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To achieve its carbon neutrality goal before 2050, many places have taken various measures and carried out many facility improvements. The main focus of all these plans is to save energy wasted in the form of heat energy and make buildings more energy efficient.
Cavity wall insulation is a way to improve energy efficiency. Cavity wall insulation basically fills the cavity between the inner and outer leaves of brickwork with insulation material. This is a cost-effective solution to save energy and prevent heat loss. However, before installing cavity wall insulation, you should pay attention to these issues.
A typical cavity wall has two layers of brick masonry with a cavity between them. Problems with cavity wall insulation are rarely related to the insulation itself. Usually, the problem stems from pre-existing conditions, such as defective walls, brick cracks, mortar disintegration or gutter leaks. Improper installation may also be the root cause of the problem.
Another important factor is rainfall, especially in areas with frequent rain. Special care should be taken in these areas because the walls of the house will be hit by rain, leading to a higher possibility of water entering the cavity. The main reason for having cavity walls is to keep water away from the interior, the habitable side of the property. If there are cracks in the external wall, water will enter the cavity. No matter which insulation material you choose, it will become redundant when continuously exposed to moisture. Insulation material will absorb water, causing it to no longer function as an insulator, mold infestation, wall connection failure and structural damage. No insulation is better than wet insulation.
All new buildings will have cavity wall insulation installed during the construction phase itself. Cavity wall insulation felts are designed to be as waterproof as possible. For example, this may be why problems related to cavity wall insulation rarely occur in new buildings, but are a big problem in renovated wall insulation. Before we delve into the problems of cavity wall insulation, let's first look at the advantages and disadvantages of each insulation material used to isolate cavity walls.
Rock wool board cavity wool:
Cavity insulation wool made of rock wool is a cost-effective solution for insulating cavity walls. With correct installation, you can make full use of the installed cavity insulation layer. It must be said that these types of wall insulation, whether wool or foam boards, are only feasible in new construction or extensions, etc., because you actually have to remove the wall to install them. Even on new walls, incorrect installation can lead to many problems, including: moisture problems: cavity wool made of rock wool is water-resistant but not waterproof. If exposed to a continuously humid environment, rock wool will absorb moisture, thereby leading to a huge risk of water penetrating into your home. Moisture can also lead to mold growth and property damage.
Sagging: rock wool will sag or collapse over time or when it gets wet. It will create gaps on the cavity wall, thereby leading to heat loss.
And foam insulation is also one of the common methods for insulating cavity walls. By drilling holes in the wall, polyurethane foam is sprayed into the cavity. Using foam insulation to seal the cavity helps control moisture and reduce the risk of mold growth. But its own disadvantage is that foam may contain harmful substances such as formaldehyde, which are also released when mixing foam on site.
When the foam expands, it will exert excessive positive pressure on the walls of your home. Too much, so if installed improperly, it may damage the structure.
And common problems with cavity wall insulation:
1. Problem of insufficient ventilation:
As we discussed earlier in our blog, adequate ventilation as well as correct installation are crucial for maximizing the use of your house for insulation. The same is true for cavity wall insulation. If cavity wall insulation is not properly installed or there is no ventilation around it, it will collapse over time, leading to cold spots on the walls.
2. Condensation on cavity walls: Condensation on cavity walls may be due to the following reasons:
Interstitial condensation: For example, when humid, warm air flows through breathable insulation materials such as rock wool, the moisture-filled air will reach its dew point, thereby depositing water in the insulation material. Water droplets formed inside the cavity can lead to structural damage, corrosion of metal wall strips, rotting of wood frames, etc. These may not become apparent until the condition significantly worsens.
Cold bridges: If the cavity contains sharp edges or gravel, this may cut into the insulation layer, forming gaps. These gaps can lead to heat loss and form cold spots along the walls. When moisture-filled air comes into contact with these cold spots, they will condense, thereby leading to mold and structural damage.
3. Moisture:
Problems related to moisture will only occur if the cavity wall insulation is not properly installed or the cavity has not undergone pre-existing repairs before installing the insulation. Water will enter the cavity if:
Your home is located in an exposed position, i.e., not immediately surrounded by buildings or trees.
Your home is located in areas with more wind and rain, such as the western coastal region.
Pre-installation inspection was not done well, and no cracks in brickwork, mortar joints, plastering were found, or whether the external wall was poorly constructed.
The insulation material in the cavity will absorb moisture, thereby reducing its performance and insulation performance. It can cause the insulation material to sag or collapse, thereby creating gaps, which leads to heat loss. Dampness is usually followed by mold, which is potentially dangerous to the health of occupants.
This is why pre-installation surveys are so important. After installation, it is crucial to ventilate the area, followed by daily property care, such as re-pointing mortar joints and regularly monitoring gutters. Doing so can prevent dampness.
4. Gravel in cavity walls: Many cavity walls, especially on older properties, are filled with gravel and all kinds of things at the bottom. When installing insulation material in the cavity, this gravel will form moisture bridges, thereby reducing insulation effect and performance. In addition, if filled with gravel, the blown-in insulation material may not fill the cavity as expected.
5. Not sleeving subfloor vents: Subfloor vents are used to prevent dampness and rot in suspended floors of older properties. Very commonly, they form part of the main cavity. If these are blocked, then you are inviting wet rot and dry rot into your home, which is a disaster. Cavity wall insulation installers should ensure they are sleeved before carrying out any insulation installation.
6. Improper covering of drill holes: If insulation is installed through drill holes, these holes must be properly covered to obtain the maximum benefit of the insulation. Poor coverings not only look unsightly, but also reduce the insulation effect.
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