The Existing District for Tomorrow, a concept for quick and clean passive house renovation for mass housing in the Netherlands

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1 The Existing District for Tomorrow, a concept for quick and clean passive house renovation for mass housing in the Netherlands Authors: Herwin Sap¹, MSc; Prof. Ronald Rovers¹, MSc; Maurice Vincken², BBE Affiliation: 1> Zuyd University, Fac. Bèta Sciences and Technology, Sustainable Building Group, 2> Housing corporation Heem Wonen, Kerkrade, The Netherlands Tel: ++31-(0) herwin.sap@zuyd.nl, ronald.rovers@zuyd.nl, m.vincken@heemwonen.nl Abstract Since the 1920 s the housing stock in the Netherlands is dominated by low-rise mass housing development. At first by municipalities and housing corporations, later also by project developers. This has resulted in only a few, very common, typologies which have been used for a large number of houses throughout the Netherlands. The appearance of these houses may vary, but the structure and floor plans are mostly identical. A very common typology that is developed from the 1950 s onwards is the doorzonwoning ; a type of terraced housing with an open floor plan and large windows in both façades. This typology dominated the mass housing design of the 1970 s and 1980 s. These dwellings are originally barely insulated and contain due to the method and speed of construction- many air leaks. In spite of later renovations and retrofit insulation of these houses, their energy performance is inferior. Despite differences in appearance, detail and energy performance, these houses are quite similar to contemporary mass housing design concerning dimensions and floor plan. The quantity, popularity, structure and potential for improving the energy performance of this housing typology makes it highly attractive for the development of a passive house renovation concept for mass production. Such a concept, with the potential to be repeated on a much larger scale, has been developed for the passive house renovation of 153 social houses (from 1974) in Kerkrade West, the Existing District for Tomorrow. Typically for this concept is the use of prefab timber-frame elements for façades and roof. Piping and wiring is integrated in these prefab elements. The prefab roof elements are covered with integrated PV and thermal solar panels. This concept makes it possible to renovate a terraced house into a passive house within 10 days with minimal inconvenience for the tenants. The houses remained inhabited during the whole renovation process. This paper will elaborate on the process of development and engineering of the mentioned passive house renovation concept, the experiences of using this concept in Kerkrade West, the first results of monitoring of the energy performance and the potential for further application of this concept. Context The sustainably targets of the Dutch Government for 2020 are; 30% reduction of CO2 emission, 20% reduction of energy use and 20% production of sustainability energy. In

2 order to meet these targets a substantial transition towards sustainability is needed in the built environment. In 2012 a national program 1 for energy reduction in the existing building stock has been launched. This program strives to improve 2,4mjn houses and other buildings before 2020 and make them averagely 20-30% more energy efficient. In this strive the Dutch Housing corporations play an important role. These housing corporations are non-profit organisations with a long-term planning and own 1/3 of the Dutch housing stock. The housing corporations have agreed to reduce the use of gas in their housing stock with 20% and the total use of energy with 33% towards If we focus on low rise mass/social housing, the main typology since the 1960 s has been the doorzon house; a type of terraced housing with an open floor plan for the first floor and large windows in the façades. The appearance of these houses may vary, but the structure and floor plans are mostly identical. The bearing walls (separating the individual houses) are made of concrete or building blocks, floors are semi-prefab concrete slabs. In the facades large window frames with partial infills of wooden planks are used, often covering almost the entire facade. Ca. 1,4mjn houses of this typology have been built between The width of these doorzon houses is 5,4-6,3m. Dept of these houses is 7-8,5m. In contemporary mass lowrise housing the typical doorzon floorplan is still dominating. Main variety in the floorplan is the layout of living and kitchen; living facing the garden and kitchen facing the street or vise versa. These houses are still popular because of their spacious floor plan and plenty of daylight. Figure 1. A selection of typical 'doorzon' houses The wish to built these houses fast and at low costs in the 60s- 70s resulted in many air leaks in facade and roof. Natural gas was plenty in the Netherlands so insulation was not a priority. In spite of later renovations and retrofit insulation of these houses, their energy performance is, certainly to current standards, inferior. On the other hand the quantity, popularity, structure and high potential for improving the energy performance of this typology makes it attractive for the development of a passive house renovation concept for mass production. Case Kerkrade West This paper focuses on the passive house renovation of 153 doorzon houses in Kerkrade West built in The aim of this project was to develop a quick and clean renovation concept based on prefab elements with integrated piping and wiring; renovation taking only a few days per house. During this works the house should stay inhabitable. Furthermore the costs of this renovation should be such that the increase in rent could be less than the savings on energy costs; per month the tenants should pay less for living in these houses Convenant Energiebesparing Huursector, 28 juni 2012

3 Figure 2. Typical doorzon floor plan (kitchen faces street, living faces garden) Before renovation the exterior and surroundings of the houses where in a rather neglected state. The housing corporation hesitated for quite some years whether to demolish or renovate these houses. The wish for a sustainable and long term solution and the outcomes of a SWOT analysis made the housing corporation decide for a innovative passive house renovation. At the basis of this decision also lies an ongoing research project concerning the sustainable transition of Kerkrade West 3. Main conclusion of this analysis was that the tenants appreciate the spaciousness of the houses, that the houses are structural solid and that the facade is relatively easy to replace by a new facade in order to improve insulation, comfort and aesthetics. Energy performance of the original houses Air tightness of the original houses, as tested with a blower door test, was approx. ca. 3,3 q v;10 [dm³/s] per m2 floor space 4 (0,15 is needed for a passive house). The average use of gas was 1600m3 per house per year (Dutch average for a house of this size is 1350m3 per year). The use of electricity was with 3970kWh/year on the average of Dutch households. Criteria for renovation In 2010 the decision was made to renovate the houses to the level of passive house. The housing corporation wanted to renovate on the basis of clear performance indicators. Renovation of exterior and installations only, not the interior Energy performance at passive house renovation Building speed of approximately 8 days per house (for exterior and installations) The houses should stay inhabited (inhabitable) during the renovation works Contractors should have an open and clear communication with the dwellers/tenants Aesthetic/architectural improvement 3 R. Rovers, H. Sap, et al. (2010) The Urban Harvest Plus approach to 0-impact on built environments case study Kerkrade West. In R.Rovers, et al. (ed.) Towards 0-Impact Buildings & Built Environments, (pp ). Amsterdam; Techne Press. 4 Measurement by Caubergh Huygen Consulting Engeneers

4 Four contractors where invited to make a proposal in order to meet these conditions. BAM Woningbouw 5 scored best and could built on experience with a previous passive house renovation project (a 19 th century housing block in Rotterdam) and experience with Lean Building. A design team was formed with housing corporation Hestia 6, contractor BAM Woningbouw, TeekenBeckers Architects, Caubergh Huygen Consulting Engineers, Zuyd University. Together the initial proposal of BAM Woningbouw was improved, engineered and simulated/calculated. Basics of the developed renovation concept Timber frame prefab elements (half the width of one house, 2 storeys high) supported by studs resting on the existing foundation. Additional insulation (EPS) is added to the prefab elements. Insulation value of facade; R= 10 m 2.K/W or U=0,1 W/(m².K)) Passive house vinyl window frames with triple glazing, integrated in prefab facade elements (U f+g = 0,8) Prefab timber frame roof elements (also half the width of one house) that are placed over the existing sub roof. R= 7 m 2.K/W or U=0,14 W/(m².K) Insulation of bottom of ground floor (accessible by a crawling space) with PUR foam. (R= 5 m 2.K/W or U=0,2 W/(m².K)) Insulation of the foundation with XPS foam (R= 7 m 2.K/W or U=0,14 W/(m².K)) Installations Roof with integrated PV panels (approx. 2800Wp per house) and solar panels. Mechanical ventilation with heat recovery. Small efficient gas furnace (hot water / heating) to supplement the solar panels. Heat distribution with low-temperature convector panels Night cooling with natural ventilation All piping for heating and ventilation is integrated in prefab facade elements, as well as roller shutters for the windows Initial planning for the renovation of a single house Day 1: Excavation of foundations, placing of supports for new facade Day 2: Removal of the facade on the front and placing of the prefab facade elements Day 3: Removal of the facade at the backside and placing of the prefab facade element Day 4: Removal of roof covering and placing of the prefab roof elements Day 5-8: Installing new installations, placing extra insulation on facade elements, cladding, roofing (including PV and solar heat panels). In 2012 the renovation concept was tested on 2 houses. The renovation of these example houses was used to test the building system, building process and energy performance of the concept and it was a strong instrument to show the tenants how their new houses would look, feel and perform. After testing the concept on these houses the concept was further 5 A division of the Royal BAM Group 6 Current name is; Heem Wonen

5 optimized. Main conclusions where; too much hinder (delay, noise, dust, dirt) for the inhabitants due to work on the installations inside the houses. The solution was found in integrating all the piping for the heating system in the prefab timber frame elements. The cladding and roofing took more time than initially planned (because the PV panels were not included in the initial plan) but since this is on the exterior and not hindering the inhabitants too much this was accepted; the average time it takes to renovate a complete house in this project / with this system turned out to be 10 working days. Renovation concept in detail The prefab timber frame elements are 2,8m wide and Fig. 3. Renovation shown/tested in example 5,2m high. The elements are already closed on both sides and filled with 14cm of thermal insulation (glass wool). The elements come with window- and doorframes (including the triple glazing) already installed. This saves time on the building site and guarantees an airtight fixture. Besides doors and windows also roller shutters and piping for ventilation and heating is integrated in the prefab elements. The elements are supported by metal studs which are placed on the existing foundation. A new facade is installed on the same day that the old facade is removed. After installing the prefab facade elements an additional EPS insulation is added and the facades are finished with a white stucco. Renovation of the roof is also based on prefab timber frame elements. These roof elements are placed over the existing roof; only the roof tiles and battens are removed. These roof elements are placed on metal anchors which are connected to the concrete attic floor. The roofs are partially clad with roof tiles and partially with building integrated solar and PV panels; these also function as roofing. In the attic the original gas furnace is replaced by a combination of solar heated thermal storage tank and high efficiency furnace, also a ventilation unit with heat recovery is installed. Because the renovation concepts only involves facade and roof floor heating was not an option, wall heating was rejected because of the large % of glass in the facades. The heat distribution units therefore are low temperature heating convector panels. Figure 4. Placing of a prefab facade element Figure 5. Renovation of the roof in different stages

6 Energy performance Based on PHPP calculations 7 the expected energy needed for heating the houses (both single family and 1-on1) is kwh/m2 per year (depending on orientation) for a mid-terrace house (2 facades) and kwh/m2 for a corner house (3 facades). One PHPP datasheet is given at the end of this paper. For cooling no energy is needed because of selective use of heat reflecting glass and night cooling with natural ventilation. The actual energy performance is being monitored in 65 houses with data from their digital energy meters. The housing corporation is in negotiation with the tenants about further, more detailed, monitoring and research on rebound effects etc. Unfortunately the tenants start to feel like labrats 8 and are reluctant to cooperate. Finances The costs per house are on average ,- incl. PV panels, garden fencing and storage sheds. The municipality will invest in further improvement of the public space; public gardens, playgrounds, etc. This relatively large investment forms a drawback for this type of ambitious renovation. In order to justify this investment the houses are expected to last for the next 50 years and the rent was raised. This raise of the rent however is kept lower than the expected cost savings on energy of the tenants. The raise of the rent for a single family house is 64,- (incl. PV panels). The expected energy saving is 101,- (based on current energy prices). Therefore a family saves expectantly 37,- per month on costs for housing (rent+energy). Figure 9. Detailed section of the new facade Conclusions In conclusion can be stated that passive house renovation of repetitive terraced houses can be done in just 10 days by using large prefab elements. This concept can be applied for a vast number of similar houses all over the Netherlands. The costs of this renovation project however are a drawback and require further consideration. Economies of scale and increasing experience may result in lower costs. Settling for a slightly less high ambition may also reduce costs. For example using ordinary window frames (instead of passive house window frames) with triple glazing may drop the costs but still result in 25kwh/m2. Further research, design and experience is needed to find the optimum between energy performance and investment costs in these large scale projects. At the same time similar prefab renovation concepts at the moment are being developed for owner occupied houses as well; a development Zuyd University is also participating in. 7 PHPP calculations made by Caubergh Huygen Consulting Engeneers 8 Their own choise of words