Some guidelines for better, healthier, low energy, low cost house construction:
Understand basic physics.
Avoid the architecture-of-the-week construction trends.
Set your targets:
Size vs cost?
How long do you expect to live there? Price of energy vs better insulation?
Maintenance: type, frequency, amount, cost?
How important is it for you to reduce the environmental impact?
Start small and expand later, or start big and later rent out part of the house?
Stay open minded about the solutions and designs. This makes a huge difference. The building codes and municipal restrictions are often the most limiting factors on how "good" a house you can build. Don't add _unnecessary_ restrictions on top of that. Look around at different solutions, not just what the local construction companies offer. Travel and see how things are solved in other countries.
Use simple construction methods and design. Reduce the number of construction tasks necessary, and make each task simple. A significant real world problem with normal passivhaus construction is that while designed well, they are often very complex to actually build, and small mistakes by the construction crew can have a large impact on the energy requirements as well as cause health hazards.
Well insulated windows, walls, floor and ceiling also drastically improve the comfort feeling of the house, not just the energy bill. When done right and coupled with properly designed ventilation they also improve the health aspects of the indoor environment.
Many low energy houses built today require that the indoor air is kept very dry when the temperature difference between inside and outside increases. This has a lot of negative health effects. By choosing different insulation and interior materials they can be made to allow high indoor humidity. Your lungs, throat, nose, eyes and skin will thank you. Internal humidity around 50-60% also reduces air transmission of many viruses.
Thermal mass is mentioned in some other posts here. Make sure to place it inside the insulation layer, not on the outside. Water and stone have similar high volumetric specific heat capacity. By using water circuits and storage, the mass can be moved out of the way, and often coupled to very efficient heating/cooling systems.
We have developed a construction toolbox for houses and industrial buildings with very low total life cycle CO2 footprint, suitable for climates down to around 0C annual average temperature (northern Scandinavia, around the polar circle). They are fast and cheap to build and provide superb internal environment. If you're interested in more info I'm happy to share. You can ping us at StoneWoodGreyBeard at gmail.