Product category:
Roofing and Roofllights
News Release from: Fakro GB | Subject: Roof window installation
Edited by the Buildingtalk Editorial
Team on 06 July 2007
Roof window installation
Helpful hints installing roof windows from Fakro GB.
Despite the trend in favour of using loft space to extend, little attention tends to be focussed on hints to assist roof window installers For the most part, such a relatively straightforward procedure passes without mishap
This article was originally published on Buildingtalk on 7 Jul 2008 at 8.00am (UK)
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Fakro FTP-V centre pivot roof windows have been used in an unusual office redevelopment in North Wales.
Roof window trend towards an L-shape
With greater use of roof windows for their contribution to interior design, there has been a marked trend towards use of L-shaped windows.
But, as with most aspects of building, easily avoidable examples of fitting errors do come to light and are becoming commoner as product usage increases.
Installing a window upside down is about as bad as it can get but, according to manufacturer Fakro, investigation of supposedly leaking windows has actually shown this to be the cause.
Instances of side-hung escape windows being installed the wrong way around also crop up, though such occurrences are, thankfully, rare.
Further reading
New automatic vent for Fakro roof windows.
With the increasing demand for more thermally efficient buildings, Fakro is changing the air inlet used in all its standard roof windows to a new, automatic vent.
Roof window chosen for BRE Demonstration House.
A bespoke Fakro FPP preSelect timber roof window has been used in Osborne Homes' Demonstration House at the BRE Innovations Centre.
Roof window switches from top to centre pivot.
Fakro's FPP preSelect roof window uses a unique, patented mechanism which enables opening to be switched from top to centre pivot at the flick of a switch in the frame.
Even so, advances in window design, while increasing flexibility for designers, do leave the contractor with plenty to keep up with.
Centre pivot windows are still by far the most popular option, but even they can present problems where, for example, a design involves fitting either side of a ridge beam.
Depending on beam thickness, if a steep pitch is involved, typically of 50deg or more, windows may touch if both are opened.
This is one facet of design guidance which Fakro routinely provides.
Of more fundamental concern is when to cut rafters.
Use of two 55cm wide windows side by side is common as it invariably avoids any need to do so while providing a practical and structurally sound configuration.
Installation of larger windows, particularly in refurbishments of older properties, may require advice from a structural engineer if the weight is likely to cause undue stress on rafters (as occurs when windows are slammed).
Whichever sizes are used, a combination of smaller windows is always preferred; such grouping can even be used to provide an intrinsic visual element of the interior design.
To provide adequate daylight, the glazing area must, in addition, exceed a proportion of 1:8 of the floor area where rooms are in constant use.
It is worth remembering taking into account then that a product such as Fakro's FPP, with its operating handle in the lower part of the sash, provides up to 10% greater glazing area over traditional alternatives of the same size.
If fitted towards the apex of the roof, a window such as this offers the ideal combination of daylight maximisation and user convenience.
Factors such as U-value, ventilation and acoustics are now key aspects of building performance for contractors to be aware of.
Fakro Technical Specifications Manager Phil Lambkin commented "We find that contractor recommendation plays a large part in final product choice, so understanding critical differences in performance can make all the difference".
"Comparison of U-values can be misleading if manufacturers' quote figures purely to cover glazing performance rather than complete window construction".
"The end result can be a distortion of perhaps 0.3W/m2K, so for a window with a performance of 1.8Wm2K this could actually place it outside minimum Building Regulation standards".
"Fakro has also found inconsistencies in ventilation performance information, some of which is clearly not supported by consistent and proven testing criteria." Use of correct flashings is another potential pitfall, though invariably the manufacturer will ask with which tile profile a window is to be fitted.
Flashings are designed to provide efficient drainage and a neat, weatherproof finish.
As well as the tile profile they must also be suitable for the depth at which a window is to be installed.
A number of special flashings are produced as a result, good examples being installation of windows joined either side of a ridge or in a mansard combination.
As an additional point to remember, ridge combination flashings can also be manufactured from copper, titanium-zinc or aluminium.
And with a number of new tiles such as large format clay profiles having been introduced recently, use of 'standard' flashings should certainly not be taken for granted.
Security should also be a major consideration, and it's something of a surprise that the poor performance of some windows has not received greater attention.
Tests have shown that certain locks provide little meaningful deterrent compared to others which, by contrast, require the glazing to be broken completely before entry can be gained.
Just as importantly, windows should provide security in a choice of open positions and Fakro's windows have been designed to do just that.
And a final thought.
Unsealed timber invariably results in damp causing mould formation such as 'black combing' where the timber can't dry out effectively.
Answers to queries concerning what treatment and finishing the timber has received will say much for a product's potential long-term performance.
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