Is triple glazing really worth your client’s investment and the extra issues it brings? Ben Brocklesby from Origin considers the relative benefits and drawbacks of both double- and triple-glazed window and door options
While in terms of aesthetics it is the frames of doors and windows that make the biggest difference to a project, the glazing also has a pivotal role to play in managing acoustics and thermal efficiency.
On paper, triple glazing has a clear advantage over double glazing, especially when it comes to insulation; better at preventing heat transfer from inside to out as well as stopping cold air from entering a property. This of course means it will assist in keeping homes feeling warmer in the winter and cooler in the summer.
For example, a particular window can have a U-value of 1.2 W/m2K in its triple-glazed version, compared to 1.4 W/m2K with a double-glazed equivalent. This added performance will help reduce energy bills, which is a particular concern for many at the moment.
Although triple glazing can achieve lower U-values, it is possible to achieve high levels of thermal efficiency with double glazing. Such levels are achievable thanks to careful design, plus the use of special thermal breaks to limit the transfer of heat.
The additional pane of glass in a triple-glazed window or door can also help reduce external noise pollution as well as improve acoustics, which can be an advantage for properties in urban areas or those located near a main road. However, there are some important considerations to weigh up before recommending triple glazing as standard for your clients’ projects.
The cost problem
The price of triple- versus double-glazing is likely to be the biggest deciding factor for homeowners. A triple-glazed unit can cost up to twice as much as a double-glazed alternative, so you should consider whether the value added to the property through energy savings is enough to outweigh this. If the client plans to stay in their home for the long term, then they are more likely to be concerned with the long-term return on their investment, meaning that the energy savings of triple-glazing might be appealing.
The extra pane also results in the unit’s overall weight being much heavier. This means that fewer units can be delivered per van to site, as there will be a likelihood of exceeding the maximum load weight. As the installer will be able to transfer fewer units at once, projects may take longer and incur more costs. Some may also require machinery to lift large expanses of glass, adding further cost. Being much lighter, double-glazed units shouldn’t generally present as many issues in terms of transport or installation.
Sightlines
One of the main benefits of doors with large areas of glazing is uninterrupted views outside. However, the additional weight of triple glazing can impact the maximum panel size possible – depending on the system. This is particularly relevant for products like bi-folding and sliding doors, and means instead of a few, wide panels, doors have to be specified with a higher number of glazed panels to avoid them being too heavy to operate individually. With more panels, comes more frames, meaning that the uninterrupted view people desire, as well as the amount of natural light, will be affected. The frame material will impact this. For example, aluminium’s strength allows it to bear more weight, allowing for larger panel sizes.
Looking ahead
As a specifier working on multiple projects per year, it’s also worth keeping abreast of the wider context of the triple- versus double-glazing debate. Last year, the Government updated Part L of the Building Regulations, which brought in more stringent thermal efficiency standards. For some manufacturers, this meant they had to switch to triple-glazing as standard to meet the new regulations. However, the Future Homes Standard, which is being introduced in 2025, will take the Regulations even further, presenting a problem for those manufacturers already relying on triple glazing to meet the current standards. When specifying fenestration products, whether it’s for a renovation project, self-build, or new build, it’s wise to consider whether the suppliers that can deliver now will be able to do so in the future.
Clear conclusions
It’s an interesting debate, and while triple glazing wins on the long-term benefits of reducing energy bills and noise pollution, homeowners looking to make a statement with large panes of glass, or who hope for a significant return on the investment in the short-term, won’t reap the benefits. This is where consultation with your client is essential to understand what their long-term goals are. If they are building their ‘forever’ home, then it makes sense to opt for triple glazing, which will eventually pay for itself.
Ben Brocklesby is director at Origin