Questions tagged [building-physics]

The application of physics to the built environment, particularly with regard to the movement of heat, air, moisture, pollutants and light through buildings.

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Mechanics of an elevator bed/platform in a Tiny House

I'm building a Tiny House that will have a platform that moves about 1 meter up and down. Given that I have little to no experience using pulleys, cogwheels or any of the like, I'd like some feedback ...
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Why can thin sponge lining soundproof earmuffs but not walls?

Every webpage that I can find says that sponge is bad soundproofing material for walls because it's light and physics says that materials with more mass isolate better. So my question is how come thin ...
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Building orientation - how come both summer and winter solstice used for a facade?

I am planning to build a shed atop my terrace. I was analyzing the sun path to determine the overhang length, facade height etc, but got stuck with a conflict as below. The summer sun's location peaks ...
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Gravitational forces of a building

In trying to understand the gravitational forces of a building, I have devised a thought experiment: A building is floating in space. The building's mass is asymmetrically distributed. Inside it also ...
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Is destratification ventilation more efficient at ceiling level?

This question is more of a practical physics question. In buildings with heating systems, heated air tends to rise and create air temperature stratification - hottest air near the ceiling, coldest air ...
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1 vote
2 answers
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Will a platform only supported by a column in the center fall? (Excluding weather)

My friend told me that without wind, a building with a platform that only has a column supporting it would be balanced and not fall, given that there is no wind. I said that the platform would fall ...
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How much do I need to trickle my faucet in cold weather (as a function of x,y,z)? [closed]

I am told that, in cold weather, I should let my faucet trickle a little to prevent pipes from freezing, especially if some portion of my above-ground pipes are likely to get cold. Are there any rules ...
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How could a structure be earthquake-proof?

I was just doing some research about earthquake-proof buildings and I couldn't figure out how some buildings achieve that. All what I found was very brief and I just wish there could be an article or ...
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What is the difference between architecture of buildings in zero gravity and on Earth? [closed]

how is the architecture of buildings in zero gravity (space) different from buildings on Earth. like there is no concept of floor and ceiling in zero gravity so how are the buildings or spaceships ...
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How does the tuned mass damper on Taipei 101 work?

I'm interested in how the tuned mass damper on the top floors of Taipei 101 works, particularly how do engineers ensure that it dampens oscillation rather than making it worse. The damper can be ...
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What's the required compressive strength and density for a material out of which to build a pyramid of a given angle and height?

I've got a pyramid (really a wall with inclined edges), that for our purposes is infinite in length. It is 1 kilometre high, and the edges have an internal angle of 60 degrees. Here's a cross-section: ...
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4 votes
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When a skyscraper sways in the wind, in which direction is the motion?

Skyscrapers sway in the wind (Source here). Which direction, relative to the wind, do they sway, ignoring effects of other buildings nearby? I can imagine wind from the North blowing a skyscraper's ...
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'Drummy' sound when striking with a hammer

In building there is a common test for masonsry structures that involves striking the structure with a hammer and listening to the resulting sound. If the sound is ringing the structure is fine but if ...
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Proportion of heat or energy passing through a window by radiation vs conduction

I'm trying to understand how modern window films or coating (so-called "Low-E" coatings) can improve the "R" value of the window just by reflecting internal room radiant energy (presumably long-wave ...
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Big motor vehicle's body vibration [closed]

What is the main cause of vehicles like cheaply designed busses to vibrate it's whole body at high or low engine RPMs??
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Why was the glass broken in the Lobby but not above the impact zone? - 9/11

Disclaimer: I do thoroughly believe that 9/11 was a terrorist attack, so please don't start arguing whether it was an attack or inside job, focus on the question. Also: I was about to post this in ...
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How to model heat movement and loss of a house? [closed]

I was recently looking at the recommended insulation values for houses, and was surprised to find wall insulation recommendation was not just moderately less than the attic, but a tiny fraction of it. ...
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How to construct a 12-micron thin layer of powder+epoxy?

Okay, this is more of an engineering tactic question perhaps, but any insight into any possible process will be very, very appreciated. So I'm mixing a powder with epoxy, making a pasty, fluid semi-...
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Is it possible to build an atom smasher in your backyard?

Michio Kaku once said that He build an atom smasher in his garage as a science fair project in high school. He said he used 400 pounds of transformer steel and 22 miles of copper wire. But I would ...
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The Perfect Bridge [closed]

Is it possible to calculate the amount of weight a perfectly designed bridge(not necessarily known) can hold given certain parameters and under ideal and perfect conditions: amount and type of wood ...
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If we let let explosives go off under one of the side of a skycraper, what will happen? [closed]

Imagine a skyscraper under which explosives are placed, but only beneath one of its sides. After detonation of the explosives, will the side under which the explosives were placed come crumbling down, ...
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if a building sways because of a constant wind will it sway back past its equilibrium [closed]

If I have a building that acts analogous to a spring at equilibrium and a constant wind comes from the north forcing the building to sway to the south will the building ever sway back towards the ...
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Building a parallel plate capacitor [closed]

I have failed to built a parallel plate capacitor using a pair of Aluminium foils as the parallel plate and air as the dielectric medium. The capacitor is not working at all. My applied potential is ...
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processes that cause heat loss in buildings [closed]

I'm looking for a fair study in which they assessed the importance of different processes that cause overall heat loss in buildings. With processes i mean convection, radiation, conduction trough the ...
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How does a building lose heat through a gap in the external wall?

Consider a building in a cold climate with a temperature difference of 20 degrees C, i.e. external temp. is 0 degrees C and internal temp is 20 degrees C. How does a building lose heat through a gap ...
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Why do tall buildings have low resonant frequencies?

I know that tall buildings have low natural frequencies, hence they're more vulnerable to earthquakes, but why do they have low natural frequencies?
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Surviving collapsing buildings: Which floor maximizes your chances of survival? [closed]

Although this is not a purely physical question, I think this is the best StackExchange place to ask it. When a building collapses, which floor should you go in order to maximize your chance of ...
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What is "hydrostatic uplift pressure"?

I was reading Wikipedia about the St. Francis Dam and came across this sentence. Water that collected in the drainage pipes under the dam to relieve the hydrostatic uplift pressure was carried ...
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Vortex shedding

So I was reading about vortex shedding, and got to know that it causes the building to resonate. Is there any way to use this resonance to generate electricity (maybe use quartz?) I am trying to make ...
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5 answers
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If I replace all my lights with LEDs will my heating costs increase?

A number of nations are passing bills to phase out incandescent light bulbs. The thinking is that the tungsten filament is an inefficient method of turning electricity into light, the rest of the ...
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1 vote
2 answers
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Best method for building balsa-wood bridge [closed]

I'm building a bridge out of balsa-wood strips for school, and wanted some advice. These are the specifications: Height: 2 to 6 in Length: 12 inches, plus 1-3 inches on each side resting on tables ...
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Why is an air conditioner more efficient in a low-thermal-mass house?

Why is an air conditioner more efficient in a low-thermal-mass house? I recently read To get these efficiency gains it is important to use the air conditioner as it is intended: the unit has to ...
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4 votes
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Can sound be separated from air?

I would like to open up a window in my house, let the air in, but keep the sound out. Could a device be designed to put up on the window, like a screen, and accomplish this?
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Water flushed down, water pumped up (in buildings)

I live in a tall building (20 floors) on a mountain. Because the water pressure from the water company is not enough, there is a water pump at the last floor which is activated each time someone is ...
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Maximum efficiency for a counter-current heat exchanger (double flux controlled motorized ventilation)

I am not sure if I can explain the question correctly because I don't know the name of this mechanism in English. This is my explanation attempt: In a house, a tube is expelling the air from the ...
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Air velocity in a double-skin facade

I was wondering how the air flows in a double skin facade? Say I have a glass facade with a depth of 1m, a height of 200m and a width of 10m. It is a single vertical shaft all the way up with openings ...
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Should I heat my room when I'm not here, energy-efficiently speaking?

I was wondering as it's getting cold : is it better for my electricity bill to shut down completely my (electric) heater during day, and to turn it on again when I come home (then it will have to heat ...
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18 votes
5 answers
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Which direction does air flow?

I remember learning this in high school, but have forgotten it, and can't seem to find it anywhere online. Air travels from areas of high pressure to low pressure...correct? So if I have a cold room ...
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Does opening the oven door heat the house more than if the door is closed?

In the winter I am in the habit of opening my oven door once I am done baking so that I can add the heat to the house. However I recently thought about it and it would seem that even if the door is ...
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What instrument will measure voids in a brick wall non-destructively?

Let's take what's ostensibly a solid brick wall. It looks solid from the front and the back. It's typically at least two widths of brick thick, plus some. What techniques could we use to non-...
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3 votes
3 answers
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Function of air conditioner

What i always thought that air conditioners blow the cool air without knowing that they actually take the warm air from indoor and from outdoor. But whats the point of taking air from indoor and ...
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3 votes
2 answers
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What devices could be taken round dwellings to measure the thermal conductivities of buildings in situ?

Your lateral thinking and knowledge of lab kit could help us solve a tricky measuring problem in building-physics. One of the problems we get in modelling the heat demands of buildings, is getting an ...
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