Mark Harber - Design solutions to mitigate apartment overheating
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IAQM Indoor Air Quality conference 2020 Outdoor Indoor Air Quality Interactions: Current Issues
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Mark Harber - Design solutions to mitigate apartment overheating
- 1. Design Solutions to Overcome Apartment Overheating 2 2 ND J UN E 2 0 2 0 - MARK H ARB ER. IAQM Indoor Air Quality Conference
- 2. Cool & Quiet. − A real issue – why it matters. − Overheating in our homes. − Noise and air quality impact to occupants. − Solutions: what we’ve learnt & our vision. Balancing overheating & noise through good design
- 3. “In a survey of people involved in managing or building homes, 80% said overheating was a problem and 65% confirmed this was a significant concern for their organisation” Source: Investigation into Overheating in Homes, 2012
- 4. “48% of the 2,750 people surveyed in England and Wales felt that their home life was being spoilt by noise, with one in five saying it kept them awake at night” Source: UK National Noise Attitude Survey 2012
- 5. Camden High Street 1904 Westminster Serves “The Tenant was faced with a no-win situation where if things had remained, the tenant would be expected to choose between either the problem of excess noise or excess heat” Improvement Notice to Landlord. July 2012 issue 64
- 6. “Almost 30% of people would be willing to pay more for a home that enhanced their health and wellbeing” T H E U K H O M E , H E A L T H A N D W E L L B E I N G R E P O R T , S A I N T G O B A I N , 2 0 1 6
- 8. “The phenomenon of a person experiencing excessive or prolonged high temperatures within their home, resulting from internal and/or external heat gains, and which leads to adverse effects on their comfort, health or productivity” Z E R O C A R B O N H U B , 2 0 1 5
- 9. Regulations / Compliance- Part L ‘Criterion 3’ Overheating − Part L1A of Building Regulations endeavours to address dwelling overheating with “Criterion 3” − “The dwelling should have appropriate passive control measures to limit the effect of heat gains on indoor temperatures in summer” − This check is often overly simplistic and does not provide an accurate indicator of overheating risk − It also does not take account of site constraints, such as acoustics or air quality − As such, compliance can usually be easily achieved by assuming openable windows − When windows are simulated closed then compliance can often be achieved with enhanced mechanical ventilation rates of 2-3 air changes per hour
- 11. What is it? Overheating Adaptive Criteria (less onerous, allowing higher internal temperatures, linked to outside air temperatures) Fixed Criteria (<3% of occupied hours >26oC) Mechanical Ventilation Natural Ventilation
- 12. CIBSE Guidance Overheating 0 5 10 15 20 25 30 35 Temperature(C) London Weather Centre Dry-bulb temperature (°C) Max. adaptive temp. (°C) FixedModel - ThresholdTemperature (°C) − Fixed (<3% occupied hours above a fixed maximum temperature of 26oC) − Adaptive (Less onerous criteria, allowing higher internal temperatures, linked to outside air temperatures) − The Adaptive method applies to predominantly naturally ventilated dwellings. − The Fixed method applies to predominantly mechanically ventilated dwellings.
- 13. What does it actually mean? Overheating − 50% June and 70% of July exceed the threshold. − Peak period in July of 6 days when internal temperature does not drop below the threshold of 26oC. − In July there are 6 nights when temperature does not fall below the threshold of 26oC and 16 nights when above threshold for part of the night..
- 15. GLA Cooling Hierarchy (and Good Practice). Overheating. 1. Minimise internal heat generation through energy efficient design 2. Reduce summer heat gains: orientation, shading, albedo, fenestration, insulation, green roofs/ walls 3. Exposed internal thermal mass and high ceilings 4. Passive ventilation 5. Mechanical ventilation 6. Active cooling systems (selecting the lowest carbon options) Passive design Active design
- 16. Passive Design Overheating Window openings and (integrated) blinds Cross ventilation Indicative glazing proportions Movable shutters Other potential shading measures Façade: − Building orientation & massing − Dual aspect apartments- courtyards for acoustic shielding − Glazing areas balancing solar vs daylight vs views − Suitable glazing g-value & visible transmittance − External shading (balconies, etc), shutter design. − Consider thermal mass (albeit generally not helpful in bedrooms, as it affects night-time temperatures) Ventilation: − Practical & effective ventilation opening areas (windows & doors)
- 17. Residential Corridors Overheating − TM59 stipulates <28oC for under 3% annual hours. − Utilise lower temperature heating distribution pipework − Locate risers / utility cupboards so as to minimise horizontal pipework runs − Ventilate LTHW risers − Enhanced insulation to pipework distribution - including bends and fittings − Maintain separation of cold water and heating pipework to avoid temperature pick up − Utilise smoke ventilation shafts for additional ventilation as a minimum and consider tempering supply make-up air
- 18. Acoustics & Air Quality In Homes
- 19. Noise & Air Pollution Adverse effects matter… Noise map showing variation of noise across proposed facades
- 20. Risk category Internal sound levels Implication Day Night >50 dB LAeq >42 dB LAeq High Risk Category Open windows unlikely to be acceptable. 40-50 dB LAeq 35-42 dB LAeq Moderate Risk Category Open windows may be acceptable for limited periods of time. 35-40 dB LAeq 30-35 dB LAeq Low Risk Category Open windows is not likely to result in adverse effect ≤35 dB LAeq ≤30 dB LAeq Negligible Noise How much noise is acceptable?
- 21. x Noise How much noise is acceptable?
- 22. Applying the AVO Guidance Noise Predicted Acoustic Risk Categories – Complete for day and night!
- 23. Ventilation Design Impact Air Quality − The importance of improving air quality has been recognised by the GLA and features in the London Plan. − A detailed assessment of local sources of air quality would be undertaken to determine air pollution concentration at the different façades across the development. − Air quality mapping can then be completed and risk categories assigned (similar to Acoustics) to consider whether opening windows are feasible. − Typical AQ mitigation measures for apartment ventilation systems include: - Inclusion of NOx filtration on the intake air connection of the MVHR - Bringing outside air in from roof level via an intake air shaft
- 25. Regulations / Compliance- Part F Apartment Ventilation − Opening windows need to be provided to all habitable rooms for purge/rapid ventilation. − Background ventilation to each dwelling to comply with one of the following systems set out in Part F. - System 1- Intermittent extract fans and trickle vents - System 2- Natural passive stack and trickle vents - System 3- Continuous extract fans and trickle vents - System 4- Continuous supply and extract system (MVHR) − Part F minimum mechanical ventilation rates are minimal and would not meaningfully deal with overheating. − MVHRs are used in 95% of our residential projects (especially in London where the heat recovery is needed to meet the GLA energy targets). Fresh-Air into Dwelling Stale-Air Extract Stale-Air Exhaust Incoming Fresh Air Heat Recovery Mode Summer Bypass Mode
- 26. Opening Windows (Passive / Adaptive) INTAKE MVHR EXHAUST SUPPLY EXTRACT OPENING WINDOWS
- 28. INTAKE MVHR EXHAUST SUPPLY EXTRACT BOOST EXTRACT FANS PASSIVE VENTILATORS Passive Ventilators with Boost Fans (Passive / Adaptive)
- 30. INTAKE MVHR EXHAUST SUPPLY / EXTRACT BOOST FANS SUPPLY EXTRACT MVHR with Boost Fans (Mechanical Vent)
- 31. MVHR WITH INTEGRAL HEAT PUMP INTAKE EXHAUST SUPPLY EXTRACT MVHR with Integral Heat Pump (Mechanical Vent)
- 32. MVHR INTAKE EXHAUST COOLING PLANT COOLING COIL CHILLED WATER PIPEWORK SUPPLY EXTRACT MVHR with Cooling Coil (Mechanical Vent)
- 33. MVHR INTAKE EXHAUST COOLING PLANT FAN COIL UNITS CHILLED WATER PIPEWORK SUPPLY EXTRACT Fan Coil Unit (Full Cooling) (Mechanical Vent)
- 34. Indicative Performance / Capital Cost Comparison of the Solutions = Passive Solutions (*NOTE: TM59 compliant under adaptive criteria) = Capital Cost KEY:- = Mechanical Ventilation Solutions TM59 THRESHOLD (MECH VENT)