Guide to Insulation
When insulating a building, it’s best to consider the long term benefits of a particular product rather than the upfront cost. After all, proper insulation can turn a house into a comfortable and livable home. In this guide, we’ll explore some great options to help make your decision process that much easier.
Contents
Intro
Insulation is an essential factor for homeowners because it helps to retain heat and prevent cold air from getting into your home. Choosing to install an insulation product in certain parts of your home can not only significantly lower your heating bills but also make your home more energy-efficient.
Here are some of the common insulation applications:
- solid wall insulation (internal or external)
- cavity wall insulation
- underfloor insulation (solid floor, suspended floor)
- loft insulation
- flat roof insulation
- pitched roof insulation
- room in roof insulation
Types of Insulation
Insulating residential homes and commercial properties can require various installations, including in the walls, the roof and under the floor. Choosing the right product for each application is essential for optimal performance. There are many products available on the market, including insulation boards and rolls. These are available from leading manufacturers such as Rockwool insulation and Kingspan Insulation that offer quality assurance and durability, often with sound and fire protection built-in.
Other common types of insulation include polyurethane foam, known as PIR foam such as Ecotherm, reflective foils such as Superfoil and polystyrenes such as Jablite. Each type works differently to trap or repel heat, for example, Superfoil works by reflection the same way thermos flasks work, and it is common to see people wrapping themselves in this form of insulation when they have finished running a marathon.
Depending on the level of thermal coverage you need, insulation is available in various thicknesses. An important component to consider when deciding on thickness is the insulations U-value. The U-value, also known as thermal transmittance, describes how efficiently a product prevents heat from escaping outside. A product will perform better as an insulator if it has a low U-value.
Loft Insulation
One of the most effective ways to insulate your home is by installing loft insulation. If you are unsure whether you need to upgrade, try measuring its thickness. Building regulations state the minimum thickness for loft insulation is now 270mm. However, this was a lot lower in the past. As a general rule, any existing insulation less than 100mm is so old it’s best to replace it altogether. If it measures 100mm or more, you can simply add insulation on top.
There are two options; cold roof insulation or warm roof insulation. The former is installed between the joists, and the latter is installed between rafters. The difference between these processes is the installation, which we will cover under roof insulation. Both work great for a loft conversion where heat is lost through the roof. Alternatively, if your loft is used only as a storage space, you might invest in insulating the floor instead. This process prevents heat loss into the loft from the rest of the house. It also benefits from being cheaper and easier to install.
When insulating the loft floor, it’s important to remember that installing 270mm or greater of loft insulation will exceed the height of the ceiling joists, if the space in the loft is not going to be used, then this will not be an issue, if it is to be used for storage, there are solutions available for example using Ecotherm cut and fitted between the ceiling joists. This tends to be more expensive than using traditional loft rolls, so maybe just use this in specific areas. Loft rolls are more commonly used because of their ease of use and cost. They are perforated at 400mm and 600mm centres so they can be torn to suit different ceiling joist centres.
Roof Insulation
Heat often escapes through the roof making roof insulation an effective way of saving energy. According to the Energy Saving Trust around 25% of heat loss escapes through the roof of an uninsulated home. Installing roof insulation can be done relatively easily.
There is a wide range of roof insulation products suitable for flat roof and pitched roof. Expanding foam is one of the most common and effective ways to insulate cracks. Roof insulation products are available in rolls, slabs and boards in various thicknesses. Remember to consider the U-value when deciding the appropriate insulation for your roof.
The first concern you must address when installing roof insulation is whether you are working with a flat or pitched roof. A flat roof will have a pitch of approximately 10°. There are two ways to insulate a flat roof: warm roof insulation and cold roof insulation. A warm roof is where the insulation lays on top of the timber. This means the roof area remains at a warmer temperature, usually similar to that of the rest of the building. Cold roof places the insulation between or below the timber rafters. This method is easier to install and more cost-effective. However, you should invest in an adequate flat roof ventilation system to prevent vapour build-up. This method is more commonly used for renovations on older houses because you do not need to remove the roof cover to access above the rafters. One good example of flat roof insulation is Ecotherm, a high-performance option with zero ODP (ozone depletion potential).
When insulating at rafter level, there are a few options available, Kingspan or Ecotherm can be cut and fitted between and underneath the rafters, Superfoil is stapled to the inner face of the rafter and can also be used with Kingspan or Ecotherm between the rafters. This method of insulation, creating a warm roof, is ideal if the loft space will be used as a loft room, as once the insulation is installed, plasterboards can then be installed and why not add in a Velux at the same time to allow natural light in?
Floor Insulation
By installing floor insulation, you can minimise heat loss into the ground by 15% and reduce draughts. Ordinarily, it is more economic and practical to solely install ground floor insulation. However, it may make sense to add suspended floor insulation if a room is situated above an unheated space, such as your garage. Additionally, insulation between flooring can be excellent to reduce noise transfer.
How you insulate your home will depend on the type of flooring you have. For example, if you reside in an older home you are likely walking on suspended timber floors. In this case, the best practice is to retrofit insulation between the joists underneath your floorboards. Rockwool insulation is a good option as it is denser than traditional fibreglass, meaning it is more thermally efficient. It is also moisture, fire and mould resistant. If you are living in a newer build, you may have a solid concrete ground floor. In this case, we recommend using insulation boards because of their high compression resistance. A good example is Jablite polystyrene insulation. We also suggest installing a damp-proof membrane to both types of flooring to prevent moisture access.
Floor insulation thickness is incredibly important when it comes to choosing insulation. In England and Wales, flooring must adhere to a U-value, this is the measure of how quickly heat will travel through the floor. Currently, this is set at 0.25 W/m2k or less and can usually be achieved with around 70mm of foam insulation and 150mm of wool insulation.
Wall Insulation
The very first step to examine when choosing wall insulation is the kind of house you live in. For instance, if you’re living in an old house, you likely have solid walls, simply because cavity walls were not widely available until the 1920s. Another way to know if your house has solid walls is if the outside walls have alternating bricks rather than bricks laid out lengthways. If your house is painted, you can tell by measuring the walls. Narrower walls are a telltale sign of solid brick. You should check out the next section if you have determined your house has cavity walls.
Solid wall insulation is an expensive process but if done correctly, it can make your home more energy-efficient and much nicer to live in. Internal wall insulation is usually cheaper to install, however, the process can be incredibly disruptive to your daily routine. If you decide to install internal wall insulation, one option you might consider is rigid insulation boards, these are extremely thermally efficient without being too thick. If your walls are very rough and uneven, you might benefit from dry lining, this process involves fixing battens on the walls, fitting insulation between them and then covering with plasterboard.
External wall insulation can be great for the longevity of the brickwork and it is a great way to weatherproof your home and reduce sound disruption. However, we do recommend checking with your local council about planning permission. Expanded polystyrene insulation, is a popular option for insulating your external walls because of its cost-effectiveness. Alternatively, if you would like to save space, K5 boards provide excellent insulation without being too thick. Finally, mineral wool can offer great sound insulation for walls.
Cavity Wall Insulation
If you are living in a newer building, you will likely be looking for cavity wall insulation options. Filling cavities with insulation is a must if you want to save money and energy. Your house may already have insulation if it was built in the last twenty years, you can check with your local authorities building control department.
Some good options for cavity wall insulation include mineral wool, Superfoil and foam. Rockwool insulation is an example of mineral wool that can be used for filling cavity walls. It is known for its thermal consistency, fire resilience and breathability. It is also a suitable option for reducing noise transfer. Superfoil is compiled of insulation, a vapour control layer and a radiant barrier, which work together to thermally insulate really effectively. Finally, foam insulation is extremely thermally efficient and today, most brands use foaming agents that don’t use CFCs or HCFCs, meaning they are much safer for the earth's atmosphere. According to Checkatrade, you can expect to pay £30 – £65 per m² for polyurethane foam and £25 – £30 per m²* for glass wool.
Sound Insulation
Sound or Acoustic insulation can require higher density fibrous insulation or other dense materials, such as Soundbloc plasterboard. In residential applications, a combination of both fibrous bats such as Rockwool and layers of Soundbloc are commonplace and will provide significant acoustic benefits. Soundproof insulation can also be used indoors between rooms. For example with Rockwool sound insulation, you will get a high-density mineral wool insulation that effectively insulates the sound between internal areas. In most homes that are only exposed to general low-level noise, thermal insulation will do the job well enough that you shouldn’t need any additional acoustic insulation.
Another option to minimise the travel of sound is to invest in spray foam insulation. This method is very versatile, able to fit into awkward areas like corners and cracks. If installed correctly, it is also air-tight which can extend the life of your building by quite a margin. Foam insulation can also dry, crack and pull away from the structure if not installed by an expert, therefore, unless you are an experienced professional, we do not recommend installing it yourself. If you choose to invest in sound insulation, you can drastically improve the comfort and privacy of your space, creating a much-needed barrier between you and the noisy world of today.