The renovation of Rastaala School

Rastaala School in Karakallio, Espoo, has about 650 pupils in grades 1–6 in its older and newer sections. When the users of the Alatalo building, built in 1956, started to grow concerned over the indoor climate, Sweco performed an indoor air and moisture condition survey at the site. 

“Some of the staff noticed a smell of a cellar and suffered from symptoms related to insufficient air quality,” says the City of Espoo’s manager of indoor air matters Elisa Vene. 

Usually, there is no specific initial data available for buildings from the 1950s, which requires the condition surveyors to be familiar with the special qualities of the era. “In buildings of this age, the damage is usually in structures sensitive to moisture and organic construction materials, such as the template boards and fillings in layered intermediate floors,” says Sanna Pohjola from Sweco. She inspected the facilities, prepared a survey plan and reported the results. 

Long-term moisture damaged the structures 

The condition of the structures was inspected from top to bottom. “We opened up the structures and took samples to determine their microbiological condition,” Pohjola says. Damage was found in the old kitchen facilities, in which dry rot and rotting fungus had developed in the structures. “The structures were dry, but the microbial damage indicated long-term moisture concentrations.” 

Surveys on the quantity of air, moisture and airtightness were also performed at the site. In addition to this, the functionality and cleanliness of the ventilation ducts were also surveyed. “Due to the negative indoor pressure, impurities could enter the indoor air via the air leaks in the structures,” Pohjola says. 

The City of Espoo is happy with the consultants’ work. “Everything went according to schedule, and our requests for urgent surveys were responded to immediately,” Vene says. The client was also immediately informed of additional survey needs. “This way, we could ensure that the facilities were inspected as extensively as was necessary.” 

Users are happy with the renovated facilities 

Sweco’s experts presented the results of the condition survey to pupils’ parents, among other groups, at the information events for users. Elisa Vene finds it better that the results are communicated by a neutral third party. 

“It’s more believable when the results are presented by consultants who are familiar with the initial data and who have prepared the survey plan and inspected the building. They have the best knowledge, and we trust them.” 

Sweco’s experts recommended that intermediate floor structures be replaced, plastic mats be removed from the basement facilities and sealing repairs be made. The facilities remained operational for a while before the renovation, and during this entire time, indoor air quality, pressure differences and microbiota were monitored. “Air purifiers were also used in some of the facilities for the entire time,” Pohjola says. 

In 2018, a one-year renovation project started in Alatalo, where the floors, wet rooms and the ceiling plastering were disassembled, among other structures. All intermediate floors, interior surfaces and ventilation machines were renewed, and the exterior walls of the basement were sealed. No complaints have been received for the new facilities. 

“That’s always a good sign when dealing with indoor climate!” Vene says, delighted. “The only feedback we have received is that the pupils and teachers like the renovated facilities.”