Installing solar-powered roof ventilation

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Some time back we installed a R3.5 batts in the roof of the original half of the house, along with reflective foil. Despite this, the roof space still gets very hot in summer, and after a run of really hot days, we can feel the heat radiating down into the rooms over night.

For this reason, it’s highly recommended to ventilate the roof space during summer. While traditional ‘wheely birds’ are an option, what I’ve read suggests that they simply don’t draw through enough air in an hour to make a real dent on a typical roof.

We therefore focused on an active ventilation system. There are heaps of different options, but my search narrowed down to two products, both solar-powered:

In the end, we went for the Solar Star, which seemed like the better fit for our needs. For the size of our roof, a single Solar Star RM 1200 model was the recommended option, and we  bundled in a thermostatic control.

The Solar Star unit, sitting on our table before installation.

Installation was simple enough. It comes with a plastic flashing suitable for a corrugated roof, plus the necessary screws and instructions. We further simplified the process by fitting the unit directly under the ridge capping, which allowed us to skip a lot of the more fiddly waterproofing steps.

The flashing installed for the Solar Star, looking through to the reflective sarking underneath (which we cut a hole through at the end of the job).

All up, the job took about an hour, most of which involved getting the tools onto the roof and generally stuffing around.

The Solar Star installed, just under the ridge of the roof. Not pretty per-se, but far from ugly.

Ideally, at this point I’d be able to report (with graphs!) the roof temperature before and after installation, compared to the outside temperature. But life has been busy!

So I can report that the fan runs steadily and quietly, and I’ll post later with a purely qualitative assessment of the impact.

Pantry and cool cupboard in action

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Our new walk-in pantry, with hand-made kauri shelves

No kitchen should be without a walk-in pantry. We had a temporary pantry in our old extension, and this proved the benefits of storing stuff in shelves, rather than lost in the back of kitchen cupboards.

So a pantry was a key element of the new house design. It ended up behind the rammed earth wall, conveniently off the entrance to the kitchen. We asked Ian Thomson to make the shelves, which are a simple construction out of kauri (the same as the kitchen benches and floors).

The cool cupboard, with doors open

A key element of the pantry is the cool cupboard. This is an idea that I stole from somewhere, but I forget where now.

As shown in the diagram below, the cool cupboard works as follows:

  • cool air is drawn up from under the floor
  • this cools the cupboard, making it suitable for storing potatoes, eggs, drying herbs, etc
  • the air is then expelled out a chimney through the roof
  • the system is driven by the heat of the fridge, which is vented into the upper part of the cupboard
How the cool cupboard works

This is a win-win solution: the cupboard is much cooler without any active cooling or fans. And the fridge runs up to 30% more efficiently, due to the extra ventilation.

Inside the cool cupboard, showing the wire shelves with plenty of space for a big harvest

How much cooler is the cool cupboard? The results speak for themselves:

  • Kitchen –> 23°C
  • Pantry –> 21°C
  • Cool cupboard –> 12°C

That’s cooler than the ambient temperature outside, which is 18°C at the moment in our mild Sydney winter. Not bad!