Our house has never gone above 25.4*C during this heat wave that has covered Ontario for the last 4 days. Without A/C how did we stay cool inside when outside it was 33*C and felt like 39*C?
The secret is in the construction: Glass, Mass and Insulation.
Our large windows face south and do not get direct sunlight because of the 5ft. overhang. This gives us plenty of natural light without the heat from the sun's rays entering the building. On the east and west windows we have curtains and yesterday I added bubble wrap to give us an extra layer of insulation in those windows.
Our walls are ICF blocks filled with concrete. This gives us a huge thermal mass which stabilizes the indoor temperature, taking a much longer time to warm up or cool down. Unlike most ICF blocks our blocks keep all the insulation on the outside portion of the block. This allows the concrete to absorb the cool night air when we open the windows after the sun goes down. During the day we close everything up so the heat stays outside and the cool concrete can help cool the house.
Our home is wrapped in insulation giving us R40 in the walls, R60 in the ceiling, R30 under the slab. Since we are off grid we wanted to avoid the use of A/C and so far everything has worked as predicted. We are comfortable, not freezing but much cooler than the outside temperature.
If you are thinking of building, consider a passive solar designed home and don't be afraid to go with solar power if it is too costly to tie into the grid.
It's working for us. If you have any questions just let us know and we will try and answer them.