5 ms·

Dutch city redraws its layout to prepare for global heating effects

35 points by perfunctory 6y ago

hyperman1 6y ago
If you have a house there, what modifications would you make?
- azepoi 6y ago
  Brise-soleil, awnings and longer roof eaves/overhangs. Light colour roof... plant trees...
- tonyedgecombe 6y ago
  Good insulation.
- Scarblac 6y ago
  I do have a house there, and my street's WhatsApp group is currently discussing ideas to see if we can get some of that subsidy. Mostly focusing on removing the pavement on our square and replacing it with grass and trees so far. Modifications are rather hard, actually. My house is from 1903. We have the lower part (two floors, the lowest is a sort of half-basement), and my upstairs neighbours have the upper part (also two floors). The walls are single (no insulation inside), but quite thick, brickwork. The bottom floor is just cement on top of the sand the house is built on. Inner floors are made of wood with thatch and plaster ceilings. Our main problem is that once the house is hot inside, it's almost impossible to cool down again. So perhaps adding isolation to prevent that, but it means putting a thick layer of insulation on the inside of existing walls. The other thing is that heating is done with natural gas (as in most Dutch houses), and we are supposed to switch to all-electric somewhere in the next decades. No idea how yet. Rainfall from the roof is still led to the sewer system. I guess we could change that so it goes into the garden we have in the back, but it'd be quite a large operation.
  - saeranv 6y ago
    Ah you are about to face one of my favorite problems. A high-performing building is air-tight, and well-insulated, but old masonry/brick buildings rely on leaky envelopes with no insulation to maintain a dry enclosure. Basically, the lack of insulation in these old buildings means that the heat emitted through your walls is likely drying your walls during the winter. Once you add insulation on the inside, any vapour from the outside (rain-driven, or drawn through material pores through capillary action) is going to hit the cold/exterior side of the insulation and condense inside your wall (which then causes mold, conducts heat). You can calculate this by assuming steady-state heat flow across your wall during cold/moist conditions and see if the temperature drop across the wall hits the dewpoint (point where air vapour saturates into liquid). That's why it's better to have the insulation on the outside, with a vapour barrier underneath it to protect your structure. With these kind of old building retrofits, that's not possible. However, you can solve it, basically by calculating the moisture and heat flow through your wall, and identifying the maximum insulation that doesn't cause condensation long enough to grow mold (this is called hygrothermal analysis). There's also various coats you can add to the exterior that have some success in control moisture drive, but if they backfire, you are basically sealing up the moisture inside, so that's always a back-up solution. Source: I've worked on retrofitting the envelopes of a lot of old masonry/brick buildings.
acd 6y ago
Trees work like natural airconditioners. Ie trees absorb water and emit cooled water moistuire. Thus trees cool air not only by shade but also by a natural form of evaporative cooling. Evaporative cooling effect of trees. https://climate-woodlands.extension.org/trees-and-local-temperature/ https://climate-woodlands.extension.org/trees-and-local-temp... Plus trees and plants clean the air from air pollution. https://www.nrs.fs.fed.us/units/urban/local-resources/downloads/Tree_Air_Qual.pdf https://www.nrs.fs.fed.us/units/urban/local-resources/downlo... Plus trees and parks increase housing value of nearby properties.
- saeranv 6y ago
  One more dynamic to factor in: the tree canopy will also block long-wave radiation emitted from the ground, which will increase urban temperatures.
Scarblac 6y ago
It should be noted that all Dutch municipalities were asked to draw up a plan to deal with climate change, and there isn't really anything drastic in this one. Also much of the Netherlands is below sea level, but Arnhem is not.

35 points by perfunctory 6y ago

hyperman1 6y ago

If you have a house there, what modifications would you make?

azepoi 6y ago
Brise-soleil, awnings and longer roof eaves/overhangs. Light colour roof... plant trees...
tonyedgecombe 6y ago
Good insulation.
Scarblac 6y ago
I do have a house there, and my street's WhatsApp group is currently discussing ideas to see if we can get some of that subsidy. Mostly focusing on removing the pavement on our square and replacing it with grass and trees so far. Modifications are rather hard, actually. My house is from 1903. We have the lower part (two floors, the lowest is a sort of half-basement), and my upstairs neighbours have the upper part (also two floors). The walls are single (no insulation inside), but quite thick, brickwork. The bottom floor is just cement on top of the sand the house is built on. Inner floors are made of wood with thatch and plaster ceilings. Our main problem is that once the house is hot inside, it's almost impossible to cool down again. So perhaps adding isolation to prevent that, but it means putting a thick layer of insulation on the inside of existing walls. The other thing is that heating is done with natural gas (as in most Dutch houses), and we are supposed to switch to all-electric somewhere in the next decades. No idea how yet. Rainfall from the roof is still led to the sewer system. I guess we could change that so it goes into the garden we have in the back, but it'd be quite a large operation.
- saeranv 6y ago
  Ah you are about to face one of my favorite problems. A high-performing building is air-tight, and well-insulated, but old masonry/brick buildings rely on leaky envelopes with no insulation to maintain a dry enclosure. Basically, the lack of insulation in these old buildings means that the heat emitted through your walls is likely drying your walls during the winter. Once you add insulation on the inside, any vapour from the outside (rain-driven, or drawn through material pores through capillary action) is going to hit the cold/exterior side of the insulation and condense inside your wall (which then causes mold, conducts heat). You can calculate this by assuming steady-state heat flow across your wall during cold/moist conditions and see if the temperature drop across the wall hits the dewpoint (point where air vapour saturates into liquid). That's why it's better to have the insulation on the outside, with a vapour barrier underneath it to protect your structure. With these kind of old building retrofits, that's not possible. However, you can solve it, basically by calculating the moisture and heat flow through your wall, and identifying the maximum insulation that doesn't cause condensation long enough to grow mold (this is called hygrothermal analysis). There's also various coats you can add to the exterior that have some success in control moisture drive, but if they backfire, you are basically sealing up the moisture inside, so that's always a back-up solution. Source: I've worked on retrofitting the envelopes of a lot of old masonry/brick buildings.

acd 6y ago

Trees work like natural airconditioners. Ie trees absorb water and emit cooled water moistuire. Thus trees cool air not only by shade but also by a natural form of evaporative cooling. Evaporative cooling effect of trees. https://climate-woodlands.extension.org/trees-and-local-temperature/ https://climate-woodlands.extension.org/trees-and-local-temp... Plus trees and plants clean the air from air pollution. https://www.nrs.fs.fed.us/units/urban/local-resources/downloads/Tree_Air_Qual.pdf https://www.nrs.fs.fed.us/units/urban/local-resources/downlo... Plus trees and parks increase housing value of nearby properties.

saeranv 6y ago
One more dynamic to factor in: the tree canopy will also block long-wave radiation emitted from the ground, which will increase urban temperatures.

Scarblac 6y ago

It should be noted that all Dutch municipalities were asked to draw up a plan to deal with climate change, and there isn't really anything drastic in this one. Also much of the Netherlands is below sea level, but Arnhem is not.