• Main focus on new dwellings in the battle against the CO

(1)

The importance of physical and behavioural aspects when predicting energy savings in retrofitted dwellings

3-4 June 2010, Building Physics PhD-seminars 1

Mieke Deurinck Promotor: Staf Roels Co-promotor: Dirk Saelens

Problem statement

• Main focus on new dwellings in the battle against the CO

₂

- emissions (e.g. by regulations (K- and E-level))

• Less focus on the existing housing stock that generally consists of old and badly insulated houses with outdated heating systems

• Moreover, new dwellings show marginal benefits due to the decreasing grow rate So existing dwellings have to be targeted

3-4 June 2010, Building Physics PhD-seminars

decreasing grow rate. So existing dwellings have to be targeted in order to meet the demands of the Kyoto protocol

Æ How much profit is there to gain in the energy efficient retrofit of existing residential buildings?

2

(2)

retrofit of existing residential buildings?

In theory

Bottom-up models have already been developed that estimate the energy saving potential of the existing housing stock, based on standard calculation methods with fixed user behaviour

e.g. EN-ISO 13790: 1-zone-model of the protected volume, fixed infiltration and ventilation rates, simplified internal gains, fixed internal temperature (18°C)

3

In practice

Different energy efficiency projects show disappointing results:

Real energy savings are generally lower

than energy savings predicted with standard calculation methods

Problem statement

Possible reason:

The simplified models are not able to represent certain physical and

Aim of the research

Obtain an overview and reveal the importance of physical and behavioural aspects that are not incorporated in energy savings predicted with (simplified) reference calculation models

behavioural aspects that are typical when retrofitting dwellings

predicted with (simplified) reference calculation models

(3)

Research content

BEHAVIOURAL ASPECTS

-REBOUND/TAKEBACK effect

due to the price reduction, part of the theoretical energy saving is

Energy consumption

~ cost

before retrofit

∆E

p p gy g

taken back by the inhabitants as an increase in comfort

E-level

after retrofit

∆Etheoretical

BEHAVIOURAL ASPECTS

due to the price reduction, part of the theoretical energy saving is

Research content

p p gy g

taken back by the inhabitants as an increase in comfort

Energy consumption

~ cost

∆E

before retrofit

after retrofit ∆E_real

9higher temperature 9heating more rooms 9wear lighter clothes 9…

E-level

∆Etheoretical

after retrofit

after retrofit

~ rebound

(4)

-variations in

OCCUPANT BEHAVIOUR

can cause large variations on the energy consumption for space heating and hot water production

Æ

Different parameters: age, profile, number of occupants, …

Energy consumption

fixed user behaviour Realistic user behaviour

E-level

Realistic user behaviour

Research content

BEHAVIOURAL ASPECTS PHYSICAL ASPECTS PHYSICAL ASPECTS

- in reality dwellings are heated intermittently (time) and partially (space)

Æbuilding and heating season averaged indoor temperature θ_irarely equals 18 °C in badly insulated dwellings : overestimation of θ_i

Ætemperature and thus, heat losses, in the unheated zones increase after insulation measures: θ_irises with unchanged heating pattern

Building averaged

3-4 June 2010, Building Physics PhD-seminars E-level

g g

indoor temperature θ_i

fixed heating pattern Variations in heating patterns

(5)

Research content

BEHAVIOURAL ASPECTS PHYSICAL ASPECTS PHYSICAL ASPECTS

- in reality dwellings are heated intermittently (time) and partially (space)

Æbuilding and heating season averaged indoor temperature θ_irarely equals 18 °C in badly insulated dwellings : overestimation of θ_i

Ætemperature and thus, heat losses, in the unheated zones increase after insulation measures: θ_irises with unchanged heating pattern

- 2 or 3-dimensional transmission heat losses

are mostly not incorporated

i t th U l th l b id i th f i t i i l ti

into the mean U-value e.g. thermal bridges in the case of interior insulation - insulation measures can effect the

efficiency of the heating system, the radiative temperature (~comfort), infiltration/ventilation rate, …

Short-term work

• Building averaged internal temperature – Via case studies:

Directly collecting/measuring indoor temperatures

• Directly collecting/measuring indoor temperatures

• Calculating indoor temperatures based on measured energy consumptions

– Via simulation: impose several pre-determined heating patterns on a number of multi-zone reference dwellings in TRNSYS (at least day- and nightzone)

Æ Variable building averaged indoor temperature as input for simplified models?

• Impact of thermal bridges on transmission heat losses – Using TRISCO (2/3D calculation tool)

– For a number of reference dwellings e.g. interior insulation

(6)

3-4 June 2010, Building Physics PhD-seminars 11