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Put on lifesupport

September 19, 2013

A log cabin is breathing on its own. The wood itself is both insulating and yet letting air pass through. That’s the reason why so many still build cottages from massive logs instead of a frame structure which is then hermetically sealed off by plastic.

But any building in Finland that can be used around year (hint: that includes the winter) has to follow since 2010 rather strict energy criteria. Villa Linnea, with its 20cm logs, has several tricks up its sleeves to comply with the tight regulations. There is 50cm of insulation in the roof and 25 cm in the floor. Some walls in the kitchen and the bathroom have some additional 5cm of insulation. The windows have 4 glasses which is good enough for passive houses. And yet, the building permit forces us to put the villa on life support with artificial breathing.

A ventilation system pulls in fresh air from outside and blows the dirty air out through a pipe in the roof. Warm “dirty” air from the top of the two-story living room above the fireplace, from the kitchen above the oven, and in the bathroom is sucked out of the rooms. Fresh air is blown into all the bed rooms. The heat from the dirty air is converted in the ventilation machine to heat the colder fresh air. The ratio of conversion (or heat retention) is specified by the building permit. We would need to capture 67% of the heat before it is blown out the roof. I invested 500 Euros more and bought a ventilation machine that can retain up to 80% of the heat.

The ventilation machine and two silencers (for both incoming as well outgoing traffic) create this neat pile ordered in the Internet at and delivered by Onninen:


I’ve been pulling the ventilation pipes throughout the building process and started now the project of installing and connecting the ventilation machine. The project starts in the little space reserved for this purpose behind open balcony on the second floor. The ventilation pipes and the distribution boxes were assembled already last year. The ventilation pipes are from the Vallox Blue Sky system which works rather nicely due to the complex roof structure and the various corners we need to pull the pipes through.


The photo above shows the pipe int he upper left corner through which the dirty air blown out. This pipe has been installed over 18 months ago. I was hoping now that I could fit the ventilation machine (with its 50 kg weight) neatly under that pipe. That would have worked pretty well unless I didn’t forget to count in the 7 cm assembly space need for the water pipe that carries the condensation water away from the IV machine. The outlet is placed under the ventilation machine and I didn’t really plan for those few centimeters which made the whole affair even tighter. Not exactly a walk in the park either was the drilling of the 12.5 cm wide hole for the fresh air inlet through the 20 cm log wall. I had to cool down my power drill few times in the freezer. And just when I was through the wall, the clutch of the power drill resigned from its service. Luckily, Bauhaus has this 5 year guarantee on tools and my power drill was only 2 years. Hence, I got a new one for free.


With the ventilation machine in place (on the right hand side) and the two silencers connected to the distribution boxes, the last meter of connecting pipes could be laid. The ventilation machine is a Vallox 110 SE model. The silencers are of the Estonian Onnline kind. You can also see the 12 mm pipe for the condensation water on the floor which was connected to the drainage behind the silencers later on. The last meters of plastic piping was easily cut to measure. I’m still wondering why I was thinking to hire a assembly guy for this job and pay him few hundreds.


It’s  rather crowded now in this tiny space with all the pipes connected. But why waste space when I need to do clean the filters only once a year? I have started to train already the local midgets to perform the filter service on my behalf. And if that fails I still can do the job myself for the next 30 years (wheel chair access is kind of challenging).


The control unit displays nicely that the project was a success. It sucks in fresh air at 14 degrees and blows it into the bed rooms at 19 degrees. It sucks out the dirty air from the rooms at 22 degrees (which equals the corresponding room temperature) and blows it out at 16 degrees. The simple math tells us that it heats the colder air by 5 degrees and in order to that it takes out 6 degrees from the dirty air before its blown out. I guess the 5 out of 6 degrees make up nicely 80%, or what?

4 Comments leave one →
  1. September 19, 2013 7:00 pm

    Nicely assembled. One point to consider though. I highly recommend to change the filters at least twice a year. Dirty filters eat up the effiency of the ventilation machine and lead to higher electricity bill.

    Thanks for a very good blog!
    Otto. / Villa Osmankäämi.

  2. September 20, 2013 7:16 pm

    Thanks! Will do.

  3. January 7, 2016 6:47 pm

    Hi, thanks for the installation details. I have a similar system (Vallox 90SE) with 10 port air distribution boxes for fresh/stale air. You mentioned 50mm insulation in the roof and I can see some sort of heater on the right in the photos so just wanting to confirm that your unit is installed where it is warm? Our air distribution boxes are in the unheated loft and I think they should be insulated.
    Kind regards

  4. January 9, 2016 12:58 pm


    yes, the area is heated by an electrical radiator with its own thermostat. Just keeping 10 degrees minimum in check during the winter.


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