I spent quite a few months thinking about the best way to build a 7m long pelmet, and came up with this approach...
|Living room pelmet under construction with extra support added to curtain rail to prevent sag|
|The finished pelmet, made with lining boards recovered from the original bungalow, oiled and varnished|
The diagram below shows how the pelmet prevents convection currents in winter, during summer our eaves do most of the work by preventing any sun from hitting the north (sunward) facing windows. Sun reflection off the decking and the external temperature transfer heat through the glass during summer. We close the curtains on really hot days, keeping the room dark and reducing the heat transfer as the hot air gets trapped between the curtain and the pelmet, unable to continue to rise up. Gaps at the edges of the curtains reduces the effectiveness of this though. Extra external shading would be better, but I have been reluctant to install sails as everyone that I know that has them does not take them down during winter. Options of easily removable shading or decidous plants are more appealing, but I haven't quite figured the best way to do that yet.
|Curtains and blinds together with pelmets will help to keep heat inside the home. They prevent warm air from coming in contact with the cold glass. Source: www.sa.gov.au|
I was contacted by a teacher who was running the 'Home Sustainability Course' at Seymour's Go TAFE. She asked if she could take her group to tour our home during mid winter, and I was happy to oblige. As a bonus, one of the teachers that joined the group was an energy assessor who brought along his thermal camera. Wayne took some around the living room that show the effectiveness of curtains with pelmets in regulating temperature extremes and how aluminimum and single glazed glass act as thermal conductors.
|Sliding doors on northern window (Aluminium strip between)|
|Thermal shot showing west living room window with curtain open|
|Same location showing west living room curtain closed (with pelmet)|
|Thermal shot of west wall showing timber studs acting as thermal conductors, not as dramatic as aluminium or glass though.|