I am doing some research on the best way to heat/cool a smallish 60sqm off grid build used by (at times) people who do not quite understand many passive heating and cooling basics and are accustomed to reaching for an air conditioning/heating remote. The 2-bed build will be used for holiday accommodation....and we all know what people are like on holidays....wasteful! Being off the grid, this means something that draws huge amounts of energy is not an option. I am optimizing many passive design principles but with guests not quite understanding how to live in a passive type house the benefits are reduced. Eg. Guests in the current older building on the property leave the doors and windows open throughout the day in Winter (July) until the sun goes down. When they realize it's freezing cold only then do they close the windows and ask for a heater. I had a few ideas and needed some help;
1. Something like a Solarventi unit. I could get use the largest size (recommended for 200sqm) to pump in hot air during the day. The issue is that it does not work at night and if people are stupid enough to leave windows open then how long does the residual warm air last? In terms of cooling, it could only be used (in reverse) to vent hot air out of the build (it would be located on the roof)
2.A water tank size of 20,000L semi submerged into the ground (approx. 1m) with tubes (full of air) coiled inside. The tubes have an intake outside and the exhaust inside the building. The idea is around using the thermal mass of the water to transfer heat between the air and water. The water will remain cooler than ambient air in summer and hotter than ambient air in winter....but for how long? Pumping the air through the pipes with a small fan would cool or heat the air but would it heat or cool it enough to make a difference? Would this thermal mass benefit quickly run out with a size of only 20,000l? How much piping @ what diameter would be required and would this displace too much of the tank water?I understand it may work better in winter because of the climate (Northern NSW) but if it achieves a heating benefit only then this would be ok. Being an off-grid build we need the 20,000L tank for our water so the extra infrastructure of piping, vents and a fan is not a huge cost.
3. Same idea as #2 but circled through a solar hot water system on the roof to boost the temp of the water in winter. This solar hot water system could be used just for this purpose (separate HWS for showers, etc). This would obviously only benefit for winter heating.
For reference this It will be a new construction in Northern NSW rivers, very good insulation, double glazing and relatively good air tightness. Optimizing passive design as much as possible. Planning on using haiku fans throughout the home for some cooling with plenty of openable (cross breeze/ventilation) windows.
Any other suggestions would be great! We are limited on the electricity we will have available (especially in winter) so conventional methods aren't very helpful...especially because people are wasteful and don't think to turn things off when they should.
