Most windows fail at the edge. Endur is built for it.
Window labels lead with U-factor and solar heat gain. Those numbers only hold while the seal between the panes holds. Endur is Cardinal’s insulating glass designed around that seal, with a stainless steel warm-edge spacer and two layers of sealant.
When the edge fails, moist air gets between the panes, the argon leaks out and the glass fogs from the inside. No amount of cleaning fixes it. This design exists to keep that from happening for decades.
If we installed your windows around 2014, there is a good chance this is the glass inside them. Today our windows use a TPS warm-edge spacer, the next step down the same road. This page explains the glass you already own.
- 80+weeks in the P-1 test
- 1–2°warmer glass edge
- 20 yrCardinal seal warranty
Five parts that keep the seal tight
Every layer has one job: keep moisture out and argon in.
- 1
Stainless steel spacer
Roll-formed stainless steel with no polymer content, so there is nothing inside the unit to off-gas and fog the glass. A corrugated profile adds strength.
- 2
Bent corners
The spacer bends around each corner instead of joining with plugs, leaving one continuous metal barrier that keeps argon in and moisture out.
- 3
PIB primary seal
Polyisobutylene is the first line of defense. It resists moisture and UV light and is one of the strongest argon barriers available.
- 4
Silicone secondary seal
A specially formulated silicone adds adhesion and structural strength, and it holds up to sun and moisture year after year.
- 5
Beaded desiccant
Molecular sieve beads inside the spacer soak up stray moisture, with starting frost points below −65°F.
Built to outlast the toughest seal test
Cardinal runs insulating glass through the industry’s P-1 test until the seal gives out.
- 140°F
- Constant UV light
- 100% humidity
Competing seal systems fail in 8 to 22 weeks. Endur IG routinely passes 80 weeks with dew points still below 0°F, which means the air between the panes stays dry. Cardinal also reports the lowest seal failure rate after 20 years in the industry, and backs its units with a 20-year warranty to the window maker.
Out of 1,000 windows, how many fog?
A small change in seal failure rate is the difference between a window you forget about and one you replace twice.
fogged units at an 8% seal failure rate, the comparison Cardinal uses for weaker seals
fogged units at 0.2%, about what Cardinal’s seal durability data shows over 20 years
Every failed seal means a new glass unit, a service visit and a window that never looked as clear again. Better insulating glass is designed to keep you in the second column.
A warmer edge means less condensation
The sightline is where the glass meets the frame, and it is the coldest part of most windows in January. That is where condensation shows up first. The Endur spacer raises the sightline temperature by 1 to 2 degrees compared with the XL Edge spacer it replaced, and it can improve the whole window’s U-factor by up to 0.005.
A degree or two sounds small, but it can be the difference between dry glass and a wet sill on a cold morning. Fog on the room side is still mostly about indoor humidity, not the glass. The Department of Energy covers U-factor and the other ratings in more depth.
The coating does the work, the seal keeps it working
Low-E coatings control heat and light. A tight insulating glass seal keeps the argon and the coating performing for the life of the window.
LoE³-366
Balances daylight with strong solar control, a good fit for west-facing glass.
LoE-180
Lets more of the winter sun’s heat in for rooms that need warmth.
LoE-i89
A room-side coating that lowers U-factor further when paired with another coating.
Neat
A naturally self-cleaning outer surface that helps rain rinse dirt away.
Then and now: two roads to a tight seal
Endur was the right glass for the windows we installed then. TPS is what we install today.
Then: stainless steel spacer
- Material
- Roll-formed stainless steel, no polymer content
- Corners
- Bent, for one continuous metal barrier
- Seals
- PIB primary, silicone secondary
- Where you’ll see it
- Windows we installed starting around 2014
Now: TPS warm-edge spacer
- Material
- Thermoplastic applied as one continuous bead
- Corners
- No corner joints at all
- Where you’ll see it
- Every window we install today, including our Nobility Platinum windows; read more in ENERGY STAR 7.0 windows
Moving to TPS was not a fix for a problem. It was the next improvement, the same way each generation of insulating glass has built on the last. Your estimate lists the exact glass, spacer and coatings in every window we quote. Browse more product technology or the product literature library.
Endur glass, answered
Short answers about insulating glass and fogged windows.
What is Endur insulating glass?
Endur is Cardinal's insulating glass unit built around a stainless steel warm-edge spacer, a PIB primary seal, a silicone secondary seal and a beaded desiccant. It is designed to keep the seal between the panes tight for decades.
What causes a fogged window?
Fog between the panes means the seal has failed and moist air has gotten into the unit. Fog on the room side of the glass is usually indoor humidity, which is a different problem.
Is Endur the same as a TPS spacer?
No. Both are warm-edge designs. Endur uses a roll-formed stainless steel spacer with bent corners, while a TPS spacer is a thermoplastic applied in one continuous bead. Endur was in the windows we installed starting around 2014; the windows we install today use TPS.
My windows have Endur glass. Should I replace them?
Not because a newer spacer exists. This glass was built to keep its seal for decades. If you ever see fog between the panes, call us and we will check the window and your warranty.
Which glass will my new windows have?
New windows we install today use a TPS warm-edge spacer. Your written estimate lists the glass package and coatings, and we are happy to walk through each one.
Who can I call with questions?
Call (937) 833-5136. Michelle, our virtual assistant, answers 24/7 and can schedule time with our team. Office hours are Monday through Thursday 9 to 4 and Friday 9 to 2.
