What is solid wall insulation?
If your house was built prior to the 1930s, the chances are that it will have solid walls – simply a solid layer of masonry bricks. Insulating your walls – regardless of whether they are cavity or solid (or even timber-framed) – is a great way to make your home more energy efficient. The insulation will minimise heat loss in the winter, saving you money on your heating bills. It will also stop your home getting too warm in the summer, helping to keep your home at a more comfortable temperature.
According to research, twice as much heat could be lost through an un-insulated solid wall as through an un-insulated cavity wall. However, the great news is that solid walls can be insulated, both internally and externally.
The science behind insulation
If hot air and cold air are partitioned by a wall, heat will transfer through the wall, eventually cooling the room until an equilibrium is reached (where the outside temperature is equal to the inside temperature). In reality this very rarely happens, because rooms tend to be heated; so as heat escapes through the wall, more hot air is supplied by your heating system, keeping it at a comfortable ambient temperature. If the thermal gradient is larger, for example on a cold and wintry day, the movement of the thermal energy across the wall will be accelerated.
Insulating a solid masonry wall helps to provide a thermal barrier, which helps to slow the movement of heat escaping out into the external environment. Less heating is therefore needed to keep the house at the required temperature.
Types of solid wall insulation for your home
Both internal and external insulation are great at keeping your home warmer, lowering your heating bills and cutting carbon emissions. However, both solutions have a different impact on your home, which is explained in the following section:
Internal solid wall insulation
There are a couple of methods to insulate a solid wall internally, which are either to use a rigid insulation board or build a stud wall. We recommend you get a professional in to complete this type of work, and you do not undertake it as DIY unless you are very experienced. Internal solid wall insulation can be as thick as 100mm, so your room will ‘shrink’ wherever it has an external supporting wall.
One way to avoid losing floor space is by using insulating wallpaper, which at only 10mm gives you some benefit of internal solid wall insulation, without impacting on the size of your room. However, the insulating wallpaper will not give you the same performance of dry-lining with the insulation boards unfortunately.
Advantages of internal wall insulation
- Cheaper than external insulation
- No aesthetic change to the outside of your home
- Works well when the home itself is going through a process of internal renovation
Disadvantages of internal wall insulation
- Will reduce the room you have in the living areas by up to 10cm, depending on the materials used
- Won’t necessarily get rid of any damp problems, which need to be tackled separately
External solid wall insulation
For external wall insulation, you need to employ a professional and you also need to consider local building regulations. This is because this process involves covering the original brickwork and could significantly alter the current appearance of the property, making out of step with the local area. Once any planning permission has been granted, the home can be insulated using an adhesive material which is fixed to the wall, then plastered over.
The finish applied to the external wall can be any combination of texturing, painting, tiling, brick slips, masonry work and/or cladding.
Advantages of solid wall insulation
- Less disruption to the household, as the work is carried out outside
- Renews your home’s external appearance and increases the lifetime of the brickwork
- Complements other refurbishment work
- An opportunity to fill cracks and holes in the brickwork, which will help reduce draughts(see Draught Proofing for more information)
Disadvantages of solid wall insulation
- More expensive than internal insulation
- Planning permission may be required
- Any work needs to comply with local building regulation
- May not solve all damp issues
- Work is not recommended if the building is not structurally sound
Costs of solid wall insulation
- Around £100/m2.
- Additional costs for downpipes, gas pipes, boiler flues and dishes
- Subject to render strength – additional cost to remove old/weak render
Measuring the effectiveness of solid wall insulation
The R-value is the measure of thermal resistance used in the building and construction industry today. The higher the R-value, the better the insulating properties of a material – so you should be looking to insulate your house with materials displaying a high R-value. Confusingly, you may hear the word U-value also bandied around. This is exactly the opposite, describing the ability of a material to conduct heat, so you want your insulating material to have a low U-value.
Installing solid wall insulation
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