Wales has been slowly moving towards using the Passiv Haus Planning Package to design and construct Passive Houses (Passiv Haus). The Ebbw Vale demonstration buildings used PHPP extensively to create very low energy homes. The Lime House and Larch House at the Future Welsh Homes site show how the principles of managing air within buildings can radically reduce energy consumption. The Passiv Haus principles are fairly simple.
Make a house airtight and then use heat exchange systems to take the warm, moist and stale air out and use it to preheat the incoming fresh air.
Use the orientation of the house to utilise free solar energy to help heat the home.
Use good insulation to keep the warmth in during the winter and the summer heat out.
Using the above principles you can relatively easily create homes that only use a maximum of 15kWh per square meter per annum. This is about 10% of an average home’s energy consumption. So with the pressure on carbon reduction this is a good thing.
However, I think that there are some issues with using Passiv Haus that is not being talked about.
1. The system works by managing the whole house, so this means that all the rooms in the house are the same temperature. We are used to having cooler bedrooms and warmer living spaces, so this is a fairly major cultural change, especially if you did not build the house. This for many may not actually be a problem, but people need to be made aware of this characteristic especially in the rental market.
2. The heat recovery ventilation system is designed to manage the volume and quality of the fresh air coming into the home. So on sunny days our natural inclination is to open windows, but this can effect the system (unless it is on summer bypass mode). So for the best efficiency you need to keep windows and doors closed when heat is required in the house. The trouble is that people associate fresh air with having windows and doors open and so having them shut goes against the way that we have lived until now and I think that again the rental market might find this feature problematic.
3. The Passiv Haus in Ebbw Vale (part of the Future Homes Project) also has to have an automatic blinds system to stop the house from overheating. These are activated even in the winter if the house is too warm as the sun’s passive heat can effectively heat the building through the glazing (such is the efficiency of the insulation in the building). Again this would not effect the self builder, but the tenant might not be happy to lose this view etc without being asked. This was certainly the view expressed by visitors to the building.
4. Heat Recovery Systems have sets of controls that need to be used. They are not complicated, but again they are very different in concept to conventional heating. On the house in Ebbw Vale you needed to turn the dial up to decrease the temperature, effectively you are turning up the volume of extracted air (for when cooking etc). This again is not a problem for most people, but I think that many social housing tenants will not get the instruction that they need to ensure that the system works properly and effectively.
These might be little issues when compared to the energy saving that Passiv Haus design and construction can bring, but I fear that it will mean that people do not live in the optimum manner due to their habits built up over time living with conventional housing, especially in the Social Housing market.
I think that there is a gap in the market for a more natural system and that this might be filled by the Bio-Solar Haus concept.
