By Tony Millichap, technical manager of Kingspan Insulation Limited.
Ensuring a high level of building fabric performance has become increasingly important in recent years as new regulations and the rising cost of energy lead to a greater demand for more efficient buildings. However the thicknesses of construction required to achieve this performance with traditional insulation materials can lead to compromises in certain areas of a building’s design. Vacuum Insulated Panels (VIPs) offer a specialised solution for this issue, achieving optimal levels of thermal performance with the bare minimum insulation thickness.
VIPs are a relatively recent addition to the UK market but have been used for several years in both Germany and Switzerland – countries which historically have been ahead of the curve in embracing new, more efficient building technologies and performance standards such as Passivhaus. In these countries the panels have been successfully used in building applications where a lack of space, due to design or the constraints of refurbishment, means that they are the most efficient, and perhaps the only viable, insulation solution.
One of the most common applications for VIPs on the continent is for balconies or roof terraces which sit directly above or adjacent to a heated room. Use of traditional insulation materials for these areas often results in either a step up between the balcony and the adjoining room or a trade-off in the height of the room below. The ultra-thin VIPs however make it possible to avoid these compromises and achieve a consistent floor level without denigrating the overall performance of the building fabric.
VIPs are made from a micro-porous core, which is ‘evacuated’ and sealed in a thin, gas-tight membrane. The membrane has to be capable of withstanding atmospheric pressure, and of maintaining the vacuum over time. The resulting panels can provide an insulating performance that is up to five times that of traditional insulation materials, providing a potential solution for problem areas where depth of construction is at a real premium.
There are a number of reasons why having this edge could be important. Although the next changes to the Approved Documents L are looking to be less onerous than they might, there will still be a firm emphasis on greater improvements to the building fabric. Looking forward to 2016, the target for zero carbon housing is still set, and the leap from the 2013 amendments will be extremely challenging. Quality of build is also coming under the spotlight, with calls from the government and bodies such as the Zero Carbon Hub for the industry to ensure that ‘as built’ meets the designed performance.
Each time performance requirements tighten there will be instances where it is extremely difficult to meet them fully, running the risk of penalties or even non-compliance. VIPs help to avoid these issues and make an excellent choice for both new-build and refurbishment specifications.
For example, a typical Edwardian terrace refurbishment of a solid concrete ground based floor, (perimeter:area ratio of 0.3), requires 95mm of EPS (0.038W/m.K) to achieve a U-value of 0.20W/m2.K. This normally involves an extended building program with a great deal of digging down and removal of earth, or the raising of floor levels, with all of the subsequent work that has to be undertaken in raising doors, lintels, skirting boards and radiators.
In contrast, to match this level of thermal performance, just 20mm of a VIP product (0.007W/m.K) is required, while 50mm would deliver an impressive 0.11W/m2.K, helping projects to meet the most demanding standards. The advantages of using this kind of system in a solid floor upgrade are clear.
High and low
As well as being very thin, the panels are also extremely lightweight, reducing potential structural loading stresses on existing buildings. This makes them an attractive solution for roof installations, particularly in cases where the building’s design or planning height restrictions require the build-up to be kept as slim as possible.
For example, just 40mm of a VIP product with a thermal conductivity of 0.007W/m.K, together with a 25mm high performance rigid thermoset PIR board overlay, can deliver a U-value of 0.16W/m2.K when used on top of a timber deck with a plasterboard ceiling.
VIPs can be used in a number of roof build-ups including green roofs and provide exceptional thermal performance that will last over the lifetime of the building. Issues such as penetrations or small gaps in the insulation layer due to the size or configuration of the area are easily dealt with using high or premium performing rigid thermoset infill panels to avoid thermal bridging.
The complete building envelope
VIPs offer a unique, space-saving solution, allowing architects to achieve designs which would simply not be possible with conventional insulation materials. The panels are able to support an increasingly wide range of applications and when used effectively they perfectly complement other high performance insulation products and allow the building fabric to meet the most demanding standards.