Let’s consider the example detached house in the drawings.
There are 22.7 meters of cavity wall lintels required. Of these, 17.7 meters can be mass-produced lintels and can easily be sourced from a builder’s merchant. If the lintels average a thermal transmittance value of 0.3W/mK it would result in an overall thermal transmittance of 5.31W/K. If these were upgraded to thermally broken lintels with a thermal transmittance value of 0.05W/mK the thermal transmittance would be 0.89W/K, saving a significant 4.42W/K!
The lintel for the 5m doors is out of scope of the lintel code, BS EN 845-2, and would likely be difficult and expensive to purchase from a builders merchant.
So, what do you do?
The majority of the time, your structural engineer will design a beam and plate lintel. Naturally they will design a lintel that the majority of structural steel fabricators can supply. As investigated in Desk Study 1, these lintels can be significant thermal bridges with thermal transmittance values of 1W/mK*. This leads to a thermal loss of 5W/K from the doors!
Depending on the construction, our lintels can achieve thermal transmittance values of 0.07W/mK* (sometimes even lower with a bit of additional work). This would make the thermal transmittance of the doors 0.35W/K, giving a saving of 4.65W/K which is a huge 92.5% reduction!
In conclusion, one of our thermally broken lintels can result in better thermal savings than upgrading every other lintel in the house combined!
We will give our anticipated thermal transmittance (psi) values and temperature factors with our quotations bespoke to your construction, so there’s nothing to lose by making an enquiry!
* – Actual value may vary depending on the beam specification and construction of the property.