The two subjects of ventilation and air-tightness are closely interlinked and it has been a trend in modern property design to pay close attention to both. Specifically, new build houses are now built in accordance with strict air-tightness principles which aim to ensure that the passage of air into and out of the house is entirely (or as close to as possible) controllable.
Modern air control regulations are contained in Parts F and L of the Building Regulations 2010, an item of secondary legislation which applies to all new structures.
The concept is to make sure that new properties are tighter than 5m³h/m² infiltration – that reduces the otherwise difficult to avoid ‘leakage’. The vast majority of the air-flow out of the house then becomes ‘ventilation’ – which should be executed by controllable means.
Of course, older homes will have varying degrees of air-tightness and particularly old houses will be characteristically very draughty indeed.
We spend hundreds of pounds a year heating our homes, but a draughty house with high air changeover rates will simply remove that heat into the outside environment. This forces our heating bills up and, most importantly in the Government’s eyes, increase the carbon emissions production required to a heat a given house.
The Building Research Establishment (BRE) who write the Building Regulations, have indicated that a house achieving the present limit of 5m3/hr will use 40 per cent less energy on space heating than the 2005 standard of 10m³/hr.
A combination of air-tightness and effective ventilation is therefore important in terms of bill reduction and protecting the environment.
Effective ‘purge’ ventilation (high volume air removal, usually achieved with mechanical fans or even just by opening a window) is essential in removing moisture-laden air before vapour can settle and condense on walls and timbers.
- Seal up gaps using tapes, adhesives and grommets as appropriate.
- Consider sealing up the loft hatch or replacing your current hatch with a proprietary product like the Manthorpe Hatch from Sustainable Building Solutions.
- Invest in a few draught excluders to stop through-draughts from under and around doors or windows.
- Consider your glazing situation – could you afford double or triple glazing?
- Do you have a wood burner or fireplace? This can change the air in your room several times an hour. When you’re not using a log burner, close all the vents and shut the door. For a fireplace, consider blocking the chimney when not in use.
But don’t forget to remove the blockage when you light a fire!
- Consider your own household habits. Do you open the window next to drying washing? Do you use the extractor fan when cooking? Try and introduce ‘purge’ ventilation when you recognise that moisture is being released into the air in significant quantities.
- Consider installing an effective ventilation system, like passive stack ventilation or a Mechanical Ventilation with Heat Recovery (MVHR) system. This is more expensive, but is arguably the most effective way of achieving the desired results – particularly in more air-tight homes.
The key to maintenance in this regard is recognising the need for both air-tightness and ventilation and making sure that the habits you change, the equipment you install and the measures you introduce stay effective in the long term. Regularly check each element and repair or replace as appropriate.
As with much household maintenance, the best way to avoid forgetting is to put a regular self-inspection in your calendar – perhaps every year before winter.
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