Anti–bacterial components
The
NHS pays £1bn a year to treat hospital-acquired infections. This
may be cut by specifying anti-bacterial surfaces. Peter Mayer
of Building LifePlans considers some options...
Introduction
Thereis a range of measures in place to limit the prevalence of acquired
infections in hospitals and healthcare facilities. These are related to
good hygiene, cleaning and surveillance. Infections are typically passed
on through contact with infected people or items. There is also an argument
for using building components with anti–bacterial coatings to limit
cross-contamination. However, authoritative guidance on using anti–bacterial
building components in healthcare buildings is limited.
Anti–bacterial building components may help but even the most effective
take an hour or two to kill bacteria, during which time infections could
be passed on. It is also important to note that they may not deal with
all bacteria. Nevertheless, anti–bacterial building components are
increasingly being specified.
The skill for designers is to achieve a balance between the additional
cost of specifying anti–bacterial components and the likely effect
in reducing acquired infections. Ideally this should be based on evidence
for the efficacy of anti–bacterial surfaces in the context of infection
risk and cost. Data from 1999 suggests that at least 300,000 patients
a year develop one or more infections- the extra costs associated with
infection because of patients staying longer in hospital and additional
treatment is in the order of £3,000 for each case.
Anti–bacterial components
Anti–bacterials are based on metals such as silver, copper, titanium or antiseptic hydrocarbon compounds. Some materials or compounds are anti–microbial which means they kill or slow the growth of fungi, viruses or parasites as well as bacteria. Practically all building components can be treated to have anti–bacterial properties by applying an anti-bacterial coating, manufacturing the component from materials that are intrinsically anti-bacterial or including an anti-bacterial material or compound in the base material of the component.
Specification options
A common-sense approach to specifying anti-bacterial surfaces is to target areas where risk of contamination is high, such as intensive care, or components where there is a high risk of cross-contamination, such as door handles, push plates or toilet seats. The anti–bacterial content may influence the durability of components where it deteriorates or become less effective with time. The cost of components with anti–bacterial surfaces varies, typically being 0 – 20% higher than an equivalent component without anti–bacterial surfaces. Calculating the whole-life costs relies on making assumptions about the probability of infection occurring as well as taking into account differences in capital, replacement and maintenance costs.Coatings
Anti–bacterial formulations may be added to paint for walls with expected repainting frequencies of between 2 and 10 years. Performance of coatings can be assessed according to the relevant parts of the paint and varnish standard BS 3900. For example. good adhesion tested to BS 3900–E6, resistance to cleaning and scrubbing to ISO 11998, impact to BS 3900–E3, humidity to BS 3900–F9, scratching to ISO 1518 and abrasion to BS 3900–E14.Doors
Doors may be made from steel with an anti-bacterial powder-coated finish or glass-reinforced fibre impregnated with anti-bacterial formulations. The performance of the hinge should be to the appropriate duty grade to BS EN 1935. Protection from impacts should be provided.Door furniture
Anti–bacterial options are available for practically all items of door furniture using:• Copper or copper alloy door furniture; expected service life: 10 – 40 years.
• Proprietary metal based anti–bacterial thin coatings on steel ironmongery - expected service life 10 – 15 years
Other components
The range of building components incorporating anti-bacterials includes ceramic glazes, floor coverings and matting, floor coatings, sealants, worktops, curtains, luminaires, suspended ceiling systems, ventilation and air conditioning filters. Specification guidance for many components can be found in the rewly revised NHS Health Technical Memorandum. However, these do not generally mention anti–bacterial options.
Specification options
| Capital cost | Net present value for 60 years | Expected service life years | |
| Wall paint finishes | £/m² | £/m² | |
| 3 Coat acrylic resin water based paint system with anti-bacterial treatment. Minimum dry film thickness 140 microns. | 8.50 | 39 | 10 |
| Polyvinyl acetate or acrylic copolymer emulsion – mist coat, two coat finish: one coat redecoration. | 5.50 | 48 | 3 |
| Doors | £/door | £/door | |
| Glass reinforced polyester internal single doorset to HTM 58 heavy duty grade with anti-bacterial surface. | 1,020 | 1,641 | 35 |
| Glass reinforced polyester internal single doorset to HTM 58 heavy duty grade. | 950 | 1,550 | 35 |
| Door ironmongery | £/item | £/item | |
| Brass (copper-zinc alloy) door ironmongery set. | 205 | 385 | 25 |
| Austenitic stainless steel to Grade 1.4301 to BS EN 10088 (UK type 304) ironmongery set coated with anti-bacterial surface. | 210 | 500 | 15 |
| Austenitic stainless steel to Grade 1.4301 to BS EN 10088 (UK type 304) ironmongery set. | 190 | 340 | 25 |
Table notes
• The table compares the whole-life costs of a limited selection
of healthcare building components with and without anti–bacterial
surfaces.
• Costs include material, installation, cleaning, minor repairs
and replacement. In the absence of hard data on the probability of reducing
hospital-acquired infections by anti–bacterial surfaces no allowance
has been made for related costs.
• Ironmongery set comprises door pull, finger and foot plates, 1.5
pair hinges to BS EN 1935 Grade 7 (tested to 200, 000 cycles)
• Note service life of anti–bacterial ironmongery determined
by life of anti–bacterial coating rather than ironmongery performance.
• A discount rate of 3.5% is used to calculate net present values.
• A cost analysis based on project specific information is essential
for a realistic best value appraisal.
First published in Building 2006
Further information
Building LifePlans provides latent defects warranty
for all buildings.
BLP Construction Durability Database at www.componentlife.com
provides durability information for building components.
Further information contact peter.mayer@buildinglifeplans.com
or telephone: 020 7204 2441.
