In the wintertime (when external temperature is less than 16☌) we need to preheat the incoming air to 16☌ before supplying it to the room. The fan power required to drive the ventilation.For conventional natural ventilation, we require no fan power all year round.This preheat will have to take place for any occupied hours which are less than 16☌.
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This means that by opening windows we are risking subjecting the occupants to cold draughts and therefore we will need to preheat the incoming air. In order to provide sufficient ventilation in the wintertime to maintain fresh air levels and prevent overheating, we will continue to use this upwards displacement ventilation strategy. Normally the low level windows will be inlets and the high level openings will be outlets. In the summertime we will assume that natural ventilation is carried out through the use of opening windows at low level and a passive stack or opening window at high level. How conventional natural ventilation works In our model the flow rate is set a 150l/s but this should be altered to suit your building, so that overheating is prevented – meaning that we can meet the BB101 standard of no more than 120 hours greater than 28☌. Boost ventilation is provided by specifying a ‘natural ventilation’ flow rate which is assigned a profile such that it operates when room temperature exceeds 25☌ during the occupied day. The mechanical system is set to provide 5l/s/person (ie. The way that IES deals with the cold incoming air is as part of a heat balance with all of the heat gains within the space, and therefore this in analogous to the way in which e-stack uses the excess heat in the room. In our model, e-stack ventilation is modelled as a mechanical ventilation system with no heat recovery. the flow rates which will require fan power). Through the use of IES we want to obtain the heating requirement of the room and the flow rates which are required to keep the room at an acceptable temperature during the wintertime (ie. In the summer (when external temperature is greater than 16☌) e-stack ventilation requires no fan power because, when we open the low level windows in the room we can rely on natural buoyancy to drive the ventilation. We also require heating in the space when external temperatures are very low, such that room temperature drops below 18☌. This fan power is 100W when providing minimum ventilation of 5l/s/person and 150W when we are required to boost ventilation to prevent overheating. For e-stack ventilation, in the winter (when external temperature is less than 16☌) we require fan power to mix the cold incoming air with warm room air. The fan power required to drive the ventilation.When calculating the energy associated with ventilation we think about 2 components In warmer weather the system typically operates with higher ventilation flow rates in order to minimize the risk of overheating, although it can be used in conjunction with thermally massive building types to exploit the benefits of passive night-cooling in which case lower ventilation rates are again used. The system ensures that the air quality remains very high but also that the building is totally comfortable to avoid the risk of cold draughts which are often associated with natural ventilation systems. The e-stack natural ventilation system uses technology based on a University of Cambridge patent which is designed to ensure a minimum rate of air change between a building and the exterior in Winter to comply with Part F of the building regulations, whilst minimizing the heating energy required.This is achieved by mixing the incoming cold fresh air in Winter with hot interior air prior to it reaching the occupants. MVHR with opening windows in the summertime.Mechanical Ventilation with Heat Recovery (MVHR).We have modelled four different ventilation strategies: e-stack We’ve also modelled a room with an exposed concrete soffit which acts as thermal mass, but you can change this too. The U-values we have used are in the table, but you can tailor the model to have constructions exactly like your building. Similarly we have run the simulations for a building with good practice U-values and infiltration rates. The simulations have been run on the Manchester TRY weather file but you can run a simulation on any weather file by downloading the IES files from the menu on the right. Occupancy: 32 people 9am-5pm weekdays with a lunch break North facing and therefore gets the least solar gain. We’ve taken the middle floor classroom which is We have modelled a typical Manchester classroom. But don’t take our word for it let us help you to model your classroom. The short answer is the e-stack system provides significant energy savings. We are often asked what IES shows for natural ventilationĪnd alternative ventilation strategies.