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July 2017 / A.Bateson / Residential overheating 26w w w . h o a r e l e a . c o m
Residential Modelling using CIBSE TM59 with Case StudiesAshley Bateson, Partner
Phil Kelly, Senior AssociateHoare Lea
6 July 2017
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“The number of heat-related deaths is projected to increase from 2,000 per year currently to 7,000 per year by the 2050s.”(Source: The Committee on Climate Change, 2015)
ContextPredicted climate change impacts on housing
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GuidanceTM59 provides specific guidance on the application of dynamic thermal modelling for residences
TM52 provides adaptive comfort guidance for non-domestic buildings
TM59 provides guidance for domestic buildings
Guide A provides environmental design guidance for domestic & non-domestic buildings
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CIBSE TM59Design methodology for the assessment of overheating risk in homes
Key drivers for the new guidance:
� Standardised occupancy profiles
� Standardised equipment heat gains
� Clarification of overheating criteria
� Highlights risk assessment responsibilities
� Will help with planning compliance (for GLA)
� SAP Criterion 3 in Part L of UK Building Regulations is insufficient
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CIBSE TM59Comfort compliance criteria
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CIBSE TM59Comfort compliance criteria
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Assessing thermal comfortAir temperature vs operative temperature
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� All high risk dwellings in a development should be identified, with a sample of units to be assessed.
� Typical risk factors include single aspect, highly glazed, top floor units with limited window openings.
� At least one corridor should be modelled if community heating pipework is present in corridor, and assessed for overheating risk. Compliance with the criteria is not mandatory, however the risk should reported.
� Heat gains from communal pipework, heat interface units and heat maintenance tape must be modelled where present.
CIBSE TM59Assessment Guidance
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� Room occupancy profiles have been standardised, with bedrooms permanently occupied (24/7), and living spaces occupied during the day.
� Window openable areas should reflect any acoustic, air quality or security constraints. Internal doors may be modelled as open, but bedroom doors should be closed overnight.
� Internal blinds should only be modelled if provided within the base-build and explained in home user guidance. Results without blinds should also be presented for reference.
CIBSE TM59Assessment Guidance
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� Weather files to be used is the Design Summer Year (DSY01) adapted for future weather (2020s High emissions 50% scenario).
� Future climate conditions to be considered.
� Ventilation from MVHR units should be included and based on normal, acoustically compliant modes of operation (as per CIBSE Guide A).
� High MVHR flow rates intended for occasional use with louder fan noise should not be assumed.
CIBSE TM59Assessment Guidance
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� Maximum – 34.6oC, Minimum -6.7oC
CIBSE TM59Design Summer Year (DSY01) 2020s High emissions 50% scenario
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CIBSE TM59Design Summer Year (DSY01) 2020s High emissions 50% scenario
� Hours >26oC – 183 across 31 separate days
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CIBSE TM59Design Summer Year (DSY01) 2020s High emissions 50% scenario
Over 26oC between 09:30 – 20:30
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Case Study 1
Analysis of an apartment block adjacent to a busy road
• All apartments designed to have MVHR unit and openable windows for purge ventilation (for Building Regulation Part F compliance and occupant control)
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Scenario 1 - Natural ventilation with standard MVHR units and no external shading
Low overheating risk but opening windows create unreasonable noise levels in the apartments due to external traffic noise
Case Study 1 Analysis of an apartment block adjacent to a busy road
18-30l/s for living rooms & bedrooms
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Scenario 2 – Reduced window opening, larger MVHR units with no external shading
Case Study 1 Analysis of an apartment block adjacent to a busy road
Apartments showing some overheating risk
60-100l/s for living rooms 36l/s for bedrooms
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Scenario 3 - Larger MVHR scenario with external shading added
Case Study 1 Analysis of an apartment block adjacent to a busy road
The addition of the external shading has resulted in fewer apartments showing overheating risk.
Further increases in ventilation rates and other measures are required.
60-100l/s for living rooms 36l/s for bedrooms
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Case Study 1 Analysis of an apartment block adjacent to a busy road
Conclusions
1. Natural ventilation (using openable windows) is not suitable at the site, given the high levels of traffic noise, although the modelling shows it would be effective in minimise overheating risk.
2. Standard MVHR ventilation rates are insufficient to avoid overheating risk at the site.
3. Higher MVHR ventilation rates reduce overheating risk when combined with external shading.
The recommended solution comprises:
¾ Large MVHR unit with high ventilation rates¾ External shading¾ Openable windows for purge ventilation
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Step 1 – Choosing the high-risk apartments
Case Study 2Analysis of multiple exposed high-rise apartment blocks
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Case Study 2Analysis of multiple exposed high-rise apartment blocks
Scenario 1 - Natural ventilation with restrictors, standard MVHR flowrates
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Case Study 2Analysis of multiple exposed high-rise apartment blocks
Scenario 2 – Enhanced natural ventilation (greater opening angle), standard MVHR flowrates
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Case Study 2Analysis of multiple exposed high-rise apartment blocks
Scenario 3 – Enhanced natural ventilation, enhanced MVHR flowrates
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Conclusions
1. High levels of glazing and restricted natural ventilation (using openable windows) is insufficient in almost all cases.
2. Enhanced natural ventilation through increased openings make a notable difference but are still insufficient, even when paired with standard MVHR ventilation rates.
3. Higher MVHR ventilation rates made limited impact in this instance, concluding that additional passive design measures are required.
Case Study 2Analysis of multiple exposed high-rise apartment blocks
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Case Study 3Modelling vs the real world…
Key issues found in one project
� Co-ordination with blinds
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Key issues found in one project
� Co-ordination with blinds
� Co-ordination with desks (& occupancy!)
Case Study 3Modelling vs the real world…
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Key issues found in one project
� Co-ordination with blinds
� Co-ordination with desks (& occupancy!)
� Internal reveals
Case Study 3Modelling vs the real world…
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Key issues found in one project
� Co-ordination with blinds
� Co-ordination with desks (& occupancy!)
� Internal reveals
� Sensor & controls locations
Case Study 3Modelling vs the real world…
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� Early analysis will identify overheating risks
� The standardisation of the methodology will improve industry consistency, help establish recognised best practise and enable better comparison between different buildings.
� Appointments for dynamic thermal modelling should be simpler to instruct.
� Compliance is likely to require a reasonable degree of passive design measures, such as appropriate glazing areas, external shading, internal blinds (in the base build) or increased thermal mass.
Adjustable solar shading at Art House residential development, Kings Cross
CIBSE TM59Benefits of new methodology
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� Naturally ventilated homes will require early stage design appraisals to check whether changes to the building form or solar shading are required.
� Residences that are predominantly mechanically ventilated will have to satisfy the comfort criteria without the MVHR units being in boost mode.
� This may increase the MVHR background ventilation rates in new homes.
CIBSE TM59Ventilation Implications
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Mitigating Overheating and Site ConsiderationsAshley Bateson
Partner, Hoare Lea
July 2017
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We need to design for better performance… not just compliance
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Busy London high street …100 years ago
Camden High Street c.1904
Electrified tram in Camden, c. 1910
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The same street…now
Modern challenges in urban locations: � Traffic noise� Retail activity / local pollution� Air conditioning units / Urban Heat Island Effect
¾ Urban heat island effect / warmer climate
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Glazing proportions in modern apartments can be > 60% of façade area
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Glazing proportions in older buildings generally < 35% of the facade
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Lack of natural ventilation / noise & air quality issues
(Source: Michael Swainson, BRE)
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Site constraints
The design needs to consider the local environment
External noise levels can be a constraint
Window design needs to be carefully considered
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Emphasis on collaboration and early assessments
Example of the review of site opportunities and constraints
(Source: CIBSE)
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MVHR – installation and access challenges
Space required for MVHR, ductwork installations and access to filters (Source: Town and Country Housing Group)
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How do you get flexi-duct through a small hole? …squeeze it!
(Source: Town and Country Housing Group)
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MVHR testing, commissioning and servicing
� Check that specified MVHR flow rates are tested and commissioning and align with the design stage assumptions and modelling expectations.
� Filters will need easy access for replacement
� Heat exchangers will require occasional cleaning to maintain performance
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Community heating systems can be a source of overheating
� Poorly insulated heating pipes can generate hot conditions in service risers
� Many community heating systems are operating 24hrs/day at high temperature
(Source: NHBC Foundation)
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Internal heat gains from equipment and occupants
Ceiling and soffit (showing underfloor heating in apartment above)
Spot light in ceiling
Underfloor heating Heat gains from occupants
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Thank you.
Any questions?
ashleybateson@hoarelea.com
philkelly@hoarelea.com
Modelling Residential Buildings: Comfort, Energy and Well Being
6th July 2017IBPSA England – London event at Hoare Lea, 12-13 Stable Street, London N1C 4AB
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