Saturday 29 October 2016

Earth Sheltering?

A key feature of the design of this house, right from the start, was that it was to be earth sheltered across the whole roof by about at least 50cm to a metre of soil. One of the reasons for this was to ensure that the high thermal mass of the house was protected from, in particular, the very high summer surface temperatures and to a lesser extent the cool winter temperatures as the prevailing wind descends down the mountains. Similarly the whole roof was to be insulated to avoid any temperature excesses.

Unfortunately things have not worked out this way.

Although large areas of the roof were insulated, prior to the waterproofing membrane and the drainage gravel being laid, the tops of the three ventilation shafts, the tops of the walls and the tops of the concrete beams were not (see photo below).

In addition the earth sheltering at the east end of the house has settled from when it was loosely put in place leaving almost a metre of the east end wall exposed to the intense summer sun.

Furthermore, due to the design of the ventilation shafts, there was a need to significantly lower the depth of the earth sheltering around and away from them to allow for water run off. This has resulted in an earth depth of only a few centimetres in places with the back wall breaking through as shown in photo below.

All of this, coupled with being unable to use the ventilators in the ventilation shafts (for reasons highlighted in previous posts), has resulted in the house being hotter throughout the summer than should be the case if it were built as specified.

The need to redesign the passive ventilation system (see previous post), with a solution that requires a chimney to be installed in each shaft, presents an opportunity to rectify the earth sheltering issues. The old ventilation windows that have caused so much trouble will be removed, the resulting holes blocked up and the whole made watertight.

The earth slope covering the east end of the house may require some intermediate terracing to ensure a suitable earth depth is achieved and maintained.

The issue of the lack of insulation on the ventilation shafts, walls and roof beams remains to be resolved.

Looking east along roof. Note walls, ventilation shaft roofs and main beams that were uninsulated.

Looking up over earth sheltering to east end wall.

Exposed, non earth sheltered east end wall.

Approximately a metre exposed fill length of wall.

Back wall showing very shallow earth covering and exposed top.

General view showing shallowness of earth covering due to non functioning ventilator design.

Looking west along roof. Note slope of earth against light well wall and this would naturally extend to cover over ventilation shafts and under PV and water heater panels.