Arola Apartments Identical Twins

Exterior -Image © Wellu Hämäläinen

It’s often quite hard to make direct comparisons as to the sustainability of different buildings in the industry as costs, supply chains, and methods of construction to name just a few things are all variable. This is even before size, location and programme are taken into account.

So this project in Turku, Finland is really interesting as it is twin identical apartment blocks identical visually externally and programmatically internally. But there is a twist one is built with concrete and the other with timber.

Section - Image from Lunden

Designed by Lunden and financed by the ARA (Housing Finance and Development Centre of Finland) to evaluate the effect of these two different means of construction, cost, time, carbon footprint, life cycle costs and indeed quality of life for the residents can all be directly compared. Identical Twins with a twist.

Plan - Image from Lunden via Puu Info

They are both 4 storey blocks each with 41 identical apartments down to the ceiling heights. But the concrete block (Kide) is built with much more traditional precast concrete elements. The Timber block (Kirsikka) is built with CLT timber units.

The plan is a double loaded apartment type which I don’t like but are the most common in Finland however the central corridor is approximately double the width than normal and the stairs have been broken up into single floor runs with double height spaces in between. This opens up that space to make it much nicer than normal. A corridor like this has to be sprinklered and I think the whole building is.

In the same plot but separate from the main apartment buildings are some covered parking with cold storage and another communal building with sauna and club room shared by all the residents.

The floors in Kirsikka are made from Kerto-Ripa floor elements. CLT is also used for the roof and balconies.

Some Comparisons

All these figure come from the Puu Info article about the project

Carbon footprint

timber 11.70 kg CO₂ₑ/m₂/a
concrete 12.89 kg CO₂ₑ/m₂/a.
Carbon handprint
timber -8.13 kg CO₂ₑ/m₂/a
concrete -1.88 kg CO₂ₑ/m₂/a.

Over the 50 year lifecycle of the building this comes out to 1,764 t CO₂ₑ of emissions (timber) vs 1,917 t CO₂ₑ (concrete) So the prediction is 9% less CO₂ consumed. Both buildings uses district heating system which is very common in urban areas of Finland.

The timber building was 10-15% more expensive to build partly due to more difficult detailing in the timber building to achieve acoustic and fire safety solutions. Also weather protection on site of timber elements added to the difference of costs.

It’s possible as some design and construction costs could be optimised, there was some extra design time for example in synthesising the two buildings to be as similar as possible. Also as CLT buildings become more common, detailing them should become more efficient.

Otherwise this is a lovely low-key look at two building technologies, one on its way out and one becoming more prevalent.

⚲ location: 60°25’30.8”N 22°12’20.1”E