In any home, windows play an integral part in keeping the property warm, dry and secure. When the time comes to replace a window unit, there are best practice methodologies, guidelines and regulations that need to be considered, not least for local authority homes or other social housing.
This CPD will look at when and how such work should be tackled, the issues of which specifiers, manufacturers and installers need to be aware, and how using materials from recycled frames can add to the overall product’s sustainability.
Windows need to be fit for purpose. They must be well made, installed correctly and able to provide enough light, retain enough heat, and afford the occupants a degree of security.
When it comes to refurbishing a window, this can be done by replacing the hardware – hinges, locks and handles – or the glazing unit, or both. The hardware elements, warranties and guarantees for which are generally one to two years, are usually the first to deteriorate.
Regular maintenance, which can be as simple as oiling hinges and cleaning out dirt from recesses within the mechanisms, is recommended. Failure to maintain hinges, locks and handles can put additional strain on a unit, so they become more prone to damage. These items can be replaced fairly easily, but regular maintenance will extend their lives.
When it comes to the double-glazing unit itself, over time there can be a tendency for condensation to accumulate in the gap between the two panes of glass. The glass is generally fairly straightforward to replace, and if both the hardware and the window profile – the uPVC frame holding the glazing in place – are in good condition, it is the only element that requires attention.
There is rarely an issue with the uPVC profile element of a window. These are produced with a warranty or guarantee of at least 10 years. However, there may be early iterations of uPVC units that have become outdated, where the glazing is thinner than later versions and the performance rating is poorer. Aesthetically these will also be inferior.
A local authority or social housing landlord may replace windows across part or all of an estate every 20 years, sometimes sooner, as part of its capital budget plan. Part of this approach is covered in the Decent Homes Standard, which was first published in 2004 and is now the subject of a government review.
In situations where external cladding is being replaced, or when insulation is being applied to the exterior walls of buildings, the local authority or housing association would look at the age of the windows, and would consider replacing units at the same time as the other work, in order that the guarantees and the lifespan covering them run concurrently with what they are replacing on the external envelope of the building.
On tower blocks, windows need to provide sufficient weather performance, in other words they must be robust enough to provide a certain level of resistance to wind, water and air pressures.
When it comes to planning refurbishment or replacement of windows, there are a number of factors to consider. For instance, the specifier will need to confirm that what is being proposed is compatible with the existing design within the building.
Many properties feature windows that are not within maximum or minimum size guidelines.
System houses arrive at maximum sizes through a series of security and weather tests at accredited UKAS test houses; this then determines their maximum size. Minimum sizes are dictated by either hardware limitations or production machinery minimums, and it is the responsibility of the profile manufacturer to stipulate these. For example, a tower block built 20 or 30 years ago may have a high number of windows that exceed the current maximum dimensions a profile manufacturer can now deliver. It is the responsibility of the manufacturer to advise the specifier and suggest an alternative design so that size guidelines can be met.
Other elements to consider include the acoustic properties of any proposed windows, since in an urban environment the glazing will need to offer sufficient noise reduction to comply with Building Regulations on allowable sound levels at different times and in different parts of the home.
An installer needs to be mindful of liaising with the tenants of the property, not least because of the need to gain frequent access to their home.
Often a company will secure the services of a dedicated tenant liaison officer. This individual will initially advise residents that a contractor is to undertake window replacement and request that they provide access for a site survey. Thereafter the liaison officer will engage with occupiers to ensure the windows are replaced in a timely fashion within the schedule of the refurbishment programme.
The responsibility is then shared with the installer, who needs to provide a continuity of communication with the occupier to ensure access is afforded to facilitate the necessary surveys and ensure the proposed replacement windows will fit.
Installers will sometimes conduct a pilot programme, working on a limited number of windows to better understand the construction environment and how the windows will fit into the existing space. This can involve checking that the sills are the right depth to provide a sufficient overhang, or seeing if there is any deviance in the external or internal dimensions that could affect the new windows’ fit and function.
Adjustments may be required to allow a window to fit the aperture and to operate as designed. Additional clearance may need to be created around the sash mechanism, or if it is a unit that opens internally – such as a tilt-and-turn window – then it may require an extension around the frame to ensure it doesn’t catch on anything when opening.
Other considerations include being aware of site conditions – welfare facilities, access and working safety – and, crucially, ensuring that the right windows are on site before attempting to install them. A delivery programme needs to be carefully monitored. It is essential that windows are not removed before confirming that replacement units are of the correct dimensions and performance.
This sounds like common sense, but on a large project there is an even greater need to check that the products ordered are those that have been delivered, and that they fit, before installation begins.
The window replacement contract may involve removal of window furniture, such as curtains or blinds. Under such terms, these elements would also need to be replaced after the main work has been completed. In addition, any cables near the windows may need rerouting – indeed anything else with the potential to interfere with an opening must also be rectified.
Similarly, a contract may stipulate making good at the end of the installation process, requiring installers to fill any holes or indentations and potentially to redecorate parts of the neighbouring wall. This might be the responsibility of the subcontractor, rather than the main contractor.
It is also important that old windows are disposed of appropriately. Manufacturers of profiles that use recycled window materials can engage with contractors to locate skips on site for this purpose.
Some of the removed material ends up in a local authority recycling processing centre, while profile manufacturers with their own recycling and reprocessing facilities may arrange for removal of old window profiles that can be recycled. These are then recycled and turned into flakes or pellets for reuse in the extrusion process to make the next generation of window frames. Offcuts from the profile manufacturing process (known as post-industrial material) can similarly be fed into the recycling system.
The use of post-consumer or post-industrial materials is part of a sustainability drive that can benefit the environment, the industry and occupiers. Some manufacturers look to feature between 50% and 60% recycled content in their window profiles, and this is likely to increase as awareness around the use of recycled content grows. For specifiers wanting a recycled option for replacement windows, a good target to aim for is 50% recycled material or more.
Recycled uPVC is extruded into the internal structure of a window profile and the use of post-consumer material will have no impact on its integrity. If sustainability is important to a developer’s building programme, it is worth specifying windows that contain as high a percentage of post-consumer recycled content as possible.
Under current legislation, replacement windows cannot perform any worse than those they replace. When local authorities or social housing landlords replace windows in homes they own and operate, they must do so in line with current legislation.
Rules addressing heating and ventilation are covered by Part L of the Building Regulations. Part L currently states a U-value of 1.6W/m2K for windows; this is a thermal measure of how much heat is lost through a window. The figure is being revised, however, with new requirements due to be published in 2022.
Often a landlord will look to install windows that are in excess of the minimum U-value, since it is considered better practice.
The standard that window profiles need to adhere to is BS 7412: 2007 – Specification for windows and door-sets made from unplasticised polyvinyl chloride (PVC-U) extruded hollow profiles. This covers the fabricator, or the company charged with assembling the window unit, including the glazing, the profiles, the hardware and so on.
The profile manufacturer meanwhile needs to adhere to BS 12608: 2003 – Unplasticised polyvinylchloride PVC-U profiles for the fabrication of windows and doors. Classification, requirements and test methods.
The security side of windows is covered by PAS 24. Any new-build is required to meet the requirements of Approved Document Q, which covers security, particularly in relation to the risk of burglary. However, it is also good practice to specify windows to this standard in a refurbishment programme.
Within the housing association community, the specification will be based around what is called Secured By Design (SBD). This is a third-party certification service, owned by the UK police force, which is designed to improve the physical security of buildings using products such as doors, windows, locks and walling systems that meet SBD security requirements. Created in 1989, its accreditors work closely with builders, developers, local authorities and registered housing associations to incorporate police crime prevention standards from initial concept and design through to construction and completion.
SBD representatives will visit manufacturers and factory-audit premises and their processes to confirm they have all the necessary compliance systems in place, certifying those manufacturers that meet SBD standards.
A number of factors must be considered when it comes to ensuring the quality of replacement window products.
Any that have specifications or adhere to standards which are out of date must be rejected. Ensuring a compliant up-to-date specification that references the relevant standards of the day is essential.
As well as selecting a profile based on compliance to those standards, specifiers must go through a rigorous pre-qualification questionnaire process to get an idea of a quality-to-price ratio – 30:70 is the norm, although recently we have seen some frameworks that are putting a greater focus on quality (local employment, apprenticeships, supply chain performance and sustainability, for instance). A rigorous tender process, one with an onus on determining the quality and price split, is advisable.
While product selection often comes down to price, making sure the right questions are asked of manufacturers can reduce the risk of later problems. It is advisable to ask for examples and evidence of installation work carried out on previous projects.
The good financial standing of the profiles house, the manufacturer and the installation company must also be checked. When corporate collapses happen, they can leave a project uncompleted, requiring clients and contractors to go through another round of procurement procedures, incurring extra time and money.