BUILDING REGULATIONS AND A HOLISTIC APPROACH TO AUTOMATING SOLAR SHADING, HVAC AND LIGHTING
By Tim Pendleton, Director, Better Blind Company, a KNX UK Association Member.
In 2006, driven by targets of reducing CO2 emissions by 20% by 2015 and 60% by 2050, the UK Government set out its objective that all new homes and commercial buildings should be carbon neutral by 2016 and 2019 respectively. We don’t have to look far for statistics which support the emphasis on energy performance of buildings – most strikingly, 40% of UK emissions can be attributed to buildings.
Document L of the Building Regulations, 2010 applies to new building work and extensions/refurbishments. The objective of this document is “Conservation of Fuel and Power”. It specifies target CO2 emission rates that buildings must not exceed. It focuses on limiting heat gains and heat losses, as a means of reaching these targets.
Importantly, there is now an emphasis on monitoring, meaning energy certificates must be provided to authorities both prior to development and after completion. This ensures that the energy performance upon which planning approval was granted is indeed met by the occupied building.
One need only look at the predominant style of modern architecture to understand the regulations’ focus on solar gains and heat losses. Large glass surfaces are aesthetically pleasing, and it is also understood that people feel and, in the case of commercial buildings, work better when they have exposure to daylight and eye contact with the outside world. However, such expanses of glass increase potential for solar gain in summer, increasing energy consumption through artificial cooling, and heat loss in winter, leading to energy consumption through artificial heating. Therefore, Document L advocates the use of glazing with appropriate U (heat transmittance) and G (solar gain transmittance) values.
The comfort of building occupants relies on stability of internal conditions including temperature and lighting levels. Outdoor factors such as the weather that cause heat loss and solar gain are dynamic, varying between seasons, between day and night and from hour to hour. However, glazing’s energy performance is inherently non-dynamic.
Consider the façade of a building to be like a jacket. You wouldn’t wear the same jacket in summer as you would in the depths of winter. Glazed façades, even when supplemented with manual blinds or fixed external shading, offer this degree of inflexibility. This means that the effect of the dynamic external conditions have to be compensated for by artificial lighting, artificial cooling/ventilation and artificial heating in order to achieve comfort and stability indoors.
Energy-intelligent solar shading in the form of automated internal blinds, curtains and external shading can use interior temperature, exterior weather sensors and sun tracking technology to trigger automated behaviour. When used in conjunction with the most appropriate level of glazing, solar shading provides the ability for a building facade to be dynamic and respond to changes in external conditions, thus reducing load on HVAC and lighting systems.
Energy-intelligent solar shading, HVAC and lighting experts agree that the days of independent systems and controls for the management of each have now passed, and the ambitious CO2 emission targets in Document L can only be met by adopting a joint and integrated approach to planning and implementation. It is suggested that building automation system integrators bring together suppliers from solar shading, HVAC, and lighting disciplines at the outset of the building specification process. Many building automation systems integrators offer blinds and curtains on an ad-hoc basis; some profess to be able to derive energy saving benefits by automating HVAC and lighting. However, few offer HVAC, lighting and solar shading as a holistic energy saving solution.
Partnering with a solar shading company will be key to driving additional sales by achieving real energy savings, cost savings, and occupant comfort for clients.
Modelling software such as Somfy’s DISC or the British Blind and Shutters Association’s (BBSA) Shade Specifier enables solar shading companies to liaise with mechanical engineers and architects to model the energy savings provided by different combinations of glazing, shading product types and fabrics.
Open KNX shading controls offer more complex control over an unlimited number of zones and shading units. Building automation control systems based on open protocol bus networks, such as KNX, offer a greater degree of integration, customisable behaviour and compatibility between different types of controls and systems and are therefore more suited to the holistic and integrated approach, obtaining optimum benefits.