Denna studie handlar om ett flerbostadshus på 9-våningar beläget i Borås, uppfört av Peab. Det nuvarande flerbostadshuset är byggt med en betongstomme år 2016 och denna studie syftar till att undersöka vilken skillnad det gör på byggnadens totala klimatpåverkan och kostnad, vid val av trä som alternativt stommaterial. Syftet med studien är att lyfta fram skillnaden val av stommaterial kan göra på byggnadens totala klimatavtryck, med målet att konkretisera skillnaden genom undersökning ur ett livscykelperspektiv. Klimatpåverkan från de båda stommaterialen beräknas i en livscykelanalys upprättad utefter mängder på de faktiska stomvalen applicerat på flerbostadshuset. Beräkningen utgår ifrån generiska värden på material i ytterväggar, bärande innerväggar och mellanbjälklag. Verktyget som använts är IVL Svenska Miljöinstitutets klimatberäkningsverktyg, Byggnadssektorns miljöberäkningsverktyg (BM). Samtliga konstruktionsdelar i betong är hämtade från referensobjektets ritningar där konstruktionsdelar i trä har tagits fram med hänsyn att motsvara kraven på betongkonstruktionen. Utöver klimatberäkningarna har även en kostnadskalkyl genomförts för att konkretisera kostnadsskillnaderna. Studien omfattas även av intervjuer som visar på att KL-trä och prefabbetong har få skillnader i produktionsskedet. Intervjudelen ligger också till grund för val av ingående delar i beräkningen då undersökningen visar på att en träbyggnad på 9-våningar kräver stomstabilisering av olika inslag. Uppskattning från beräkningar visar att samma flerbostadshus på 9-våningar i Borås hade minskat sitt klimatavtryck med 60 % vid val av en trästomme. Samtidigt skulle det nya stomvalet generera i en total kostnadsökning på 3,38 % i förening med en intäktsminskning på 0,54 % till följd med minskad boarea. Samanställning av beräkningen visar på att trä har en lägre klimatpåverkan jämfört med betong samtidigt som betong har en lägre kostnad. Produktionsmässigt är trä ett effektivare material att bygga med och i takt med att samhället växer behövs det värnas om en hållbar framtid genom val som generar i en minskad klimatpåverkan. / This study is about a nine-story residential building located in Borås, built by the construction company Peab. The current residential building was built with a concrete frame in 2016, and this study aims to investigate what difference of choosing wood as an alternative frame material would make on the building´s overall climate impact and cost. The purpose of the study is to highlight the difference that choice of frame material can make on the total carbon footprint, with the goal of concretizing the difference through a life cycle perspective. The climate impact from the two frame materials is calculated in a life cycle analysis based on the quantities of the actual frame choices applied on to the residential building. The calculation is based on generic values of materials in eternal walls, load-bearing interior walls, and intermediate floor slabs. The tool used is the Building Sector Environmental Calculation Tool (BM) developed by the Swedish Environmental Research institute (IVL). All concrete construction components are taken from the reference object´s drawings, where wooden construction components have been developed to meet the requirements of the concrete construction. In addition to the climate calculations, a cost calculation has also been calculated to make the cost differences concrete. The study also includes an interview survey showing that cross-laminated timber (CLT) and prefabricated concrete have few differences in the production stage. The interviews is also the basis for the selection of components in the calculation since the investigation shows that a nine-story wooden building requires stabilization of concrete elements. Estimates from the calculations show that the same nine-story residential building in Borås would reduce its carbon footprint by 60 % if wood were chosen as the structural material. At the same time, the new structural choice would generate a total cost increase of 3,38 % in addition to a 0,54 % decrease in income due to reduced living area. The calculation shows that wood has a lower carbon impact compared to concrete, while concrete has a lower cost. Production-wise, wood is more efficient material to build with, and as society grows, it is necessary to protect a sustainable future trough choice that result in reduced carbon impact.

In the mid 1990s a previous prohibitions against multi-story buildings higher than two floors with a wooden frame was changed. Today multi-storey buildings are being built in Skellefteå, Sundsvall, Växjö, and Stockholm with others. Despite this only one of five houses being built today has a wooden frame. Since the municipality is a key force to get projects with wooden frames, this papers purpose is to improve tender document for the opportunity to submit bids and building with wooden frames. To help us forward with our work three questions were formulated. 1) What is the basis from a wooden constructions company perspective, of which they determines if they can place a bid or not? 2) What is the difference between tender documents made by a municipality compared to a private buyer? 3) How can tender documents be improved to create an opportunity to place a bid containing an alternative frame system? To answer these questions a literature study was carried out. The literature study is the basis of this paper. To obtain empirical data a document analysis of tender documents was carried out. The result of the study shows that wood frames are hard to adapt to an already finished technical specification, or to a tender document containing an extensive technical specification. To obtain alternative solutions, the buyer should focus on object design, form and function, or a general technical specification. Instead the technical specifications should be drawn up by the supplier, or in collaboration with them. The tender evaluation should be made by the most economically advantageous rather then the lowest price. Then the buyer can evaluate the offers against each other, rather then choosing the lowest price. This also gives the possibility for suppliers to make a bid containing an alternative solution. As a continuation of this paper, we recommend a study on which impact a general technical specification has on the project final cost.  Furthermore a study exploring which possibilities partner procurement can have alternative solutions in the Swedish procurement act. This report deal exclusively with how tender documents should be formulated. Life cycle analysis, carbon dioxide emissions and strength calculations will not be executed.