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Aluminium joinery is currently the "norm" in the New Zealand construction industry. With cold (non-thermally broken) joinery the predominant choice with double glazing and perhaps a low E coating. We have been through a leaky building crisis and are now, thankfully moving towards designers considering thermal comfort as a must, rather than an afterthought.
I was recently asked to look at SIPS (structurally insulated panels) in terms of aluminium joinery installation, and I wanted to step you through the process of considering how to install thermally broken joinery in a thermally efficient manner....in my opinion, it's much harder than you might think.
Where do I begin with joinery installation? = E2
In New Zealand, given our history, I always start with E2 as the baseline for all installation, even with deviations away from the "norm". E2 - Acceptable solutions and verification methods for External Moisture, with the objective being to safeguard people...blah blah...hopefully you've read it cover to cover. If you have, then hopefully you realise when someone states "E2" from an installation perspective, they are usually referring to E2/AS1, one of the acceptable solutions for installation. Of the 192 pages of E2, E2/AS1 has 160 pages of pure delight available for anyone constructing to NZS:3604, timber-framed buildings. Other acceptable solutions are AS2 - Earth buildings (10 pages dedicated to Earth Buildings...wow...ok, is that because they are less complicated than timber frame construction??) and AS3 - concrete and concrete masonry buildings (1 page...well, 4 lines on that page which points you to CCANZ CP 01).
If you are wondering why the Window and Glass Association of New Zealand (WGANZ) didn't put out their own industry best practice guide - we did - 2002 WANZ Wis, which was "sucked" into E2/AS1 in 2005, and now there is a WGANZ guide to E2/AS1 available to download here. The Associations technical committee is now working through thermal installation details for review and consideration by MBIE as a new (possibly...hopefully) AS4. These details are not mine to share....yet....
E2/AS1 does not suit, what now?
HHHmmm...right, so I've looked at E2/AS1 and either the cladding type is not an acceptable solution, OR, the designer wants to improve the energy efficiency of the installation and install the joinery differently.
As a base point, we need the buildings wrap (or sheathing/rigid air barrier), the tapes and the base installation to be as effective as the layers of protection provided in E2/AS1. I'm not an expert in this area, and defer to suppliers (or designers) in the market who know how to create the baselayers appropriately....please and thank you....
From there, we step to the window install....
I considered what would an E2/AS1 SIPS panel installation would look like?
But, why do this? Why use a superior thermal envelope only to smush it with a generic E2/AS1 installation detail....but in reality, we do this ALL THE TIME....!!
Am I hearing you ask why I didn't just start with the SIPS window installation detail!!??
I did...but I didn't really "get" how all the transitions were meant to work, as I could only find a head detail.
But I did try to make my own jamb and sill details....and guess this works....but I'm not sure it's a great thermally efficient installation detail??
So while I was busying doing installation details, I figured why not look at how that SIPS generic head transitions into a sill and jamb....
I didn't really like how the generic SIPS window installation translated into an overall install method....so I looked at pushing the joinery back to the centre of the panel insulation - and it got REALLY tough....
Please keep in mind, that window could sit anywhere within that panel and this is just a representation of it sitting right smack in the middle.
Thermally, would it be better to push it forward?
In my opinion, I think it would be better if the sill flashing could be replaced by cladding, or timber, rather than aluminium flashings as these require carefully installation onsite - is timber possible/preferable (like timber windows sill facing...)...now I hear you say, "why not just use Timber"!? Well, of course, you can, but the cost of the project just went up....considerably....
I removed sill liners/reveals, and returned the panelling and lining into the liner pocket. This allows for an internal air seal at the nailing fin line, rather than further back, as per usual E2/AS1 details.
So that's where I'm currently at. I thought I would share where I'm at with this detail because we are all facing this dilemma - how do we improve the installation of thermally broken joinery, while still considering E2/AS1....let's discuss....
