1PRES_RS_JN-20151207-CIBSE Guide A 2015 and Overheating-CIBSE Yorkshire-Rev A

Yorkshire CIBSE

CIBSE Guide A 2015 and Overheating

Jon Nuttall and Richard Stokes

08.12.2015

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1. Overheating Risk and Thermal Comfort

The problem with minimum compliance

Latest and greatest CIBSE assessment methods

Case Studies

2. Mitigation Strategies and the Cooling Hierarchy

3. Final Thoughts

Contents

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About Hoare Lea

Offices throughout the UK and overseas

Founded in 1862 by Henry Lea

Remains a partnership wholly owned by the Partners

Fee turnover in excess of £50 million a year

Quality Assured to ISO9001

Over 420 design led technical staff, 500 in total

Award winning graduate recruitment and training scheme

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We lead the way in energy strategy planning submissions

At least 50% more energy

strategy submissions than any

other consultant.

We also cover a wide range of

project sectors and sizes of

development

Source: South Bank University

Number of energy strategy submissions made to the GLA

responding to the London Plan: March 2009

Submissions to GLA

Energy Strategy Work

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Our approach to sustainability

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Overheating in Homes

Overheating Risk

Source: The Zero Carbon Hub

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Overheating Risk - Introduction

Thermal Comfort

Thermal comfort is complex and subjective.

Source: CIBSE TM52:2013

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Overheating Risk

Thermal Comfort

Overheating directly leads

to a low levels of thermal

comfort which can:

Lead to unhappy

occupants

Reduce the value of

new buildings

Expose design teams to

risk

Source: The Sunday Times

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Overheating Risk

Source: www.building.co.uk

Source: CIBSE Journal

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Overheating Risk

Introduction

Overheating occurs

when energy transfer

through building

envelope is

unbalanced

Heat Gains

Heat Losses

Source: Bing Images

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Overheating Risk

Heat GainsSource: Zero Carbon Hub: Overheating in Homes

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A Modern Building Problem?

Although Part L has improved the efficiency of buildings in recent

years, a side effect is that increased insulation and reduced levels

of air leakage can limit beneficial heat loss in the summer.

Overheating Risk

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A Modern Building Problem?

Additionally modern buildings are highly glazed…

Overheating Risk

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A Modern Building Problem?

… and local conditions may inhibit the use of windows for

ventilation…

Overheating Risk

Source: Zero Carbon Hub: Overheating in Homes

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A Modern Building Problem?

… whilst some dwellings can be particularly difficult to protect

from excessive solar gains, particularly single aspect West facing

homes.

Overheating Risk

Source: Zero Carbon Hub: Overheating in Homes

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Overheating Risk

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A Contributing Factor

Climate change is contributing to warmer summers.

Overheating Risk

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A Compounding Issue

The urban heat island

effect also effects new

dwellings in cities.

Overheating Risk

Urban Heat Island Effect in London

Up to +10°C Peak Daytime Temperatures

Source: Zero Carbon Hub Source: Arup, UK Space Agency, University College London

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Cumulative Effects

Overall, the risk of

overheating increases

with design, occupation

and surroundings.

Overheating Risk

Design

SurroundingsOccupation

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Assessing Overheating Risk

Overheating Risk

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Overheating Risk

Part L Criterion 3

The Building Regulations (Part L1A

criterion 3) only require simplified

calculations for new homes.

SAP Methodology determines the

‘likelihood’ that internal

temperatures exceed a threshold.

It is minimum compliance and also

mandatory for new dwellings.

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Overheating Risk

Part L Criterion 3Source: SAP v9.92

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Overheating Risk

UK – Average Temperature Data (1910 to 2015)

0

5

10

15

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5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

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Temperature (°C)

Average Temperatures June July August

SAP uses the average

from this period

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Overheating Risk

UK – Peak Temperature Data (1910 to 2015)

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Temperature (°C)

Average Temperatures June July August

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5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

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Temperature (°C)

Peak TemperaturesJune July August

+6°C

In reality, peak

temperatures are much

higher on average…and

could be even higher…

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Overheating Risk

The Problem

It is based on:

SIMPLIFIED models

AVERAGE internal temperatures

AVERAGE monthly weather data

HISTORIC weather

RURAL weather

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Overheating Risk

The Problem

The Building Regulations (Part L2A

criterion 3) only considers solar heat

gains and is just for guidance.

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Overheating Risk

CIBSE Guide A 2006

Considers frequency of overheating

Uses 3D modelling

Dynamic hourly calculations

Results for each room

Proven in industry

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Overheating Risk

CIBSE Guide A 2015 / CIBSE TM52

For naturally ventilated buildings

Considers frequency, severity and a

maximum limit for overheating

Uses adaptive comfort, recognising

people accept warmer indoor

temperatures when its warmer outside

Customisable so can account for future

weather and urban heat island effect

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Overheating Risk

Adaptive What?

Research shows

people accept

warmer indoor

temperatures when

its warmer outside.

Therefore the

acceptability limits

(or comfort

threshold) should

also change.Source: CIBSE TM52: 2013

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Overheating Risk

CIBSE Guide A 2015 / CIBSE TM52

3 criteria to assess the risk of overheating.

A room or building that fails any two of the three criteria is

classed as overheating.

1) The number of hours that the operative temperature

can exceed the threshold by 1°C or more during the

occupied hours of a non-heating season (1 May to 30

September) shall not exceed 3%.

2) The severity of the overheating within one day must not

exceed a daily limit. This limit is defined in CIBSE TM 52

Section 6.1.2 (b).

3) The absolute maximum daily temperature of a

room is 4°C above the threshold.

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A Note on Other Documents that Include Overheating…

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Case Study: Kirkstall Forge

Overheating Risk

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Overheating Risk

Example Analysis Part L1A Overheating vs. CIBSE Guide A

Kirkstall Forge, Leeds

Large Mixed Use Development

900 + New Homes

Hoare Lea providing Building Services, Acoustics and

Sustainability

Anticipated completion of first phase in 2017

http://www.kirkstallforge.com/

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Overheating Risk

Example SAP Analysis

Assessments carried

out using NHER Plan

Assessor v6.1.2

Assessing Part L 2013

Compliance

Criterion 3 Analysis:

1-2 Bed ~ 2.5 ACH

3-4 Bed ~ 2 ACH

?

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Overheating Risk

Example CIBSE Guide A 2006

Analysis

Assessments carried out

using IESve 2015

Bespoke thermal comfort

modelling

Analysis highlighted a

greater risk of overheating

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Overheating Risk

Example CIBSE Guide A 2015 Analysis

Assessments carried out using IESve 2015

Analysis indicated that a lower air change rate could be used

to minimise overheating risk

Source: CIBSE TM52: 2013

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Overheating Risk

CIBSE Guide A vs Part L – Analysis Summary

Entire Dwelling

Part

L1A

Cri

teri

on

3

Bedrooms Living Rooms

CIB

SE

Gu

ide A

2006

CIB

SE

Gu

ide

A

2015

Pass

All Pass

Pass

PassPass

Fail

Fail Fail

Fail

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Overheating Risk

Overheating Risk Mitigation

Cooling Hierarchy

1. Minimise Internal Heat Generation

2. Limit heat entering the building

3. Managing the heat within the building

4. Passive ventilation

5. Mechanical ventilation

6. Active cooling systems

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Overheating Risk

Minimise Internal Heat Generation

Recent beneficial trends:

Efficient internal equipment

Cloud based IT

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Overheating Risk

Limit Heat Entering the Building

• External shading / shutters

• Reduced glazing extent

• Tinted glass

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Overheating Risk

Limit Heat Entering the Building

• Interstitial shading within glazing

• Fritting

• Dynamic ‘smart’ glass

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Overheating Risk

Limit Heat Entering the Building

• ‘Light’ Internal Blinds

• ‘Light’ External shutters

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Overheating Risk

Thermal mass relies on

cool summer evenings

Less likely to occur

with urban heat island

effect

Managing Heat Within the Building

Source: Blue Ridge ICF

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Overheating Risk

Passive Ventilation

Openable windows

Stack ventilation

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Overheating Risk

Mechanical Ventilation

Can be limited by other measures

Spatial and cost implications

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Overheating Risk

Active Cooling

Excluded from Part L calculations, must comply without cooling

Can be designed out through passive design measures

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Summary

Overheating Risk

FeatureBuilding Regulations

Part L Criterion 3

Best Practice Dynamic Modelling

(CIBSE Guide A 2015)

Detail Fixed assumptions Fully flexible 3d model

Accuracy Monthly average temperatures Hourly inputs and outputs

RiskDoes not assess risk.Actual temperatures

can vary significantly from estimates

Modelling is predictive to assess the likely risk

of overheating

Weather Data Historical / average dataWorst case design summer year and future

weather can be used

ComfortOnly air temperature for dwellings and solar

gains for other buildings

Can report on adaptive thermal comfort and

percentage of people dissatisfied

Frequency Not identified Frequency of events can be identified

Severity Not identified Severity of events can be identified

Peak Only average data used Peak temperatures can be identified

Ratings None presently, may be input into HQMContributes to BREEAM and WELL Building

Ratings

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Final Thoughts

Overheating Risk

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Overheating Risk

Outdoor Thermal Comfort

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Urban Heat Island Effect

More Heat Rejection

Warmer Outdoor

Environment

Increased Cooling Demand

Increased Energy Use

Respiratory

difficulties

Heat cramps

Exhaustion

Heat stoke

Heat related

mortality

General

discomfort

Overheating Risk

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Overheating Risk

An Indicator for Outdoor Thermal Comfort

The temperate of dark materials can be several degrees hotter

than light materials

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Overheating Risk

Material and Landscaping Opportunities

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Overheating Risk

Solar Reflective Index (SRI)

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Overheating Risk

Opportunity

There is enough waste heat in London to

meet the existing heating demand. This heat

is from:

Buildings

Geothermal

Infrastructure

Transformers

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Overheating Risk

Opportunity

XXX

Source: London Borough of Islington

Source: Ooms Civiel (Netherlands)Source: GLA Secondary Heat Report

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Overheating Risk

Example: New York Cool Roofs

80°C

0°C

40°C

60°C

20°CWhite Painted Roofs

Black Painted Roofs

Surf

ace T

em

pera

ture

s

Source: www.coolroofs.org

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Overheating Risk

Example: 20 Fenchurch (Walkie Scorchie)

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Thank you.

Any questions?

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