COWBOY window installers could be fined £5,000, imprisoned and charged £50 per window on sub-standard installations.

A new law, which became effective from April 1, legislates that the windows and doors in your home could be breaking the law and may have to be removed as instructed by the local building inspector.

All replacement glazing installations sold after April 1 must comply with the new British Building Regulations Part L, relating to conservation of fuel and power.

Contrary to public belief that transport is the biggest cause of the greenhouse effect, people's homes are the UK's number one domestic contributor to global warming -windows and doors being a significant inefficient contributor.

To minimise this energy loss, the latest building regulations forbid the installation of replacement windows and doors that do not meet the specific requirements.

These regulations focus on the use of thermal compliant products that achieve the minimum measurement of heat loss on all PVCU or Hardwood framed windows. Many cheap window and door products sold today may not meet this requirement.

The new regulations state that it is illegal for a window company to accept orders for glazing that does not meet this requirement. All orders placed before this date using non-compliant products must be installed by July 1. So, if you have an order for new windows, it's good advice to check out their compliance and installation date.

Check your contractor is registered with FENSA. Also ask your supplier to put it in writing that the product you are buying meets the legislation and is of a suitable standard to satisfy FENSA and or the local authority building inspector.

A guide to the new legislation has been produced by BAC, manufacturer and supplier of replacement windows and doors. This can be obtained from a telephone hotline (0870 444 6227).

John Savage, BAC technical director, saidthe new regulations were a victory for common sense and consumer interest: “This will probably put the 'cowboys' out of business, as they cannot absorb the extra production costs in their bargain basement prices.”