounted Options

Solar Whiz residential units are available as gable mounted units.

If the pitch of your roof is too steep to fit a roof ventilator, we’ve got you covered.

Flat Roofs and Cathedral Ceilings

Houses with flat roofs or cathedral ceilings generally have little or no roof space. In these situations, heat radiates straight into your living spaces and becomes trapped in your home. A Solar Whiz can be mounted with an extension collar with a closable vent installed directly underneath the unit. This will extract heat directly out of your home.

We work with you to achieve the desired ventilation results you need to keep cool.

 

Budgeting

How Quickly Does it Pay Itself Off?

Without roof ventilation, trying to cool your home with air conditioning is a losing battle. You’ll spend more money trying to actively cool down a house that has heat trapped in the roof. Heat trapped in the roof radiates down through the ceiling into the living space, making your air conditioner work even harder.

Calculations & Citations

Canstar Blue 2018, How Air Con Temperature Settings Impact Costs, https://www.canstarblue.com.au/electricity/air-con-temperature-costing/

N/A 2018, Appliance Calculators: Air conditioning calculator, https://apps.ergon.com.au/calculators/airconditioner.aspx

We base our mathematics on ducted air conditioners, running at 6.0kW, 21°C at 8 hours per day, 22 weeks per year. This averages out to $599.42 (AU) 20% of 599.42 equals $119.88.

This is a rough estimation, and not to be taken as an example. This can be affected by variables we haven’t taken into account such as ambient temperature indoors and outdoors, airflow, or daylighting hours.

All prices are reflective of rates as of 19th December 2018 and are subject to change according to rates. Consult your energy provider for rates indicitave of when you are reading.

Roof ventilation can improve your air conditioning.One of our dealers suggests that there is a 20% efficiency gain for ducted air conditioning systems. Assuming you set up an SW-RAF2100, a single unit under optimal conditions can help shave off near $120.00 per year on A/C usage. This is the result of preventing heat in your roof space from penetrating ducting or radiating through your ceiling.

However, it doesn’t stop there. When you install a Solar Whiz the amount of heat radiating down into your home will be dramatically reduced. As the heat gain is reduced, you can also expect to run your A/C 25% less often.

A Solar Whiz SW-RAF2100 could pay itself off in roughly approx. 5?? years when relying solely on solar power, all the while helping you stay cooler from day one.

Avoiding Budget Roof Ventilators

You can find budget roof ventilators at your local hardware warehouse. Roof whirlybirds, cheap solar roof ventilators—the lot. These are tempting inexpensive solutions for roof ventilation; there’s no doubt about that. The important things to note are the Real Airflow Capacity, the cost of installation, and the reliability of these units.

Cheap aluminium or tin roof whirlybirds are prone to hail damage and provide very little airflow. Do yourself a favour and put them back on the shelf. Read our whole article on why roof whirlybirds suck. There are very good reasons why every solar roof ventilation company tells you not to buy one. The patent for whirlybird designs is over 100 years old! You wouldn’t be caught using a 100-year-old fridge in your home, would you?

Budget roof ventilators can be as cheap as $100 – $200 and can be installed by any competent handyperson. These are attractive to many consumers as they are affordable and promise to pay themselves off. Cheap units can use incredibly poor-quality components in order to scrimp on manufacturing costs for profit. Components likely to be affected by this are:

  1. Motors: Without a powerful motor combined with a well-designed fan blade, a roof ventilator won’t be effective. Poor-quality motors may run well initially but are prone to breaking down or moisture damage. Without a good warranty to cover the motor, you’ll be left in a hot spot during the summer.
  2. Fan blades: Fan blades can be made of acrylic, various types of plastic, or cheap metals. Some are effective, but others may warp under heat or stress. Once again design and choice of material is important. Metal blades are more likely to lose their shape and generally produce more noise.
  3. Flashing: Poorly designed flashing can be the difference between a comfortable mount and water leaking into your roof space and causing serious damage.
  4. PV panels: The wattage of the PV determines how much power can be supplied to the motor and therefore the capacity of the roof ventilator. Ensuring that the PV is mounted at the correct angle to get maximum sunlight is also important. A flat panel mounted directly on top of the unit means that the unit will only perform efficiently for a couple of hours each day, provided it is facing north. Adjustable panels ensure that a unit can run at optimum capacity for most of the day. Poor-quality PV panels can also be fragile or wear down quicker under the elements.

Solar Whiz offers units with tried and tested components which have been developed and continuously improved since the introduction of Solar Whiz in 2010. We strive to ensure that our units can withstand the harsh Aussie climate.

What else should I consider?

As heat becomes trapped in your roof space throughout the day, you will experience a significant rise in temperature. 25% to 35% of heat in your home radiates down through your ceiling in summer. The most important things you need to consider if you want strong, reliable and effective ventilation are:

  1. Replacement air: Installing eave vents or roof cowls allows you to draw in cooler, fresh air from outside. Trying to ventilate without vents or alternative replacement air intake will cause any roof ventilator unit to struggle. The lower these air intakes are placed, the cooler the air will be. We highly advise using eave vents, which we can readily supply. Remember, without replacement air, no roof ventilator will be effective.
  2. Night time ventilation: Our Night Operations Kit/Constant Current Module allows you to use the system at night. This is especially useful in summer when heat can remain trapped in your roof after sunset. Having a Solar Whiz ventilating overnight will help you feel more comfortable while you sleep and prevent heat build-up in your roof space over multiple days.

Ask the right questions: If you’re looking to get a quote, make sure a supplier can tell you the airflow capacity, and how they tested their unit to get that measurement. Ask them what unit you need for your home. You want a team that knows what they’re selling and has the knowledge to understand and explain what you really need, including accessories to give you extra control over the unit and provide access to replacement air.