Zola Window Install Detail – Is the Alum Angle Really Needed? Anyone installed Zola?
Hello,
My friend is in the process of building a house in Montana and I am helping him with the drawings/details. He is working with Collective Carpentry for the prefab enclosure and Zola (all aluminum) for the windows.
For background I am a licensed Architect and CPHC.
Regarding install of Zola window: In their detail they have an aluminum angle backdam screwed to the window which has a very strange interaction with the sill material. They are the only ones I’ve seen with this angle, and it says its to eliminate the clips at the sill.
My questions are:
1. Has anyone installed Zola windows before, and did you install the aluminum angle? If not, what did you end up doing?
2. Whats so bad about just using clips at the sill? This is how we install all the other window manufacturers we have worked with.
3. Zola shows backer road and sealant at head and jamb and mention this is a crucial detail (vs tape or something else). We’ve hit passive house cert with tape at the window in the past. Am I missing something?
Thanks in advance, appreciate any insight.
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Replies
ECNEWDesign,
1. I've had no experience with Zola windows, so my comments are speculative. The angle being called out in their installation instructions poses a problem, as omitting it may void the warranty.
2. All I can think is that the angle is used to provide a back-dam for the membrane on the sloped sill as part of the drainage path. It really does complicate the inside casing though.
3. I've always seen the two as either/or alternatives which both work.
+1 to what Malcolm says; that interior sills seems impossibly thin at the the top most rabbet. FWIW I would call Zola; their team is very responsive to these questions (in my past experience). Like you we've always installed straps with aluminum windows and when particularly zealous have routed the plywood bucks to accommodate the thickness of the straps and screw heads to simplify interior trim installation. Good luck!
We installed zolas a few years ago and the detail they provided at the time used wigluv. IDK if something changed but seems like it would be fine. they also did not have that backdam detail. I would probably just stick with a standard plywood backdam if i went that route. also the bent clips are a pain in the butt, and practically they should have designed the window so you could use wood shims between to clip and ro and then given enough space so that your trim (gyp or whatever) would have space on the frame to land (maybe there is on your frame, and this is how I would install them). They are a solid window but not super impressed with the design and install details.... also that lower drip edge is a bit of a pain to integrate....
Anything you'd do differently? I'm noticing that with a mid-mount window and a plywood buck, its almost impossible to have a mechanically positive lap over the sill material and slope the substrate underneath. We want to use wood sill material, which means we're just caulking it to the frame and then relying a the extoseal/subsill to be bombproof. Anything beyond brake metal is too thick to slope and slide under the lip of the Zola frame. Unless we increase the RO at the sill more. We're already 1/4" more than what Zola says, I'm not sure how you make their recommended 1/2" RO at the sill work with a mid mount. Were yours mid mount? What RO gap did you use at the sill?
I would use countersunk screws and allow a small gap at the window. I think the gap would look 'neat' and if it is all painted could be caulked, but at any rate it would simplify the trim. A single back cut of 1/8" for the flat part of the angle
Just the thought of aluminum windows makes me feel cold.
Yes, they have a thermal break unlike the ones from my childhood. I have to question how affective the thermal break is.
Walta
This is tested through NFRC testing. U values for fixed and operable are 0.16 and 0.18 respectively.
Thanks everyone for the input. I did end up getting ahold of Zola and discussing this. They said turbo screws or straps could be used, the angle was just a way they were trying to make air sealing at the sill easier I guess. They also said tape is fine, again they were thinking caulk was an easier detail.
https://475.supply/products/contega-fiden-exo?srsltid=AfmBOoob958cg43vhpUSZCqbZUUt34T9-edwLBD-t04gJcH98fvMdpMi
i used that on the bottom of my tilt and turn windows -- not that exact product, but from md supply in the US.
its waterproof when fully compressed , so it adds a bit of redundancy and air tightness to the sill which is otherwise a little more annoying to seal up. you can also run it around the entire perimeter of the window frame, but can be very annoying to work with. if it expands before you get the window in, then youre in for a fun time.
ezpz on sills only, though.