Do you use Fiberglass windows on school projects?

Hi Keihly, We've been using commercial fiberglass windows on schools (and higher ed) for years in Oregon. We've pretty much limited ourselves to Cascadia because they have proven to be consistently the most reliable and we've had field testing issues with other manufacturers. I've heard no post occupancy complaints. We used to use aluminum but default to fiberglass now for the much better thermal performance (and air/water performance compared to storefront systems). The downside is that I'm not aware of an equal to Cascadia, so sometimes we end up competing with aluminum on cost. For egress entry doors, we still use an aluminum door and frame nested in the fiberglass frame, and fiberglass can't do what curtain walls can do. However, Cascadia does have a window wall system, but it's not something we've used on a school (they simply developed a floor bypass system that works with their Universal Series windows). I'm not sure about Cascadia's availability on the east coast (we keep them pretty busy over here), or about equally reliable products in your market. Hope this helps! Mike Manzi RA, CCS, LEED BD+C Associate Principal he/him Bora Architecture & Interiors

Hi Keihly,
We also use a fair amount of commercial fiberglass windows on K12 projects (including a recent 141,000 gsf middle school) similar to Mike's comments above.  My understanding is that Cascadia Windows offers the best combination of performance (air/water testing) and larger sizes, with their field splicing options to connect factory units together in the field within a larger rough opening.  At the risk of sounding like a product rep, they compare performance similar to aluminum curtain wall systems due to the pressure-equalized seals; which I understand requires less frequent Owner maintenance for sealant joints (10-15 years?) compared to repairing sealant joints at aluminum storefront every ~5 years(?).  A few years ago, the Cascadia pricing was said to be closer to aluminum storefront, due to a shortage of local skilled labor (Portland, Oregon) for field-installed stick-built systems.  But labor and sourcing has been so volatile lately, I know that some of our current projects are running up against cost limitations, and also consider aluminum unit windows, or aluminum-clad wood among other systems. The only comparable product to specify along with Cascadia Windows that we've found is Accurate Dorwin, which has similar high-pressure air/water infiltration testing standards for both factory and field testing.  However (as of a few years ago) they did not offer a fiberglass splice detail to combine multiple factory units into a larger rough opening in the field.  I recall the approximate size limits were ~5'x10'+/-(?) for Accurate Dorwin's factory units installed into punched openings. A lesson I learned from our recent middle school, is that if we want true competitive pricing between both manufacturers, it may work best to design toward the "punched opening" approach using the more restrictive sizing of A/D and then let Cascadia Windows bid that as well without their unique field-spliced mullions.  While that could help reduce window to wall ratios, it may not work for all design approaches. Ditto to what Mike said about nested aluminum door frames within the fiberglass frame system - especially at high-traffic entrances.  Cascadia reps can share a factory detail for this approach, although it may not be on their website.  Typical K12 door hardware requires reinforcement that is more durable when installed into aluminum frames.  I understand Cascadia's fiberglass door frame system is more applicable for low-traffic conditions.  Since these aluminum frames were typically at airlock vestibules for our school, we accepted the higher U-value and lower air tightness in order to get the more reliable door hardware for 1,100 daily students.   Another note about durability (of Cascadia Windows) is that the underlying color of the fiberglass frames is white, before they are factory painted.  This painted finish can/will get nicked in the field, yet can be touched up.  It doesn't seem quite as durable as a PVDF (Kynar) paint finish on aluminum, but it’s generally OK at most windows.  This is another reason to consider aluminum doors and frames at primary high-traffic entrances. We are always hoping to find comparable products to specify for cost-effective (results may vary) high performance of commercial fiberglass windows.  I’d love to hear more from others’ experiences.    Stephen Endy AIA, Associate
Mahlum Architects 
Portland, Oregon

A small school project we did a few years ago had Alpen fiberglass windows installed. At that time, at least, they did not have a pressure-equalized system similar to Cascadia, so we had to rely on some additional sealant to get them to pass the specified performance in the field. Not a bad choice, though, if the costs are that significantly different, certainly way better than PVC. One of the envelope consultants we work with said they were having some field testing issues with Accurate Dorwin windows, so we haven't used them yet. Cascadia can field test to 15 psf for water penetration (curtain wall levels, as Stephen mentioned), so that's the standard we try to adhere to. I think Cascadia knows they've set the bar high, and I suspect that's why their price has crept up over the years compared to other options. Alpen or Accurate Dorwin are good options if your criteria isn't that high. Mike Manzi RA, CCS, LEED BD+C Associate Principal he/him Bora Architecture & Interiors

We also try to use fiberglass (Cascadia) on our K12 projects whenever possible. We've had only positive experiences with durability and performance. Like Stephen's firm, we do projects in both Seattle and Portland. Stephen, I don't know what your experience has been but we've had much better success (i.e. much better pricing) in the Portland market than Seattle. The GCs and glazing installers in the Seattle K12 market don't have a lot of experience with fiberglass and they prefer the Kawneer/EFCO etc supply chains they are accustomed to. As a result, the install quotes we receive often feel inflated. I attribute it to a "I don't really want to do this" markup. This often results in projects abandoning fiberglass before they get to the bid phase. It's a lot of extra work to develop both aluminum and fiberglass details, and coordinate the various design constraints of both systems, in order to carry a bid alternate for fiberglass. So teams, especially on GCCM (general contractor construction manager) projects, will drop fiberglass if it seems like a long shot due to high price quotes early on (especially the last couple years, where cost escalation is a serious problem for our K12 project budgets). For whatever reason, Cascadia seems to have better penetration in the Portland area and we get much more competitive pricing on Portland projects. A couple other comments/thoughts on fiberglass in K12: First, we've studied the energy performance and cost/benefit of higher performing windows on numerous projects now, and we can never make it pencil out. We can't make the argument that paying a premium for better-performing fiberglass windows makes economic sense in the long run. The payback periods are too long- like 150 years. That's partly because our energy prices in the PNW are quite low and also because we've found that after meeting energy code, especially our very stringent/progressive WA State Energy Code, our envelope performance has hit the point of diminishing returns. Increasing assembly u-values makes only marginal improvements in energy use (e.g. 0.3 EUI. Note that we're comparing to double-thermal-break aluminum with argon IGUs). That's because the K12 energy load is dominated by ventilation. Once the envelope is performing at a certain level, it's more effective to focus on energy efficiency in the HVAC system, like heat recovery and ground-source heat pumps. That's a long-winded way of saying that I haven't felt it's that urgent for us to push fiberglass when the pricing doesn't look favorable. The payback equation may work differently in your Boston climate. And it's very different for other occupancy types. Second, I've looked into embodied carbon comparisons of aluminum vs fiberglass. The information is limited, as neither Cascadia nor anyone else had an EPD for fiberglass windows at the time (let me know if that's changed!), but what I found is that the frame is only a small contributor to the EC of a window unit. The EC is something like 10% frame:90% glass, or more. Given that, even if fiberglass has a fraction the EC of aluminum then the EC of the window unit doesn't change drastically. Rolled into a total LCA, it's an almost imperceptible difference for a whole project's embodied carbon. My takeaway from that exercise is that if we want to lower the EC of glazing systems we need to focus on finding better options for glass, before worrying about frames. Kristian

I don't see EPDs yet from Cascadia, but they do have a Declare label (red list free). Mike Manzi RA, CCS, LEED BD+C Associate Principal he/him Bora Architecture & Interiors

FWIW, I poked around a while ago looking for EPDs for fiberglass window systems and found this one from a company in Sweden (CPIC Fiberglass).  As my sainted mother used to say, "Bad breath is better than no breath at all."