Triple Glazing Reflections


Harry Clarke the famous artist made his livelihood satisfying peoples fascination with refraction of light through glass.


But as well as allowing light to pass through, glass will also reflect and distort light.  This will happen at various rates depending on many factors but including glass type, thickness, colour or tint and whether or not the glass has any particular coating or film. The use of double and triple glazing add additional layers of reflection. Each sheet of glass or film produces a reflection resulting in the phenomenon of multiple reflections.  Films or coatings used to laminate glass sheets or prevent excessive heat gain can also result in colour distortion in these reflections.


Reflection and refraction can be dealt with by the introduction of lighting or by tilting the glass as most will be familiar with in the case of car show room windows. Films can be applied to make glass one way meaning the glass acts as a mirror on one side but is translucent on the other.


The use of artificial light both internally and externally can also influence the extent of visibility through glass and impact on the issue of total internal reflection where the glass acts as a mirror.


I have reviewed your photographs and note the obvious three reflections as a result of the use of triple glazing with some colour distortion also visible. This appears normal.


The external glazing however appears to be reflecting all light and acting as a mirror. This will significantly reduce the amount of light entering the house. Clearly you did not expect or desire this property of the glass used. The supplier says this is normal however you are unhappy with this.


In my experience there are many types of glass and many finishes that can be applied as part of the manufacturing process each with their own particular results.


In order to be more informed on this matter I suggest that you ask the window supplier to nominate two other sites where they have provided the exact same specification of glass used in your home.


You should note the specification of glazing used in your case. This is typically recorded on the window panels and ismarked on the plastic separator placed between the individual sheets of glass. This will give the date of manufacture and the glass thickness used. A British Standard reference may also be given or a kite mark indicating that the glassis toughened.


You should visit both sites with your designer,  if you have retained one to assist with your build,  or with a Chartered Building Surveyor and first check that the markings indicating the specification match yours exactly. Establish if the same level of external reflection is occurring. This should be readily apparent.  If the reflections are similar to those you are experiencing then it may be that although not desired these are standard “trade-offs“ against the additional benefits achieved by using the specification of glass provided.


If you do not notice the same level of reflection and light reduction then something is different and you clearly have an issue. If the specification matches but the date of manufacture is different the issue may be as a result of a manufacturing fault.


With this information you will be in a better position to get engagement from the window supplier. As with all such issues suppliers are slow to raise their hand but are usually willing to quickly replace items if it is found that a fault exists. Word of mouth and referrals are key in the construction industry your last job being the best example of your work.



Noel Larkin & Associates Chartered Building Surveyors


First published in Irish Times 30th Jan 2020