You will probably already have heard of a Velux window used as a term to describe a window inset into a roof slope. Remember that this is merely a brand name and what you really should be thinking about is a skylight or a rooflight. However, as the ordinary person thinks and talks in terms of the name ‘Velux’ we will use that word throughout this article.
Whatever we call them there can be no doubt that Velux windows are a great bonus to have fitted into your roof.
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What construction materials are available?
Velux windows are always made from a timber or metal frame with a glazed panel in the centre. Although you can buy Velux windows made from metal or wood, the commonest material is metal. The advantages of metal framing like a Velux and the other brands that offer the same is that the frame will not require painting every year and will not rot like wooden ones. This is an important advantage because accessing a roof to replace or paint a skylight can be very difficult and after installing scaffolding to assist with access, can work out very expensive.
The glazing material can vary too. A Velux is always glazed with safety double glazing, whereas a skylight could be glazed with glass or with plastic. The choice of glazing material is dependent on a few factors:
- Local climate.
- Position on the roof.
Plastic is less expensive than glass but is more prone to discolouration from ultraviolet sunlight and will develop scratches over time, whereas glass will not. The aesthetics of discoloured plastic glazing may not seem so important if the skylight is hidden out of view and the only reason to have one is for the natural light it will bring to the attic room. However, if the room is to be used as a bedroom or some other kind of living room then glass may be your only option. Additionally, plastic glazing is not as good a thermal or acoustic insulator as double glazed glass and it certainly is not such a good security barrier either.
Glass is far more expensive, will last longer, and will not discolour. Double glazed units are superb insulators both of heat and sound and it is far more difficult to break a double glazed laminated glass panel than a plastic one. Glass in skylights can be made from laminated or tempered glass with low-emissivity coatings, UV blockage and as self-cleaning glass. Each additional extra you choose for the final skylight will add another benefit, eventually finishing with a window that is highly energy efficient, is very difficult to break if there is an accident and will provide a good security barrier.
There is a choice of framing material as well as glazing and each material has its own benefits. Velux windows, as well as other brands, are supplied with wooden, metal, polyurethane or ABS plastic frames.
Velux Window Accessories
By accessories, I mean added extras that will make your skylight easier to operate, easier to maintain and protect the items and people that are indoors.
If you choose Velux roof windows as a way of bringing sunlight into your roof space, you will find there are a number of accessories to make life so much easier, such as:
- Ultraviolet light filters. This is a special coating added to the glass to protect occupants of the rooms from overexposure to UV light and the health risks that this can bring as well as reducing the prospect of fading of dyed furnishings and fabrics.
- Solar powered opening. If your skylights are too high for the average person to reach, solar-powered electric Velux windows will be the answer. Windows are in an ideal location to use the sun’s rays to generate electricity and this can be used to open and close the skylights via remote control.
- Velux window blinds. Just take one look at a typical Velux window installation and you will see that ordinary curtains or Venetian blinds will be of no use to provide privacy or shade. There are different sizes and types of Velux roof blinds that are designed specifically to fit onto all the different Velux window sizes.
- Self-cleaning glass. Glass that is fitted into normal vertical windows becomes dirty with the normal grime that is in the air so think how much more dirt will land onto a pane of glass that is partially pointing towards the sky. Grime will settle as well as the occasional passing bird. Self-cleaning glass operates in two ways, firstly it is coated with a photocatalytic layer that reacts with sunlight to break down anything organic on the surface. Secondly, the surface is hydrophilic which means that instead of forming droplets, the rain spreads out into a sheet of water that runs off the glass, taking any dirt with it.
- Double glazing. Velux provides double glazed panels that can be fitted when the window is first installed or used as Velux replacement glass if for any reason the panel becomes damaged and needs to be replaced.
- Automatic ventilation. Some Velux windows can be motorised with the activation linked to a temperature sensor. When the temperature in the room reaches a certain pre-set level, the window will automatically open allowing the free ventilation of the room. When the temperature drops below the required level, the window will close.
How much does a Velux window cost?
Velux windows come in just about all sizes to suit the roof space you need to open up. Although the average Velux windows aren’t what you would call cheap to buy, the price is comparable with other types of window. The Velux window installation cost isn’t just about buying and installing the window itself, there are also heaps of other work involved in making the opening in the roof, and making it watertight again after the window has been installed.
- The roof tiles, battens and roofing felt have to be stripped back exposing the roof rafters.
- The rafters have to be cut, trimmed and strengthened to produce an opening the correct size and in the correct location to suit the required skylight dimensions.
- Construct a raised timber framework to support the Velux frame.
- Install the window onto the framework.
- Add lead flashing, replace the felt, replace the tiles. Ensure everything is weathertight and looks good.
- Make good to the ceiling inside the roof space.
Remember too that most of this work must take place from outside the roof so the installer will require appropriate scaffolding to make a safe working platform.
Although this may seem very difficult, for a professional it is relatively easy as long as the location is accessible. For this reason,, we do not recommend that it is done as a DIY project unless you have fitted one before.
All of this extra work together with the hire of the scaffolding will increase the cost of the overall job. The extra costs will vary depending on the size of the opening made in the roof, the style of the existing roof, the type of roof covering already in place, how far the working area is from the ground and how accessible it is. Luckily, even cheap Velux windows are designed and made to be mostly modular, meaning that there will be relatively few problems if accessories are required.
Velux Window installation Costs
Bearing in mind what has just been said about the extra costs involved in fitting a Velux skylight, typically the following prices would not be too far from the actual costs.
|Item||Dimensions (mm)||Minimum cost||Maximum cost||Typical uses||Notes|
|Small Window||660 x 980||£850||£1,200||This size window would be ideal for a bathroom.||Price includes installation, flashing kit, insulation, collar, alteration to roof and waste disposal|
|Large Window||1340 x 1600||£1,400||£1,800||Loft conversions, single storey extensions|
Window replacement Costs
If you already have a Velux window installed in a roof, but you need to have it repaired, the costs will be slightly less than those involved with installing a Velux from new. Depending on the damage, you may not need to have the entire unit replaced. In many cases, just the protective cover strips, flashing or the glass might need replacing. If this is the case, a skilled professional will not find this difficult to do.
On the other hand, if a complete replacement window unit is needed, the following average costs would be typical.
|Item||Dimensions (mm)||Minimum cost||Maximum cost||Notes|
|Small Window||660 x 980||£650||£1,000||Remove existing window, replace with new and dispose of waste.|
|Large Window||1340 x 1600||£1,200||£1,500|
Any problems that might occur?
Remember that to a skilled professional, fitting a Velux window will be no problem at all and you will end up with a beautiful looking and weathertight additional window. For this reason, it is always important to make sure you only employ someone who has had experience of installing windows, fitting flashing and altering roofing.
Apart from the specific designs of a house roof, which really are not of concern here, there are two types of roof, differing in how they are designed and constructed.
- Cut roof. This is the type of roof you will probably find in a house that was built before the 1970s. Basically, each rafter used in the roof will be individually cut on site and installed one by one. There will also be a ridge board and purlins that all help to give the roof structure its strength and stability. A professional carpenter and a roofer will understand how the weight of the roof is transferred through the rafters and will be able to cut and trim the existing rafter to fit the window frame.
- Roof Truss. A truss roof is present in most houses built after the 1970s (although definitely not all). They are made of timber of cross section just large enough to support the weight of the roof. The main difference between these and cut roofs are that a truss arrives on site having been previously made in a factory. The dimensions of each piece of timber have been calculated to provide just the correct amount of strength so that when they are all fitted together they provide a strong and stable roof. The disadvantage with this type is that because the size and bracing of each piece of the truss has been calculated, they are not really suitable for cutting to fit a Velux window unless the window has been taken into account in the design and calculation phase or it may be possible to insert the Velux without interfering with the trusses whatsoever. Having said all that, as most factory made truss roofs are designed and constructed with braces between the rafter and joist sections, the roof space available in this type of roof is not suitable for converting into a room anyway unless major roof alterations and strengthening take place.
Does the work need Planning Permission or Building Control?
Installing skylights, in general, do not usually require Planning Permission as long as certain requirements are complied with:
- The windows must not protrude more than 150mm past the average level of the roof plane.
- Nothing can be higher than the highest portion of the roof or be above the roof ridge.
- The side facing windows must be filled with obscure glass for privacy and must not be able to open unless they are more than 1.7m above the floor level for safety purposes.
There are other restrictions that may be enforced, such as whether you live in a conservation area or if the property is a listed building. It is always a good idea to check with your local planning office beforehand.
Because the proposed work is altering the roof structure and adding an external window, Building Control will definitely be required. As well as those two factors just mentioned there are also fire regulations to consider as well s thermal insulation. Velux window units always comply with the Building Regulations so it is just a matter of choosing the correct one and ensuring the installation method is correct.
Fitting a Velux roof window to open up a roof space is always a good idea as it will provide extra living room in your home. Before you go ahead with your plans however always check with the local planning department, Building Control and a local building company with a few years experience to see if your roof type allows the work to be done.