Ventilation & Air Tightness
Obviously the two go hand-in-hand, but there is a conflict. Ventilation is necessary for health and comfort but fresh air needs to be heated. Too much ventilation means that energy is being wasted.
In older properties, with open fire-places, ventilation (or draughts) could account for 30% of the overall heat loss. And draught-proofing is the simplest and cheapest way of reducing your fuel bills.
In a new build the Building Regs call for a maximum permeability of 10m³ per hour at a pressure of 50 Pascals. How much air that is is largely irrelevant. It is a level of ventilation that can be achieved with standard building practices and without the need for mechanical ventilation.
The standard is set to change in the near future; probably to 7m³ by 2011 and something below 5m³ by 2016. At that level a ventilation system will be needed, be it mechanical or passive.
The options available are :
- Natural – trickle vents and the like
- Passive – a specifically designed system that allows air to enter at designated points, to flow through the house and be extracted by natural means.
- Mechanical – as passive but relying on fans and ducting to extract and introduce air. These tend to work at very low pressures, for 24 hours per day and typically have filters on the incoming air.
- Heat Recovery – as mechanical but the incoming air is warmed by the air extracted from bathrooms, kitchen etc.
Passive ventilation System Heat Recovery Ventilation
The key, in efficiency terms, is to select the type of system that will you’re your lifestyle and design it to introduce the right amount of air in the right places – and to extract the right amount of air from the right places too.