There is no doubt that sustainability, energy efficiency and renewable technology will be major drivers in the future direction of the UK construction industry, which is partly about reducing carbon emissions and our impact on the environment, partly about reducing dependency on fossil fuels and partly about developing a workable infrastructure for future low energy building solutions.
However, one area still appears to be overlooked in the desire to achieve low/zero carbon building solutions, and that is the quality of the indoor environment which has a direct effect on our health well being. In the EU today, we spend 90% of our time indoors, in buildings where we consume over 40% of the total energy use. In addition, up to 30% of the current building stock does not contribute to nor provide a healthy indoor climate. Therefore, looking into a future perspective of how we construct and renovate buildings, it is necessary to consider climate change, resource supply and human health.
The ultimate objective of future construction is three-fold. It should ensure that the energy consumed in the construction and subsequent use of a building is taken into account in the design phase; it should employ modern technology and visionary design to create an efficient building envelope without compromising the highest standards of comfort and health; and it should have the lowest possible impact on the climate by using renewable energy sources and adopting the concept of climate payback.
It must be remembered that although we have adapted to living indoors, we are all outdoor animals, with our gene code still designed to live on the savannah. As outdoor animals therefore, we need to live in a natural environment, not an artificial one and so this need, coupled with the desire to improve the sustainability and energy efficiency of buildings, requires a change in mind set to encourage and ensure improvements in building performance, without limiting the performance of occupants.
“You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete.” Buckminster Fuller
The Model Home 2020 project is a series of 6 experimental homes built around European directive 2002/91/EC. The UK experiment consists of a pair of 3 and 4 bed semi-detached houses and for the purposes of this paper we will focus on the 3 bed home.
The philosophy of the UK project, the ‘CarbonLight Homes’, is about using today’s technology to create comfortable, sustainable indoor environments that improve the quality of life for the people within, without limiting lifestyles. Essentially, by minimising energy usage and promoting respect for our environment, the homes help generate a sense of community and of responsibility, the concept of which is applicable to all buildings, not just houses.
By sharing the results from the project, this will support the need to prove/disprove theory as compared to practice and help to establish a bridge of dialogue in order to qualify theory and thereby future practice.
Daylight has been used for centuries as the primary source of light for building interiors and the unique variability in intensity, colour and direction of natural light has a huge influence on both the thermal and visual environments and as yet, has still not been fully replicated by artificial means.
The amount of daylight in a room is evaluated through average daylight factor levels at a horizontal workplane set 850mm above the floor. With the strategic placing of windows, the CarbonLight Homes were modelled to achieve an average daylight factor throughout of 5%, which is in accordance with level 1 under section 3.2 of the Active House specification - 1st edition. This is more than 3 times greater than the UK Code for Sustainable Homes requirement of 1.5% in living spaces and not only provides the physical benefits from more daylight, it also reduces the need for artificial lighting and thus reduces energy consumption.
It is well known that direct exposure to daylight provides many health, well being and performance benefits and yet the design of daylight into buildings is still not given the consideration it deserves. This could be partly attributable to the perception that high fabric efficiency equals low U value, which means less glazing, and consequently it is likely that window sizes will be reduced, or windows removed from the design.
In 2001, it was discovered that there is an extra light receptor in the eye which has raised awareness of the potential positive influence of the non-visual elements of daylight such as photobiological effects, circadian rhythms and light therapy. Consequently, it has been recognised that we not only need new ways of measuring light, but assessing the impact of light.
With high levels of glazing, there will always be the risk of creating visual discomfort and excessive solar gain, so adequate means of sunscreening must be incorporated into the design to manage the potential glare and reflection issues as well as the possible overheating of the internal space.
Most buildings rely on the reaction of the occupants to activate blinds and screens, which quite often can result in too much overheating before action is taken, or if the building is vacant, then no solar shading will be in place at critical times. Individual perception of what is
comfortable can also affect judgement of the operation of the sunscreening devices and cause unwelcome discomfort to others. By using a building management system to control the sunscreening, this removes the need for occupants to respond to the changing environment (both inside and outside) and the system can be designed to interpret occupant’s preferences and balance the internal comfort levels accordingly.
The system can also be designed so that the house works for the comfort of the family whilst unoccupied and can keep the indoor environment fresh and comfortable for when the family returns. A simple setting is utilised on the CarbonLight Homes to ensure that when the house is unoccupied, the lower windows are secure, the high level windows provide comfort ventilation and the external awning blinds are all brought down to protect glazing from solar gain and consequently, overheating.
The natural ventilation in the CarbonLight Homes is controlled based on the internal temperature, the CO2 concentration and the relative humidity. When the CO2 exceeds a predefined set point, natural ventilation is used and windows are opened automatically. In cold periods, the natural ventilation strategy is maintained, but with support from a mechanical ventilation system with heat recovery which, between them, continuously adjust the ventilation rate to ensure that the predefined CO2 concentration level is maintained.
Consequently, the purpose of ventilation is not just to freshen up the air inside of the home by removing moisture, smells and particles, it helps to maintain good air quality as well as good thermal comfort.
Thermal comfort is not just about keeping the inside space warm in winter, it is also about keeping the space cool in summer, which is where the natural ventilation strategy and solar shading plays a big part.
We have a strange mentality in the UK in that on hot summer days, we return home, throw open all of our windows and let hot air in to what could already have been a comfortable inside space. The CarbonLight Homes strategy includes a setting whereby if the outside temperature goes above 26°C, then the windows will close and the external awning blinds will come down to seal and protect the inside space, whether the homes are occupied or not. However, it will be interesting to see how this approach will be received by the occupants as it is well known that the habit of opening windows causes an increased air flow through the building and this increased air motion can create a cooling sensation of 1 to 2°C, as shown in the standard BS EN 15251.
It is important to design in as much flexibility into the use of the heating and ventilation systems as possible and the CarbonLight Homes has every room as a separate zone so that the spaces can be adjusted to suit each person’s own preference using a full building management system with adequate individual overrides.
BUILDING MANAGEMENT SYSTEMS
The WindowMaster NV system used on the CarbonLight Homes supports all types of buildings from small residential to large commercial and uses KNX cabling to communicate between control panel and components. The system is simple to over-ride where adjustments to temperature, ventilation and sunscreening can be made using the touch panel interface.
The CarbonLight Homes uses the BMS to control all the building services, using the solar thermal collectors as the primary source of heat for the domestic hot water and space heating, with an air source heat pump (ASHP) as a supporting measure all year round. This keeps the running of the system simple and effective. The solar thermal and ASHP both heat up a thermal store which provides for the domestic hot water and space heating. There is also a mechanical ventilation system with heat recovery to recycle the heat from cooking and showering etc around the house.
All of these installations are monitored and controlled by the BMS to ensure that the predefined comfort levels are maintained. If it is found that the preset levels are consistently not providing the comfort level required then adjustments can be made to the monitoring and operation of the BMS to suit.
The other and equally important aspect of integration is to ensure that the effectiveness of the design with regards to energy efficiency, indoor climate and impact on the environment promotes architectural quality, comfort, health and well being, all of which represent the true value of the building.
The CarbonLight Homes are designed so that the use of fossil fuels for energy is reduced to a minimum and the decision was taken to be all electric on the basis that it is not possible to de-carbonise natural gas and that gas supplies are a finite and dwindling resource.
In addition to the energy choice, the energy strategy had to comply with current building regulations, the Code for Sustainable Homes and the latest government definition of ‘zero carbon’. This was achieved by:
o Highly insulated building fabric with a ‘U’ value of 0.11 W/m²°C for all walls, floor and roof
o Very airtight envelope to achieve air permeability through the structure of less than 3m³/h.m² at an air pressure of 50 Pascals (50N/m²)
o Triple glazed windows to the colder side (east elevation) to provide improved thermal protection and double glazed windows to the warmer side (west elevation) to take advantage of solar gain
o High levels of glazing generally to take advantage of solar gain and improved natural daylight
o Hot water and space heating using solar thermal collectors, air source heat pump and mechanical ventilation with heat recovery
o Natural ventilation strategy all year round with no mechanical cooling
o Low energy light fittings throughout (LED)
o Automated window operation and blind control to reduce solar gain, prevent glare and reduce internal CO2 levels using strategically placed sensors
The target for energy consumption was to at least match our expectations for the EU regulations in 2020 and modelling calculations were in accordance with EN ISO 13790 using the TAS software, adapted to
suit residential. It is important to note that energy production is in the form of heat and reduces the need for electricity in running alternative appliances to provide domestic hot water and space heating.
The testing and monitoring will be part of a VELUX initiative where all six of the Model Home projects around Europe will provide data to be collated, reviewed and reported. The monitoring of the CarbonLight Homes will be for a minimum of 12 months and will be split into two sections:
o The quantitative data will be taken from the numerous sensors around the house to measure the performance of the building, but also to measure the performance of the people (e.g. use of artificial lighting when daylighting levels are deemed adequate)
o The qualitative data will be in the form of interviews and questionnaires to find out how the family feel about living in a low carbon home and in some respects to measure how their perceptions change during the course of the monitoring period.
It will then be possible to compare actual performance against the Active House specification.
The Active House vision defines highly ambitious long term goals for future building stock. The purpose of the vision is to unite interested parties based on a balanced and holistic approach to building design and performance, and to facilitate cooperation on (e.g.) building projects, product development, research initiatives and performance targets.
Active House proposes a target framework for how to design and renovate buildings that contribute positively to human health and wellbeing by focusing on indoor and outdoor environments and the use of renewable energy and is evaluated on the basis of the interaction between energy consumption, indoor climate conditions and impact on the external environment. The results of the performance of a building under separate performance headings can be shown in the form of the Active House radar.
What we have learned shows that there is a distinct gap between theory and practice. The real challenge is to establish a bridge of dialogue to close this gap in order to qualify theory and thereby future practice. The development of an idea goes from theory to practice and back into theory by way of testing and iterary loops, continuously developing from project to project. The key target is that we enable ourselves to build houses based on qualified theory that meet the requirements for user well-being.
We have also learned that not only do good programming and planning matter, but construction quality is vital. A sustainable building will be no better than the people who build it or the people who manage the start-up and optimisation process and these people must understand how the house works if they are to build in a way that is not detrimental to the performance of the finished building.
SUMMARY AND CONCLUSION
The importance of daylight and fresh air in the design of new buildings should not be underestimated and the CarbonLight Homes aim to show that these elements are critical in supporting the need to provide healthy indoor environments, as well as improving the energy performance and reducing the energy need of buildings.
VELUX Company Ltd commissioned a report in 2010 which concluded that the current approach to housing design overlooks elements that are central to promote well being. These include sunlight, natural ventilation and radiant heating. The report suggests that housing could be designed to reduce the burden of ill health caused by poor design. ‘Health’ is defined by the World Health Organisation as being a state of complete physical, mental and social well being and not merely the absence of disease.
Consequently, new building design should promote good health rather than just designing out elements that cause ill health and thus address the wider implications of improving the health and well being of occupants, which will not only help to reduce the number of ailments arising out of poor indoor environments (and thus the burden on the NHS), but will improve the comfort within home and working environments as well. Building Management Systems can play a crucial part in achieving this balance between energy efficiency, livability and good health and can help to ensure that an individual’s perception of comfort is not detrimental to other users of the building and indeed to themselves.
A BMS provides the essential link in integrating technologies to ensure that systems perform to optimum standard, as well as making the user interface simple and easy to understand to allow users the ability to adjust settings and maintain the comfort levels that suit them.
Of course, no two people are the same and so by developing a BMS that can automatically adjust parameters to suit the differing lifestyle of families and building users, this substantially reduces the problems associated with the ‘one size fits all’ approach and will not only support the lifestyles of the occupants, but will enhance the performance of the building and make it an altogether more attractive place to live and work.
Sustainability & Design Manager
VELUX Company Ltd, Glenrothes, Scotland
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