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Doctoral thesis: old wooden rural house CAN BE made more energy efficient

04. September 2017

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In Estonia, there are more than 190,000 detached houses, 61% of them have wooden load-bearing structures. A PhD student of the TUT Nearly Zero Energy Buildings Research Group of the Department of Civil Engineering and Architecture at the School of Engineering Üllar Alev researched the opportunities and results for renovating and making these structures more energy efficient in his doctoral thesis «Renovation and Energy Performance Improvement of Estonian Wooden Rural Houses».

Approximately half of the wooden houses in Estonia are older than 100 years. „This already proves the durability of wooden houses and well-considered renovation would extend the service life of the houses for at least an additional 100 years. Only the inhabitants’ expectations for comfort have changed over time. There is, however, no insurmountable obstacle, which would prevent having conveniences and indoor climate in such houses equivalent to the ones in modern dwellings after the houses have been thoroughly renovated,” Üllar Alev explains.

Due to resource scarcity, the owners of rural houses renovate their homes step-by-step and often during a long period of time or almost continuously. The doctoral thesis suggests that such renovation works should be carried out concurrently and thoughtfully, which would reduce extra work, inconveniences accompanying construction works and, ultimately, the total cost of construction works.

The main damage to old log houses built before World War II has been caused by precipitation and soil moisture. „In most of the century-old log houses the first log rows and the rotten logs under the windows need to be replaced,” Alev claims.

Structurally, the weak spot of these log houses is the lack of air tightness, which is why during renovation attention should be paid to sealing of log grooves and joints in the structure. Despite the sparse exterior envelope of the building, natural ventilation does not ensure adequate air exchange and to guarantee good indoor climate a mechanical ventilation system with heat recovery needs to be installed.

Excerpt from the doctoral thesis (Üllar Alev 2017)

„Additional insulation of the external walls significantly reduces the energy costs of the houses. In my doctoral thesis, I also analyse the possibilities for insulating the interior side (in case installing exterior insulation is not possible), however, exterior insulation should still be preferred.” Alev says.

With complete renovation (additional insulation, a ventilation system with heat recovery, an effective heating system and solar collectors or PV panels) depending on the initial state of the house, the heating costs of rural houses, including costs of ventilation and domestic hot water, can be reduced by two to four times while guaranteeing a significantly more convenient indoor climate.

„Improved indoor climate means warm floors, stable temperature (absence of hot evenings and cold mornings) and cleaner indoor air (less dust). These are the qualities the current owners of old log houses complained about in the research carried out in the framework of this thesis,” the author of the doctoral thesis explained.

Read the full doctoral thesis in TTÜ e-library!

Source: Tallinn University of Technology.

 

 


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