UK Building Regulations
for Ventilation and 
Energy Conservation
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  Ventilation Energy and Environmental Technology
                                     from VEETECH Ltd.              Updated 11th November  2009

Building Airtightness - Is Tight Right for British Homes?
Mechanical Ventilation Case Studies point to an 
Energy and Indoor Air Quality Disaster for Homes 

Bedroom Ventilation

The Problem - Ventilation in modern airtight homes can be woefully inadequate.

Adult time spent in bedrooms can be at least 8 hours a day. Children may additionally use their bedroom as a den in which case they could spend almost all their home time in the bedroom. It is essential, therefore, that bedrooms are properly ventilated. Based on European CEN Standard 13779 ventilation for 'medium' air quality should be at least 10 L/s per occupant (15 L/s for high indoor air quality). This equates to a steady state metabolic carbon dioxide concentration (CO₂) of no more than 800 ppm. It is now known that poorly ventilated spaces create adverse symptoms as well as exacerbating the probability of high humidity, condensation mould growth and the presence of house dust mites. Symptoms of drowsiness and poor reaction time are also common. A night in an inadequately ventilated bedroom is likely to result in poor daytime health and, possibly, long term damage to health. Recent times have shown a dramatic rise in allergy related illnesses such as asthma. The conditions in poorly ventilated spaces are precisely those that can create such problems.

Measurements of actual ventilation rates, based on CO₂ concentration, have consistently shown bedroom ventilation rates to be dangerously inadequate. Illustrated below is a not untypical result in which the carbon dioxide is seen to reach a steady state approaching 5000 ppm. This corresponds to an occupant ventilation rate of about 1 L/s. This is woefully inadequate but is typical of a bedroom with closed windows and doors. Such a low ventilation rate is simply not healthy but is probably quite common in the modern airtight home.

Solutions

The solution depends very much on climate. In mild climates the easiest solution is to sleep with an open window. A simple top hung window is best, open by about 1 cm for each person. Provided the window is open, sufficient ventilation is normally possible with the bedroom door closed. In areas in which night temperatures  close to freezing are occasional there should be no harm, on these nights, to sleep with the bedroom door open and the window closed.  This might not provide the best ventilation but it will be possible to use the reservoir of air trapped within the whole house itself.  If in doubt measure the carbon dioxide concentration. Such measurement devices may still be seen as expensive ($300 US, £200 GBP) but, relative to health, they are extremely valuable. 

In very cold (and hot climates) mechanical supply to bedrooms with heat (or cold) recovery may be needed. Window opening in severely cold climates is simply not practicable. Mechanical ventilation should, however, be sized to meet the bedroom need (i.e. a minimum of 10 L/s person). Performance can quickly deteriorate if filters become clogged. Ideally, again, CO₂ concentration should be regularly checked.