Natural Ventilation in Schools and Commercial Buildings (CPD No. 31) Issue 2 May 2017

Transcription

1 Natural Ventilation in Schools and Commercial Buildings (CPD No. 31) Issue 2 May 2017

2 Passivent

3 Passivent Accreditations ISO Environmental Management OHSAS Health and Safety ISO 9001 Quality Management Systems.

4 History of Natural Ventilation The principles of natural ventilation have been proven over the years. Ancient buildings in the middle east use natural ventilation There is some evidence that dates buildings back to 3000 BC in Iran. Uses wind and building structure to provide comfort.

5 History of Natural Ventilation Development of forced ventilation in England was spurred by the common belief in the late 18th and early 19th century in the miasma theory of disease, where stagnant 'airs' were thought to spread illness. Some buildings that you might recognise? Natural History Museum Houses of Parliament

6 NatVent Project Formed to overcome the perceived barriers the industry had of natural ventilation in the commercial sector Developed practical solutions for naturally ventilating commercial buildings The study identified many benefits of natural ventilation

7 Benefits of Natural Ventilation Environmental gains Reduction in CO 2 emissions Avoids use of ozone depleting substances Productivity gains 90% of occupants surveyed prefer natural ventilation buildings Fewer incidents of sick building syndrome

8 Benefits of Natural Ventilation Cost efficiency 15% lower capital costs 75% lower maintenance costs Less space needed for plant room 50% less energy consumed than with equivalent air conditioning system

9 Climate Change 37% of CO 2 emissions in the UK derive from energy consumption in buildings Heating and cooling can account for up to half of a buildings CO 2 emissions A well controlled and energy efficient ventilation system is a must to reduce emissions

10 Climate Change UK drivers to reduce climate change The UK Climate Change Act (80% reduction by 2050) Renewable targets in specific authorities Approved Document L targeting Carbon Neutral commercial buildings by 2019 Minimum BREEAM Very Good rating for schools

11 Climate Change update UK emissions were 38% below 1990 levels in 2015 The first carbon budget has been met UK is on track to outperform the second and third carbon budgets Currently not on track to meet the fourth period,

12 Regulations & Guidelines Regulations are aimed at reducing building CO 2 emissions within our buildings by providing a healthy indoor environment Documents to overview Approved Document F1 Approved Document L Building Bulletin 101 Building Bulletin 93 Scottish Technical Handbook 2015 (nondomestic)

13 Approved Document F Means of Ventilation ADF ventilation guidance on Indoor Air Quality (IAQ) CIBSE AM10:2005 for design guidance General offices ventilated at 10 l/s/p, overheating requirements ADL2A. For Schools ~ Department for Education Building Bulletin 101

14 Approved Document L 2013 Conservation of Fuel and Power - Aimed at reducing building energy consumption by placing upper limits on CO 2 emissions - Recommends that solar gains are reduced to lower internal summer temperatures. - Directs the reader to BB101 for the internal overheating criteria for schools.

15 Technical Handbook 2015 (Scotland) Section 3.14 states.. Air quality must not be a threat to the building or health of the occupants Promotes well designed natural ventilation Opening area of 1/30 th of the floor area Background ventilation is also required within the space. CIBSE Guide A or CIBSE AM10

16 Importance of Ventilation Need to maintain space CO 2 levels below minimum levels. Excess CO 2 can - reduce the performance of occupants - cause nausea, sickness and headaches Internal temperature needs to be regulated, to prevent overheating by controlling the incoming air in peak summer periods.

17 Building Bulletin 101 Schools (2017) BB101 Updated version due for imminent publication Will replace the 2006 version The document looks wider than ventilation, includes Thermal Comfort and Indoor Air Quality.

18 Building Bulletin 101 Schools (2017) References the Environmental circle. Ventilation is a key part of holistic design for indoor environmental quality (IEQ). BB101 Figure 1.2 refers to types of ventilation system possible, either natural, hybrid or mechanical.

19 Building Bulletin 101 Schools (2017) Section 2 and 3 cover the Regulatory requirements; The Workplace (Heath, Safety and Welfare) Regulations 2013 is the basic requirement Natural Ventilation and Hybrid systems to have a daily average of 1,500ppm and max concentration of 2,000ppm for no more than 20 consecutive minutes each day.

20 Building Bulletin 101 Schools (2017) Thermal Comfort Guidance in line with ISO 7730 for underlying comfort standard Adaptive thermal comfort criteria in line with EN to prevent summertime overheating (also CIBSE s TM52). Modelling required. Prevention of cold draughts from incoming air Positioning of inlets and outlets

21 Computational Modelling Computational modelling of a building can involve different stages Bulk Airflow Calculations Full Dynamic Thermal Model

22 Designing a Nat Vent Strategy A good nat vent strategy is one that delivers cost effective, energy efficient ventilation, whilst ensuring the legislative requirements are met. Fully Natural Ventilation Enhanced / Hybrid Ventilation Natural Vent with Mechanical Re-circulation (Hybrid)

23 Ventilation Strategies - Fully Natural Single Sided Fresh air is bought in usually at low level through modulating louvres. Air is extracted through the same façade at high level though modulating louvres. Effective depth is 2.5 times floor to ceiling height.

24 Ventilation Strategies - Fully Natural Cross Flow Fresh air is bought in usually through the façade through modulating louvres. Air is extracted through the opposite façade usually through modulating louvres or opening windows. Both at high level. Effective depth is 5 times floor to ceiling height. Cross Flow Ventilation

25 Ventilation Strategies - Fully Natural Passive Stack no mechanical assistance to provide ventilation. Minimal energy to operate and can reduce building energy consumption through effective and intelligent control. Effective depth is 5 times floor to ceiling height.

26 Ventilation Strategies - Fully Natural Displacement Ventilation Fresh air is bought in at high level through roof mounted terminals. Warm air is extracted at high level through the same terminal. The terminal is segmented so that the fresh incoming and CO 2 laden outgoing air do not mix. Wind driven.

27 Ventilation Strategies - Fully Natural Direct Air Dispersal Better throw of air around the room due to diffusers.

28 Ventilation Strategies - Fully Natural Remote Air Dispersal Ducted to a zone of the building allowing the air to be supplied to, and extracted from different areas as desired.

29 Hybrid Ventilation Strategies Natural Mode Operates as standard natural system - during most of the year. Suitable for most types of building designs Minimal energy usage Forms part of a standard NatVent strategy

30 Hybrid Ventilation Strategies Boost Mode Allows higher levels or air to be transferred. Operates in boost mode during peak summer temperature only Suitable for most types of building designs Low energy usage through low power fan

31 Hybrid Ventilation Strategies Re-circulation Mode Operates during winter conditions Reduces amount of heating required, allows for re-circulation of warm air already in the building Minimal net energy usage due to reduced heating load Suitable for most types of building designs

32 Design Considerations Performance of products significantly affects the design of the ventilation system. 2 important product figures are; Geometric Free Area Cd value

33 Bulk Air Flow Calculations Uses approved software - uses the sizing of natural ventilation openings. - utilises the performance specification on nat vent products - show s the amount of airflow a specific opening Used at design stage - sizing of, and number of nat vent components to achieve the required bulk air flow

34 Dynamic Thermal Model Uses airflow rates from bulk airflow calculation and ventilation strategy. Gives full modelling of the whole building Based on building fabric, services and orientation. Provides hourly air flow rates, CO 2 levels Number of hours where peak temperature levels exceeded.

35 Control Required to respond to the internal and external environment Automatic control enables Adapts air flows to accommodate CO 2 Energy efficient running Require no user interaction

36 Control BB101: the occupant must have the ability to reduce CO 2 levels by increasing airflow in to the building so any control system must allow a manual override to allow for occupants to control Important factors within the control strategy are: - Speed of reaction - Set Point levels - Safety and Security

37 Acoustics Nat vent strategy requires air paths between rooms, which can cause noise to pass between rooms Important areas Corridor in to a classroom Meeting room to open plan office

38 Acoustics Building Bulletin 93 BB93 (2014) Acoustic Design in Schools - Aim is to ensure the teachers and pupils can hear each other effectively - minimum sound reduction performance should be 32dB (D n,e,w ) between classrooms and noisy spaces - 37dB (D n,e,w ) for SEN classrooms and noisy spaces.

39 Ventilation Components Air inlets (and outlets) allow fresh air in to the building Insulated louvres can be used within wall or window constructions Louvres are controlled by the nat vent control system Louvre units can allow for inclusion of acoustic components, mixing of air or pre-heat units

40 Ventilation Components Roof Terminals allow air to be vented from the building to the outside environment Normally include a controllable louvre to regulate the amount of air that is extracted Similar style terminals can also be used to allow air in/air out as part of a displacement ventilation strategy

41 Ventilation Components Acoustic air transfer units allow air to pass through rooms whilst reducing noise ingress. The prominent noise issue speech and footfall attenuation achieved by any units is targeted at the most relevant noise source and frequency range

42 Design Assistance Designing of a ventilation system is a complex and specialist undertaking. You should seek advice of a professional and a company that is able to provide insurance cover for the design and modelling of the building.

43 Thank You Do You Have Any Questions?