Draft

A draft is an air movement due to a difference in air pressure . While with " Wind " directed, stronger air movement in the free atmosphere is called, is to "draft" or " train " or " drafts " a mostly weaker air movement and especially within confined spaces or inside of technical equipment ( fireplace , Combustion system ).

definition

According to the Beaufort scale , one speaks of a "quiet train" when the wind speed is 1 Beaufort. This corresponds to 0.5 to 2.1 meters per second or 1.9 to 7.4 kilometers per hour . An even weaker wind is classified as " calm ", a stronger wind as "light breeze ".

Drafts in rooms

A draft hole plugged with a newspaper on a skylight. A wasp's nest was built in the newspaper. (1933)

"Drafts" can exchange stale air .

Among other things, drafts can occur

• in leaky rooms
• by opening windows and doors
• due to high (vertical or horizontal) temperature differences in the building

Drafts in poorly sealed buildings (so-called joint ventilation ) cause heat loss and waste of energy. The airtightness in buildings can be measured using differential pressure measurement methods ("blower door test"). Passive houses have a particularly tight building envelope.

Health effects

Drafts can cause muscle tension ( hardening of the muscles ), especially if the body is sweating heavily and is not covered. As a concomitant influencing factor, drafts can promote the outbreak of infectious diseases such as the common cold after a virus infection.

Mythology and popular belief

Before the connections between pathogens and diseases were known, there was the idea that colds could be triggered by cold or drafts alone. This unscientific thesis has been vehemently denied in the past, especially in the USA. But with this, every causal connection was gladly dismissed as an irrational myth. There are currently scientists, such as Angela Schuh , who do establish a relationship between sick drafts, viruses and colds.

A fear of demons and wind used to be common in several cultures. Streets in cities were built as narrow as possible because it was believed that otherwise the wind could more easily bring diseases between and into houses. (It was only in modern times that people understood that narrow construction was partly responsible for the spread of the disease.)

Protection against drafts

The draft can be reduced through structural measures, in particular the installation of doors in open multi-storey single-family houses. Drafts at entrance doors can be reduced by using revolving doors or double entrance doors (in the form of entrance sluices).

Draft animal in the shape of a cat

Also tailor doors and windows or window frames to prevent drafts. Gaps may be closed by rubber seals and / or elongated felt strips that are glued to the lower edge of doors and touch the floor, as well as strips that have downward bristles or hair or curtains made of dense fabric. These are materials that also adapt well to unevenness in the floor when moving the door. Another way to protect against drafts is that colloquially known as draft animals : a usually round, oblong, modeled after an animal fabric roll with a diameter of a few centimeters, which is placed in front of the door or window columns.

Draft

Threading is in everyday language , a strong draft indoors. It is often perceived as annoying and is occasionally brought about on purpose for the purpose of faster air exchange ( ventilation ).

Typically, these are relatively uniform air currents that are caused to the outside by a pressure gradient between at least two openings (e.g. windows, doors, leaks) in a building. Such a pressure gradient already exists in weak winds when windows on opposite sides of a building are opened ( cross ventilation ).

The fact that a sustained flow of air can lead to the cooling of body parts in the flow may explain negative perceptions of the “draft” phenomenon.

A vertical variant of the draft caused by convection is the chimney effect , which occurs as useful as it is harmful . B. can be perceived as a draft in glazed stairwells when exposed to sunlight .

In heating systems with combustion systems , the passage of air is an essential prerequisite for operation, as it usually brings about the oxygen for combustion . To increase effectiveness, a forced draft is sometimes created in addition to the chimney effect , for example with the blowpipe in the smoke outlet of steam locomotives .

Modern calorific value technology when burning fuel gas in particular in a heating system cools the exhaust gas to well below 100 ° C in order to use the heat of condensation of the exhaust gas, which is rich in steam. In order to safely discharge the oxygen-poor and CO ₂ -rich exhaust gas over the roof, an electrically driven fan is required in the exhaust chimney.

In order to be able to ventilate windowless rooms in particular, often bathrooms and toilets, easily via an exhaust fan, easy access for indoor air must be created through slots in or under the connecting door. Warm air heating systems in houses, which mostly operate on floors, also require precisely planned draft options.

Individual evidence

1. ↑ Medicine: Be careful with the draft! Deutschlandfunk Nova , July 17, 2018.
2. ↑ Angela Schuh: Biowetter: how the weather influences our health , Beck, Munich 2007, ISBN 9783406536168 , p. 109f, preview Google Books .
3. ↑ Expert interview: drafts are harmful to health . In: Spiegel Online . July 2, 2014 ( spiegel.de [accessed July 29, 2019]).
4. ↑ Angela Schuh: Biowetter: how the weather influences our health , Beck, Munich 2007, ISBN 9783406536168 , p. 109f, preview Google Books .
5. ↑ Frederik Jötten: Expert interview - drafts are harmful to health , Spiegel Online, July 2, 2014
6. ↑ DER SPIEGEL 20/1968 - Demons at the window

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !