Housing block in Riihimäki
Reasons of the renovation
It is the city-owned social housing block located in the Peltosaari suburb of Riihimäki in Southern Finland. The building had been decaying for the last years, which decreased its market value and also created social problems; it needed urgent renovation.
In order to allocate the mass of people moving to the cities from the Finnish countryside in the 60’s and 70’s, large residential areas were built using pre-fabricated concrete elements. This technology, that is, the use of industrially made concrete sandwich elements, made it possible to build in short period of time housing for hundreds of thousands families. Building has flat roofs, concrete bearing wall structure, and its facade is made of prefabricated sandwich elements with a washed concrete finish. The facade elements had serious problems, common to this type of structure: insufficient insulation of both walls and windows, decay of the element joints and deterioration of the outer surface of the sandwich elements due to aggressive weather conditions.
In order to make the process fast and economically feasible, standardized solutions (layout, floor plans) were implemented in all the new housing areas. Due to this fact, the problems which appeared in those buildings after 30–40 years of service are very similar. During the past few years, the number of housing estates in need of integral renovation has increased all over Finland.
The most common features of such buildings were:
- linear multi-family blocks with staircases serving 3-4 apartments
- 3-storey buildings with no elevator or 5-8 storey buildings with elevator
- common spaces and services in the ground floor and/or basement
- facades composed of modular elements (usually repetitive)
- double windows with 3 glass panes (2 + 1)
- modular balconies for all apartments of more than one room (earlier versions of this type of buildings did not include balconies at all)
- flat roof (non-accessible)
- common laundry and drying room/s
- common sauna (electrically heated) with showers and dressing room
- shower rooms with no shower plate (the floor has a slope towards the drain)
- bathrooms with bathtub were built applying the same principles as in case of the shower rooms
- floor drains in every bathroom
The new energy efficiency requirements are putting pressure on the building owners to improve the energy performance of the buildings. This is planned to do in connection with the other refurbishment measures required. The building elements in greatest need of upgrading are the piping (cold and hot water, drainage), the heating system including thermostatic regulation, the windows and balcony doors, and the ventilation system. An integral renovation intervention can introduce energy efficiency measures to comply with present regulations.
Country and it’s climate
The residential area is located in the Helsinki region (Finland) - a residential suburb in the city of Riihimäki. It is a representative of the building stock of the period previously described, and therefore the solutions implemented can be easily replicated in other parts of the country, where there are plenty of similar buildings. Finland is one of the Nordic Countries so there is no problem with satisfying the Nordic Countries weather requirements of renovation process.
Due to the outdoor air temperature, the number of degree-days in Finland varies between 4250 in Helsinki and 6240 in Sodankylä, 17.5oC is used as the basis. High level and large geographical variation sets high requirements on the heating systems reliability and costing. In Helsinki, the heating systems are designed according to -25oC and in Lapland to -35oC outdoor temperature.
The coastal areas of Finland are rather windy, which increases the sensation of cold in winter. In addition, rainfall in the windy areas causes additional problems to the facades of buildings (so-called horizontal rain). Though a large portion of central and eastern Finland is covered with lakes, the climate in those regions is mainly continental. There are four weather zones in Finland (Fig. 1). The climate description is presented in Table 1 and Table 2.
Fig. 1 Weather zones in Finland
Table 1 Calculation of default and average temperatures for the different weather ones
Table 2 Monthly weather data in Weather Zone I, Helsinki-Vantaa
The case is about a city-owned social housing block located in Southern Finland.
Main picture of the building
Fig. 2 Social housing building block in a suburb of Riihimäki
The facade of this building was made of concrete sandwich elements. In this case, the poor condition of the insulation and the outer pane of the sandwich elements called for their demolition and substitution. A more radical intervention was proposed, by introducing a timber-framed TES-facade (Fig. 3), which incorporates not only insulation and windows, but also ventilation ducts and the first layer of facade rendering.
Fig. 3 Timber-framed TES-facade
The solution to be implemented was the winner in a competition (Innova refurbishment), and it stressed the importance of a fully industrialized prefabricated new facade, achievable at a reasonable cost (feasible). The project was funded by Sitra, the Finnish Development Fund, and monitored by VTT, the Finnish Technology Institute.
The renovation included new doors and windows, balconies, additional thermal insulation, and new mechanical ventilation with efficient heat recovery (rotating heat exchanger). The building envelope was scanned with a thermal camera to detect heat losses (Fig. 4). It was also measured by laser scanning and modeled for dimensioning the new facade elements that were going to be manufactured at a factory. The finished elements were going to be transported to the building site and lifted vertically, as each element had a height of four full floors (12 m). This method was going to reduce the construction time down to 5 months, which is half the time it took to complete the renovation of similar buildings in the suburb of Peltosaari.
Fig. 4 Results of a thermographic analysis
The windows were replaced with two double glazing panes, argon fill and selective film. The balcony doors have triple glazing, argon filling and selective film. The old reinforced concrete balconies were demolished and replaced by steel-framed balconies. In Fig. 5 and Fig. 6 demolition of old insulation is shown.
Fig. 5 Demolition of old insulation and outer pane of facade
Fig. 6 Demolition of old insulation and outer pane of facade
What Are Argon Gas-Filled Windows?
Argon gas windows feature a sealed unit, filled with gas between panes of glass to increase energy efficiency. Argon is an inexpensive, non-toxic, odorless gas that is used on residential windows to prevent frost from occurring at the bottom of the window and at the same time will increase sound proofing characteristics of the window.
Argon gas windows, energy star rated too, offer better insulation than natural windows because the gas is heavier than air. There are also three paneled argon-filled windows that provide two layers of insulation.
Argon gas window can offer the following benefits:
- Offer increased R-values
- Increases the soundproofing characteristics
- Minimizes heat exchange through the window
- Triple pane windows offer superior benefits than even double pane argon gas windows
- Reduces the possibility of condensation and frost
- Can be used in all climates as the windows are sealed with the gas and it will not leak out.
- This type of windows can even block ultraviolet rays
- The additional cost of having argon gas windows will be recouped on a really short time
- Available in different commercial sizes depending on how they are going to be used
- Argon will not corrode the window material as Oxygen will do.
- Your heating and cooling systems will work more efficiently when you install argon gas windows
- Can be installed from floor to floor ceiling, shorter windows or open/close design
- The gas is non-toxic and will not contaminate the environment.
- The ideal spacing between glass panes for argon is ½”
- Argon gas filled windows will only add $30 USD to $40 USD per window
Argon gas windows although really beneficial for homeowners, also have some drawbacks, for example:
- Argon gas windows will not expand or contract, however, the glass does and you would like to make sure it has been sealed properly, especially in high altitude area. Pay special attention if these types of windows are being installed at altitudes of 5,000 feet or more, you might have to look other alternatives.
- It will eventually dissipate from the window; however, there is no actual information on the rate that this will happen.
- If the window seal has even a small gap in it, you will lose your argon but worst of all you will not notice it.
- If the argon has been pumped using two holes, the window is more likely to fail than one hole window.
- Metal spacers are not good because they will allow gas to leak out over time as well as conduct heat and sound. Considered should be non-metallic spacer to reduce the failure probabilities
Fig. 7 Phases of full renovation with TES facade elements (source: arch. Kimmo Lylykangas)
Fig. 8 Building after full renovation with TES facade, new balconies and new tilted roof (source: arch. Kimmo Lylykangas)
There are no available information about the costs of the renovation.
U-value & energy savings
Thermal transmittance, also known as U-value, is the rate of transfer of heat through a structure (which can be a single material or a composite), divided by the difference in temperature across that structure. The units of measurement are W/m²K. The better-insulated a structure is, the lower the U-value will be.
The new windows, with two double glazing panes, argon fill and selective film, have a U-value of 0.66 W/m2a.
The improved insulation of the exterior walls resulted in U-value change from 0.40 to 0.10 W/m2a.
The building’s energy demand is reduced by 75%.
Pictures before & after
- Social housing building block in a suburb of Riihimäki before renovation
- Building after full renovation with TES facade, new balconies and new tilted roof (source: arch. Kimmo Lylykangas)
Summary of the case
A better energy performance of the whole building, targeted to meet the Passive House standards, is achieved by the improved insulation levels of the envelope (exterior walls = 0.1, roof = 0.08) and a highly efficient heat recovery in ventilation (75%). The use of very efficient windows (U = 0.66) contributes to improve the energy performance of the envelope.
Energy simulation of the building was carried out by VTT using IDA-ICE software. According to the simulation, the building’s energy demand is reduced by 75%. Also the performance of the new wall structure is being monitored by VTT after the completion of the building’s renovation. The target level for air-tightness is 0.6 l/h or less.
The high degree of manufacturing in all new structural elements contributes to radically shorten the construction time, which can thus be reduced to 50% of the standard in Finland for similar renovation projects. Industrialized construction also guarantees a better quality control, less waste, a reduction of faulty assemblies, and prevention of moisture damage during installation.
The case was performed thanks to a project named “Central Baltic Cooperation in Energy Efficiency and Feasibility in Urban Planning - ENEF” with Central Baltic INTERREG IV A Programme as a funding programme. It was held from January 1, 2011 till December 31, 2013.
First objective of the project was to develop a practical handbook of best practices in EST, FIN, SWE and LV on how to increase energy efficiency in buildings considering architectural and cultural values. The investigated buildings were both single use public buildings like schools, kindergartens and dwelling buildings built in 1960-1980 as well as building blocks and areas of cities.
Secondly, it was to develop national and joint networks to transfer innovative practices and tools of increasing the energy efficiency of buildings to regional and municipal planners, architects, engineers of construction companies, etc. within and among the participating countries.
Then, to exchange and transfer experiences of the use of different computer programs for calculating energy efficiency or analyzing the impact of different architectural or technical solutions in the planning stage on practical level.
And finally, to organize an International Conference and exhibition in 2013 to discuss and transfer results of the project.
The main result was a development of a handbook containing information about climatic conditions of participating countries, best case examples of building retrofitting as well as giving the overview of commonly used simulation software and calculation programs to determine the energy use of buildings.
According to a case, weather protection during demolition and installation of new structural elements of the building’s envelope has been provided and carefully planned. The importance of weather protection during the demolition, storage and assembly process is very high, as any rain or condensation accumulated during the process will lead to moisture damage and subsequent appearance of mold. Therefore, the roof was protected with a temporary tube structure (Fig. 10) covered with a canvas, after which demolition of the existing waterproofing and thermal insulation could be performed.
Fig. 10 Protected roof structure with a temporary tube structure