
Dutch city redraws its layout to prepare for global heating effects - perfunctory
https://www.theguardian.com/world/2020/jul/29/dutch-city-arnhem-redraws-layout-prepare-global-heating-effects
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acd
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-temp...](https://climate-
woodlands.extension.org/trees-and-local-temperature/)

Plus trees and plants clean the air from air pollution.
[https://www.nrs.fs.fed.us/units/urban/local-
resources/downlo...](https://www.nrs.fs.fed.us/units/urban/local-
resources/downloads/Tree_Air_Qual.pdf)

Plus trees and parks increase housing value of nearby properties.

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

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Scarblac
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.

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hyperman1
If you have a house there, what modifications would you make?

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Scarblac
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.

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saeranv
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.

