p>To build a sustainable and energy efficient home in a cold climate you will need sufficient insulation and an airtight building envelope. There is not one perfect wall system we would point you towards, but rather give you some tips on how to determine that yourself. The building science basics video on this page is a good starting place to see how we came to settle on a wall design for a demo house we built in 2015 –</p> <p><strong><a href="/guides/2248/building-science-made-easy-video/" target="_blank">LEED Platinum Wall Design Building Science Video</a></strong></p> <p>This is not the only way or even the best way to build a wall, it is just what we settled on. That house is insulated with <a href="/products/1135/rockwool-rockwool-comfortboard-80/" target="_blank">Rockwool Mineral wool insulation</a>. Our latest demo house was insulated with <a href="/guides/2266/dense-packed-cellulose-insulation-wall-systems/" target="_blank">dense packed cellulose insulation (recycled newsprint)</a>, you can <a href="/guides/3549/zero-carbon-homes-s1600-prefab-eco-home-gets-close/" target="_blank">read more about the LEED Platinum prefab kit house here</a>.  I would also suggest you go through our building guide as you will find a lot of pages on <a href="/guides/2372/choosing-the-right-insulation-the-pros-cons-and-applications/" target="_blank">choosing the best insulation</a> and <a href="/guides/query/air+barrier/" target="_blank">how to make a house airtight</a>. Things to consider for sustainable home design go beyond just the performance of a particular insulation, but to be considered sustainable it is important to consider the overall carbon footprint of building materials (as in embodied energy) that you choose to build with. I hope that helps, if you have more specific questions about anything in those pages don’t hesitate to ask. </p> <p> </p> <p> </p> <p> </p