«Authors: Kleiven, Tommy1; Woods, Ruth2; Risholt, Birgit3 SINTEF Building & Infrastructure, Trondheim, Norway, tommy.kleiven SINTEF Building ...»
Retrofitting with prefabricated modules. Stakeholders' views and needs.
Kleiven, Tommy1; Woods, Ruth2; Risholt, Birgit3
SINTEF Building & Infrastructure, Trondheim, Norway, email@example.com
SINTEF Building & Infrastructure, Trondheim, Norway, firstname.lastname@example.org
SINTEF Building & Infrastructure, Trondheim, Norway, email@example.com
Abstract: This paper is based on work carried out in RetroKit, Toolboxes for systemic
retrofitting within the FP7 programme. The scope of the presented work is to identify the views and thoughts of stakeholders on the use of prefabricated modules in retrofitting of apartment buildings. Quantitative methodology in the form of a questionnaire has been used to provide data in 11 European countries. The intension with our research is to provide indicators with which to understand societal trends associated with deep retrofitting in general and retrofitting with prefab in particular. The main research questions are: What characterizes good retrofitting design? What are the success criteria for prefabricated solutions? What are the architectural requirements for prefabricated modules? The findings show that the three most referenced characteristics of good retrofitting design are energy efficiency, cost and aesthetics. The greatest pitfalls associated with prefabrication were seen as limited architectural freedom resulting in poor architecture.
Keywords: Retrofitting, Prefabrications, Stakeholders, Architecture, Energy Introduction Multi-family apartment buildings constitute more than 50% of the EU building stock and the building typology consumed 68% of the total final energy use in buildings in Europe in 2009 . The majority of these buildings were built between 1945 and 1980 and are now ready for retrofitting. A huge energy-saving potential is within reach if priorities are right. The apartment buildings are located all around Europe and share many common features like architecture, structure and materials. This makes them suitable for retrofitting with prefabricated modules which allow for cost efficient mass production. Building service technologies can be integrated in the modules and the residents can stay in their homes during retrofitting. To make sure that good retrofitting concepts and solutions are developed, knowledge on the needs and views of stakeholders involved in retrofitting is crucial .
Research show that retrofitting solutions should address more than just energy efficiency to be attractive. Added benefits such as improved indoor environmental quality and architectural expression should be part of the retrofitting concept, as energy efficiency is not always the primary driver for upgrading . The objective of the questionnaire survey is to identify the views and thoughts of stakeholders involved in retrofitting about the use of prefabricated modules for retrofitting. The survey covers Poland, Romania, Germany, Switzerland, Ireland, Italy, Spain, Greece, Sweden, Norway and The Netherlands. The informants were building owners, architects, consultants, contractors, prefab manufacturers and authorities. The main research questions are: What characterizes good retrofitting design? What are the success criteria for prefabricated solutions? What are the architectural requirements for prefabricated modules?
Method Quantitative research methodology in the form of a questionnaire has been used to provide data about the use of and expectations related to retrofitting with prefabricated modules. The quantitative research approach has its roots in positivist theory where the intention is to empirically test hypotheses explaining and predicting the what, where, why, how and when phenomena occur . However, due to the exploratory nature of our research, the intention has not been to test a hypothesis but to provide indicators with which to understand societal trends associated with retrofitting using prefabricated modules. Quantitative methods, such as questionnaires, provide numbers and offer the means to understand, describe, and explain them. Quantitative research relies on an objective standpoint, where different points of view may be compared and the research results can be verified, if necessary, at a later date .
Hence, if the questionnaire survey were to be repeated, the results should be the same.
However, the questions in our survey are not of a nature which is easily quantifiable. The respondents are not asked, for example, to number how many prefab projects they have participated in, rather they are asked about architectural requirements and success criteria from their point of view. These aspects are based to a large degree on subjective experience and taste, making the answers more subject to fluctuation. It is hard to measure subjective data quantitatively . The data from the questionnaire does not give in-depth information on the respondents' motivations, standpoints or personal perceptions. The data from the questionnaire instead provides indicators about societal requirements, success criteria for prefab solutions and characteristics of good retrofitting design.
The questionnaire was developed in an iterative process amongst the researchers in the RetroKit consortium and then tested on a representative test group before it was presented in its final digital form 1. The questionnaire consists of 16 questions arranged in four thematic sections. The questions fall primarily in the ordinal-polytomous category, where the respondent has more than two ordered options. The survey was conducted during the spring of 2013 using the electronic questionnaires system EasySurvey . The majority of the informants were approached using e-mail invitation to participate in the survey. The invitation was sent to 4697 genuine e-mail addresses among the target group in the 11 countries. A total of 526 answered the questionnaire, giving a response rate of ca. 12%. It is not possible to draw 100% reliable conclusions on this empirical data set, but the material gives a good indication about the views and needs of the stakeholders involved in retrofitting. The distribution of answers is shown by role in figure1 and by country in figure 2. Norway, Germany and Spain stand out with the highest response rates. Architects dominate the response rate in Germany and Spain while authorities dominate the response rate in Norway.
Figure 1 Distribution of answers in relation to role. The two numbers in parenthesis separated by a slash denotes the percentage of answers and the number of answers (frequency) for that group.
Figure 2 Distribution of answers in relation to country. The two numbers in parenthesis separated by a slash denotes the percentage of answers and the number count of answers (frequency).
Findings The respondents were initially asked to rate their knowledge and experience with ambitious retrofitting as well as their experience in using prefabricated modules. The results show that there is more knowledge than practical experience with ambitious retrofitting even though approximately 2/3 of the respondents have experience with ambitious retrofitting, see figure
3. When it comes to the experience in using prefabricated elements only 6% report extensive experience while 43% report limited experience. This indicates that on site production in the traditional way is more widespread than the utilisation of prefab modules.
Extensive 2 3 4 Limited
0% 25% 50% 75% 100% Figure 3 The respondents self-rating of own knowledge and experience with ambitious retrofitting (top and middle) and experience in using prefabricated modules in retrofitting (bottom).
The respondents were asked if they were aware of the regulation requirements for retrofitting in their country, and in a follow up question they were asked to point out the main challenges with the regulations as they see them. More than half of the respondents are not fully aware of the regulation requirements for retrofitting in their country. Incompleteness was reported as the greatest weakness associated with the regulations for retrofitting, and a generally negative response was document among the respondents pointing to frustration, confusion and inefficiency.
In order to find out which qualities a prefabricated retrofitting module should possess the respondents were asked which criteria (i.e. characteristics) would be most important in their choice of a particular prefab system for deep renovation. The respondents were asked to rate the importance of 11 different criteria on a scale from 1 (not important) to 5 (very important).
0% 25% 50% 75% 100% Figure 4 The respondents' answers to the question: What would be the most important criteria in your choice of a particular prefab system for deep renovation?
By summarising score 4 and 5 for each criteria and ranging them by importance we can reveal a profile which suggests the mutual importance of the different criteria. The three criteria receiving the highest score were Thermal performance (91%), Robust and low maintenance needs (88%) and Quality of craftsmanship (85%). These three leading criteria were closely followed by Cost (79%) and Ease of application (79%). Then there is a step down to the next three criteria which scored within the range of 58-61%, namely Availability of prefab modules, Variety of finishes and Suppliers reputation. Finally, the least important criteria are Freedom in architectural expression (52%), Renewable energy production integrated in the prefab module (51%) and Ventilation integrated in the prefab module (47%). It can be argued that all the criteria are rated important as most receive a score above 50%, but it is still possible to rank them. The low score on "Freedom in architectural expression" is rather surprising considering the high response rate from architects.
In order to uncover the difference between prefabricated and on site production the respondents were asked to identify the advantages and the pitfalls of retrofitting with prefabricated modules as opposed to on site production the traditional way. The advantages of prefabricated modules lie primarily within the practical implementation of a retrofitting project. Respondents suggest that retrofitting with prefab modules will encourage efficient construction, make it easier to secure a dry building and cause fewer building defects.
Improved built quality also scores high as an advantage with prefabricated modules. In addition, 72% of respondents believe that retrofitting with prefabricated modules will cause less disruption for residents during the renovation process.
The pitfalls of prefabricated modules lie primarily within the field of architectural expression and high costs. Limited architectural freedom was regarded as the greatest pitfall of retrofitting with prefabricated modules. Cost was regarded as the second greatest pitfall, implying that many of the respondents see prefab as a more costly way of retrofitting than on site production in the traditional way. The third greatest pitfall was that retrofitting with prefabricated modules will result in poor architecture. The latter being the logical outcome of limited architectural freedom in the design phase.
The respondents were asked to select the 5 most important requirements a prefab system would have to meet to be attractive from a list of 9 requirements. They were also given the possibility to elaborate in their own words, but only 20 respondents did that. It is unclear whether the multiple choice options cover the field well enough, or whether the respondent did not take the time to fill in comments. The answers given in the comments relate to low maintenance needs and the safeguard of cultural and historical values. Summing up all the responses provides the following five architectural requirements a prefab solution should meet to be attractive (by importance): Energy performance, Adaptability to the building, Efficient construction, Flexibility in design (room for tailoring) and Adaptability to the residents' needs.
In a follow up question to the theme of flexibility in design, the respondents were asked to rate the importance of various aspects related to flexibility in architectural design, see figure
5. More than half of the respondents consider all the suggested aspects as important, but Precision of joints and connections stand out as most important of all. 88% of the respondents rate it either as very important (60%) or as important (28%). There are minor variations in importance among the other aspect. Surface material (texture, colour) is the second most important aspect where 65% rated it either as very important (24%) or as important (41%).
Proportion of module (shape) and Integration of solar shading devices were rated equally important with a score of 59% and 58% respectively (important and very important summarized). Possibility for creating relief in the facade (depth, rhythm) was considered as the least important aspect with regard to flexibility in architectural design. 43% of the respondents rate it either as very important (14%) or as important (29%). It can be argued that all the suggested aspects are important for the flexibility in architectural design as all score over 50% on very important or important (except for relief in the facade). This is confirmed by the low score all aspects received for "not important", less than 6%.
0% 25% 50% 75% 100% Figure 5 With regard to flexibility in architectural design, rate the importance of the aspects from 1 (not important) to 5 (very important).
The final question of the questionnaire provided respondents with the opportunity to elaborate freely upon the questions previously asked by summarising what they personally prioritise in retrofit design. A total of 176 responses were received and analysed. However when evaluating the open answers we have chosen to focus on the answers from the countries where there was the greatest number of responses, Norway, Germany and Spain. 38 respondents from Norway provided comments, 29 from Germany and 45 from Spain.