# Window-to-floor area ratio calculation in 4 easy steps (SANS 10400-XA 4.4.4.1 & 2)

First some background: New legislation in South Africa dictates that it is necessary to determine the window-to-floor area. This ‘regulation’ is applicable to many other countries, not just South Africa. (LEED in USA, Green Building – various countries, Energy Star etc…)

“SANS 10400- XA 4.4.4 Fenestration

4.4.4.1 Buildings with up to 15 % fenestration area to nett floor area per storey comply with the minimum energy performance requirements.

4.4.4.2 Buildings with a fenestration area to nett floor area per storey that exceeds 15 % shall comply with the requirements for fenestration in accordance with SANS 204.”

This window-to-floor area ratio balances energy, first cost, and indoor environmental quality. This will prevent solar gain from overheating the living space. Having too little glazing misses out on free solar energy – but too much glazing can result in excessive heat gain in the summer and unnecessary heat loss in the winter.

From a purely economic viewpoint, lower window area ratios lower the first cost to purchase. Window-to-floor area ratios above 15% for standard construction require increased envelope performance ratings and mechanical equipment efficiencies.

While energy use increases with window area, the penalty is not significant when high performance windows (double or triple glazed) are used. But of course the first cost to purchase for these are much, much more higher.

How to:

I am aware that there are “fenestration calculators” available (there is even one for purchase?) But these still require the user to manually count the windows (Yes, 1, 2, 3, 4….etc) together with their relevant height x width.  In-fact this method is daft and pales in comparison to the speed and ease that this is possible to achieve using ArchiCAD.

In this example I used the standard “ArchiCAD 15 Template” (INT English). The example building is a 2 story office building. Ground Floor = 260m2 and First Floor = 260m2. Therefore 260 x 15% = 39m2

Place a zone stamp on the floor plan to establish the total floor area per story (this can be done with one click)

How to do this in 4 easy steps:

In the Navigator – Project Map > Schedules > Element double click on “Window list” to open it.

Click on “Scheme Settings…”

Under Criteria / Window List – click on “Add” and change criteria to “Story” (this will filter the window schedule by story) Just remember to change this to “1”. Later on you can also duplicate the Scheme – Window List and “Rename” it to Window List Ratio Ground Floor and Window List Ratio First Floor for example.

Under Fields / Window List Copy – find the field “W/D opening surface on the reveal side”. Related to each selected schedule field, 3 buttons are available at the right to fine-tune sorting criteria. Choose  display a “sum” to add a schedule cell that will contain the sum total for all items of this field.

Click on “OK” to close the Scheme Settings window. You will then see the total square meter displayed for all the windows for the story selected.

Summary: As per the result (which only takes a minute to set up) one can clearly see that in this example both the Ground & First floor fenestration do not exceed the 15% per floor area ratio. Of course the windows can be modified and optimized, individually or globally, and the resultant ratio established by a simple click on Window List to recalculate the result in seconds.

# Door/Window Functionality Survey (Wish-list)

I am conducting a survey on the functionality of doors and windows.

Starting off with “standard” Door/ Window Dimension Markers available in ArchiCAD. This  is the result of increasing number of clients wanting to know where they find a door / window marker represented by the pictogram highlighted in the screenshot below….. it depicts a circle divided horizontally with a door number top and suffix below.

An interesting aside to the above question is that ArchiCAD is available in 21 languages and additional localized versions. What this means is that a lot of countries share similar objects (same object but different language description) but also distinct objects “applicable” to their market. Remembering that these objects can be 3D or 2D. In the “perfect world” wouldn’t it be wonderful if we could share some of these objects if they suite our needs?

At the risk of stating the obvious take a look at the screenshot below

The second question is a request for “accurately” looking steel door frames. Take a look at doors found in the INT Library – for example “D1 Metal…”. The door frame does not look anything like a metal door frame, nor can it be manipulated to look like one.

But now look at the same door “D1 Metal…” found in the USA Library, it is found in the folder “08 11 00 Metal Doors and Frames” with the obvious difference that it has a steel frame option.

And take a look at it placed in plan at a scale of 1:20

Your response to the above would be appreciated.  (only 2 questions are asked)

# Wall intersection issue/ control of – creative use of the Polygonal Wall

Sometimes when dealing with certain configuration of wall intersections, a problem can occur with the correct display of “tricky” intersections. In this example 4 walls joining create an intersection with an overlap. Changing the reference line of the walls by inverting them can sometimes help. But one can waste time trying out different permutations and in this instance I want control over the ‘sharp’ corners. A much overlooked, simpler option is to make use of the polygonal wall.

For more information and instructions on the use of the polygonal wall visit my page ArchiCAD Help and use the context-sensitive Help system by searching for “polygonal wall”.

In this example I selected the polygonal wall and started tracing the outline of the intersection. Please note: that this method allowed me to control the construction of the sharp corners that would have been difficult to plaster.

Once completed I then trimmed back the other walls using the split command. To do this select the wall and then Command/ Ctrl click the edge to split, then delete the ‘fragment’ wall.

I was then left with a clean wall intersection that I had complete control over.