Best options for roof ventilation/cooling

[deslea]

I'm on the body corp of a small, cheap and cheerful complex of row townhouses in FNQ. Main building footprint is approx 60m x 10m, two storey, truss tin/iron roof about 1.6m high at peak, with about five gables to break up the roof line. We'd like to spend some money to reduce heat in the roof and hopefully reduce heat/cooling costs for residents. My budget is $3300 including handyman install. (That's a hard limit unless we go back for another owner vote). Ultimately we will do a roof refurb and reflective coating but that's out of budget for a few years.

I have estimates for ridge vents on the gables, or eave vents, or solar fans (although in the tropics you really need heat extraction at night as well, so I question the merits of solar-only fans) - all priced to fit into the budget, so the number is driven by economics more than strict calcs of the space involved. There is common power in the roof so we could also do electrical fans, but I haven't priced them.

There are variables at the ceiling level. We can't control what individual owners do. A few have insulation, most don't. Also, it is pre-building code, roof space joined up, no firewalls, and not feasible to add them. (If they were walled off, honestly, I'd probably just cool my own!)

All other factors being equal, which of these options would you recommend, and why? Or is there another option I haven't considered?

[JaneK]

Welcome to the Bunnings Workshop community @deslea. It's great to have you join us. I hope you'll get some advice about the pros and cons of ridge vents on the gables, or eave vents, or solar fans from other members in Far North Queensland. Our resident expert @MitchellMc will also be more than happy to assist when he is back on the site on Friday. Many thanks for your patience in the meantime.

Jane

[MitchellMc]

Hi @deslea,

Many thanks for your question.

The volume of air that solar fans extract will be significantly higher than passive ventilation. Solar extractors do their work during daylight hours when the heat is being actively generated. Although most don't function at night, the roof cavity will settle to the same ambient temperature as outside. Our premium varieties like the Ezylite 200mm Premium Solar Roof Vent Fan will continue to run after nightfall for up to four hours.

Have you considered rotary vents? If you were to install several units and eave vents, then they would do a reasonable job. Whatever type of vent you choose, you also must invest in eave/gable vents as they dramatically help vacate the hot air from the cavity.

I would presume that much of your budget will be utilised on the installation. You might like to get a quote on the various options, which will give you a better idea of what type of ventilation you could go with.

Please let me know if you have further questions or need assistance.

Mitchell

[deslea]

Thank you, that's very helpful!

Overall I'm leaning towards solar fans but my body corporate manager is very nervous, he sees a lot of complaints about noise from fans once they're a few years old. (Not specifically these, just any fan that runs for long periods, like exhaust fans etc). He's wary of the maintenance overhead and/or likely time before it would need replacement, particularly in FNQ (nothing exposed to weather ever lasts anywhere near expected life up here, even commercial grade stuff you have to assume it will only last half or less). What is the lifespan of a typical mid-range solar fan, and is there anything you can do to keep them quiet as they age (like a routine of lubricating them in some way)?

[MitchellMc]

Hi @deslea,

I've spoken to Ezylite our solar roof vent supplier. They have advised that their units have a life expectancy of between five and ten years and come with a two-year warranty. I asked about the likelihood of fans becoming noisy after some time, and they've had little to no issues regarding that.

Mitchell