A well-ventilated roof stays cooler on a hot summer day ¹ resulting in more comfortable living spaces and cheaper cost of air conditioning. Roof vents with a solar-powered fan have been touted as more effective than passive or wind-powered vents like Whirlybirds. Although these can be bought from Australian suppliers, there seems to be little awareness that the sometimes the same product can be bought directly from the Chinese manufacturer.

Do roof vents cool down the house?

Although roof vents cool down the roof cavity, there is a lack of quality evidence on how effective they are at cooling down the living areas. Of what we do know, H. Willrath performed a simulation study of Australian houses which found ceiling insulation was the single most important contributor to thermal performance of a house. The author found that: “Roof space ventilation rate has very little influence over the [thermal] performance of a house, if the ceiling has R2.5 insulation installed” ². However, this simulated a ventilation rate of 10 air changes per hour (AC/h) - a measure of often the volume of air in the roof cavity is exchanged - which is similar to a Whirlybird performance found in an experimental study ³.

Solar roof vents use solar panels to drive a fan and are touted to move 10 times ⁴ to 20 times ⁵ more air than a Whirlybird, so are theoretically more effective at cooling down living areas. In the thesis of the H. Hillrath, the author simulates a ventilation rate up to 45 AC/h and find a decrease in annual energy requirements of 3-4% compared to no ventilation ⁶. Although I cannot easily find any experimental studies, the limited evidence suggests solar roof vents, which are even more powerful than 45 AC/h, cool down a house and lower energy costs.

Selecting my solar vent

I wanted to install a solar roof vent on a double story house where it would be difficult to get to if it broke. Hence, I wanted a reliable fan and used length of warranty as an imperfect heuristic of reliability.

The solar roof vents with the best warranty seem to be Solatube’s Solar Star product line with a 5 yr warranty on the solar panel and motor and a 10 yr warranty on the housing ⁷. Next are roof vents from Eco Solar Vents and MJ Products with a 5 year full warranty. They had the feature set I wanted and were reported to be reasonably quiet ⁸.The similarity between the solar vents offered by Eco Solar Vents and the 25W solar vent from MJ Products made me suspect they can from the same manufacturer.

Sunny International Power Limited (SIPL)

The Eco Solar Vents and MJ Products vents looked identical to those from a chinese business called Sunny International Power Limited, who I suspect are the manufacturer. They have an Alibaba storefront with the exact solar roof vent along with more powerful options. They also carry a wider range of accessories than Australian resellers, including an adjustable thermostat.