Most builders and home owners understand that high-performance insulation and airtight building envelopes are key factors in reducing energy bills and lowering heating/cooling loads.
But many homes still have thermal bridges, and the impact of these gaps in the insulation can dramatically reduce a home’s performance. These gaps are caused by metal wall ties, wood studs and steel framing.
Loss of conditioned air
Thermal bridges allow heat to escape or enter a home more easily and create a range of problems that have the potential to compromise both the energy efficiency of a building and its occupant comfort. They can lead to condensation, resulting in mould growth and potentially damaging the building materials; they also result in cold spots on interior walls, causing discomfort for occupants and making it difficult to meet energy performance regulations.
Using the thermal inertia of the wall, researchers such as Martin with others have demonstrated that even high insulation thicknesses foreseen by building regulations can be subject to significant losses due to thermal bridging. This is especially the case for insulated metal and wood-framed buildings.
A thermal bridge is a point in your insulation where highly conductive material penetrates the insulation, creating a path of least resistance for the flow of energy. This doesn’t render your insulation completely inept, but it can significantly reduce its R-value and thermal resistance, reducing the overall effectiveness of your insulation.
It is possible to avoid thermal bridging by ensuring that insulation is continuous, which can be achieved by wrapping the entire exterior of your building with an insulating jacket. You can also install a continuous insulation such as rock-wool board over the sheathing of a wall before you put up the drywall.
Increased risk of condensation
Thermal bridges in a wall cause cold spots and encourage interior condensation that can contribute to moisture problems. This can damage the structure and lead to mould growth. In addition to that, condensation can also lower the surface temperature of the insulation and reduce its effectiveness.
When it comes to the energy efficiency of a home, thermal bridges are a serious problem. These areas provide a path of least resistance for heat to move in the building envelope, so they significantly reduce the overall R-value of a wall. In the case of steel studs, thermal bridging can reduce an insulated wall’s R-value by between 40 and 69 percent.
In new construction, these thermal bridges must be carefully designed to minimize their effect on the R-value of a wall. This requires careful planning, detailing and construction of the walls and framing. In existing homes, it may be possible to mitigate the impact of these thermal bridges by retrofitting with continuous insulation. However, it’s still important to take into account their effects on energy efficiency when calculating the U-factor of a building.
Increased risk of mould growth
Thermal bridges are the areas where the surfaces of building elements with high thermal conductivity meet those with low thermal conductivity. Typically, they occur at the component joints, edges, transitions and penetrations of standard building components.
When it comes to new construction or renovation, it is essential that architects, engineers, enclosure professionals and tradespeople identify any possible thermal bridges within the building envelope. This will prevent the need to spend more money on energy efficiency measures later on in order to make a building comfortable and healthy for the occupants.
If not addressed correctly, thermal bridges can significantly reduce the performance of insulation systems and lead to a number of negative effects on building structures. These include:
Moisture condensation due to thermal bridging can result in the development of mould, which is a serious problem and can have lasting consequences on the health and wellbeing of the occupants. It also poses a risk to the structural integrity of the building, with long-term moisture penetration potentially leading to rot and rust.
The best way to avoid this is by using continuous insulation, which effectively eliminates thermal bridging. This is achieved by using materials that stop the flow of heat between a wall and the surrounding area, such as Quinn Lite insulation or Quinn Therm products. These types of products can be used in a range of construction details to create thermal breaks that significantly improve the performance of insulation in buildings.
Decreased energy efficiency
Even in airtight, insulated buildings, thermal bridges can account for up to 30% of heat loss. While this may not sound like a lot, it is enough to decrease overall building energy efficiency, making for an expensive home.
The reason for this is that these bridges create a pathway for heat to travel through the insulation and escape the building during cold weather, or to travel into the building during hot summer days. This increases heating and cooling demand, makes the building vulnerable to condensation and leads to mould growth, which can be both aesthetic and health related.
Fortunately, there are steps that can be taken to reduce the effects of thermal bridges. For example, metal studs can be replaced with wood studs where possible to minimize the amount of steel in the wall. Thermally broken fasteners can also be used to minimize the amount of heat that is transferred through these critical connections.
Finally, it is recommended to use a higher R-value of insulation where possible and to limit the amount of space in the wall where air can pass through. These measures will help to ensure that a home is well insulated and that there are no gaps or bridges that can compromise its energy efficiency. In the case of new construction, these measures can be implemented during design.