KCRag Forum

FangKC wrote: ↑Tue Jul 25, 2023 3:40 am Density without Delight: Vermonniitty’s Lessons for Urban Planners

https://urbanfinland.com/2023/07/24/den ... -planners/

FangKC wrote: ↑Tue Jul 25, 2023 7:47 pm And Port KC. As I looked at some of those photos in Finland, I was reminded of Berkley Riverfront development.

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Many of these diseconomies are the result of building taller. Each additional floor adds load to the floor below, requiring heavier structural framing and more extensive foundations. Lateral forces rise non-linearly with height (bending moments rise with the square of height; sway and deflection rise with height to the 4th power), requiring stronger lateral systems and a stiffer structure.

The taller your building gets, the more complex your mechanical systems become, and the more elevators you need to add, which encroach on the rentable space below (shorter buildings, on the other hand, might not need elevators at all). A taller building has more stringent fire safety requirements, requiring the use of expensive, non-combustible materials or fire protection systems. Every additional floor in a building requires proportionally more infrastructure, and requires proportionally more construction time (since it takes longer to move people and materials to the top.

Cost of building with regards to height for US construction, via Eriksen 2021. The jumps at 8 floors are from additional fire safety requirements once your building is a “high rise”. Adding even more floors results in more costs per floor.

A building that just got larger horizontally would also face diseconomies (though fewer, and they might not apply to certain types of buildings such as industrial buildings). Larger buildings require larger parcels of land that will be more difficult to assemble. They face more opposition from the community. They may have increased market risk since they’ll be adding a large volume of available space to the market all at once. They take longer to construct, making the investment returns less attractive. And larger occupancies have stricter fire code requirements even outside of building height.
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Construction starts sunk in recent months as turbulence hit supply and demand in the multifamily market and construction financing gets harder to secure.

In June, there were an annualized run rate of 477,000 apartment units in the starting phase of construction, according to U.S. Census Bureau data reported by Commercial Real Estate Direct. The figure marks a 16.5 percent drop from the previous month and the first time the annualized run rate has sank below 500,000 units since December.

The Census Bureau defines the start of construction as the beginning of excavation for footings or a foundation.

A primary cause of the construction start drop is the difficulty facing financing for projects. As interest rates have ticked upwards over the last year and a half, developers have struggled to find ways to fund projects.
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aknowledgeableperson wrote: ↑Sun Jan 21, 2024 11:31 pm An interesting article.
https://www.scientificamerican.com/arti ... s-by-2100/
"The Urban U.S. could look very different in the year 2100, in part because thousands of cities might be rendered virtual ghost towns. According to findings published in Nature Cities, the populations of some 15,000 cities around the country could dwindle to mere fractions of what they are now. The losses are projected to affect cities everywhere in the U.S. except Hawaii and Washington, D.C.

“The way we’re planning now is all based on growth, but close to half the cities in the U.S. are depopulating,” says senior author Sybil Derrible, an urban engineer at the University of Illinois Chicago. “The takeaway is that we need to shift away from growth-based planning, which is going to require an enormous cultural shift in the planning and engineering of cities.”"

shinatoo wrote: ↑Mon Jan 22, 2024 10:49 am

aknowledgeableperson wrote: ↑Sun Jan 21, 2024 11:31 pm An interesting article.
https://www.scientificamerican.com/arti ... s-by-2100/
"The Urban U.S. could look very different in the year 2100, in part because thousands of cities might be rendered virtual ghost towns. According to findings published in Nature Cities, the populations of some 15,000 cities around the country could dwindle to mere fractions of what they are now. The losses are projected to affect cities everywhere in the U.S. except Hawaii and Washington, D.C.

“The way we’re planning now is all based on growth, but close to half the cities in the U.S. are depopulating,” says senior author Sybil Derrible, an urban engineer at the University of Illinois Chicago. “The takeaway is that we need to shift away from growth-based planning, which is going to require an enormous cultural shift in the planning and engineering of cities.”"

All this depopulation doesn't seem to be helping with the housing shortage.

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Sixty years ago, the renowned Bangladeshi-American architect and engineer Fazlur Rahman Khan demonstrated the exponential impact of a building’s height on the amount of material needed to build it. Indeed, doubling the height of a building could triple the structural materials required. A stronger structure, using more materials, is needed to withstand greater wind and earthquake loads on taller buildings.

This means there’s a large “embodied carbon premium for height”. This premium is the additional greenhouse gas emissions from producing the extra materials needed for a taller skyscraper.
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We took a detailed look at Dubai, a city celebrated for its towering skyline. We found the collective vanity height of its 100 tallest buildings adds up to more than 3.5 kilometres.

We estimate these decorative elements contributed at least 300,000 tonnes of greenhouse gas emissions. That’s both the direct embodied carbon of the spires and, much more importantly, the embodied carbon added by reinforcing the buildings to support the extra structural loads.

To put this impact into perspective, 300,000 tonnes of emissions is equivalent to the embodied carbon associated with building about 2,400 average Australian homes. It’s a hefty price to pay, simply to adorn 100 skyscrapers with pointy hats that inflate their heights and status in global rankings.
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