Wednesday, 6 June 2012

Self Sufficient Efficiency


  To meet our clients brief and provide them with an energy efficient home means more than just providing an air tight, highly insulated building. In line with the requirements of the code for sustainable homes, our design scheme includes the provision of supplementary technologies which will further increase overall energy savings and make better use of resources. 

Harnessing the power of the Sun.


  One of the most costly areas of fuel consumption in the home comes from heating water for all our daily needs. It takes about 4 times the amount of energy to heat a given volume of water compared to an equivalent volume of air heated to the same temperature, and of course the water we use to wash up for example is heated to a much higher temperature than our living rooms, this obviously means that a good proportion of those ever rising fuel bills is down to us needing a hot bath!

  So what can we do?, there are several different options available for providing a percentage of your own hot water and heating without firing up the boiler. Ground source or air source heat pumps can be utilized to heat both water and air, the first harvests heat stored below ground through an exchange system, and air source heating extracts heat from outside air, this system works a little like a fridge in reverse. In each case one system may be more suitable than another, for example, installing a ground source heat pump is more costly and may require more land than is available while an air source heat exchange system yields the most benefit in an air tight construction. Another option is to install solar thermal collectors, which in this case is what our clients have chosen to do, making good use of the south facing roof space. Solar thermal collectors are generally either flat plate or evacuated tube arrays, the latter being the type of installation planned for this energy efficient home. Solar thermal collectors should not be confused with P.V (photovoltaic) panels which generate electricity.

Above: The mounting fixed on the south facing roof ready to receive the solar collector.

  An evacuated tube solar collector is based on array of air vacated glass tubes, each containing a heat pipe connected to a heat absorber plate. Heat from the hot end of each heat pipe is collected and transferred to the heating coil of a domestic hot water tank inside a heat exchange manifold. The manifold is insulated and encased to protect it from the elements. Our clients intend to have this system connected to supply both the hot water tank and the central heating system. During summer months this system could potentially supply most of the hot water, though in winter months secondary heating may be required.

Above: Viesmann flat plate & evacuated tube solar collectors, image courtesy of

Above: Descriptions & schematics for  daily hot water & central heating systems using
'Viesmann' solar thermal collectors. Images courtesy of 

Much of the external render has been painted.


Tuesday, 5 June 2012

Natural Light & The Heat Loss Fight


  The greatest potential for heat loss is through glazed windows and doors, fortunately modern triple glazed units  can now achieve a  transmittance or ‘U’ value as low as 0.7 W/m2K which is far more effective than a traditional single glazed unit with a ‘U’ value of around 4.5 W/m2K. Both triple and double glazed units of the highest rating will be utilized in the new house. 

Double glazed windows will be used in the south facing elevation as the area of glazing is nearly half that of the north elevation, this will take advantage of the extra sunlight a south facing window receives and will help to balance the overall solar gain. The larger north facing glazed units afford the best view from the property but will also suffer the most from wind chill, because of this, all windows and doors facing north will be triple glazed. Both the double and triple glazed units will be Argon filled and manufactured with low emissivity glazing. The glass within low 'E' glazed units has special reflective coatings which reflect heat back into the room, the coating has very little impact on the transparency of the window unless tinted by design, a very slight tint may be visible from outside under certain conditions.