Out of all the components, windows (and glazed doors) single-handedly have the greatest impact on the Passive House design. They are also expensive, at least up until now. When exact or complete material data isn’t available, designers are forced to guess. That requires leaving a margin in the design.
Getting window material specifications out of window suppliers is most usually difficult. It’s a source of pain for everyone. Passive House designers typically can’t get the data sheets until the windows are ordered/deposits have been sent. Windows suppliers and manufacturers field duplicate requests from designers wanting the same information. And as certifiers, our time is wasted when we have to nag the designer for the window data that hasn’t been fully entered. We can’t and won’t start the pre-construction review until all this information is complete.
Designers, we know you need the window data at your fingertips at the earliest stages of design. That way you can compare options, see how it impacts both performance and budget and specify the best windows for the job. Plus there’s no need to overcompensate on wall or roof insulation, for instance, in order to leave some margin or be forced into expensive rework of plans because the windows underperform your estimate.
You’d get to the best outcome for the best price and save time, money and aggravation as well. What could make you (and your client) happier?
This is precisely the situation we here at Sustainable Engineering are focused on creating. We have a database coming on stream that lists currently available windows suitable for Passive House projects. Against the manufacturer and model number/name, you’ll find the numbers you need to enter into PHPP: Uf, frame width, glazing edge thermal bridge.
If you use the exact name as it appears in the database and the correct values in your PHPP file, you do not have to provide the material data sheet when you submit the project to us for certification. It will be unnecessary, because we already have it on file and there is no doubt which windows you are referencing.
Currently all the certified Passive House windows are in the database. Go have a look. If there are windows you like to specify and they do not yet appear in the database, give your supplier a nudge about how useful it would be if they were included.
There are four tiers of information in order from best/most complete to least.
Tier 1 Certified file by PHI
Tier 2 Flixo files on record, either provided to or calculated by Sustainable Engineering
Tier 3 Complete reports provided to ISO10077-2
Tier 4 Incomplete dataset and conservative assumptions included or no fRsi data
We can use Flixo (software that calculates thermal bridges) to generate reports for suppliers or manufacturers, or review files supplied to us. We’d check that the boundary and material conditions are accurate.
Complete reports are a step down in terms of evidence but still acceptable. Sometimes for instance, it might be in a language other than English, making it harder to interrogate. We will review a complete report thoroughly—once. Then it can be used as evidence for multiple projects.
Incomplete reports typically don’t include the data across the entire range. For instance, operable windows may be calculated but not the fixed ones. We can work with this. Whether it is sufficient will be determined on a case-by-case basis and will require conservative assumptions. Obviously this is the least desirable circumstance.
This database is also valuable for window suppliers and manufacturers. It should turn the steady stream of individual emails asking for window data to a trickle. It will make it easier for non-certified (but suitably performing) windows to be specified. And there is an obvious competitive advantage to having a complete set of offerings in the database.
Sustainable Engineering’s team can produce Flixo reports at reasonable rates, or review and/or complete reports. We’re here to help. We all benefit when the certified Passive House sector grows, not least of all the people who live and work in these outstanding buildings.
NB More detail for designers is provided in a handy “How to Use” sheet you’ll find in the windows database. (You can also read more about how to choose windows here).