Residential Modelling using CIBSE TM59 with Case … 2017 / A.Bateson / Residential overheating 26...

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


“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

July 2017 / A.Bateson / Residential overheating 28

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


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


CIBSE TM59Comfort compliance criteria


Assessing thermal comfortAir temperature vs operative temperature


� 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


� 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.



� 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.



� Maximum – 34.6oC, Minimum -6.7oC

CIBSE TM59Design Summer Year (DSY01) 2020s High emissions 50% scenario



� Hours >26oC – 183 across 31 separate days



Over 26oC between 09:30 – 20:30


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)


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


Scenario 2 – Reduced window opening, larger MVHR units with no external shading


Apartments showing some overheating risk

60-100l/s for living rooms 36l/s for bedrooms


Scenario 3 - Larger MVHR scenario with external shading added


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



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


Step 1 – Choosing the high-risk apartments

Case Study 2Analysis of multiple exposed high-rise apartment blocks



Scenario 1 - Natural ventilation with restrictors, standard MVHR flowrates



Scenario 2 – Enhanced natural ventilation (greater opening angle), standard MVHR flowrates



Scenario 3 – Enhanced natural ventilation, enhanced MVHR flowrates


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 3Modelling vs the real world…

Key issues found in one project

� Co-ordination with blinds




� Co-ordination with desks (& occupancy!)






� Internal reveals






� Internal reveals

� Sensor & controls locations



� 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


� 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


Mitigating Overheating and Site ConsiderationsAshley Bateson

Partner, Hoare Lea

July 2017


We need to design for better performance… not just compliance


Busy London high street …100 years ago

Camden High Street c.1904

Electrified tram in Camden, c. 1910


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


Glazing proportions in modern apartments can be > 60% of façade area


Glazing proportions in older buildings generally < 35% of the facade


Lack of natural ventilation / noise & air quality issues

(Source: Michael Swainson, BRE)


Site constraints

The design needs to consider the local environment

External noise levels can be a constraint

Window design needs to be carefully considered


Emphasis on collaboration and early assessments

Example of the review of site opportunities and constraints

(Source: CIBSE)


MVHR – installation and access challenges

Space required for MVHR, ductwork installations and access to filters (Source: Town and Country Housing Group)


How do you get flexi-duct through a small hole? …squeeze it!

(Source: Town and Country Housing Group)


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


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)


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


Thank you.

Any questions?

[email protected]

[email protected]

Modelling Residential Buildings: Comfort, Energy and Well Being

6th July 2017IBPSA England – London event at Hoare Lea, 12-13 Stable Street, London N1C 4AB

Residential Modelling using CIBSE TM59 with Case … 2017 / A.Bateson / Residential overheating 26...

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