Frequently Asked Questions

If you’re thinking of purchasing double glazing, it is always useful to know something about the product. I have listed some FAQ’s on double glazing together with some unbiased answers.

Maintenance Free UPVC Windows

Q: Do I have to clean my replacement windows as I have been told they are maintenance free?

A:Providing the UPVC used to make the double glazing profile is of good quality you should not encounter any discolouration and all of our products are guaranteed against profile discoloration however moving parts such as hinges and locks should be oiled bi annually as with any moving parts.

Double Glazing U Values 

Q:What is the U value?

A: Double glazing can be measured on its energy efficiency whilst comparing it to other windows, by using a calculation system known as the U value (or U factor).
The U value can be adopted for any kind of home construction and measures how effective that component is at retaining heat. Importantly, the lower the U value, the more proficient the window is at saving energy.

Clyde Promise

We will produce a window with a minimum U-Value of 1.1 Wm2K or a maximum higher value of 1.4 Wm2k depending on your choice of energy efficient glass.

What are the benefits of measuring double glazing with the U-value? Above all, installing new windows that are fitted with double glazing reduces heat loss, which in turn leaves a smaller carbon footprint as carbon dioxide emissions are cut by up to 50%. What are the standard U value measurements? The nationally recognised rating method for double glazed panels is for the whole window, including the glass, frame and spacers. However, sometimes a centre-of-glass U Value is given, which simply measures the performance of the glazing alone.

Clyde Promise

We will always give you a U-Value of your complete window rather than just the glass unit U-Value.

South Facing Double Glazed Units

Q: I am thinking of replacing a window to the back of my house which is south facing with a double glazed patio door will this make the room hot if so will I need some form of shading?

A: Yes this will make the room a bit warmer on a sunny day, we suggest that you upgrade to heat reflective glass that will protect your furniture and keep the room cooler, most energy efficient double glazing will protect you from the UV Heat in the summer as well as the cold in the winter.

Clyde Promise

We will also offer you Glazing options to counter act the effects of heat entering through your windows for both incoming heat in the summer months and losing less heat in the winter months.

Sound Proof Double Glazed Units (Acoustic Glass Options)

Q: I am considering having double glazing fitted to my house I live near to a busy road that runs down the side of my property will this help to sound proof my property?

A: Yes, by fitting double glazing to your property will certainly improve the sound proofing. We suggest that you have double glazing sealed units with a gap of a minimum of 20 mm, we can also offer you noise reducing or acoustic type glazing on various levels to stop any noise issues that you are suffering.

Clyde Promise

We will advise you on sound proofing acoustic glass options as tests have shown that by manufacturing the glass unit with two different  thicknesses of glass (i.e. 4mm and 6.4mm)  is nearly as efficient as acoustic glass but at a fraction of the price. When it comes to acoustic glass there are many different options available, contact us to discuss this further.

Box Sashes - Sash & Case Windows (To Replace Or Not To Replace)

Q: I am thinking of having double glazed sash windows installed in an old terraced property, which currently has sliding box sash windows. Having received three quotes, I have also received three views on whether the whole sash box should be removed or the new units simply fitted within the existing sash box, leaving the internal wood in place. One double glazing window company said the whole box sash should be completely removed to ensure a good job, the second said there was no need as the wood was original and was in good condition, the third said it doesn't matter, but fitting within the sash box will be cheaper. Please could you tell me who’s right?

A: When replacing box sash windows both methods can be used, some companies believe leaving the original 'box' in place and fitting the new double glazed sash windows within the existing box sash should be perfectly acceptable providing the timber is in good condition and without major timber rot showing. Also this will have all the original mouldings as finishes. Complete replacement is best if the old timber is rotten, If you would like more information on double glazed sash windows contact us for free and friendly advice. 

Clyde Promise

Our surveyor on site will show you how we propose to install each individual job and also explain as to whether we think boxes should be removed , partially removed or completely removed depending on current condition of windows and box sashes.

Double Glazing / UPVC Windows in Conservation Areas

Q: I live in a conservation area, and I am considering having UPVC double glazed sash windows fitted to replace my old timber windows would there be any restrictions?

A: Yes there could be restrictions, if you live in a conservation area or a listed building. Our experience has found it is best to discuss this with the conservation officer or your local planning officer to find out more please contact your local authority as the criteria may differ from one area to another. 


Q: We suffer from bad condensation; will double glazing help prevent this? Condensation is not caused by windows or doors it purely shows up on glass due to internal and external temperatures and atmospheric conditions, When water vapour from the air comes into contact with cold surfaces, the vapour condenses on the cooler surface of the glass forming a foggy effect.

A: By replacing old draughty windows with energy efficient windows may reveal condensation due to humidity which will always have present in the household, this is not a fault, in fact this shows how un effective  your old windows were.

We also use warm edge technology spacer bars which dramatically reduce condensation simply by not having any metal within the double glazed unit which allows cold to transfer through the aluminium bar.

On the other hand  if your old windows were/ are not draughty, Replacing your old windows with new may help as the sealed glass unit will be a warmer surface due to the newer technology / specifications such as Argon filled cavities, black warm edge spacing bars and Low E Glass which can all help toward reducing condensation.

Clyde’s Advice

While this condensation can be annoying, it is perfectly normal, however indicates excessive humidity inside the room. To eliminate this you will need to reduce the relative humidity of the room, which could be as simple as additional ventilation e.g. extractor fans in the kitchen and bathrooms to remove excessive humidity.

A higher specification of insulating glass such as Vista-Therm may also help this problem as it will always keep the inner pane of glass better protected therefore not as cold a surface internally.


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