Monday, February 11, 2008

Not that simple

Being a meditation on precision and accuracy.

Having spent over four hours on Sunday recalculating the building volume and envelope, and despite my overconfident assertions on Saturday, I have to admit that there were significant errors in my methodology first time around (in November). The building volume is 3.8% smaller than I thought, and the envelope is 3% larger. It's an enormous difference, the missing volume is equal to 56cm in height across the entire footprint of the building; the extra area is equal to the floor area of a typical McMansion. The reduction in the building volume is good, it will save on (predicted) construction and heating costs, but the increased envelope size will do the opposite: a larger surface means more heat lost to the environment in winter.

It interests me to note that the difference (increase) in envelope is entirely underground, whereas only 60% of the decrease in volume is below ground level. Half of the difference in volume can be explained by a simple mistake: I counted the ground-floor slab twice, in both basement and ground floor volumes. Duh.

Having arrived at (a) those figures and (b) 6 p.m. on Sunday, I went home; and now here I sit and wonder whether that can really be true. How can I have been wrong on that scale? I am certain that my methodology this time is superior to November: I have actually listed every surface and every block of building volume, and written out their dimensions on the prints, and have gone through the list and verified and checked off every number. My original notes from November are pencil sketches and scribbled numbers, on letter-size pages stapled together; the prints from that time hold only the totals, not how these were arrived at.

Counting large numbers of small things which cannot all be seen at once is always fraught with potential inaccuracies. We still laugh about a large hotel we designed in the mid-90's, where I would arrive at a different number of bedrooms every time I counted them. (In fairness, the project was still in flux: rooms did actually come and go even while it was being built.) In the end, I spent a half-day on the site with plans in one hand and coloured chalks in the other. I walked the length of every corridor and colour-coded every doorway, both in reality and on paper, and came to a definitive count—and to a number that had never come out any time I counted the rooms from my desk.

I shall make a cup of coffee, take a sharply-pointed red pencil and a fresh set of prints, and once again check off each dimension one by one. This is what architects do, my dears, regardless of what you see in films and on TV.

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5 Comments:

Blogger zhoen said...

I believe you.

February 11, 2008 at 2:12:00 PM GMT+1  
Anonymous JoeInVegas said...

Good thing that you checked again. But how did the hotel get built without accurate plans?

February 11, 2008 at 5:12:00 PM GMT+1  
Blogger Pacian said...

I think you should redecorate the TARDIS next. You clearly have the necessary experience.

February 11, 2008 at 9:47:00 PM GMT+1  
Blogger brooksba said...

That's a lot of attention to detail. Good luck and I hope that your rework of the plans shows the same number or a better one. I'd be lost.

February 12, 2008 at 9:01:00 AM GMT+1  
Blogger Lioness said...

Oh and it sounds ravishing. Your having occasional problems with counting things affords me great comfort, I'm normal, NORMAL!

February 12, 2008 at 11:18:00 AM GMT+1  

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