I have as many questions as answers unfortunately, but it will at least get us started. First of all, where exactly are you located in relation to Vancouver? Prices will vary a lot by region so it's very difficult to pin down a cost for you, you're better to get even a ballpark from individual builders. We don't have a list of regional builders for you unfortunately, but if you aren't too far out of Vancouver I would recommend looking into a Vancouver company called Lane Fab Design Build, even if they aren't close enough to build it for you they can help you with design, and possibly supply you with prefab walls as well, maybe even give you the name of another suitable builder if you're out of their range.
And are you looking just to build to a Net Zero standard or to get it certified? If so here is the Canadian Home Builders Association page on their Net Zero program, they may also be a resource to help you find a builder. I didn't want to leave you hanging too long without an answer, but I have a few lines out asking for more information for you, hopefully I will be able to add more to this soon.
Do you have suggestion for non-toxic closet design company, or materials?
If you are looking for non-toxic cabinetry materials for shelving, we recently did a lot of interior finishing on our new Demonstration house in Wakefield QC with a formaldehyde-free UV treated plywood called PureBond from Columbia forest production, try that out.
If you are looking for a box store solution, to the best of our knowledge the manufacturing process of Ikea in North America is the same as in Europe where they meet a high standard of low-toxicity for their cabinetry materials. We have asked the company to confirm this and we will update the page as soon as we hear back from them.
For choosing flooring materials, there are options such as cork or marmoleum, be sure to get a low or zero VOC adhesives such as Bostik GreenForce, building adhesives are where some of the most nasty fumes will come from if you don't select them carefully. I hope some of these pages help, have a read and let me know if you have any additional questions.
We will have more providers of kit houses soon, and there is a sign up on that page for more info on prefab kit homes, with that you would get a notice as soon as we have more to offer. Hope that helps!