How to install windows

Installing a window properly to avoid air and water leaks is left up to the installer, there is no certification that we know of. There are different ways to install windows that work, so one would hope that a window detail would be properly drawn by a designer. We agree with you that some installation techniques are bound to fail, or simple mistakes that could have been easily avoided can lead to higher energy bills from heat loss (usually air leakage around the frames), and water infiltration and damage if there wasn’t a strategy in place to avoid standing water and repel driving rain. Here is our page on window installation with some easy to follow tips that will improve the performance and durability –

How to install windows properly

I know the page doesn’t cover stucco specifically, but window installation should direct all water to the building exterior no matter what type it is.

You will see on that page two methods of air sealing we tried and we were really happy with how little air leakage we found when we relied not on caulking but rather on a high-performance building tape.

You can either purchase a flashing pan to collect and divert water or you can build your own with the right materials like we did in the window installation video on that page.

Are you just planning to build just using Passive House targets and performance standards or are you going for certification through a Passive House institution? A Passive House designer will be the one to determine the overall design and how many windows can be accommodated and still meet the performance criteria. This page will be helpful I think – 

All you need to know about Passive House certification

But to address your question about windows – there is an overall performance target that needs to be met for any Passive House building, so the more windows you have in your design, the more you will need to beef up the insulation levels of other parts of the home. You mention using ‘high performance’ windows, but that they aren’t triple pane. In any cold climate, a window that isn’t triple pane just does not fall into the category of ‘high performance’, and it would be a smart upgrade in any home but particularly a  Passive House, read  here about windows to make your best selection, triple pane is very much worth the added cost– 

How to choose the best windows for High Performance Homes  

As an example of how the total window surface area and quality of windows affects design, here is an example -  a Passive House we know of that has significant glazing required 24 inches of sub-slab insulation to make up for the loss through windows in order to achieve certification. There is simply no place on this globe outside of besides the North Pole where 24 inches of rigid insulation makes any sense. It is a bit of a glitch in the Passive House system regrettably, where the underlying goal - to reduce climate change causing emissions from buildings - goes right out the window in search of certification. You would be better at that point to forgo certification and reduce the insulation levels since there are more emissions from manufacturing that amount of insulation than it will ever save in the lifespan of a home. So... limit your window use if possible, and try to upgrade to triples!