Will our house be Passive?
We are hoping to achieve 'towards passive', i.e. as near as we can to the standard. In modelling it has achieved below passive for energy consumption but apparently it may not perform as well in reality.
What is a Passive House?
Passiv Haus is a German standard for low energy buildings. Buildings are designed so that they require very little energy for heating and/or cooling, less than 15kWh/m2 (apparently the average house in the UK uses about 120kWh/m2). They do this by using huge amounts of insulation, high performance glazing and paying a lot of attention to airtightness. They also bang on about 'cold bridging'.
They normally have a mechanical ventilation system (MVHR) to circulate and refresh air throughout the building, as there are no draughts and trickle vents for all your heat to escape through. This system minimises heat loss by using the stale air to heat the incoming air.
Consideration is given to the placement of the windows and their size in order to maximise solar gain (heat energy from the sun) but the design also needs to prevent the summer sun over-heating the house. This is often done by using solar shading e.g. louvres, brise soleils, deep window recesses.
A true passive house will have minimal heating or cooling systems as the idea is that the house is so well insulated that the energy provided by solar gain, inhabitants, cooking etc will provide enough heat which can't escape.
To assist with this type of design architects/designers can use PHPP, a computer modelling application developed by the Passivhaus institute. There are only a small number of people in this country trained to use this programme. We are very pleased to have had our designers, Charlie Luxton Design, use this in our house design process.
There are other criteria for Passivhaus certification which you are more than welcome to look up yourselves...!
Are you mad? It just makes so much sense to build houses which by design minimise energy use. Why waste energy? Why pay for more energy than you really need?
Why aren't all new houses passive?
It costs more to build them. Hopefully these costs are coming down. It is hoped that our house could become an exemplar of how to achieve near passive without spending big bucks.