Insulation & fabric performance
Upgrading your property’s thermal efficiency as part of a renovation is a great way to enhance the performance of your heating system and save money on bills. Richard Webber takes a closer look at the options
Richard Webber discusses how to enhance your home's thermal efficiency as part of your renovation project, establishing a comfortable abode with low heating bills
Insulation and fabric performance are integral elements in any renovation project. It’s estimated that around a third of a building’s heat escapes through poorly prepared walls. Even more seeps out through ill-fitting windows, doors and lofts. Yet despite such stark facts, it’s so easy to focus too much on more aesthetically pleasing aspects of a property update, while underestimating the importance of the performance of the envelope itself.
Fabric first approach
A building’s structure – including walls, floors, ceilings, windows and doors – needs to be insulated as effectively as possible to prevent heat loss and, ultimately, minimise fuel costs. “Some people are more likely to spend, say, £20,000 on a kitchen rather than those things you can’t see, such as insulation,” says Simon Storer, chief executive of the Insulation Manufacturers Association (IMA), the representative body for the rigid polyisocyanurate (PIR) and polyurethane (PUR) insulation industry.
Fabric performance determines how a building will function in terms of retaining heat and providing comfort. “It’s important that the shell of the house – the chassis, if you like – runs efficiently,” says Simon. “In winter, you don’t turn the heating on and open the windows. But, in effect, that’s what you’re doing if you have poor performing fabric.”
Upgrading insulation
There are myriad materials to choose from when it comes to wall insulation. The first decision to be made is whether an internal or external application, or cavity wall insulation is best for the property you’re working on. The walls of your house form the largest part of your insulating decision, so it’s important you make the right choice. Every building is different, however, and the style of yours will dictate what type of application and product is most practical.
A huge advantage of pumping insulation, such as mineral wool, polystyrene beads or polyurethane foam, inside a cavity is that it doesn’t affect the building’s external appearance. Nor does it eat into the internal floor space or lead to extensive decorating. However, many older properties don’t have any cavity walls. According to the National Insulation Association (NIA), about a third of UK homes have solid walls, so insulating the outside of the property or interior walls is the only option.
One benefit of an external application is that the work can be completed without adversely disrupting your dayto-day living. But opting for exterior insulation isn’t always practical because it alters the appearance of the building significantly. If the property is a listed structure or situated in a conservation area, this may be prohibited.
Interior products usually comprise ready-made rolls or boards. It’s often cheaper than external insulation but will impact on your floor space and result in everything on the walls having to be removed, including sockets, picture rails and skirting boards. One advantage, though, is that internal wall insulation can be carried out on a room-by-room basis.
To reduce the amount of floor space lost to insulation boards, consider using the thinnest material possible with the greatest performance level. “The product only needs to be applied to the walls facing the elements outside. “So if you’re a mid-terrace house, it’s just the front and back walls,” says Simon. “PIR is a good solution for these situations because it’s among the most thermally-efficient available. But there are other options, including sheep’s wool, cork, polystyrene and more. But often the thicker the component, the poorer the performance.”
For floors and lofts, PIR boards are equally useful. “If you’re in an older house, you’re more likely to have joists with a void underneath,” says Simon. “So you can insert the material between joists underneath the floor boards without affecting air flow as you’re not filling the void.”
Insulation materials
There is a wide choice of insulating materials on the market these days. Christine Lellig, campaign director for
Wood for Good, the timber industry’s campaign to promote usage of timber in design and construction, says using wood fibre insulation in a renovation has many benefits. “Natural fibres like this contain chemically-bound water, which absorbs heat energy and helps prevent overheating in summer. Wood fibre is very dense, which also slows the passage of heat through the fabric. This is especially important for rooms in the roof.”
Among the material’s selling points is that it helps regulate humidity and prevent condensation and mould growth. “Wood fibre has good breathability, allowing the dry transport of moisture,” says Christine. Made from renewable resources, these fibre boards can be reused and are easily recycled at the end of their life, too.
Cork is another alternative that’s becoming increasingly popular for use as insulation. Kieran Streames, director of SPD UK, which supplies a wide range of products made from this natural material, including insulation boards, says “Cork can be used in both flooring and wall applications.
The unique honeycomb structure of its cells means that it has a low conductivity to heat, noise and vibrations.
It’s also highly energy efficient.”
Another important factor to consider from a safety perspective is that cork is fire retardant and burns without a flame. “This can help to slow the progress of fire in your home and avoid the emission of toxic gases, which other materials can produce when burned,” says Kieran.
Extensions
For anyone whose renovation project centres on a new addition to the property, you need to follow the Building Regulations when it comes to insulation. That said, it’s worth remembering that when the government last updated the rules regarding performance in buildings back in 2013, extensions were excluded. Minimum standards, therefore, remain at 2010 levels. So, liaise with your designer or builder to ensure you get the best performance rather than the minimum required under the current rules.
Conversely, attaching a thermally-efficient extension to a poorly insulated home won’t make it cheaper to run overnight. If finances allow, consider improving the efficiency of the whole house. “If not, all you’re doing is heating the environment,” says IMA’S Simon Storer.
Understanding weak spots
It’s estimated that a typical property loses up to 20% of its heat through air leakage. This often happens through gaps around windows and doors, for example. Mike Easdon, vice chairman of the National Insulation Association (NIA) says, “Draught-proofing can greatly reduce leakage. It’s not just cold, windy days when valuable heat could be lost. As warm air accumulates inside a property, it’s also escaping through gaps all the time.”
While insulation and eliminating draughts from weak spots – such as windows, doors and roofs – are vital in producing an efficient house, attention must be paid to implementing adequate ventilation, too. “Airflow is important. You don’t want to create other problems, such as condensation and damp, which is why the work must be carried out professionally,” says Simon.
The Energy Saving Trust reports that for a standard detached home, up to £255 per year can be saved on energy bills by installing cavity wall insulation. Adding loft insulation could increase this sum by a further £225. Protecting solid walls creates an even bigger total – up to £435 – while draught-proofing windows and doors adds additional savings. So, choosing the right workforce is vital to achieve the maximum benefit from your project.