When looking at the range of options for conservator and orangery glazing it is important to look at the roof and the wall glass separately as they are being asked to perform slightly different roles.
Wall glass is probably the most understood type as many people will have installed, replaced or maintained other windows around the home. In terms of what type of glass it is useful to look at the ‘worst case scenario’ to make sure that the right choice has been made. My ‘worst case scenario’ is for someone to have their arm go through the glass pane. What is wanted is for the glass to fall away so that the arm does not have to be pulled back trough the broken glass. Toughened glass will do exactly that, breaking into small pieces away from the injury.
Roof glass has a different ‘worst case scenario’, that of someone being inside the structure and a heavy object (such as a brick) lands on to the roof panel, breaking it. A natural reaction from inside is to look up at the noise. Small pieces falling down is not a good idea in this scenario which is why laminated glass is preferable for these units, the laminate will hold the broken glass up[ in the roof so as to cause no further damage.
The other key area in decision making is what kinds of coatings are desirable for conservatory glass. I will go through the pros and cons of the most popular types below:
Low ‘E’ glass; Low ‘E’ coatings (such as Pilkington K and Saint Gobain Planitherm) are a way of increasing the insulation value of the glass. These types of glass are worthwhile in my opinion as you can look at the effective ‘payback time’ for yourself (that is the additional cost of the glass, less the savings that can be made to heating costs. Broadly speaking the payback time of low ‘e’ is about three to seven years, with fluctuating energy costs only making this type of coating more attractive.
Solar reflective glass; These coatings essentially reflect energy from the sun helping conservatories from summertime overheating. My difficulty with these coatings is that while they are effective for the two months that there is too much sunlight, they also reflect away for the remaining ten months that you really want to maximise free heating from the sun! The difficulty lies in the principles of conservatory ventilation that, unfortunately modern conservatory design completely ignores. Modern conservatory design holds very little of the principles that the Victorian engineers applied when designing the first conservatories (and unsurprisingly they ventilated well). I would try not to have to resort to using this type of glass..
Self-cleaning glass; This is a new type of glass using nano technology to resist and actively clean small particles on the glass. This glass is relatively unproven in long term tests and will certainly not stop a bird dropping! I would only look at this type of glass if access to the units is really difficult. I would look closely at the ‘pay-back time’ for this additional cost – the last time I checked a glass cleaner could be used twice a year for over seven years before the cost has been covered on an average conservatory! (and that includes the windows on the rest of the house..
In conclusion I would take an objective look at the types of glass that you are being sold. What is necessary, what is not all conservatory companies will be commissioned and or have profits included in any upgrade options) and question whether the glass options will add pragmatic value to the project as a whole. lightweight conservatory roof replacement