Storming the schematics, energy modellers will all too often give computer software carte blanche to select a set of energy efficiency measures with a 1 dimensional perspective of performance parameters.
This approach means the broader value offered by glazing replacement as an energy efficiency measure is seen as offering a low ratio of carbon reduction to a high price point, other improvements are typically prioritised.
At what cost does this have upon the homeowner’s comfort?
High-performance glazing can offer impressive thermal comfort and well-being benefits that can be left unrealised.
Within a dwelling, glazing is typically the coldest internal surface. Glazing will ‘radiate’ heat and coolth into a room. Put simply, a cold surface will ‘shine’ the feeling of cold onto occupants, meaning the perception of thermal comfort is dictated by more than simply air temperature alone.
For example, let’s say it is a cold winter’s day. It is dark outside, but you have the wood heater on to make the house toasty and warm. The last thing you want is for all that warmth to escape. Utilising high-performance glazing, radiant heat is reflected back into the house rather than seeping through a poor-quality window. Thus ensuring you stay warm and comfortable.
On the flip side, if it is the middle of summer, with the sun seemingly focusing all the heat on your house, glazing can reflect excess heat. The light passes through the glazed window. However, the heat rays from the sun (or longer-wavelength infrared light if we are being pedantic) are reflected back, preventing the heating of the house and reducing the need for expensive and energy-intensive cooling options.
Not only offering thermal control benefits, but high-performance glazing can also drastically improve the acoustics within a home. Blocking out the sounds found in built-up urban areas has been scientifically shown to improve the quality of living for the residents with increased rates of heart disease, stroke and reduce life expectancy.
High-performance glazing does have its drawbacks, the main being the cost. This could be justified in a relatively short time period when the broader benefits beyond simply simulated energy efficiency are considered.
Glazing also needs to have a good balance between what is called visual transmittance (letting light through) and infrared reflectance (bouncing heat back). Otherwise, the deployment could prove problematic.
Drastically improving the glazing specification of a home is one of the key components of the Passivhaus approach. Taken to this level, thermal comfort is achieved at lower internal temperatures, adding significantly to the energy savings beyond the simulated performance results provided by compliance software.
Approaching a retrofit project, are the slightly increased marginal benefits offered by other EEMs worth sacrificing the potential long-term wellbeing and thermal comfort of the home?
