Why the replacement of glazing alone cannot achieve sufficient energy savings and constitute a stand-alone intervention

It is often reported that replacing only the glazing in an old frame is capable of saving significant amounts of energy.

This is a myth because apart from the relative reduction in the thermal transmittance of the existing frame, replacing the glazing offers no other benefits. On the contrary, replacing the entire frame (frame and glazing) offers the maximum benefits to the consumer and significantly increases energy savings for the reasons discussed below.

By replacing the frame, the overall thermal transmittance of the frame is significantly reduced because modern aluminium profiles with thermal break are used which have low thermal transmittance coefficients, while at the same time they allow for the installation of glazing with a larger gap which has a lower (better) thermal transmittance coefficient compared to what could be installed in existing frames.

The new frames will have significantly better coefficients of air permeability, so there will be no heat loss from the frames due to air leakage. The new technology frames offer significantly better air tightness due to the modern design and elastics used.

In addition, with the complete replacement of the frame, the proper sealing of the connection joint of the windows and facades ensures their proper usability. An incomplete seal is often the main cause of damage to the building.

The most important functions of waterproofing are:

  • Separation of indoor and outdoor climatic conditions with vapour and air barrier.
  • Sound protection.
  • Thermal protection (protection from condensation) inside the joint.

Rainwater barrier.
With the total replacement of the frame, we can also deal with the phenomena of thermal bridges in existing structures, which occur at the joints between the frames and the masonry and result in the escape of significant amounts of energy.

A thermal bridge is defined as that part of the building envelope where the thermal resistance appears reduced compared to the thermal resistance in the rest of the building envelope and consequently at that location the heat flux is increased.

For this reason, thermal bridges are considered to be the ‘weak’ points of the building envelope and are detrimental to its thermal protection. They affect the energy performance of the building and reduce the feeling of thermal comfort inside the building, while they also encourage the condensation of water vapour and the growth of mould fungi and various micro-organisms on the surface of the building elements.

*Article from POVAS