#2 The House: Core Design Decisions

Before I began writing this text, I asked for some feedback on the previous posts. One of the things that has become clear to me thanks to the feedback is that I've been writing too many scientific papers: whereas these are full of passive voice, this might not be the best for a blog. I didn't realize I was doing that until it was pointed out to me: thanks for that! Therefor, I'm going to try to change - starting with this entry - let's see if it works out...

It took some time to get to this...

When I started this project I often thought about what the house would look like in the end. The only thing I knew for sure was that it would be a log house. But what kind of log house? How big did I really want it to be? Would it be on one or two levels? With an attic? Maybe an A-Frame? And a log is a log, right?

Initial thoughts

The first thing I started to ask myself was: how much space do we really need for our family of four? In a cold climate, the smaller the place, the easier to heat. I also didn't want to have tons of space that would end up being 'storage' or otherwise unused most of the year - such as a dedicated guest room. A bathroom with shower, and a sauna on the other hand were pretty crucial, but the sauna didn't necessarily have to be part of the main house and could go into a separate sauna building. This separate building could also house a guest room: this would save me from having to heat it all the time, but would offer a private place for guests with their own bathroom. I also needed the place to put the batteries, solar stuff, hot water tank, etc. which I didn't want in the main building. All this lead me to a total of three buildings: three bedrooms, living room, kitchen and bathroom in the main building, a sauna building with bathroom and guest quarters, and a technical building. I'll focus on the main building in this post. 

Once this idea solidified, I also automatically concluded that I didn't want two floors and didn't need, or even want, an attic. This also lead me to conclude that an A-frame wouldn't be a good option. You tend to lose a lot of space due to the angled walls, and you'd want to add at least a loft to make proper use of the available space. Because I spent a lot of time on the land before building, I also found that the view on the building spot would be amazing, so I definitely wanted large windows (and not just in the living room) to enjoy the view, no matter what time of year.

Let there be light, sometimes.

Being off-grid, I wanted to maximize the use of natural lighting. This is especially great in autumn and spring days, but not so much in summer since it would easily get too hot inside. The solution for this are overhangs that let the sun enter the building when it's low at the horizon, but blocks it at mid day when it is high in the sky. I can not state enough how important overhangs are for this: you want the house to be south facing (or at least close to it) in order to get maximum sun in spring, autumn and winter, but in summer you want to keep the sun out. In addition, the use of overhangs prevents a lot of rain water from hitting the logs, protecting the walls from water damage.

I initially started designing the house myself and intended to get an architect to make the project based on these drawings. I went through several iterations, and checked every available house from existing suppliers to see if something close to it already existed. This would ultimately save time and money compared to doing it completely from scratch, and existing building companies would be able to offer customization on their models much easier. This all failed horribly because a) I'm terrible at designing a house and b) finding people to work with on a project like this is hard - until I came across the Nuuna model from a company called Kuusamo Hirsitalo. It pretty much checked all the boxes: single floor, 120m², huge windows at the front, even larger overhang, etc.

3D model

In order to make sure this house would work on the plot and performed as I wanted it to, I created a 3D model of the building according to the available floorplan and dimensions, virtually oriented this model in 3D rendering software, and simulated different seasons. With a bit of programming, I tracked the sun in this virtual world and rendered an animation to get an idea of how much of the sun would be coming in. 

The sun in winter

This short segment of the animation shows how the sun moves in front of the windows, allowing maximum sunlight in the main room (and the room beyond the door in the distance) in the middle of winter. The sun barely comes up and skims across the horizon; this is simulated with a dawn at 10:00 and sunset at 15:00 which coincides with the shortest day of the year in my area (about 4.5 hours of 'daylight'). No additional light sources were used and the walls, ceiling and floor are deliberately kept at a slightly darker shade to increase the contrast. In summer, the sun rises much higher in the sky, and in that case the overhang prevents the sun from shining directly in the house, keeping it cool.

All logs aren't made the same

Since this is a log house, one of the decisions I had to make was what kind of log to go with. There are a few choices: typical round logs, square logs, and engineered log - and they come in a variety of thickness. Round logs are very traditional, but they require chinking to provide better insulation and air tightness. Square logs provide a more uniform insulation since the thickness is the same everywhere, and can provide better air sealing without the need for chinking. 

Engineered log

The engineered log (also called laminated log) are essentially logs that are cut, kiln dried, and glued back together, after which they are machined in the right shapes using CNC technology. There are several advantages to making logs like this: they won't settle and shrink as much since they are fully dried, much less cracking since the grain is oriented differently within the same log, excellent air-sealing across the entire log because of machining and added insulation between logs, perfect fit everywhere, and no need for chinking since they are sealed over their entire square profile. It is also more environmentally friendly since there is less waste since more trees are suitable for this treatment and more of the tree can be used compared to more traditional approaches.

There are lots of discussions regarding the energy efficiency of a log building versus more contemporary building methods. This often leads to discussions regarding R values, U values etc. General consensus (and building science) is that the insulation properties of a modern wall are higher than that of a log, but that a log does act as a thermal battery and causes temperature changes to be more gradual, i.e., it releases the heat stored during the day overnight (thermal mass). Of course, the thicker the log, the better insulation, but you'd have to go extreme to meet the same R value of a regular modern wall.

Personally however, I did not care too much about best insulation properties of the walls for several reasons: for one, I wanted lots of windows and those are not very good at retaining the heat to begin with - to say the least. The windows are triple pane and filled with argon gas to get the best results, but there is only so much one can do. Secondly, a large percentage of heat losses in a building are through the roof and floor. For this reason, I decided to have a very well insulated roof and floor, and a ventilation system with heat recovery, while not going for maximum log thickness. I ended up going with the engineered log - it just made the most sense. The thickness of the logs are 203mm (8 inch), which is a very common choice where I am. It is important to know that while this place is built in a heating-dominated climate with long winter, we don't necessarily have extreme cold temperatures: -20C is common for short periods, but -30C and below not so much. Winter averages are around -10C. Cold, but it's not the Arctic.

Energy certificate

All these aspects combined, and the fact that the place will be heated with renewable sources means the energy certificate I got was a B (In accordance with Energy Certification Regulation 2018). New buildings are required to have at least a C rating, and we're actually not that far off from an A certificate. We're doing quite well here.

Speaking of heating, there are  two main sources of heat: the masonry stove and an underfloor radiant heating system. The masonry stove works on the principle of heating up a large mass of stone, and releasing the heat gradually over 24 to 36 hours. The radiant floor heating operates on a similar concept where the concrete floor transfers the heat as radiation to the objects and people in the room. 

Radiant floor heating is considered the most efficient and effective heating method. It prevents cold spots and provides a comfortable temperature gradient across the entire building. The hot water is generated in wood boiler and stored in a 3000L tank, but the solar system will also be used to dump unused power into this tank. This means that in the summer months, I have as much hot water as I need without having to burn a single piece of wood. I'll go into these systems in a future entry. 

In the next post, I'll discuss the foundation for the house.