Low Energy house record of temperatures.
Attached is a temperature chart relating to a low energy house, the front of the property is North facing, therefore subject to lower temperatures. Temperatures in this building were recorded over a period of two years and the attached is a sample dating from 1st March 2011 to 3rd March 2011. It highlights the possible variations in temperature that are typical in Ireland with a low external temperature related to the high external temperature variation of over 20 degrees in a very short time scale. This also highlights the particular difficulties faced with low energy buildings in Ireland, emphasized internally where the temperatures were not automatically controlled. A quickly varying environment generates conditions that require constant internal monitoring and control in order to facilitate comfortable living conditions. At times the relative humidity internally in this house became uncomfortable. Throughout the period of this study, solar gain featured predominantly. In the total two year period there was no period of more than three days where solar gain did not provide valuable heat. Other than appliances there is no heat source in this building. This highlights the need for temperature control in low energy buildings through automatically monitored and controlled ventilation. The energy requirements for this automatic ventilation have ben calculated as being in the order of 900 kW/h per annum for a 260 sq.m. house for the space heating / controlling energy demand. This equates with less than 4 kW/h per square metre per annum. This cost relates to the energy requirements of the Heat Recovery Ventilation system. For comparison, Irelands BER (Building Energy Rating) for an A1 rated house (the highest rating) of less than 25 kW/h/sq.m,/annum. Other energy use within the building is included in this BER rating, lights, appliances, hot water, etc. The average electric use in houses in Ireland per annum is about 6,000 kW/h. To apply the average use, the total BER rating of this house based on performance would be in the order of 5591 kW/h/a or have a BER rating of A1. However, the average energy use per occupant assumes that this is based on there being three, which is correct for this house. The passive house standard is 15 kW/h/sq.m,/annum. This may be achieved with the use of low energy units, ‘A’ rated appliances, etc. These have been implemented in this particular house and the standard has been achieved. However the average use of electricity per person has increased over the years. For instance and as a guide to possible future developments in Ireland the average electricity use per person in the USA is more that twice that for those in Ireland. Were Ireland to follow the USA in this regard the passive standard would become impossible without having an ecological and efficient means of production within each development. These could include Photovoltaic solar panels, hydro generators in streams or small windmills. Perhaps the best solution is for each of us to review our energy use.
Low energy or passive buildings require high levels of insulation and air tightness. Imagine wearing a knitted woollen jumper on a cold windy mountain. The wind will penetrate the jumper which will be of little effect. Add a wind proof though light layer and the effects will be highly improved. Air tightness is of high importance. The cost of applying these improved systems to new buildings is reducing due to increasing demand. There are also more options on how this effect can be achieved.
Other elements of sustainable architecture include the source of materials, that they are both suitable and easily obtainable. Transport and manufacture costs should be included in any analyses as part of the energy design process.
In sum, low energy use can be achieved. The passive standard while achievable is subject to corruption with ever changing requirements in energy use. The best that we can do is the constantly seek to be the best that we can be.