atlas@eurac.edu
GENERAL INFORMATION RENOVATION PROCESS RETROFIT SOLUTIONS EVALUATION

Half-timberframed house in Alken, Belgium

Ridderstraat 10

B-3570

Alken, Belgio

architetto

Liliane Vandeput
Minderbroederstraat 52/3, 3500 Hasselt

Owner

Tom en Katrien Govaerts-Maes
Ridderstraat 10 – B 3570 Alken

User

idem

Contact Details

Nathalie Vernimme
Flanders Heritage Agency
nathalie.vernimme@vlaanderen.be
0032475814291

Other Information

The data were collected from the architect with permission of the owner in the context of a research project initiated by the Flanders Heritage Agency on the energy efficiency of heritage buildings used for housing. The research was conducted by ANTEA The research results are published in Dutch: Verdonck P., Beel R., Vermeiren E. & Grieten B. 2017: Energiezuinige maatregelen in monumenten met woonfunctie, Onderzoeksrapporten agentschap Onroerend Erfgoed 70/1 ISSN 1371-4678 and online available: https://oar.onroerenderfgoed.be item/450

Related publications
Verdonck P., Beel R., Vermeiren E. & Grieten B. 2017: Energiezuinige maatregelen in monumenten met woonfunctie, Onderzoeksrapporten agentschap Onroerend Erfgoed 70/1 ISSN 1371-4678 and online available: https://oar.onroerenderfgoed.be item/450.
Half timber framed, rendered vernacular detached building with late 17th century core, expanded on both sides in the 19th century. The building was out of use and in a very bad state at the moment of renovation. The purpose of the total building renovation (including improvement of energy performance and comfort) was residential reuse. The building renovation comprehended renovation of the roof, the external walls and windows, floor insulation as well as some other interventions such as introduction of a new condensing gas wall boiler, underfloor heating for the ground floor and radiators for the first floor.
GENERAL INFORMATION RENOVATION PROCESS RETROFIT SOLUTIONS EVALUATION
Energy performance
no data available

Climate Zone Climate zone CfB

Altitude 38 s.l.m.

HDD 2033

CDD 59

Protection level Listed

Conservation Area:
No

Level of Protection:
protected monument

Building age 1600-1700

Year of last renovation:
2016

Year of previous renovation:
0

Building use Residential (rural)

Secondary use:
NA

Building occupancy:
Permanently occupied

Number of occupants/users:
4

Building area Net floor area [m²]: 288,13

Building typology:
Detached house

Number of floors:
2

Basement yes/no:
Si

Number of heated floors:
2

Gross floor area [m²]:
329,9

Thermal envelope area [m²]:
1002,89

Volume [m³]:
1241,0

NFA calculation method:
Useful area (BE)

Construction type
Timber frame

External finish:
Rendered

Internal finish:
timberframe/ rendered - plastered on substructure

Roof type:
Pitched roof

+ MORE - LESS

RENOVATION PROCESS

Architecture

BUILDING DESCRIPTION

Half timber framed, rendered vernacular detached building with late 17th century core, expanded on both sides in the 19th century. The type of architecture is a double house with an increased ground floor. It consists of 8 bays and one building layer. The building is situated in Alken in the province of Limburg (Flanders). The structure of the building, the various construction traces in situ and the cadastral investigation showed that the half-timbered house probably did not have an agricultural function, and was not part of a larger agricultural entity. The building knew on the contrary a trade and/or craft function in combination with a residence. According to the cadastral research, the owners were successively an innkeeper, a baker and a miller. In 1888 there was a conversion of the half-timbered house to a private school with a residence. The half-timbered construction was once typical and characteristic for the entire building territory of Alken.
Urban context
Alken is a small village with 11.500 inhabitants situated in the Fruitregion Haspengouw in the province of Limburg in Flanders, Belgium. The village was first mentioned in documents in 1066. In developed in the valley of the river Herk. The half-timbered house, is situated in the village centre. The house has today largely retained its semi-isolated character.

State of repair

Conditions of the envelope
From a physical point of view, the building was in a very poor condition and almost completely stripped down to the bearing structure. Some valuable interior elements such as wooden doors, floortiles and remains of 17th century joinery were still in place.
Description of pre-intervention building services
The half-timbered house had virtually no modern technical equipment, with the exception of some under construction placed electrical lines. Heating was done with fireplaces, idem for the production of hot water.

HERITAGE SIGNIFICANCE

ELEMENTS WORTHY OF PRESERVATION
From a heritage point of view some elements were considererd worhty of preservation : -The lattice and roof structure. -Visualization of the 17th and 19th century cores. -Use of artisanal techniques and materials of the same kind and dimensions. -The remnants and traces of the 17th-century joinery. -The wooden style and lattice work of the inner walls -Reuse of the floor tiles if possible.
Heritage Value Assesment
The building is one of the only 3 remaining half timberframed houses in the towncentre of Alken. It has an important historical and architectural value. It appeared in old maps such as the Ferrariskaart (1771 – 1777), and the Buurtwegenatlas (ca. 1840). Originally it was situated in the more rural fringes of the village. Up til today it hes kept this semi isolated position. The building also has a socio-cultural value as the half timbered building represents a local vernacular building tradition with its own esthetical and visual qualities. The house was protected as monument on november 4th 2002.

Aim of retrofit

Renovation + Extension
The building was out of use and in a very bad state at the moment of renovation. The purpose of the total building renovation (including improvement of energy performance and comfort) was residential reuse. The passage on the left of the building was retained. A kitchen was built on the rear façade. This new building volume is modern and can be visually distinguished from the original building. The building renovation comprehended renovation of the roof, the external walls and windows, floor insulation as well as some other interventions such as introduction of a new condensing gas wall boiler, underfloor heating for the ground floor and radiators for the first floor. There is added a Ventilation system D balanced ventilation with heat recovery
Was there any change of use?
Originally the building had a craft/trade function combined with residence. It was later converted to a private school with residence. The residence function is retained. After the renovation, the two floors would be in use. Previously, the attic was not inhabited - it was empty.
Was the intervention planned following a step-by-step approach?
The interventions were supervised by the heritage authorities and followed the approach as set in the regional legislation. All interventions were discussed with the heritage consultant and implemented in the conservation-restoration file.
Lessons learned
It is not evident to test a methodology with private owners. Most of them have already a very precise idea of what interventions they want and what their priorities are. Heritage values is not always number one on the list. The budget is also a key indicator in how and what choses are taken.
Stakeholders Involvement
Public sector
Flanders Heritage Agency
Koningin Astridlaan 50 bus 1, 3500 Hasselt
info@onroerenderfgoed.be
Research Development
Antea Belgium nv
Roderveldlaan 1 2600 Berchem (Antwerpen)
Architect
Liliane Vandeput
Minderbroederstraat 52/3, 3500 Hasselt
Conservation Consultant
Erfgoed & Visie
Lierselei 84 B -B 2390 Malle
architecten@erfgoed-en-visie.be
Energy Consultant
Stiev Schockaert
Achterstraat 6b, B-9550 Herzele
info@igenia.be
Tools used
Was the renovation process done following a specific methodology? the research project tested a methodology for the implementation of energysaving interventions in heritage buildings similar to (but less complex than) the methodology of EN 16883.
Energy calculation EPB-software v8.0.4
Hygrothermal assessment Blowerdoor (after renovation)
Life Cycle Analysis (LCA) A life cycle analysis was not carried out but the renovation was done with respect for local grown materials.

RETROFIT SOLUTIONS

External Walls

outer wall made of wooden framework filled with loam and brickwork, rendered with loam

outer wall made of wooden framework filled with loam and brickwork, rendered with loam

For energetic reasons, the loam and brickwork of the outer walls has been replaced by a combination of a framework and mineral wool insulation and wood wool fiber boards. The exterior finish of clay plaster was retained as it has heritage value. A pipe pillar was provided on the inside.

The visual perception of the wall has not altered. The modifications made to the wall (insulation on the inner side of te wall) in function of energy-efficiency were approved by the conservation authority.

U-value (pre-intervention) [W/m2K]: 1,93 W/m²K U-value (post-intervention) [W/m2K]: 0,29 W/m²K
More Details
Original wall build-up
Render - Outermost finishing loam :
 30 mm
Other - filling of framework structure: loam + wooden fence (oak):
 120 mm
Plaster - innermost : plastered:
 30 mm
Retrofitted wall build-up
Render - Outermost finishing loam:
 20mm
Insulation - framework+ fiberboardinsulation 40mm+60 mm:
 100 mm
Other - framework + rock wool insulation 63mm+60mm:
 123 mm
Wood panelling - OSB 18mm+ frameworkelements 43mm+plasterboard 2X12,5mm:
 86 mm


Windows

casement window

casement window

The windows were in a very bad state. There were windowremains from the 17th, 19th en even 20th century. At some places the windows were absent. The remaining wooden joinery in the half-timbered house has been completely replaced by typologically appropriate - to existing model-, new joinery. The new windows have double glazing (adjustment of the profile thickness).

Substitution of all windows to existing 17th century model with insertion of double glazing (U=1,1W/m2K).

Existing window U-value Glass [W/m2K]: 5,7 New window U-value Glass[W/m2K]: 1,1 Existing window U-value Frame [W/m2K]: 2,36 New window U-value Frame [W/m2K]: 1,66
More Details
Existing window type Casement window
Existing glazing type Single
Existing shading type NA
New window type Casement window
New glazing type Double
New shading type NA

Other interventions

ROOF

GROUND FLOOR

OTHER

MEASURES TO INCREASE AIRTIGHTNESS

ROOF

The original construction was almost completely preserved. The roof, a saddle roof with wolf end, was covered with a temporary roof construction at the time of renovation. This was placed to protect the building against further water seepage and consequential damage, awaiting the final restoration works. Because of its original character and architectural-historical value, the roofstructure preferably had to remain visible on the inside including the rafters, especially in the late 17th century core. Therefore it was preferable to insulate according to the sarking roof principle. To this end, a planking was placed on the rafters. In the 19th century section the insulation was placed between the rafters.

The visual perception of the roof has not altered. The modifications made to the roof in function of energy-efficiency were approved by the conservation authority.

U-value (pre-intervention) [W/m2K] 5,07 U-value (post-intervention) [W/m2K] 0,26
More Details
Original roof build-up
Tiles - 'Boomse' Tiles:
 20 mm
Retrofitted roof build-up
Tiles - type Pottelberg 451 vieilli:
 17 mm
Other - wood fibre insulation board:
 22 mm
Other - wood fibre insulation:
 120 mm
Other - Airgap- pipe pillar:
 22 mm
Other - plasterboard:
 1 mm
GROUND FLOOR

Since all floors were disassembled or removed, the opportunity could be used to provide a new stable, waterproof and insulated floor structure. The floor was insulated in such a way that the current EPB requirements are met.

From the conservation point of view it was regretted that the floor tiles were not reused. They were not original and dated from 19th en even 20th century but they were typical for an earlier renovation.

U-value (pre-intervention) [W/m2K] 0,76 U-value (post-intervention) [W/m2K] 0,3
More Details
Original groundfloor build-up
Other - Floor tiles:
 10 mm
Retrofitted groundfloor build-up
Concrete slab - concrete slab- underfloor:
 200 mm
Other - filling layer:
 50 mm
Damp Proof Membrane - damp proof membrane:
 1 mm
Insulation - PUR:
 60 mm
Damp Proof Membrane - damp proof membrane:
 1 mm
Other - screed:
 70 mm
Other - floor tiles/ wood:
 20 mm
OTHER

New doors/ insulation inner walls and floorinsulation (first floor)

The new doors have been executed according to current standards. the visual impact on the heritage values is acceptable. The floor insulation on the first floor and the insulation of the inner walls was approved by the heritage agency

MEASURES TO INCREASE AIRTIGHTNESS

In the situation before renovation the building was leak. There were multiple openings in windows, roofs, walls.

Airtightness (pre-intervention) [ach@50Pa] 12,00 m³/hm² Airtightness (post-intervention) [ach@50Pa] n5019: 3,0 h-1 - v5020: 4,9 m³/hm²

HVAC

HEATING

VENTILATION

DOMESTIC HOT WATER

HEATING

Before the renovation there were only stoves for local heating. after the renovation the Ground floor is heated with underfloor heating and the First Floor is heated with radiators

There were no important interior wall elements that needed preservation. So the radiators where not a problem. But the floor tiles on the ground floor were not reused after the installation of the underfloor heating. They were replaced by a new floor.

More Details
New primary heating system
New system type Condensing
Fuel Gas
Distribuition system Radiating floor
Nominal power (1.6 - 35 kW heating, 33.5 kW domestic hot water) kW
VENTILATION

Ventilation system D balanced ventilation with heat recovery

The installation of a ventilation system is obligatory in case of total renovation.

More Details
Original roof build-up New ventilation system
Type ventilation system Centralized
Type flow regime
Heat recovery Si
Humitidy recovery No
Nominal power kW
Electric power kW
Control system
DOMESTIC HOT WATER

33.5 kW domestic hot water

acceptable

More Details
New DHW system
Type with heating system
Hot_water_tank No
With heat recovery No

Energy Efficiency

Energy Performance
Energy performance certificate: E94
Voluntary certificates: No
Energy Use
Consumption_estimation_Before: 103264 kWh/y

Primary Energy
Consumption_estimation_Calculation_method: Steady state simulation (e.g. EPC, PHPP)
Documents:
results EPB .jpg
Consumption_estimation_Before: 170358 kWh/y
Measured Parameters
Construction
Type_of_monitoring: Punctual

Internal Climate

Temperature

The building owner evaluates the temperature as comfortable.

Indoor Air Quality

The building owner evaluates the indoor air quality as pleasant.

Daylight

The building owner evaluatde the daylight supply as sufficient, even in winter.

Acoustic Comfort

The building owner and guests evaluate the acoustic comfort as positive. The appartments towards the courtyard have better acoustic conditions, as they are turned away from the street