036. Design consideration: window shades

I've mentioned a few times already that it is crucial that a good plan be made for shading the (transparent elements of the) house from the sun in the summer to avoid overheating. Generally speaking, this topic is especially relevant in these times of rising global temperatures and there is a strong effort underway to find the best (low-energy) solutions. Organizations such as the European Solar Shading Organization (ES-SO) have some information in English on their websites[1]. Minergie in Switzerland provides guidelines for good practice. See Figure 22 in Post 29 to get an idea of the size of the problem for our house, as calculated for a particular set of parameters.

The German Institute for Standardization (DIN = Deutsches Institut für Normung) provides a useful listing of the rough efficiency factors for different types of shading systems as given in Table 4 below (visit the ES-SO link to see illustrations of these systems). Of course, the actual numbers will vary with the details of the type of materials used. In general, the best systems are those that are installed outside the glazing. For residential applications, roller shutters[2] seem to be the usual choice over here. Aesthetically they're not my favorite as I find them chunky and obstructive. A better alternative are external venetian blinds, with adjustable louvers that allow a view of the outside. They're rather high-maintenance from a cleaning point of view but WA assure us that in our locality we won't have to clean them more than once every couple of years.

Table 4. Solar gain reduction factors for different window shading systems. Smaller is better. Source: DIN 4108-2

	Reduction factor
Type of shade	Fc
No shading	1
Internal installation or between the glass panes
White or reflective surface with low transparency	0.75
Light colors or low (less than 15%) transparency	0.8
Dark colors or high transparency	0.9
External installation
Rear-ventilated adjustable louvers	0.25
Blinds and materials with low transparency, rear-ventilated	0.25
Blinds, general	0.4
Shutters, roller shutters	0.3
Overhangs	0.5
Awnings, ventilated	0.4
Awnings, general	0.5

---

[1] A nice list of the different types of shading systems can also be found at their site → European Solar Shading Organization

[2] Actually, I'm not sure this is the right term for the objects I'm thinking of which are called Rollläden in German

035. Design consideration: roof and facade

There are so many details of the house under consideration right now that it doesn't make sense to talk about them until we come to some sort of agreement. I'm going to try to write updates as we get close to decisions, to keep a record of the evolution of the process. First up, a discussion of the choice of roof and siding material.

The unusual angular shape of our house demands a smooth transition between the roof and the walls. Ideally, the cladding should be of the same material and this limits the choice to slate, metal or fiber-reinforced cement board[1]. Factor in the cost, and only the last option remains.

In Switzerland there is only one[2] supplier for this material: Eternit. Eternit cladding stock is composed (by volume) of 40% Portland cement, 11% limestone powder and similar, 2% reinforcing fibers such as PVOH[3], 5% process fibers, 12% water and 30% air in the form of pores. The precursor to this material used asbestos fiber, but since 1991 all Eternit products have been asbestos-free. For more information on asbestos cement, see the report at the link at footnote 2.

I haven't been able to find a good example of an unconventional house completely clad in Eternit boards in a way similar to what we're considering, so below are a couple of examples in slate where the roof-wall differences are eliminated. The details here are not important (for example, our house will definitely have gutters), the point is that the same material covers all the surfaces and the format of the tiles is uniform over the two building elements (roof and walls).

Figure 26. House in Wallis by Nunatak Sàrl Architects[4].

Figure 27. House in Basel by Luca Selva Architects[5].

---

[1] Faserzement in German, I'm not sure of the generally accepted English translation. Fiber cement board and fibrated concrete are some of the terms I've come across.

[2] An Austrian named Hatschek invented fiber cement (using asbestos) and patented it in 1901. He licensed the production method to only one manufacturer per country and it seems to remain that way. More information can be found in this report which deals with the asbestos aspect → The Tragedy of Asbestos

[3] PVOH is a synthetic polymer → Polyvinyl alcohol

[4] Details at ArchDaily → Zufferey House

[5] Details at ArchDaily → House in Lupsingen

034. The one that got away

I should say: the one we let get away.

Once in a while, I like to look back at my collection of notes to see how things have come along since we embarked on this house project. I had mentioned before that our architects had originally (in November 2008) presented us with two distinctly different designs to choose from. In the interest of keeping complete records, here are a couple of drawings of the one that we decided against.

Figure 25a. Plan B upper level.
Figure 25b. Plan B lower level.

There were many things we liked in this plan, but in the end we happened to like the other one better. I would have selected this design if we had neighbors living closer to us. In that case, the secluded garden and courtyard would have been more desirable. What is not apparent in these drawings is that the garden and courtyard are actually on different levels (the stairs are not drawn in).

Given the particulars of our land, with the open southern exposure, we think that the design we chose (click here to go directly to the post where I discuss that) makes better use of it. I particularly like that all the rooms, including the main bathroom, have views out on that side.

Which one might you have chosen? Feel free to leave a comment.

033. Choosing planners

Over the last few weeks, our architects — I'll refer to them as WA[1] from now on — collected bids from various planning firms for specific aspects of the house. It seems that construction activity around Switzerland, at least in the part where we live, is still quite intense and several of the companies that WA have worked with in the past decided not to submit bids for our project. Even so, WA made sure there were at least two bids in each category and we had a meeting last week to make the final selections. The categories we covered were as follows:

- the Bauingenieur: the people who calculate things like the statics of the building, in particular the parts in the ground which must be executed in concrete
- the Holzbauingenieur: the people who will do the details of how to construct the house in wood
- the HLS-Planer: Heizung (heating) Lüftung (ventilation) Sanitär (sanitation)
- the Elektroplaner: responsible for planning the electrical network

Once these "third-party" plans are in, they'll be sent out for bids from firms that actually do the work, such as build concrete structures and install plumbing. Meanwhile, WA are looking at every detail of the house and re-evaluating them, looking for the best solutions. New ideas are still being considered. I'll be giving updates here as things are finalized. We had not realized that so much designing would be done after the Vorprojekt (initial project) phase and I must say that we're really, really pleased with all the effort. This is our first experience working with architects and so far it has been excellent!

---

WA → Walker Architekten