Any thoughts on cooling roof cavity?

[Marc]

We extended our home 2 years ago, and part of that renovation included building in a double garage within the roof line of the house. I put some smarthome stuff throughout at the same time and one of the Z-wave relays installed in the roof cavity just happened to include a temperature sensor. I discovered that our ceiling cavity can get upwards of 40 degrees C and closer to 50 mid-summer. 

While I appreciate hot air rises, I can't help but think that the cooler the cavity, the cooler the home? Is it worth looking into ventilations systems of a roof cavity to reduce the overall internal temperature of the home, or, at least allow the AC to work less?

[Full Range]

A Cardiff air system or similar 

Also the traditional Whirlybird roof vent 

I have both fitted 

Edited March 30, 2022 by Full Range

[Prof Tournesol]

Whirlybirds look good spinning in the breeze but in practice, they have very poor airflow with a limited impact on cavity temperature. You really need an active fan system with good air exchange matched to the size of your roof cavity.

[Pokitren]

On 29/03/2022 at 1:51 AM, Marc said:

We extended our home 2 years ago, and part of that renovation included building in a double garage within the roof line of the house. I put some smarthome stuff throughout at the same time and one of the Z-wave relays installed in the roof cavity just happened to include a temperature sensor. I discovered that our ceiling cavity can get upwards of 40 degrees C and closer to 50 mid-summer. 

While I appreciate hot air rises, I can't help but think that the cooler the cavity, the cooler the home? Is it worth looking into ventilations systems of a roof cavity to reduce the overall internal temperature of the home, or, at least allow the AC to work less?

Have you thought about reflective materials on the roof? It would reduce the heating of the roof and the rooms immediately under the roof.