Conservatories and Sunrooms - Pilkington K Glass, Low E Glass.

Our "Ask an Expert" section receives a very large number of questions on Pilkington K Glass and Low E Glass in general. Many of the questions are very similar. This section will answer some of your questions.

In particular:

What glass would you recommend for a domestic house or conservatory for South facing applications?

or

Do I require two different types of glass to achieve heat retention in winter and keeping heat out in the summer?

Here is just one example of a typical Pilkington K question along with our answer.

"We are just organising the purchase of a conservatory for our new house. As the garden is south facing and as such being a new house, it has no natural shade around it at all at the moment. Having opted for a glass roof we are now looking at Pilkington K with an anti-sun tint. Is this possible? We very much like the idea of using the conservatory in the winter months but both want to avoid the suns glare in the summer as much as possible. Our conservatory company is saying that K glass is not necessary and will cause us a lot of problems with heat retention in the summer and also that K glass and anti-tint would work against each other."

OUR ANSWER

In designing a conservatory for all year use the two main problems that need to be over come are making sure that your conservatory is not too cold in the winter and too hot in the summer!

Pilkington K Glass is one way to greatly improve on the levels of insulation and help reduce the condensation risk. This glass varies from normal clear glass in that one side of the glass has a special metal coating, technically known as a low emissitivity, or Low E. coating. This microscopic metal coating (which is almost indistinguishable from normal clear glass) allows through short-wave radiation, like sunlight, but reflects longwave radiation, such as heat from fires and radiators, back into your conservatory making it easier to keep warm.

Pilkington K Glass is not a solar control glass and if this is a big consideration you should consider combining it with a type of solar control glass. Many people do however not bother combining with a glass such as "Antisun" (now called Pilkington Optifloat Tinted) because of the additional cost. Perhaps they consider that a conservatory that's too hot can be "managed" with blinds, roof openers etc, whereas a conservatory that's too cold in winter is much more difficult to "manage" and may mean rebuilding in order to get a "four seasons type" conservatory.

NOTE:
Any glass-roofed conservatory (with or without Pilkington K Glass) - especially south facing conservatories, will feel pretty hot without blinds etc. Some suppliers will claim that that it will only be excessively hot when Pilkington K Glass is installed. This we feel is "clouding" the issue. Are they really suggesting that you will not have problems with excessive heat in a standard glass roofed conservatory?

It's also worth noting that some conservatory companies don't like Pilkington K Glass as it's more likely to mark / get scratched during the manufacturing process. (The process requires a cleaner more sophisticated manufacturing space - which some smaller sealed unit manufacturing plants are often not "geared up" for.)

The K glass (prior to being made into a sealed unit) needs to be handled with a lot of care and we are aware that some companies think this "more trouble than its worth". Often this is the real "agenda".

After all your conservatory is going to be pretty hot and will need heat management / control with or without Pilkington K Glass. Rarely do we find conservatory companies mention heat build up with "normal" glass or that you may need blinds. We are however aware that some companies will use heat as an argument to not use Pilkington K glass - usually because they don't wish to supply it because of the reasons given above.

Pilkington K Glass and Antisun glass (now called Pilkington Optifloat Tinted) can be combined.

For more information on Pilkington Products visit: http://www.pilkington.com

HERE IS ONE TYPICAL FAQ's

1. Do I require two different types of glass to achieve heat retention in winter and keeping heat out in the summer?

The Pilkington Optifloat Tinted (formerly known as Pilkington Antisun) range has long been an industry standard for low-to-medium performance glass with the Pilkington Suncool range suiting high performance needs. The Pilkington Eclipse range fits between the two.

To maximise the reduction of solar gain, the ideal position for a solar control glass (e.g. Pilkington Optifloat Tinted) in a double glazing unit is the outer pane. Pilkington K Glass is not a solar control glass: however, its presence in a double glazing unit can considerably improve its thermal insulation (reduce the U-Value) over conventional units. The ideal position for the Pilkington K Glass low emissivity coating is on the inner pane facing the cavity. Hence, if the requirements are for reduced solar gain and improved thermal insulation, both types of glass can be combined in one unit. Both Pilkington K Glass and Pilkington Optifloat Tinted are available in toughened and laminated form.

Another alternative - the Pilkington Suncool High Performance range offers high light transmittance, low heat transmittance and excellent thermal insulation, with U values as low as 1.1 W/m2K with double-glazing. Two recent additions, Pilkington Suncool High Performance Brilliant and Titan also provide a neutral appearance, which may meet your requirements.

FINALLY:

It may also be worth noting that its estimated that by 2002 all glazing in new build situations in England and Wales will be subject to amendments to the building regulations - Part L, following the British Governments commitment to the Kyoto Protocol on the environment. When these new proposals are fully implemented around 2004 the required U Value for insulation will be 1.8 - something that will mean that K glass or Low E glass will virtually be a standard requirement for new build.