For architects and window specifiers, vacuum glass presents an attractive proposition. Low heat loss, a long service life and fewer materials could make it a compelling option for projects where thermal performance matters. Getting those benefits, however, means confronting some less comfortable questions about price, delivery and the small but visible dots within the glass.
Paul Murphy, of vacuum glass specialist Werkman Tech, sets out three principal advantages and three drawbacks. His assessment illustrates both the technology’s potential and the practical considerations that can determine whether it makes it into a building.
Longevity is central to the sales argument. According to Murphy, vacuum glass units carry guarantees of between 20 and 25 years, depending on the product. Werkman Tech offers a 25-year guarantee, although the company’s expected service lives extend considerably beyond that.
Murphy puts the anticipated lifespan of its metal edge units at 35 to 40 years, rising to 60 years for units with powder glass edge seals. Those figures describe expected durability rather than the period covered by the guarantee, a distinction that matters when assessing the long-term value of a specification.
Thermal performance provides the second attraction. Murphy says units using a single silver low-emissivity coating typically achieve U-values of between 0.58 and 0.62 W/m²K, with light transmission of about 80%. Multiple low-emissivity coatings can bring those values down to between 0.42 and 0.48 W/m²K.
Yet headline figures require scrutiny. Murphy warns that some distributors promote lower values supported by independent testing without making clear that the measurement excludes the support pillars within the unit. Those pillars create thermal bridges and affect the performance of the finished glass.
For specifiers, the question is therefore what a quoted figure actually measures, and whether it provides a fair basis for comparing products.
The environmental argument combines reduced heat loss with the construction of the units themselves. Murphy describes two sheets of toughened glass joined using powder glass or tin, enclosing a tiny vacuum cavity. Stainless steel or semi-clear ceramic pillars keep the panes apart.
The units he describes require no noble gases, plastics, silicones or butyl rubber. He argues that their thermal performance can reduce heating demand, while a longer service life can lessen the need for replacement. The strength of that proposition rests on how the products perform over time as well as their initial specification.
The immediate obstacle is cost. Murphy quotes prices for toughened vacuum units ranging from Werkman Tech’s £210 per square metre to £540 per square metre at the upper end of the market. Even his company’s price, he acknowledges, remains substantially above triple glazing.
He expects costs to fall as demand increases and larger shipment volumes reduce transport costs. Until then, buyers must weigh the upfront premium against the value they place on thermal performance and anticipated longevity.
Delivery presents another constraint. Murphy puts the fastest lead times at four to six weeks, associated with the most expensive offering. Werkman Tech and some competitors operate at eight to nine weeks, while other suppliers take 12 weeks or more.
He attributes the difficulty of establishing production closer to UK customers partly to energy costs, arguing that cheaper fuel overseas favours manufacturing in China and the US. Local production could shorten delivery times, but his account suggests that the economics remain challenging.
Then there are the dots. The support pillars are essential to maintaining the vacuum gap, but their appearance introduces an aesthetic compromise. Murphy says many products use pillars about 0.8mm in diameter, arranged on grids with spacing between 20mm and 55mm.
Their dimensions also influence thermal performance. Larger pillars create more thermal bridging and are more visible. Werkman Tech says its latest technology uses pillars measuring 0.5mm on a 50mm grid, reducing their visibility.
Vacuum glass consequently demands a specification that looks beyond a single performance number. Price, delivery, appearance and the basis of durability claims all deserve attention. For buyers persuaded by its long-term benefits, the remaining challenge is making those advantages fit the budget and timetable of a real project.
Paul Murphy is Managing Director of vacuum glass specialist Wekman Tech
Why This Matters: Paul’s balanced and honest assessment highlights both the promise and practical hurdles of vacuum glazing in the UK. Its attractive thermal performance underpins its potential, while anticipated longevity strengthens the proposition. Growing demand and larger shipments could reduce costs, but buyers must currently weigh the premium against these benefits. Wider adoption will depend on scrutinising delivery times, appearance and durability claims, then ensuring the technology fits customers’ budgets and project timetables.
