As we strive to make our homes more energy efficient, we’re in danger of forgetting two of the fundamentals of life: light and air. Both are essential to keep the indoor environment healthy and pleasant but overheating and air quality are potentially big problems in highly insulated and airtight homes - they can result in increased energy use and may affect our wellbeing. 

 

So how are these issues being overcome? I visit a good many ‘eco’ homes and it’s one of the first questions I ask. The simple answer is through ventilation and shading but it’s a bit more complicated than that.

 

Let’s start with ventilation. Without ventilation, condensation, pollutants and odours will build up, leading to damp and mould growth and sometimes allergic reactions and asthma. Indeed, studies have shown that the indoor environment can be up to ten times more polluted than the external environment.

 

The easiest way to provide ventilation is simply by opening a window for a short time but this isn’t always terribly efficient. A more controlled solution is through mechanical ventilation. Increasingly this is done in conjunction with a heat recovery system so the warmth, and therefore the energy, is not lost from the building. Whole house mechanical ventilation with heat recovery systems (MVHR), from companies such as Vent-Axia, extract warm, moist air from ‘wet’ rooms via ducting and pass it through a heat exchanger before it’s exhausted outside. Fresh incoming air is preheated by a heat exchanger which can recover up to 94% of the heat energy that would otherwise be wasted. 

 

An alternative is natural passive stack ventilation which I’ve seen in action in eco homes such as the Prince’s Natural House and those at BedZED. Here the distinctive wind cowls that provide the ventilation are an eye catching architectural element. Passive stack ventilation relies on the movement of air resulting from the difference in temperature between the outside and the inside of the house and the effect of wind passing over the roof. As the internal temperature rises due to activities such as cooking or showering the air flow increases. Fresh air is brought into the building from outside through vents in living areas.

 

Using shading against the heat from the sun needs equally careful thought. While closing curtains or blinds may appear to help, they trap a layer of hot air between them and the glass which will increase the room temperature. Shading fitted to the outside of the building is the real answer. This is why external shutters, blinds or retractable awnings are a common feature on south and west facing windows on the continent, blocking the heat before it enters the building. 

 

One manufacture taking this further is Velux. It makes windows that can be opened by remote control and, along with the blinds and awnings, they’re linked to an intelligent home control system that opens and closes them when necessary. They even shut automatically if it rains, probably the most essential feature in the British climate.

 

Images: Velux, Roger Hunt 

 

This post was written by Roger Hunt at http://huntwriter.com/