Windows - A Total Cost Approach





All building operators, contractors and specifiers are familiar with the "cost" of windows but new generations of windows and glasses are making the choices more difficult and more complicated. Recent trends in building ownership to "design and operate" contracts and the recognition that local authorities do not simply pay for the initial installation are changing the way we look at the cost of windows and the economics of the purchase. We need to look at the "total cost of ownership" of the window rather than the simple first purchase price.

The appliance approach.

Windows are often seen as simply a fixed part of the building fabric which are specified, fitted and then forgotten, but the truth is that there is much more to the cost of a window than these simple first costs. The cost components of a window are shown below and these include some factors that are rarely, if ever, considered.

The modern window is an "appliance" similar to any other appliance in a building (such as a refrigerator) and the "running cost" must be considered. As with any appliance, windows use energy and the energy cost during the product use stage (which can easily be greater than 40 years) will generally exceed the purchase cost. This running cost is rarely considered in any of our assessments of total product cost. This is important for Local Authorities and other building operators where the cost of running the window "appliance" in schools and other similar buildings is paid directly by the authority that specifies the product.

The environmental cost

The environmental cost is not a strict financial cost but concern for the environment is universal and must be considered. There is confusion over the relative environmental impact of competing window frame materials and misleading arguments regarding "natural" and "man-made" materials have been put forward. The most appropriate tool for assessing the relative environmental impact is the technique of Life Cycle Analysis (LCA). LCA assesses the environmental loads of competing products in terms of all the inputs and outputs from the whole life cycle of the product. LCA is carried out for completed products and avoids the misleading claims of pressure groups lobbying for different materials.

Various LCA studies have been carried out in Europe (e.g. Novak and Ecker in Austria - 1991 and Richter in Switzerland - 1996) but the conclusions of all the studies to date have been the same - Given reasonable levels of recycling there is very little difference between the total environmental impact of any of the current window frame materials.

The specification cost

The right specification can minimise the total cost of the window if all the correct factors are included in the specification. A specification or other selection procedure, which concentrates on the initial cost of the window, will almost certainly lead to a more expensive total product.

The manufacturing cost

In the long term, the initial manufacturing cost of a window becomes a relatively small cost, yet this is one of the primary concerns of specifiers. The increasing number of companies holding ISO 9002, Kitemark or other similar accreditation schemes (e.g. the Timber Window Accreditation Scheme for wood windows) has inevitably raised the general manufacturing standards in the UK. The relatively low incidence of reported manufacturing concerns is indicative of ever improving quality standards. Using certified manufacturers is no guarantee of purchasing a good window but it certainly increases your chances and provides a degree of reassurance that the manufacturer is serious about his quality standards. The base manufacturing cost is important but should not be allowed to overshadow the true total cost of the window.

The installation cost

Correct installation will allow the window to function correctly, optimise the product life and improve the energy efficiency. The cost of installation is actually very small in relation to many of the other costs involved in the life of a window. Despite this, general experience shows that at least 85% of the quality concerns with windows come directly from poor quality installation of otherwise good products.

The specifier can save on installation costs by cutting corners but it is certain that they will pay for the savings with increased concerns throughout the life of the window!

The running cost

The maintenance cost

There is no such thing as a "maintenance-free" window. Whatever the frame material, windows have a maintenance requirement. All windows should have regular cleaning to prevent dirt build-up and all hardware needs regular cleaning, lubrication and inspection. Wooden frames inevitably need repainting but modern factory applied finishes have greatly improved the longevity of wooden frames. These costs can be estimated and factored into the total cost of the window.

The energy cost

This cost is rarely, if ever, considered for windows but the "appliance" approach is particularly important in finding out the total cost of the product.

The comparison can be made with a car - Would you buy a car that cost slightly more initially but used no petrol or even generated petrol for other uses? The same is true of a window. For too long we have regarded windows as energy losers and current Building Regulations encourage this viewpoint by only looking at the negative or loss aspects of windows. Windows can actually add energy to the building system and this statement is easily proved - sit in front of a window on a sunny day and the sun's radiation will instantly warm you. The window is gaining energy from the solar radiation! Yet when we consider windows and their effect on the energy efficiency of a building we currently ignore the solar heat gain and concentrate on entirely the energy losses - this about as sensible as trying to assess how fuel efficient a car is by looking at the weight of the car!

It is NOT enough to say "We replaced single glazing with double glazing" - the energy cost savings possible by using the latest technology windows make the energy savings made with conventional double glazing look almost trivial. In fact it can be more profitable (in both energy and money) to replace fewer windows with higher efficiency products than to replace a whole building with conventional double glazing. This is not "future high technology" because the methods exist and are in common usage in other parts of the world.

The disposal cost

The end of life cost of any product must be considered and the Life Cycle Analysis calculations include any recycling of the materials in the window. This is not the end of the story because all waste is now rapidly falling under waste disposal regulations and these will inevitably become more stringent. You may not be around to see the disposal phase of the windows you decide to install but this must be a factor in your consideration of the total cost of a window.

The total cost of a window

The total cost of any window is therefore not what you first thought of. As with most appliances, the "running" costs of a window exceed all the other costs combined. Yet these costs are rarely even considered in the purchase decision. Isn't it about time that we started looking at the "true and total cost" of these most important building appliances?

Last edited: 11/03/10  

Tangram Technology Ltd. 2000

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