Special timber sash solves conversion problem

Creative adaptation broadens scope

The substantial renovation of a commercial building into smart domestic dwellings in  London called for Mumford & Wood’s Conservation timber sash windows – with a difference.

Specialists in the manufacture of the finest traditionally styled windows and doors, Mumford & Wood could easily satisfy the requirement for a substantial order of sash windows which would remain in keeping with existing surrounding properties.  However, several of the windows needed creative adaptation to increase their capacity to cope with smoke dispersal and meet the requirements set out in Part B of the Building Regulations and BS5588.

By the very nature of a sash window design concept, only half of the total openable area can be utilised at any one time and in this case did not contribute sufficient geometric volume, that is, the amount of through ventilation required to disperse smoke build-up in the event of fire.  To maintain consistency of appearance externally, Mumford & Wood’s bespoke design expertise addressed not only the aesthetical requirements but also the ventilation specification by providing an inward opening leaf in a sash window frame.

Using one full height sash set in the inner sash run with a horizontal glazing bar correctly proportioned and positioned to replicate the meeting rails of adjacent windows, the windows, set on door hinges, are capable of opening inwards.  This provided a clear opening that complies with the 1.5m2 geometric volume in accordance with the current legislation requirement for ventilation and control.

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This type of window must essentially open automatically and this called for the application of actuators linked to the smoke detectors.  The specific windows for the lift well were supplied to site by Mumford & Wood without ironmongery and the main contractor brought in specialists; S E Controls of Lichfield, Staffordshire who designed and fitted the AOV control gear and smoke detection.

More information: www.mumfordwood.com

Why choose timber windows?

There’s a feel-good factor

Olav Skretteberg of Broxwood, a forester and independent windows supplier, says people in the UK like timber. There’s a definite feel good factor about it. Sourced from managed forests- often from my homeland of Scandinavia- timber is an environmentally friendly, thermally efficient, good looking material.

Modern, factory-manufactured timber products, such as windows, are also proving themselves in terms of performance – offering durability, low maintenance and competitive cost.

Currently around 12 million windows of all types are sold each year in the UK, with timber windows accounting for 25% of that market.  57% of timber windows sold in Britain are used by the public sector and 42% by the private; 86% of these in refurbishment projects and 14% for new build applications. (Figures from FSC website.)

Over the last ten years in particular, the evolution of timber windows in terms of quality, durability and design has been dramatic, in response to both regulation and marketplace.  Factory finished and treated against rot, with frames which are fully protected from water and UV light, modern high-performance timber windows can have finish guarantees for up to 10 years and rot free guarantees for up to 30.

Dual sealing and factory glazing will help maximise the life of a unit and sophisticated design details, such as drained and vented glazing rebates, are used to prevent deterioration and lengthen the life of the timber

How long a window frame will last depends on many factors. The National Building Federation’s “Standards in Quality and Development” gives PVC windows an expectancy of 20 – 25 years where as it gives vacuum treated softwood 25 – 35 years. According to the Green Builders Digest, “well designed and well maintained timber windows can and do last the lifetime of the building in which they are installed”.

In addition, manufacturers are now producing timber windows that will take single, double and even triple glazed insulating glass units, to suit particular specifications, and capitalise on advances in timber technology.

STANDARDS & REGULATIONS
The main British Standard for timber windows is BS644. This is a comprehensive standard, encompassing other standards on quality of timber, glazing etc. and those specifying timber windows, which are third party certified to this standard, will meet all current UK requirements.

Specifiers may also wish to include certain levels of safety and security in their window specification. While most modern timber windows offer a good basic level of security, third party certification to Secured by Design standard ensures a enhanced levels. Interestingly, most of the windows my company imports, from a wide variety of Scandinavian suppliers, already meet Secured by Design standards.

We have nonetheless decided to put our popular top swing tilt and turn window through the Secured by Design process for marketing purposes, as this certification is increasingly being demanded by customers.

Another important aspect of specification is ensuring that timber windows meet current thermal requirements. Timber is, of course, a natural insulator, which when combined with the glazing system, (air, argon or krypton filled), insulating glass and draught sealing, has no difficulty in providing a window which meets current requirements of a U value of less than or equal to 2.0W/m2K.

Part L also refers to window energy ratings which follow an A-G scale with E being equivalent to the 2.0 U value. In fact, these standards are not particularly demanding and the technology exists to create a timber window three times as energy efficient!

One final reason for choosing timber for your windows. Planning controls often restrict the use of PVC windows in conservation areas and in buildings of historical interest for aesthetic reasons. This is because PVC windows require a bigger section than timber windows to meet strength requirements and therefore often cannot match the fine detailing of traditional windows, in the way that modern timber replacements can.

More information: www.broxwood.com

Practical ramifications of sustainable development

A mix of potentially conflicting advice!

The green agenda seems to be on every housebuilder and building products maufacturer’s mind, but the practical ramifications of how sustainable development is actually going to be implemented are still unclear, writes Jim Lawrie, chief executive of Black Millwork, UK and Ireland distributor for Andersen Windows.

At the moment we have a mix of potentially conflicting advice but no clear defining official standard incorporated into the Building Regulations.

For example, the government is encouraging the building industry – primarlily in the public sector – to follow its ‘Code for Sustainable Homes’ (CSH).  The British Research Establishment (BRE) has also brought out a ‘Green Guide’ with its A, B, C star rating system for products and materials which can earn points towards Eco Homes

Of the common traditional window materials so far assessed, the only summary rating ‘A’ given is for pre-treated softwood frames, double glazed, and painted inside and out. Surprisingly, hardwoods are not rated as highly – maybe because sensitivities may still remain relating to the sustainability of their managed sources. Other commonly used window materials like PVC-u, powder aluminium and aluminium faced timber composites also receive a lower summary rating.

Based on eco points alone, we could be looking at a return to softwood frames, but there are also other performance factors to consider when specifying windows, such as strength, low mainenance and aesthetics, for which other materials may be better suited.

There is clearly a need for new sustainable materials that will meet both the environmental and practical requirements of house builders and the end user.

At present, the only option of this kind on the market is Fibrex®, an entirely new composite materal from Andersen Windows.  Currently incorporated into the Woodwright™ range of sliding sash windows, it is made from recycled wood fibre coated with a specially formulated thermoplastic polymer, which provides the strength and appearance of wood and the low maintenance properties of PVC-u.

As the wood is harvested from renewable sources and 50% of the overall material is  made from recycled waste materials, once assessed for its rating by the BRE as every new material has to be, Fibrex® could well prove to be a highly popular option.

Until incorporated into the Building Regulations,  sustainable development is still a matter for the moral conscience and so, whilst the green agenda is clearly important, maybe we should be careful not  become too diverted from the fundamentals of creating safe, affordable and desirable homes with ‘kerb appeal’.

With Andersen’s system of modular construction, and its range of over 200,000 different shapes sizes and colours of windows and patio doors – plus made to measure options -  virtually any glazing configuration can be created cost-effectivley, from a small feature window to an expansive wall of light.

More information: www.blackmillwork.co.uk

New underfloor heating system for upper floors

Same cost as conventional radiators?

Warmdec claims to be “a revolutionary” new underfloor heating system for upper floors developed and patented by Alvesta Ltd. It overcomes the current barriers of cost and safety when it comes to installing an upper floor system.

The main break through, it is claimed, is that the Warmdec costs the same to install as a conventional radiator system. It has no joints apart from at the control manifold and can be installed by semi-skilled staff at first fix without the need for safety bagging or boarding.

Under floor heating can show a 25% energy saving over conventional radiator systems as it requires water heated to only 50-60oC instead of the 70-80oC that radiators require.

Warmfloor also has a partnership agreement with Mitsubishi Electric Europe to distribute their latest reversible air source heat pumps which can be installed in most loft or garage spaces and, being reversible, they not only help to heat the property but also cool it in the warmer months.

Alvesta chief executive, Adrian Ladds, says: “These pumps take energy efficiency to a new level and when combined with our Warmdec under floor heating and solar collectors we can get very close to a zero carbon footprint.

“Energy efficiency is becoming very important in the building of new housing and, provided that the householder uses a “green” electricity tariff, Alvesta is probably unique in being able to offer an ongoing effectively zero carbon footprint option at such a reasonable cost.”

More information: www.warmfloor.co.uk

Modern methods of construction on display

OFFSITE 2007 exhibition leads the way
Following a similar, highly successful event in 2005, the Building Research Establishment in conjunction with the East of England Development Agency (EEDA), are staging another four-day event called OFFSITE 2007 covering modern methods of construction for new builings. It takes place from 11-14 June.

Tougher building regulations and the ever increasing challenges of sustainability are encouraging major growth in the development of innovative construction methods and advanced technologies for buildings.

With full scale exhibits and demonstrations and a case study based conference programme, OFFSITE2007 will explore how these innovations are coming together to deliver higher performing, more sustainable and smarter buildings for: