Inquire about insulation issues: Heat conductivity pathways
Getting to Grips with Thermal Bridges: A Conversation with Matthew Evans, Technical and Regulatory Affairs Director at Kingspan Insulation
In construction, thermal bridges — points or areas that let heat pass faster than the surrounding materials — can be a real pain in the neck. They crop up at junctions between different building elements, like walls and windows, and they're bad news for energy efficiency and comfort. But fear not, for Matthew Evans, technical whiz and Director of Regulatory Affairs at Kingspan Insulation, is here to shed some light on the subject.
What the Heck Are Thermal Bridges?
Move over black holes guarding the secrets of the universe, here comes thermal bridges, the question mark placed against the building envelope. Simply put, these are areas in a building where heat escapes more readily than elsewhere due to materials that conduct heat better clustering together in spots, creating 'bridges' between the inner and outer layers of the construction. Often this happens due to holes in the insulation layer or when an element, such as a joist, goes through the construction.
Where Do They Pop Up?
From your average wall junction to openings around windows, thermal bridges have a slew of hiding places. By understanding these, you can get a leg up on minimizing them. You'll want to watch out for repeating thermal bridges occurring at regular breaks in the fabric of the building, like studs or wall ties. Linear thermal bridges hang out around openings, such as windows or doors, or places where a more heat-friendly material passes through the insulation layer. Geometric thermal bridges make themselves known at spots where two or three different planes meet, such as junctions between different building elements, and finally, point thermal bridges lurk at penetrations, like pipework and flues, as well as isolated steel beams and columns and fixings and fasteners.
What's the Risks of Having Them?
The main issue? Heat loss. As we add more insulation to our buildings, thermal bridges start taking up a larger share of total heat loss. Research suggests they can account for as much as 30 percent of total losses, making them a big part of the performance gap between the expected and actual energy demand of a building. They also pose another problem: if they're colder than the surrounding construction, they can lead to condensation on the internal face of the construction or interstitially within it. This can cause issues, including mold growth and damage to structural elements.
Do Rooflights Need Approval?
In most places, installing rooflights on existing roofs falls under something called permitted development rights, which means no approval required. However, if the building is listed or in a conservation area, you might need planning permission, as the authorities will most likely have slapped an Article 4 direction on it.
How Can We Design Them Out?
Here's the key: keep insulation continuous across the building envelope. You'll want to pay special attention to junctions. To knock thermal bridges out, you could consider extending wall insulation below the top of the perimeter insulation for floor slabs, or using a flexible insulation at the eaves of a pitched roof to close any gaps between the roof and wall insulation. Many manufacturers now provide details with pre-calculated psi-values covering junctions where bridges commonly occur. But, these won't cover every scenario, so you may need to whip up your own custom details and dime the psi-values. Make sure these details are spot on and practical for your construction crew.
What Are Thermal Breaks, and Where Are They Used?
Thermal breaks are materials with low thermal conductivities that help interrupt heat losses in areas with high thermal conductivities. These are especially useful for metal elements, like balconies and window frames.
How Do You Spot Them on Retrofit Projects?
Keep your eyes peeled for obvious signs, like surface condensation or mold growth. In most cases, however, thermal bridges are identified with infrared cameras. These will help pinpoint areas where there's a significant temperature difference with the surrounding construction.
How Tough and Costly Is It To Squash Them in Existing Buildings?
It depends on the cause of the bridge, its location, and the building itself. Sometimes, it's as simple as filling a gap in loft insulation, but more often than not, getting rid of a thermal bridge in an existing building can be a complex and pricey endeavor. It may involve stripping back sections of the construction to get to the root of the problem and deal with related issues, such as rot caused by interstitial damp.
Is There Any Regulatory Guidance or Best Practice Advice for Both New Build and Retrofit Projects?
A smorgasbord of manufacturer and industry-created details and guidance is now available, covering actual build-ups and performance and providing pre-calculated psi-values. These databases often include process sequences that offer step-by-step guidance for your construction crew, ensuring the details you specify are accurately achieved in the final building.
For more information, check out the Kingspan website. 🙋♂️
Insights for Enthusiasts:
- Minimizing or eliminating thermal bridges is crucial for boosting building energy efficiency, comfort, and resilience.
- Strategies for designing out thermal bridges include creating a continuous insulation layer, adopting a fabric-first design approach, using thermally broken elements, ensuring proper workmanship, and verifying thermal performance with early performance assessments.
- Additional preventative measures include good ventilation and taking advantage of subsidies available in many regions for energy-efficient upgrades.
In the realm of science and health-and-wellness, addressing thermal bridges in construction is key to improving energy efficiency and promoting occupant comfort. By implementing strategies such as maintaining a continuous insulation layer, adopting a fabric-first design approach, and using thermally broken elements, one can effectively minimize or eliminate thermal bridges, thereby boosting a building's energy efficiency and resilience. Additionally, incorporating good ventilation and taking advantage of energy-efficient upgrades subsidies further aid in the prevention of thermal bridge-related issues.
