The 'Passive' vent provides an opening on a section of wall normal to the airflow direction with an effective area well in excess of the minimum requirement.
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Airflow through the opening is controlled automatically by the intervening mineral wool slab and thereby avoids undue draughts.
It is important to realise that the release of moisture vapour pressure within a dwelling to avoid condensation does not require a specific ventilation rate.
The moisture vapour pressure within a dwelling is always higher than the outside pressure therefore there will always be an escape of moisture vapour by the diffusion process through the Passive vent.
The diffusion process is slow compared with mechanical ventilation and would not cope with the copious amount of water vapour produced in a short time scale without the combined use of mechanical ventilation in kitchens and bathrooms.
Its main use is in habitable rooms where it operates continuously without noise and over a 24-hour period can extract a maximum of 2.5 litres of water/day even at low vapour pressures.
If the relative humidity of the room were 70% at 20°C then each Kg of air would hold 0.0104 Kg of water.
At a recommended maximum velocity of 0.9 m/sec (maximum velocity recommended by Local Authorities) through the Passive, it would transmit 0.0024 M3/sec (i.e. 2.42 Kg per day) of air that contains 2.5 litres of water.
Orders with a value of £75 (excluding VAT) or over qualify for FREE Delivery within the UK (ie: excluding outlying Islands & Northern Ireland). A carriage charge of £12.95 will be added to all orders with a value under £75 (excluding VAT)
For deliveries outside of mainland UK please contact our sales or export departments.
Buyer may cancel the order within 7 days of the date of delivery whereupon the costs of the Goods would be reimbursed within 30 days of notification of such subject to a reasonable deduction to cover the cost of collection and return. Loss, Damage, Shortage etc, no claims can be entertained unless advised in writing within 7 days of Receipt of Goods.