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European Real Estate Society 22nd Annual Conference, 24th-27th June 2015, Istanbul, Turkey

Dipl.-Ing. Sebastian Johann

Prof. Dr. Björn-Martin Kurzrock

Unit of Real Estate Studies

Development of refurbishment concepts – The case of multi-family houses from the 1970s in Western Germany

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• European housing stock dominated by properties built before 1980s

• often high backlogged maintenance • far behind current technical and social requirements

• Multi-family houses from the 1970s in Germany as relevant typology

• about 2.4 million dwellings • often without any major refurbishment measures • high priority for refurbishments in future

• Refurbishments create technical, functional, energetic and aesthetic improvements

Picture source: IWU 2012.

Motivation

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• Introduction of two-level process for developing supply and demand-oriented refurbishment concepts for residential buildings

• Case of multi-family houses from 1970s in Western Germany

• Identifying prioritised refurbishment measures in roof area

Picture source: Colourbox.

Purpose of the paper

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4 Source: Own representation.

Data

Typical characteristics of multi-family houses

from the 1970s and user requirements

Data of housing associations

Expert interviews no=13

Building typologies no=13

Usage based Energy passes

(Techem) no=13.711

Data of IWU no=229

Generally accepted engineering

standards from construction time

Research about life time of building

components

GdW living matrix model

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5 Sources: Own representation based on IWU 2012, p. 35; Wohnbau Lörrach 2013; GdW 2008, p. 66.

Process for developing refurbishment concepts

Typology level Individual building level

Typology characteristics Building characteristics

Refurbishment concept

User requirements

Survey on site (existing and potential new residents)

Requirement profile

Refurbishment measures

Recommendations for action

User requirements

Targets of the owner

Application recommendations

for action

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• Typically constructed with flat roofs (warm and cold roofs)

• Typical lifetimes of flat roof components

• Needs for action: • Full replacement of flat roof construction in case of material obsolescence • Repair of minor damages

Sources: Own representation based on building lifetime literature.

Typology level: Step 1 Needs for action for the buildings

Steel-reinforced concrete

roof

Building component 1974 1984 1994

roof

Vapour barrier

Roof drain (stainless steel,

synthetic)

Waterproofing with

roofing film

50 y.

58 y.

2024 2034 204420142004

> 80 y.

Light dome

25 -Thermal insulation 50 y.

20 - 40 y.

25 -

30 -

20 - 48 y.

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Target-group (no.) Domestic (9) Domestic (10) Domestic (11) Domestic (12) Domestic (13)

Type of Household Singles, couples Singles, couples Singles, couples Singles, couples Families,

multiperson

Age (in years) < 30 < 30 30-44 45-64/from 65 all

Purchasing power low middle middle to high low to

high/middle low to high

Residential

quality

Normal

High – – –

Dwelling

Modern

doors/floors

Modern layout

Easily accessible

Technology Energy saving –

Energy Modern efficiency

Renewable – –

Legend Standard Added value No/little interest – No information Sources: Own representation based on GdW 2013, pp. 122-126.

Typology level: Step 2 Needs for action of the users

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• “Must-be“-requirements: damages and material obsolescences

• One-dimensional requirements: explicit described requirements of the users

• Attractive requirements: attributes with added-value for the users

Source: Own representation.

Typology level: Step 3 Prioritisation of needs for action by the Kano model

Requirement group Area Measure Condition

“Must-be”-requirements Roof

Fully replacement of roof construction

Damages in roof construction

Repair of roof Minor damages in roof construction and adequate thermal insulation

Requirement group Area Measure Target-group 1 2 3 4 5 6 7 8 9 10 11 12 13

One-dimensional requirements

Roof

Creation of contemporary thermal insulation – – – – – – –

Creation of modern layouts – – – – – – – –

Attractive requirements Roof – – – – – – – – – – – – – –

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Measure Unit Investment cost [€]

Min. Ø Max.

Replacement of light domes, size 0,5-1,0 m² piece 1,200 1,350 1,500

Repair of roof drainage (zinc) m² 12 13 15

Repair of sealing sheets m² 65 70 81

Add new 3-layer bitumen sheeting m² 70 77 90

Add new 3-layer bitumen sheeting with gravel m² 90 99 110

Add new 3-layer bitumen sheeting, 16-20 cm insulation, gravel m² 126 144 156

Add new synthetic roofing membrane, gravel m² 85 95 106

Add new synthetic roofing membrane, insulation, gravel m² 110 124 140

Add new EPS insulation m² 41 44 48

Addition of story m² tfa 1,600 - 2,100

Source: Schmitz et al. 2014, pp. 191-198. Costs for cost groups 200-500 including value-added tax.

Typology level: Step 4 Refurbishment measures and costs

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10 Source: Own representation. M = “must-be” recommendations; O = one-dimensional recommendations

Typology level: Step 5 Recommendations for action

No. Area Current situation Target Measure

Roof

1) Functional roof waterproofing with minor damages; existing thermal insulation 2) Functional roof waterproofing with minor damages and functionality; no existing thermal insulation

1) Repair damages 2) Repair damages, improve thermal insulation

1) Repair roof waterproofing 2) Repair roof waterproofing; insulate roof with 18 cm heat conductivity group 035 as unventilated roof

Roof 1) Roof waterproofing damaged 2) Damped roof construction

Repair damages, improve thermal insulation

Demolish existing roof waterproofing; insulate roof with 18 cm heat conductivity group 035 as unventilated roof

Roof Functional roof waterproofing; no existing thermal insulation

Improve thermal insulation

Insulate roof with 18 cm heat conductivity group 035 as unventilated roof on existing roof waterproofing

Roof Demand for modern layouts Create new living space with modern layouts

Addition of story in timber frame construction

M1

M2

O1

O2

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11 Sources: Own representation based on IWU 2012, p. 35; Wohnbau Lörrach 2013; GdW 2008, p. 66.

Individual level

Typology level Individual building level

Typology characteristics Building characteristics

Refurbishment concept

User requirements

Survey on site (existing and potential new residents)

Requirement profile

Refurbishment measures

Recommendations for action

User requirements

Targets of the owner

Application recommendations

for action

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• Relevance for property owners (e.g. housing corporations, municipalities, owner communities or foreign investors)

• Assess building characteristics, needs for action and calculate capital expenditures more efficiently

• Implement demand-oriented refurbishment measures more efficiently

• Improved transparency for building owners, which could help to enhance refurbishment rates

Picture source: school-technology-services.com

Practical implications

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• Process useful for developing refurbishment concepts for other relevant building typologies

• Interconnection of results for several buildings on typology level with level of districts

• Indications for the optimum timing of refurbishment measures

• Limitations • Recommendations for action derived and calculated from a broad building stock • Recommendations may vary for individual buildings

Picture source: cep-probation.org

Future research and limitations

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Thank you for your attention.

Do you have any questions or remarks?

Dipl.-Ing. Sebastian Johann

Tel.: +49 631/205-5670

Email: sebastian.johann@bauing.uni-kl.de

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Appendix

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Ideal-typical constructions of warm and cold roofs

Sources: Own representation based on building typology literature; Dierks and Wormuth 2012, p. 690.

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The living matrix model

Picture source: GdW 2013, p. 21.

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• Location

• Layout

• Quality

• Dwelling size

• Equipment rooms

• Equipment bath room

• Equipment kitchen

• Equipment logistics

• Equipment open space

• Equipment community

• Equipment technology/energy

• Equipment other

• Equipment building

• Price segment

Source: GdW 2013, p. 122.

The living matrix: Housing characteristics

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Limitations • Limited transparency (process, methodology, classification of people) • Heterogeneities in living concepts hidden • Persons in overlaying living concepts hidden • Eastern and Western Germans summarised • Major society and migrants summarised

Reasons for selection

• Widely used by housing associations and municipalities • Specific focus on housing • Connection of requirements and willingness-to-pay • Topicality • Free availability

The living matrix model: Limitations and reasons for selection