Toggle-Glazed Hybrid SSG systems are now common – almost every aluminium window /facade system house has a version. These systems have gained popularity over the last 10 years or so because they are perceived as being cheaper than the traditional SSG systems where a DGU is bonded using a structural silicone sealant to a carrier-frame and the carrier-frame is then mechanically fixed back to a curtainwall structure.
What is not commonly realised is the fact that traditional SSG systems are generally far more thermally-efficient that the toggle-glazed hybrid systems. Moreover, the DGU manufacturers need to charge quite a high premium for using the special continuous spacer bar or pushing short lengths of channel into the DGU edge seal whilst it is still wet. See the comparitive cost further down the page. It is also worth noting that DGU manufacturers find it very difficult to achieve EN1279 Pt3 (Gas Retention) with toggle-edged DGU’s and therefore it’s worth checking that they do have certification for their product with this detail when specifying gas-filled DGUnits.
I recently ran across an article in the Dow Corning Technical Library which compared the performance of standard captive curtainwall, both new and aged, traditional SSG with both wet sealed weatherseals and a dry front gasket weatherseal as well as toggle-glazed hybrid SSG systems.
The article is available in full at:
I can recommend giving half an hour of your time to read the whole article, if you can.
Older capped/captive curtainwall systems can suffer with gasket shrinkage in areas exposed to the sun over many years, hence the fact that an “aged” captive curtainwall performance has been included in the table. Also, some toggle-glazed hybrid systems have a continuous edge channel detail, whilst others are made up of short lengths of channel, hence the two entries in the table for this type of system.
These days cost is a big issue – and in truth I think that the toggle-glazed hybrid systems came about principally because it was percieved that traditional SSG was very expensive. Indeed, SSG bonding using proper certificated materials in conditions monitored for temperature & humidity with proper project testing and sampling regimes as well as all samples being held on file for 25 years isn’t a cheap option. The upshot of this is that Dow Corning now have 30 years experience with traditional SSG systems, without a single failure to my knowledge.
Toggle-glazed systems rely on DGU’s which are almost always made off-line to the manufacturers general production runs and this will usually be an even more expensive option.
I recently asked a major European DGU manufacturer (at the Bau exhibition in Munich) how much extra he charges for hybrid DGU’s with the edge toggle channel as compared with standard square-edge DGU’s. His answer was €18-19/linear metre (of glass edge) for discontinuous systems and €26/linear metre for continuous systems (due to the different types of silicone required in each type). In comparison, our standard Dow Corning 993 SSG bond is priced at about £13.17/linear metre and the cost of our bonded channel is about £4.00/linear metre. We generally work with our customers own DGU’s which must have a silicone edge seal, freely available from a large number of quality DGU manufacturers. Toggle-glazed hybrid SSG systems are restricted to the use of only a few specialised DGU manufacturers, which can mean a further “rarity” premium on cost.
AEL have a standard SSG solution, which is fully tested to CWCT sequence B. Alternatively for less exposed conditions we can provide just the bonding channel profile which can be toggle-fixed to other curtainwall structures or grids. Because the system has a wet-pointed front weatherseal, air & water leakage is not as big an issue as with captive dry-glazed systems.
Tim Walker
Architectural Engineering (Aluminium & Steel Glazing) Ltd
07884-268537
