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Retrieval-augmented generation in home construction calculation : developing an intelligent assistance system

Stefan Kleinschrodt

Digital Library of the University of Innsbruck (University of Innsbruck), 2025

12 participants

Abstract

This thesis develops and evaluates a prototype retrieval-augmented generation (RAG)–based chatbot assistant that supports non-expert users in completing the complex input process of a home construction calculation. While existing cost calculation tools primarily target professional users, private homebuilders often struggle with technical terminology, interdependencies, and normative requirements, which undermines planning security and decision quality. To ease this process, the chatbot is integrated into an existing web-based cost calculation workflow and provides context-sensitive explanations and guidance during data entry. Following the Action Design Research (ADR) methodology, the thesis proceeds in four steps: (1) requirement analysis via a standardized survey to identify typical comprehension problems, (2) design of an intelligent assistance concept, (3) technical implementation of the RAG chatbot using LangChain, LangGraph, ChromaDB, FastAPI, and Google GenAI, and (4) empirical evaluation of user acceptance. The prototype assistant provides context-sensitive, natural-language help on demand, grounded in a curated knowledge base focused on high-friction topics such as efficiency classes and funding, roof parameters, wall materials and thicknesses, and storey dimensions. User acceptance was assessed in a controlled study (n = 12), in which participants completed a realistic planning task and then rated the system using an extended Technology Acceptance Model (TAM)…

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