Design Calculations

Designing a NATURAL VENTILATION SYSTEM

The effective design of a Monodraught Windcatcher ventilation system is carefully matched to the volume to be ventilated taking into account the fresh air requirements and heat gains to be dissipated. These calculations follow a recognised procedure.

Stage 1: Project Brief

Each project is considered on its own merits since no two jobs are alike and each project must be individually assessed.

Stage 2 : Data

The ventilation requirements are assessed so they
relate directly to the volume of each room and its occupancy. The fresh air requirement is based on the number of Occupants and the use of the building ie. Class Room, Sports Hall, Office, etc.

Stage 3 : Fresh Air Requirement

Having established the necessary data, the minimum ventilation rate can be determined dependent on the occupancy using a recognised calculation method to provide this vital fresh air requirement.

Stage 4 : Heat Gains

The heat gains will vary considerably from one room to another and depending on the predicted solar gain, the lighting and equipment heat gains to the area and most importantly, the heat generated by the occupants themselves, based on their activity. In the example shown this typical class room generates a total of 4.7kW which has to be dissipated to atmosphere.

An estimation has to be made on the building air leakage rate, dependent on many factors and bearing in mind all heat gains are calculated on the maximum or ‘worst case’ conditions. For summer use the assumption is made that perimeter windows will probably be used in addition to the Windcatcher system to provide this natural ventilation since, except for internal rooms, natural ventilation by conventional means can be anticipated to a limited extent.

Stage 5 : Recommendations

Having determined the ventilation rate required, we can select the size and quantity of the Monodraught Windcatcher systems from our in-house computer programme. The performance of each individual Windcatcher can be assessed and therefore matched to the requirements of the building and the rooms in question.

Stage 6 : Conclusions

We can offer a range of possible alternatives to suit the architectural preference of the Client, but still observing the strict ventilation criteria arrived at by our unique calculation method.

Motorised Dampers

Monodraught utilise high quality insulated control dampers, manufactured from re-cycled plastic, to regulate airflow and these provide 100% shut off when not in use.

Controlling Natural Ventilation

A wide range of automatic control systems are provided, tailored to each individual project, as set out on page 12 of this brochure. Each system, in each room is connected to a central control panel, but is provided with a manual override to fully open or close the dampers irrespective of the prevailing conditions. After 20 minutes the control panel will revert to its normal setting. For smaller offices, individual manual dampers can be incorporated according to the end user’s requirements.

Commissioning

Upon completion of the building and immediately prior to hand-over, Monodraught’s Control Specialists will attend site to fully commission the control package to ensure that all control strategies are correctly programmed, to reflect the finite usage of the rooms in question. Summer/winter setting periods are agreed, together with all time settings. A laminated instruction/ information sheet is included for each room.

Monodraught’s After Sales Service

Three months after the building has been handed over and occupied, Monodraught’s Control Specialists will return to site by appointment and after discussions with the Manager of the building, will ‘fine tune’ the control strategy to exactly reflect the client’s requirements. There is no additional charge for this service.

To see an example please download the proposal below:

Natural Ventilation Proposal: Springfield Special School - Click to view