Maximising natural light, while keeping offices and commercial interiors comfortable, is a common challenge for the building services professional. Solar radiation impacts on internal environment and therefore occupant comfort and it also affects fabric and material life costs through UV degradation. Here Ian Bower, Managing Director of Revitaglaze, looks at the potential for architectural solar control film in mitigating the carbon and costs associated with solar radiation through glazing
Solar heat gain through windows contributes to one-third of a building’s cooling load (BOMA-Kingsley Quarterly/US EPA Energy Star). A skilfully applied architectural solar control window film has the potential to save up to 30% on cooling costs during peak seasonal periods. It is a smart energy solution for commercial buildings. Such a solution works by rejecting up to 79% of solar energy, keeping interior conditions more stable and helping to moderate the use of air conditioning. In times of especially high demand the return on investment (of savings on space cooling alone) can range from 6% to an impressive 68% per year.
Because buildings are such important targets for the European Commission in reaching a 20% energy saving by 2020, the Energy Performance in Buildings Directive (EPBD) has introduced higher levels of energy conservation for new and refurbished buildings. For many buildings in the UK, solar gain may not present itself as a consistent issue impacting on energy use. However, in peak seasonal periods sunlight through glass can result in thermal hotspots within a building.
This can build up to uncomfortable temperatures for the occupants, particularly where desks are positioned near windows or glass curtain walling arrangements. The reaction is often to increase air conditioning, relying on mechanical ventilation to combat the problem which has its own energy load and associated carbon emissions.
The solution for the building services manager has to be one that makes the most of available natural light through the window, while at the same time keeping occupants comfortable with minimal energy demand.
As a retrofit solution in existing buildings solar film can contribute to compliance with Part L of the building regulations because it helps to reduce the energy demand from space cooling. In addition this glazing treatment can go some way to supporting the organisation’s Carbon Reduction Commitment obligations, at the same time as contributing to the BREEAM rating of the premises.
Heat gain through glass windows is divided into two parts, since there is a gain due to the temperature difference between outside and inside the glazing, in addition to the solar radiation through the glass. The calculation method uses CIBSE Guide A and CIBSE Guide J to calculate the energy requirement for space cooling per msq of glass.
Interior environment is a key aspect of any workplace and maximising natural light can pay dividends with happy, productive staff. Where blinds might be installed to prevent solar radiation, the knock-on effect of blocking out natural light can be eye-strain, fatigue and poor staff performance. As a result increased illumination is required, with further demand on the electricity load and a negative impact on associated energy cost and carbon footprint.
Maintenance costs and the whole life cost of interior fabrics, furnishings and even artwork should also be factored into any cost-benefit calculations. The full range of sunlight affects soft furnishings such as upholstery and carpets – around 40% is caused by UV light alone, with damage caused by visible light and infrared light too. This degrades colour and bleaches fabrics over time. An architectural window film that filters solar radiation through the glass will slow down this damage, saving on maintenance costs too.
There are multiple benefits to the installation of an architectural window film, beyond the significant cost and energy savings it can deliver. Regulation 14 under the Health, Safety and Welfare at Work Regulations imposes a duty to undertake a risk assessment of all glazing in the workplace. It states: “Every window or other transparent or translucent surface in a wall or partition and every transparent or translucent surface in a door or gate shall, where necessary for reasons of health and safety: be of safety material or be protected against breakage of the transparent or translucent material and be appropriately marked or incorporate features so as, in either case to make it apparent.”
Recommendations for a glazing risk assessment can be found in BS6262 Part 4. A specialist glass film installer will be able to undertake this as part of a site survey, prior to recommending the best course of action. For the building services engineer, working alongside a specialist in this way will ensure all aspects of glass safety compliance can be met.
Glass filming plays its role here, by combining resilient layers of high-tensile polyester, aggressive adhesives and scratch-resistant coatings for exceptional blast mitigation and impact resistance to keep the occupants of a building safe. By ensuring any film also incorporates solar UV inhibitors the pay-back period of the installation can be shortened significantly, thanks to the energy savings which stand to be made.
Maximising on natural light, while keeping interior workspace comfortable, as well as safe for all users through the use of special architectural solar window film has long term benefits. Energy, cost and carbon savings as a result of lower space cooling demand means that solar film specification makes both financial and environmental sense with a shorter pay-back period from initial installation. With multiple benefits in compliance too, professionally installed window films provide just one simple step to safety, energy savings and carbon reduction.