Frequently Asked Questions

With so many options available from so many suppliers it is quite often difficult to compare like for like quotations. Below are a few pointers to consider when it comes to getting the right rooflight for your project:

​Do I have a pitched or flat roof?

The design for a flat rooflight is different to that of pitched rooflight and flat version will require a kerb/upstand section built onto your roof. If you have a sloping roof you can generally find rooflights that can be installed between 17 and 70 degrees. It is always important to know the roof finish and mention the pitch of your roof when talking to rooflight suppliers to ensure you are quoted for the right product.

​How big can my skylight be?

Modern glazing technology allows some very big areas of glass but if you are working with an older or Listed property then it is advisable to use conservation rooflights and keep to smaller sizes. More modern projects are better served by more contemporary skylight designs which have much larger areas of high specification glazing without the more traditional glazing bars used in conservation roof windows. Just remember that the bigger the glass area the thicker and heavier the glass will be, so you may need to crane your rooflight into position.

​Do I want it to be an opening or fixed design or can it be a combination of the two?

Some rooflight manufacturers specialise in fixed skylights and others in opening. Having fixed rooflights quite often works out more cost effective because you can have larger pieces of glass without the overhead of expensive electric mechanisms. Quite often we advise our customers to have a mix of both, particularly on bespoke rooflights. This allows Stella Rooflight customers to have the best of both worlds, utilising high specification fixed glazing with smaller opening vents operated by manual mechanisms, gas struts or electric actuators.

How would I like my rooflight to open?

This will depend on whether you need ventilation or access to the roof? If you have other sources of ventilation then it is probably advisable and more cost effective to have a fixed (non-opening) roof light. Smaller rooflights tend to operate manually but if you opt for a large rooflight most will be operated with electric actuation. There are a wide variety of actuators available and products like our bespoke Stella conservation rooflight operates with a small cill mounted actuator to push the casement open. Larger bespoke rooflight designs can have concealed actuators to lift casements.

​What glass should I use in my roof light?

There is no ‘one size fits all’ option and so glass specification should be chosen to reflect your most important requirement. Stella Rooflights provide an exceptional u-value with the added benefit of self-clean, solar control glass by using BioClean Natura with argon gas cavities and Planitherm. If you need your rooflights to provide better sound performance you could opt for a more specialist glass options. Speak to one of our team concerning your rooflight glazing options.

​Will my location affect the performance of my rooflight?

If your project is located near to the coast or in an area of high pollution it can make a difference to the life of your roof light. That is why all Stella rooflights are manufactured from a 316 stainless with a C5 powder coat finish, so you can be sure that your rooflight is protected longer than any other metal rooflight on the market. High salt content or pollution can attack the protective paint coatings which in the case of standard carbon steel rooflights will reduce the effective life considerably.

We can manufacture some very narrow sized rooflights which is particularly useful for period properties where the rafters cannot be altered. We can offer bespoke fixed conservation rooflights with a rafter size width as narrow as 250mm.

This would provide a clear viewable width of 138mm. It is worth noting that the glass length cannot be greater than ten times that of the width.

Once we have obtained the relevant information from you, we will aim to get a quote back to you the same day – or at least within 24 hours of your initial enquiry.

The glazing bars on our Stella conservation rooflight are genuine bars which are manufactured from the same 316 stainless steel as the rest of the frame. We do not offer stick on bars because they will only last as long as the adhesive used to put them on and a large percentage of double sided tapes are not suitable for external applications. Furthermore, all Stella rooflights are supplied with BioClean Natura, self-clean glass and it is not recommended that tapes or glues are used on this glass as it will damage the glass.

Our rooflight glazing bars are only around 40mm wide internally and provide both strength and an original appearance that stuck on bars cannot.

Yes, we are able to produce shaped rooflights. We are most commonly asked for trapezoidal shapes which are in a fixed design but please speak to our team for further details.

Once you’ve placed your order we will issue you with an approval drawing. The purpose of this drawing is to ensure that everyone involved with the project knows exactly what is being delivered to avoid any unwanted surprises. View an example of a typical drawing you will receive from Stella.

​Our drawings contain a lot of information but the key points you need to focus on are:

1. Size

We show a number of different sizes on the drawing and these are:

​Clear viewable – This is the finished viewable size taken from the internal face of the wooden liner. This will be your finished size after the installation is completed.

​Rafter – This is the fixing size taken from the internal faces of your rafters.

​Overall – This is the overall measurement of your rooflight from one outer edge to the other. Much of the external framework will be covered by your tiles or slates.

2. Weight

This is the overall weight of your rooflight excluding the pallet. Your rooflight will be sent fully glazed and you will need to ensure that you have made arrangements for either a mechanical lift or have enough people on site to unload the delivery vehicle.

3. Lifting eyes

Lifting eyes are provided for rooflights over a certain size. These are provided to assist with a crane lift. When lifting your rooflight a spreader bar must be used to help with weight distribution.

4. Glass Specification

We will recommend the glass specification based on your rooflight size but as we do not undertake the installation or have full project details, we advise that you check the specification is suitable prior to approval and meets current regulations.

5. Delivery / Storage

As most of our rooflights are too large for a tail lift facility it is essential that you have suitable facilities to unload the delivery vehicle. We use a variety of vehicles for deliveries and it is important that you tell us about any access or issues which may have an impact on delivery. We will always arrange a delivery date with you to ensure that you have ample time to make arrangements. It is important to organise your site to be ready for delivery and avoid any additional charges

If you are not intending to install your rooflight immediately make sure you have suitable dry storage for your rooflight.

​For more info about planning for large rooflights read our Elephant in the Roof blog

Stella rooflights are regularly used to replace old rusting frames and because we only manufacture from 316 stainless steel our customers do not have the concerns about rusting, even in coastal locations.

With each Stella rooflight being designed and sized to meet our customers’ individual requirements, this means that we have the ability to match sizes from other rooflight manufacturers.

We focus all our attention into rooflight manufacturing so we do not offer an installation service. We can provide advice and guidance and even supply preformed lead flashing kits to assist with the installation of our rooflights.

Our rooflights are reasonably simple to fit although if you are using our conservation design on a Listed building we would recommend that you use a specialist contractor who understands the requirements of such buildings.

Stella rooflights use a high specification of glazing that includes both SGG BIOCLEAN self-clean and solar control glazing as standard.

In addition our rooflight glazing includes Planitherm glass on centre and inner panes, which offers excellent thermal performance.

Our rooflight units not only offer industry leading glass but the way our units are assembled ensures a long life and first class performance.

Every rooflight unit uses black warm edge thermal glazing bars and our rooflight units are silicone edge sealed which provides additional protection against UV light which can cause unit failure in those produced using polysulphide.

SGG BIOCLEAN has been designed for external use, either for application in residential or non-residential buildings and is suitable for use in roof windows and skylights. In both residential and commercial buildings, cleaning rooflights can be a huge task, whether for the occupant or the building owner, in terms of both effort and maintenance cost.

Thanks to the hydrophilic and photocatalytic properties of the coating on the glass, SGG BIOCLEAN® brings endless benefits to both the cleaning and associated drawbacks of cleaning glass.

The coating is permanent, unlike many spray on coatings offered by other rooflight suppliers. SGG BIOCLEAN® functionality will remain the same over the life of the glazing and the coating is highly transparent.

The principle of SGG BIOCLEAN® relies on the natural action of the sun and the rain (or water). SGG BIOCLEAN® harnesses the UV rays present in daylight (photocatalysis) to efficiently break down organic dirt and grime located on the exterior face of the glass. Then, thanks to the hydrophilic property, rain (or water) forms a sheet of water across the glass and washes away the broken- down organic dirt and mineral materials.

These combined properties allow an ease of maintenance so that any dirt that does appear on the glass is much easier to remove. There is also less maintenance required with a self-clean glass as the need to clean the glass is significantly reduced along with maintenance bills. Stella rooflights not only offer industry leading viewable areas but the self-clean glass offers a clearer view due to the clarity of the SGG BIOCLEAN® glass.

Stella rooflights can be manufactured with either double or triple glazed units. Our rooflight units typically use toughened glass and the thickness of these panes is determined by the unit size.

It is possible to request an inner pane of laminated glass if necessary but as standard we will use toughened. However,British Standards define that inner panes must always be laminated wherever rooflights are more than 5 metres above floor level (increased to 13 metres in limited circumstances) or are located over water (eg swimming pools).

The British Standard may permit use of toughened inner panes in other applications but only if a stringent risk assessment is carried out, confirming that its use does not give any additional risk to those below the rooflight.

If your rooflight meets any of these criteria you should always ensure that the inner pane is laminated glass. If you are uncertain or require confirmation concerning the use of laminated glass in your rooflight, please contact our office on 01794 745445.

All Stella rooflights are produced from a 316 stainless steel and have a high quality marine coastal paint application as standard. This means that wherever you live in the UK, you can choose a Stella Rooflight for your project knowing that it is built to last even in the harshest of environments.

If your property is located within 5km (5000mts) of the coast then it will be classified as a C4 environment which means that there is an increase of salinity in the atmosphere which is more aggressive to paint coatings

You may also be surprised to know that your rooflight is likely to be classed in the same category as coastal if your property is located within 5km of a salt water estuary or even a main road which is heavily gritted in the winter months.

Whilst the paint coating on your rooflight should always be suitable for the location, it is important to note that once you own the rooflight, it will be your responsibility to maintain that paint in accordance with the paint manufacturers’ guidelines. In a coastal location this can mean cleaning at intervals as short as every 3 months.

For mild or carbon steel rooflights, the protective coating is the only thing which stops your rooflight from rusting so it is essential that you maintain the paint as required. Whilst the powder coating on a Stella rooflight will also require a certain level of maintenance, our rooflights are manufactured from a 316 stainless steel to provide a superior protection against rusting when compared to other suppliers of steel framed rooflights.

Stella Rooflights are manufactured here in the UK. Not just manufactured but also designed and assembled in the UK. None of our processes or procedures are undertaken outside of the UK so you can be sure that when we say we are supplying a British made product we mean all of it.

​It is interesting just how many companies are keen to tell you that elements of their products are made in the UK. Some will tell you that their products are made in their own factory yet omit to tell you that said factory is half way across the world.

Here at Stella Rooflight, we believe that if you feel UK manufacturing is important and want to give the impression that you are supporting it; then you need to be doing it properly. That is why every single Stella rooflight is not only manufactured here but is also designed and hand assembled here.

​By ensuring that our entire product is started and finished in Great Britain we also support a wide range of other UK businesses and help to keep our carbon footprint to a minimum.

Our products are also tested in the UK so you can be sure that they meet the required standards and have not just been tested abroad to something like the required standard.

There is no doubt that setting up a factory abroad or having major components produced in the Far East, will reduce costs but if we are only interested in the bottom line then we are not being true to our beliefs.

We would always advise that you check with your local authority before installing Stella conservation rooflights. There are many factors that will decide whether you are granted permission to use rooflights and if your property is Listed, in a Conservation Area or an Area of Outstanding Natural Beauty, you may find restrictions concerning the type of rooflight that is allowed.

Fortunately, a Stella conservation rooflight replicates a traditional Victorian rooflight design in that it provides a neat and flush fitting appearance, a black paint finish as standard and can be produced with genuine glazing bars; all whilst remaining unobtrusive to the original architecture of your building.

As a Stella rooflight is fixed into the sides of the rafter, this is normally the most important size and sets the requirements for the other measurements.

The clear viewable size is the glazed area that is viewable from the inside once installed and takes into account the fitted interior wooden liner that is positioned inside the base frame.

The overall size is given to inform the installation team just how much space is required on the outside of the roof however, most of the outer section of rooflight will be covered by the tiles or slates.

The best way to get the process underway is to speak to one of our team who will be able to discuss your design requirements and application for the rooflight before putting a written quotation together.

All Stella Rooflights are made to order and as such there are a number of options that you can change to suit your own personal requirements. These include a number of options including glazing specification, colour, change the wood that your liner is made from, add or remove glazing bars and have opening or fixed casements.

​Should you decide to proceed with a quotation we will then write to confirm the order and instruct our design team to produce the approval rooflight drawings. This process can take up to 10 working days. When the drawing is prepared we will email it over to you so that you review the information and discuss with your builder or planning department. Your drawing will provide a visual of the rooflight along with full sizing and weight details. If changes are required, we will update the drawing until you are ready to sign it off for manufacturing.

The rooflight manufacturing process takes approximately 8-10 weeks.

Stella conservation style rooflights require a traditional lead flashing installation which should be undertaken by a professional roofing contractor. Stella Rooflight offer a handmade lead flashing kit which includes the flashing for the head and cill along with pre-formed soakers for the sides.

If you would like to use a Stella Rooflight flashing kit, please tell our team when requesting your quotation. At this point we will need to know whether your skylight will be situated within a clay tile or slate roof. If you have a slate roof we will require the slate sizes. For diminishing slates we can only produce soakers to the largest size which should then be trimmed on site. If you have a pantile roof application please speak to our team.

Stella rooflights have fixing lugs that position onto the side of the rafter and therefore whilst the measurement of the internal face is important, the width and depth of the rafters are less so (although you should have a structural engineer assess whether they are strong enough to support a rooflight). If your internal rafter width varies, it will be necessary to provide the smallest width and pack out and gap.

In most situations, the internal area will have a plasterboard finish that covers the rafters. The most important measurement when requesting a quotation is the distance between the rafters.

Unlike many skylight suppliers which only offer standard off the shelf sizes, Stella rooflights are manufactured as bespoke items to your requirements and there are no additional costs for having a size to suit your project specification.

Stella conservation rooflights can be used from a minimum pitch of 17 degrees to a maximum of 70 degrees. If you are using a fixed design it is possible to drop as low as 15 degrees and as steep as 75 degrees.

It is not recommended that you installation our opening rooflights into a pitch which is lower than 17 degrees as our flush fitting design may cause issues with removing water from the outer frame area. Although it is unlikely that water will enter through the casement as Stella rooflights comply to BS EN 14351-1:2006 + A1:2010, there is a risk that water will pool at the foot of the rooflight where the frame and lead meet.

The rooflight frame must not be submerged for long periods and it is vital that the pitch of the roof allows a suitable run off. We do not recommend installation below 17 degrees but should you choose to install our product below this pitch, please ensure that you consult your roofing contractor prior to installation.

All Stella Rooflights are manufactured from laser cut, folded and welded 316 stainless steel sections, and given additional protection by a paint finish to a Marine Grade application.

This combination should ensure a long and low maintenance life but is subject to the following factors:

1. The location in which the product is installed
2. The condition of the coatings when the rooflight is installed
3. The frequency and quality of cleaning and maintenance


The protective coatings applied are able to offer a predictable longevity according to the location of installation. To ensure that our Stella rooflights offer the predicted longevity, they must be installed with the paint coating intact and be regularly maintained. Building products are frequently damaged on site prior to installation and should this happen any damage to the paint coating may adversely affect its longevity. It is advisable that Stella rooflights are handled and stored with care.

Keep the rooflights well protected until they are required. We recommend that all our roof windows are checked thoroughly for chips and scratches to the paint coating both at the point of delivery and prior to the installation. If there are shallow or superficial scratches or chips then these can be treated with a touch up paint available from us. If there are deep scratches or extensive parts of the paint coating are damaged then consult the building contractor or architect as the rooflight may need to be replaced.

Maintenance at regular intervals is essential to uphold the longevity of the rooflight paint coat and to ensure the guarantee is valid. This consists for the most part of cleaning the accessible parts of the product. Cleaning should be carried out regularly and at no more than 12 monthly intervals (subject to location). In areas exposed to extreme weather or along coastal areas, this time should be reduced to every 3-4 months. As the external surfaces of the rooflight are subject to the bulk of weathering and are largely inaccessible from the inside, cleaning should be carried out from outside if possible.

If this is not possible the rooflight casement should be wound open to its furthest extent and then cleaned from the inside. Wash the accessible metal parts of the rooflight with warm soapy water, a soft cloth and rinse any cleaned sections with clean warm water. Do not use any abrasive cleaners or hard bristle brushes. The winding mechanisms should be maintained at least every six months although it can be done at more regular intervals if required. To clean the mechanisms use a damp cloth with warm soapy water. A non-oil based product such as a silicone spray or Easy Glide can be used but this may attract dust. Do not use a mineral or synthetic oil as this will eventually damage the mechanism.

Maintenance of the BioClean units must be followed in accordance with the Saint Gobain cleaning guide which can be viewed on our website. Failure to do this may invalidate the unit warranty. We recommend that you clear away any material that has lodged in the top gutter of the rooflight as if allowed to build up, an accumulation of leaves, twigs and other items can eventually lead to leakage at the rooflight head.

In addition, chemicals contained in debris can have an effect on the paint coating at the top gutter. Open the rooflight casement to its fullest degree to ensure all debris can be removed. We also recommend oiling the hinges on all Stella rooflights to reduce wear at the point where the paint coating bears upon the stainless steel hinge bolts. A light engineering oil such as WD40 or 3in1 oil will suffice. Use oil sparingly and apply only to the middle part of the hinge. Should you have any queries concerning the treatment of scratches, damage or maintenance, contact our sales office on 01794 745445.

Firstly it is worth noting that all Stella rooflights are produced to a high specification which includes marine grade 316 stainless steel, a C5 standard coastal powder coat, real wood interior liners and self-clean, solar control glazing. We will not manufacture in carbon steel or reduce the quality of the paint finish or any other element of our rooflights because saving a few pounds today ultimately costs much more in the long term.

If you want to use the highest quality rooflight yet keep costs sensible there are a few things you can do which will help:

Does your rooflight have to open?
A fixed rooflight is a lot more cost effective than an opening version. If you have alternative sources of ventilation in the room then it might not be necessary to have your rooflight opening.

If you do need it top open is it small enough to operate manually?
A rooflight which can open with our manual screwjack winder will be considerably cheaper than an electrically actuated version. Anything up to 1000mm wide x 1200mm high can operate with a manual winder so if your rooflight is only slightly bigger than those dimensions, you could save a lot of money by reducing the size slightly.

Do you need glazing bars?
If you need a conservation rooflight then quite often a stipulation of planning approval is that your rooflight has the glazing bars to divide up the glass. On smaller rooflights this involves an additional process in manufacturing and also additional time and materials in the finishing process. If your rooflight does not require glazing bars then additional savings can be made by not having them.

What about sizing?
All our rooflights are bespoke and produced to our customer requirements. This means that your rooflights can be unique as your project and sized to whatever you need. One important consideration that is often overlooked on bespoke projects is sizing and we regularly asked to price jobs which have a number of different rooflights that are only a few centimetres different in size.

This means that every rooflight has to be drawn and programed from scratch and those costs are included in each rooflight. Where you have a number of rooflights which are very similar in size, you can make a considerable saving by adjusting the sizing so that you have a number of rooflights produced to the same dimensions.

There are many different ways to describe skylights and the components used in installing and operating them. Not only this but the term skylight is also referred to as many different things such as rooflight, roof window, sky light or occasionally people refer to them as Velux, who are of course are a manufacturer of skylights.

Actuators – are the mechanisms used to electronically open and close the skylights. At Stella Rooflight we use a range of electronic actuation subject to the requirements of the opening casement. If you require your roof window to have some or all of the casements opening then our team will explain what is achievable when you make your enquiry.

​Baseplate – this is the part of the rooflight that contains the hinges for the casement to be bolted onto. The fixing lugs are located on the underside of baseplate along with the wooden interior liner. This piece of the skylight sits between the structural support timbers (rafters).

​Bespoke Skylights – this term is used to describe a rooflight which is custom made to your specification. This can be a change to a conservation rooflight, a more contemporary roof window or a range of roof windows for a flat roof application. When making your enquiry for a Stella Rooflight you have the ability to change a whole range of options including glazing specification, colour, change the wood that your liner is made from, add or remove glazing bars and have opening or fixed casements.

Casement – this is the opening piece of the rooflight which contains the self-clean glass units. This section is fixed onto the baseplate hinges. The casement is viewable once fitted in the roof

Coastal Location – We produce the rooflights to a very high standard that are suitable for use in coastal locations as standard. If you have any questions about the location of your property or the likely implications of high salinity or pollution content in the atmosphere, please talk to our team.

Condensation – condensation is the water that results from the conversion of water vapour in the atmosphere. The air in our homes always contains water vapour which is usually invisible. The warmer the air, the more water vapour it can hold but there is a limit to the amount it can hold for a given temperature. Should you require additional information, please ask our team for a copy of the Glass & Glazing Federation fact sheet.

Conservation Rooflight – during the 18th century rooflights, in their most primitive form, were used to bring light into agricultural buildings. It therefore seems uncanny that todays rooflights are yet again providing an architectural design solution to the increasing trend of converting old or disused industrial buildings into domestic dwellings or business premises.

Conservation rooflights are easily recognised by their low profile which means they sit flush and remain unobtrusive to the buildings original architecture. Another characteristic is their slender appearance as conservation requirements stipulate that a minimal amount of framework should be visible. This design feature becomes even more significant when rooflights are placed next to each other.

Contemporary Skylights – A stylish and streamlined roof window for customers who are seeking a more modern look for their roof glazing. The design remains low profile and unobtrusive whilst offering a high specification of energy efficient, self-clean glazing. These typically do not have glazing bars in the same way that conservation rooflights do.

​Escape Rooflights – although some rooflights are hinged on the side, our escape version are top hung to reduce any possible issues with light rain and to retain a matching appearance when installed alongside our standard range. Stella access or escape skylights and are fitted with gas struts so the skylight casement stays open. Supplied with a brass winding mechanism for daily use, the gas springs should only be deployed when the casement is required to stay open. Further details can be obtained when speaking to our team.

​Gas Struts – are pressurised cylinders that are attached to the rooflights so that they can remain open unaided in a similar way to the boot of your car.

​Hand Winder – is the mechanism used to open and close the rooflights when the rooflights are within reach. These typically have a handle or a wheel on the end to aid operation.

​Pole Winder – is the mechanism used to open and close the rooflights when the rooflights are out of reach. This type of rooflight mechanism would usually be operated by a separate crank pole.

​Head Detail – is the top section of the rooflight

​Jamb Detail – are the side sections of the rooflight

​Cill – this is the bottom section of the Rooflight

​Linking bars – are the bars used to link skylights together so that they are in continuous runs. Occasionally specifiers refer to these as Studio-Linked but we call them Stella Link Light.

​Listed building – a building or other structure officially designated as being of a special architectural, historical or cultural significance. If your property is Listed you will need to work closely with your local authority before making changes to the building fabric. An excellent resource for Listed property owners

​Overall Sizing – the maximum width and length of the baseplate, much of which is covered by the tiles or slates.

Pitched Roof – is a roof structure where the roof is set at a slant. Our Stella conservation skylights can be used between 17 and 70 degrees in slate and tile or 30 and 60 degrees in a pantile roof.

​Roof Window – is an architectural term for the frameset with glass which is fitted to an opening in the roof to admit daylight.

​Rooflight – is another way of describing the frameset with glass in that is fitted to an opening in the roof to admit daylight

Skylight – is another word to describe the frameset with glass in that’s fitted to an opening in the roof to admit daylight.

Self-Cleaning Glass – An important technological breakthrough was introduced to the UK in 2002, in the form of the worlds first self-cleaning glass. Considered by many to be an impossible dream, self-cleaning glass makes maintaining rooflights significantly easier. Saint Gobain BioClean is effectively the same as conventional glass, but with a specially developed coating on the outside, that once exposed to daylight, reacts in two ways. Firstly, it breaks down any organic dirt deposits through a photocatalytic process, and secondly, when it rains, instead of forming droplets, the water spreads evenly over the surface and takes the dirt off with it. It is kinder to the environment than ordinary glass and it is the ideal choice for situations where cleaning will be costly or difficult.

U-Value – often called the overall heat transfer coefficient and describes how well a building element conducts heat. Our standard triple glazed units have a U-Value of just 0.5 meaning that a Stella rooflight can achieve exceptional overall u-values from as low as 1.1.

As all our products are bespoke and manufactured to our customers’ individual requirements, we do not have standard sizes and prices.

If you have a requirement for rooflights and would like to find out more about the options which are available and the likely costs, please call one of our team on 01794 745445 or email info@stellarooflight.co.uk

All rooflights require some form of maintenance to ensure that they last their expected lifespan. In the case of most metal rooflights the maintenance of the paint is essential to prevent the frames from rusting.

As Stella rooflights are manufactured from 316 stainless steel, they offer significantly more protection against rusting than ordinary mild/carbon steel rooflights but you will still need to look after the paint finish in order to maintain the appearance.

Yes, we offer a range of pleated blackout blinds which use a honeycomb energy saving fabric to bring you the perfect combination of style and function. Available in both manual or electric options and in a range of colours.

For further details, please call one of our team on 01794 745445 or email info@stellarooflight.co.uk

Stella rooflights use a high specification of glazing and our metal frames are lined with a hardwood to reduce thermal transmittance and reduce the occurrence of condensation. Our thermal performance meets the requirements of Part L and our design minimises the risks but firstly it is important to understand that steel windows and rooflights do not cause condensation.

​Condensation occurs where humid air comes into contact with air, or a surface, which is at a lower temperature. Air contains water vapour. The warmer the air, the greater is its capacity for carrying water vapour. When warm, moist air comes into contact with a cooler surface, or cooler air, it drops in temperature, and loses some of its capacity for storing moisture, so some of it is released to form condensation in the air, as steam, or on the surface, as water droplets.

​Although it is most immediately visible on surfaces that cannot absorb liquid, e.g. windows, ceramic tiles, mirrors etc, it can form on any surface, and it may not be noticeable until mould appears, or the material starts to rot.

​It is highly unlikely that a house in the UK will ever become condensation-free, but by ensuring the building is maintained in good condition, well ventilated, and by adopting relatively minor changes to lifestyle then it can be reduced.

​Information concerning some causes and advice for condensation can be found by clicking here to view a useful guide produced by the Glass & Glazing Federation.