Putting all our energies into energy efficient homes
We have always been conscious of the environmental aspects of our developments and have implemented many measures to reduce the ‘carbon footprint’ of each home we build. These include solid block walls, solid floors, high levels of insulation, high performance external windows and doors, efficient heating systems and so on.
The future starts now
Going forward, to design and construct genuinely energy efficient homes, we will be focusing on a number of key factors, which include:
- The air tightness of the building
This is one of the most essential elements to improve energy efficiency in the home, through the design and construction of a new build property. Research has shown that up to half of the heat lost in a building is due to air leakage and uncontrolled ventilation. Whilst we have become more efficient at insulating our homes, air tightness is more difficult to achieve in an existing home, but can be controlled in a new build through care and attention in the design and construction process and accurate workmanship in the delivery.
There is concern amongst homeowners that air tightness will affect the ventilation of their homes, however air tightness should not be confused with ventilation. Both qualities are essential characteristics of a new build home, and both can be achieved independently.
Air tightness is achieved by creating a sealed ‘envelope’, through attention specifically to the joints, ensuring that air leakage through the building fabric is curtailed with the careful use of appropriate membranes, tapes, wet plastering and/or vapour membranes to form a continuous airtight barrier.
Ventilation of the home is necessary to remove moisture and other pollutants from the air and to provide a healthy internal environment with good air quality. In the case of airtight houses the air movement through the external envelope will be so small that a system of controlled ventilation will be essential. Ventilation should be provided in an energy efficient way by controllable openings, such as:- trickle vents in windows (a small slot in the window frame with a closable cover that allows a flow of fresh air to the room), rapidly ventilating a room by opening a window to quickly remove odours or air in a room or the use of mechanical extract fans as a means of extracting warm, moist air from kitchens and bathrooms to reduce the risk of condensation forming.
- The thermal mass of the building
Thermal mass is an element that enables building materials to absorb,store, and later release significant amounts of heat. Buildings constructed of sustainable concrete and masonry have a unique energy-saving advantage because of their inherent thermal mass. These materials absorb energy slowly and hold it for much longer periods of time than do less mass materials. This delays and reduces heat transfer through a thermal mass building component, leading to three important results.
- There are fewer spikes in the heating and cooling requirements, since mass slows the response time and moderates indoor temperature fluctuations.
- Buildings with good thermal mass use less energy than a similar low mass building due to the reduced heat transfer through the mass elements.
- Thermal mass can shift energy demand to off-peak time periods when utility rates are lower. Since power plants are designed to provide power at peak loads, shifting the peak load can reduce the number of power plants required.
- The insulation of the building
Where there is little to no insulation - heat flows naturally from a warmer to a cooler space. In winter, the heat moves directly from all heated living spaces to the outdoors and to adjacent unheated lofts and garages - wherever there is a difference in temperature. During the summer, heat moves from outdoors to the house interior. To maintain comfort, the heat lost in winter must be replaced by your heating system and the heat gained in summer must be removed by the ventilation.
Insulating ceilings, walls, and floors decreases the heating or cooling needed by providing an effective resistance to the flow of heat. Loft, floor and wall insulation is the most common means of insulating your home with a variety of different insulation products, these basically limit the air movement. The still air is an effective insulator because it eliminates convection and has low conduction.
High levels of good quality insulation will minimise heat loss and can be used to close gaps in the building envelope. A well insulated house will not only be more energy efficient, it will be more comfortable since it will be easier to keep it at a constant temperature.
Where possible, and as the technologies become more affordable and viable, we will also be considering the following:
- Solar gain...
Passive solar energy (the energy provided by sunlight entering buildings through windows) can make a significant saving in energy needed for heating and lighting a home, and so reduce the CO2 emitted by burning fossil carbon fuels. The greatest energy savings arise when the development site layout optimises passive solar gain combined with building designs that take advantage of solar energy. However, it is important to balance the benefits of reduced energy consumption in winter offered by passive solar gain, with the risk of excessive solar gain during summer which can cause discomfort or heat stress, and increase the demand for energy for cooling.
When considering a new development there are a number of factors we would take into consideration:
- the layout of new development should maximise the potential for passive solar gain
- The site layout should use landform and landscape to benefit from shelter to minimise heat losses in winter and avoid over-shadowing of the solar orientation of buildings
- design principles should be applied to new buildings, that maximise the capture in the thermal mass and use of passive solar energy while avoiding excessive solar gain in summer
- the site layout and landscape should provide adequate shade in summer.
- Photovoltaic panels...
Photovoltaic panels allow you to harness the power of the sun's energy and convert this into electricity. Which you can use immediately as free, green energy - or feed it back into the grid for your own financial benefit.
Feed In Tariffs came into effect on the 1st April 2010 and mean that almost anyone can now benefit from a range of energy solutions. The scheme guarantees a minimum payment for all electricity generated by the system, as well as a separate payment for the electricity exported to grid. These payments are in addition to the bill savings made by using the electricity generated on-site.
- Solar heating system
Solar Hot Water has for many years proven effective at reducing utility bills by helping to heat hot water in the home. Until the feed in tariff this product was by far the most widely used solar technology in the UK as it had a comparatively low capital outlay compared to Solar PV. Right now because of the feed in tariff Solar PV is the most popular but both have great potential in the UK.
The Solar heating system utilises both solar roof panels and a hot water tank, the panels, positioned facing south on the roof, are connected to the tank in your house by insulated pipes. These pipes and the panels carry a mixture of glycol and water and this water collects heat from inside the solar panels. A pump pumps the fluid around the pipes through your panels picking up heat, then takes that hot fluid down into your tank and heats your hot water. The system circulates until your tank is hot using as much heat as your panels can generate. The panels can get up to 200 degrees and so collect heat very efficiently, this translates into a good 50 to 60 degrees in your tank and this is regulated by a little control panel which tells the panels when the tank is hot enough.
- Rainwater harvesting...
Rainwater harvesting is a means of simply collecting the rain which falls onto our roofs, capturing it into a tank and storing it until it is required for use. The rainwater is typically captured from the roof(s) via normal guttering and down-pipes, and brought to a central point, usually a storage tank (frequently underground), where it is filtered on entry. A highly efficient and reliable submersible pump then delivers the water to a service on demand. Currently the captured rainwater can be used for a variety of non-potable uses such as watering gardens, flushing loos, washing clothes, cleaning vehicles and so on thereby significantly reducing the demand for mains water.
- Air and ground source heat pumps
Heat your home with energy absorbed from the ground. Ground source heat pumps use pipes buried in the garden to extract heat from the ground. This is usually used to heat radiators or under floor heating systems and hot water. Beneath the surface, the ground stays at a fairly constant temperature, so a ground source heat pump can be used throughout the year - even in the middle of winter.
A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe - called a ground loop - which is buried in the garden. Heat from the ground is absorbed into this fluid and is pumped through a heat exchanger in the heat pump. Low-grade heat passes through the heat pump compressor and is concentrated into a higher temperature useful heat capable of heating water for the heating and hot water circuits of the house. Ground loop fluid, now cooler, passes back into the ground where it absorbs further energy from the ground in a continuous process while heating is required. The length of the ground loop depends on the size of your home and the amount of heat you need - longer loops can draw more heat from the ground, but need more space to be buried in. Normally the loop is laid flat, or coiled in trenches about two metres deep, but if there is not enough space in your garden you can install a vertical loop down into the ground to a depth of up to 100 metres for a typical domestic home.
Heat pumps have some impact on the environment as they need electricity to run, but the heat they extract from the ground, air, or water is constantly being renewed naturally. Unlike gas or oil boilers, heat pumps deliver heat at lower temperatures over much longer periods. This means that during the winter they may need to be left on 24/7 to heat your home efficiently. It also means that radiators should never feel as hot to the touch as they would do when using a gas or oil boiler.
The principal behind an Air Source Heat Pump is much the same as a Ground Source unit, except that the energy being used to create space heating and hot water is extracted from the outdoor air, even when that outdoor air temperature is as low as -15 degrees Celsius. Water source heat pumps can be used to provide heating in homes near to rivers, streams and lakes.
For more information on the types of systems available click here
- Heat recovery systems...
New build homes, if they comply with the new Building Regulations, should be extremely air tight, well insulated and draught sealed and hence require correct ventilation. Whilst there are the simple means of ventilation as described above there are more sophisticated systems which not only take care of all the extract and ventilation requirements, but also reduce energy consumption in the home by recovering otherwise wasted heat.
A heat recovery system will keep your house fully ventilated throughout the year, whist recovering the heat already inside your home. It brings fresh air from the outside and recycles the otherwise wasted heat from bathroom and kitchen areas. Anywhere where there is a high heat or moisture content will be used to power the heat recovery unit and keep efficiencies high.
The system basically works as follows: Dirty, stale air is continually extracted from all the wet areas of the home, through unobtrusive white ceiling or wall mounted grilles. This air then makes its way through the ducting and the long rigid silencer, back to the heat recovery unit. Before being discharged outside, it passes through the plate or rotary wheel heat exchanger giving up its heat to the cold fresh air coming into the house. The highly filtered supply air is heated up to the required temperature by the water heater coil (linked to your wet heating system) or an electric heater coil ensuring no cold draughts, which must be avoided. The heat recovery unit controls the extra heat requirements automatically. The supply air is now delivered through a long rigid silencer into the supply ducting, through ceiling or wall mounted supply registers, to all the habitable rooms resulting in whole house heat recovery ventilation.
- Thermal bridging...
Thermal bridging occurs when a conductive building component, such as a steel lintel, metal fastener, concrete beam, slab or column spans the gap between the inside and outside of a building, penetrating or bypassing the insulation system. These ‘bridges’ commonly occur around openings such as lintels, jambs and sills and at wall/roof junctions, wall/floor junctions and where internal walls penetrate the outer fabric or where links are created between the external and internal fabric, such as wall ties.
Thermal bridges provide a ready passage of heat transfer to the outside air and allow a heat flow entirely disproportionate to their surface area resulting in excessive heat losses from the building increasing CO2 emissions. Condensation is also likely to form on the internal wall around the thermal bridge leading to damage to of the internal decoration.
There are a number of different solutions to addressing this situation, Ancon is one supplier who are looking for a variety of solutions:- one of which is the Teplo Wall Tie, a low conductivity range of wall ties, so even the most super-insulated homes can be built using traditional cavity wall construction methods. Others include insulated balcony connectors, ‘warm roof’ batten fixings, and stainless steel lintels.
- And this is just the beginning...
Much of the movement towards sustainable living has to do with a change in mindset of all homeowners and developers. As technology develops so to should our attitude towards it and the commitment to implementing these new systems. We at Aston Homes are working towards the development of sustainable living in the homes that we build, our efforts however are only as effective as the homeowners that are prepared to embrace them.
So for those who embrace the sustainable lifestyle wholeheartedly, we will work with you to achieve your ultimate sustainable home, so whether you are considering composting and recycling facilities, composting toilets, grey water harvesting and the rest, we can help.