With the tremendous upsurge in interest in buildings with lower heating costs, Irish people are starting to ask questions like: “What do you think of passive houses? Should we put in solar thermal heating? Are heat-recovery systems a good thing? Or should we put in a geothermal system? What about pellet stoves?” And so on.
SEI has just launched its grant aid program for renewable energy equipment and the home heating world has become very confusing for many people. From next year on, so we are told, our homes will be assessed, like a fridge or a washing machine, for its energy rating when we want to sell or let it.
People who call me want to know what the best system is. The sad truth is that the days have gone when you could tell your plumber to put in an oil or gas-fired central heating system, and that was that. Doors are closing, and we need to open other ones. The goal posts have been shifted.
There is the Passive House, which is highly insulated and fully air-conditioned. So far we hear that it is a successful approach in many other countries. The first of these have been built in Ireland. It makes sense: keep the energy in the house and you don’t have to replace it. It is a model that has not shown any major drawbacks, at least so far. In Germany the first experimental communal estates have been built in the passive house method. The occupants I have talked to were very happy to live there (www.eu-exhibition.org/en_hamburg.htm).
I have no rational reason for it, but I like to sleep with an open window. Something in me refuses to accept that the air, drawn from outside through a controlled heat exchanger system is as good as that fresh breeze in the bedroom. This is purely personal and, possibly irrational. I have heard of people with similar likings for fresh air, who felt very comfortable in a passive house, once they tried living in it.
Every house, by its nature is a bit of a passive house, simply because it has windows, through which sun radiation penetrates and heats the rooms. There are walls, to protect from the environment and keep more or less heat inside. The question is: how far do you want to take it? With the techniques at our disposal, we tried a different approach: the Active Solar House.
Floor Vents cover the length of the sunspace, as viewed from west to east.
Contrary to the ‘Passive House’, the building is not primarily constructed to keep energy inside, but to make optimum use of available ambient resources. This is achieved through a number of measures. The first and most important basic measure is the orientation, to make maximum use of solar radiation. The second—one that sounds like a luxury—is a large conservatory or ‘sunspace’ covering the south façade in order to trap that radiation or to exclude it from the inner building on hot days. The third measure is a very large solar panel on the roof, and the fourth is a heat pump.
Although each of the latter three systems can work independently with their own control device, the performance optimisation is taken care of by a building management system, which communicates with each controller and sends orders to them for coordinate behaviour.
That sounds very complicated, but is in fact no more complex than the electronic controls of a modern car; something that we take for granted today.
The house was monitored throughout the entire year of 2005, and data of more then 50 sensors was collected at five-minute intervals. The results show a net energy consumption for heating and hot water and pump activity of less then 9 kWh per square meter per year in the form of electricity. All other energy for heating is extracted from the environment, leaving us with a bill of € 270.00 for heating and hot water for the entire year.
This shows, that the ‘passive house’ is one possible solution to solving energy problems and the ‘active solar house’ may be another, equally sustainable approach.
Similarly, the different alternative heating or heat-recovery systems all seem to have their place in the new approach towards energy management. This includes options like windmills, biodiesel, biogas and photovoltaics. There appears to be no best way at present, no single or simple solution. The solutions to a sustainable future, so it looks, lie in the multitude of options and combinations of complementary technologies, like wind and solar energy.
In the near future we will be challenged to make decisions as to what we are going to use where, to supply the energy we need. This requires that we come to understand the new technologies or get advice from someone who understands them. Only then can we optimise our design for the future.
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