This is the first post from the engineering geek guy for our ShopHouse project. I will be explaining some of the more technical reasons for the design and material decisions that we are making as a couple for this project.
So why build using concrete sandwich panels for our exterior walls?? There are a variety of reasons but this decision started as a desire to find a better way to build a house and shop. And a better way to achieve our goals of having the lowest possible operating cost and the lowest possible maintenance cost.
I look at conventional 2×4 construction as “lowest common denominator” construction – while it is cost effective I find it to be incredibly wasteful and sloppy. It also has a fundamental problem that we needed to avoid to achieve our “cooler” concept of thermally isolating the inside of the house from the outside as much as possible. Every 2×4 creates thermal paths between inside and outside surfaces, thus creating thousands of holes in the thermally isolated “bucket” that we are trying to achieve.
There are certainly a number of ways to reduce the thermal paths or bridges between the inside and outside surfaces but these add complication and cost to the building process. One way is to build 2 separate walls so that there is insulation between the inside and outside surfaces. Again this can give a good thermal result but essentially you are building 2 separate houses, one inside of the other.
Another factor with conventional 2×4 construction is that exterior wall surface materials must be added to project the exterior surface from the elements. The exterior sheathing, typically plywood or OSB, must be covered to prevent degradation from rain, sun, etc. There are obviously a very wide variety of materials to use but most are susceptible to damage from the elements and require some level of maintenance. Brick can be used as an exterior material but you are again essentially building multiple walls in order to achieve the desired end result.
In almost all cases conventional 2×4 construction assumes sheet rock for the interior wall surface. I find this to be another “lowest common denominator” construction material. It is very forgiving of construction errors, easy to find people to install and finish, etc but I personally find it to be a material that I would like to avoid if at all possible. It is messy to install and finish, susceptible to damage from everyday household activities (and especially damage from dogs!), and difficult to hang items from the walls because of its low structural strength.
The net out of wanting to find a better way to build a house is that I challenged the architect/builders that we considered to design a house with no 2×4’s and no sheetrock. Needless to say the reactions were interesting. I think that most didn’t believe that I was serious – but at least one took it to heart and embraced the philosophy that this challenge required.
Coming up next – Why concrete sandwich panels for our exterior walls? Part 2 – Step 1 toward concrete sandwich panels – the exterior walls