How to insulate a building with the three methods of heat transfer
Here will be a summary of all the insulating strategies that we have
talked about. If we want to insulate a building in the context of
all of the heat transfer mechanisms, how can we do so?
First, we will want to insulate with a material that has a low rate
of conduction. Ideally, we would use a vacuum insulated panel or
something similar, however, because of their relatively high cost
and fragility, we will go with something a little more conventional.
We will use a material that has a high porosity so that we can take
advantage of the low conductivity of air, and ideally the material
that we use as an insulating material will also have a low
conductivity. With these conductive parameters in mind, we will end
up going with an insulating material such as fiberglass or mineral
wool. These two insulators both have a high porosity, low
conductivity, and are relatively cheap and common to help keep our
building's insulation economical.
Next, we will want to minimize the rate of heat loss via convection.
Even though the walls of our building are fairly thin, they are
still large enough to facilitate convective heat transfer. So, to
minimize the movement of air in our walls, we will want a material
that has a good resistance to fluid flow. Using the same materials
that we used to reduce conductive heat transfer will work pretty
well, but there are other materials that will work better. For
example, areogel has a better resistance to conductive heat transfer
than mineral wool, although it is more expensive than mineral wool.
However, for a conventional building application, mineral wool is
good enough. We will also need to make sure that our insulating
space is air sealed to prevent too much outside air from flowing
through our insulation and reducing its effectiveness.
Lastly, how can we use heat transfer via radiation to help insulate
a building? By using a reflective material that has a low emissivity
and absorption, and therefore a higher reflectance, we can reduce
the amount of heating via electromagnetic radiation that will be
transferred to the material. If our building is going to be in an
area that will experience a significant amount of electromagnetic
radiation, then installing a radiant barrier will help decrease the
rate of heat transfer that is being transferred to the insulation.
However, in areas that experience less electromagnetic radiation,
the effectiveness of a radiant barrier will probably be
insignificant. A radiant heat barrier will work very well in hot and
sunny environments that experience a lot of solar radiation,
however, since we live in Alaska, a place with highly variable
temperatures and solar radiation exposure, a radiant heat barrier
will probably not be necessary for our insulation needs. Especially
if the increased insulation capabilities of radiant heat barriers in
our environment are not worth the cost compared to increasing the
thickness of our insulation, then adding a radiation barrier would
be inadvisable.
This summary of how we should insulate our homes does neglect some
other important considerations, such as preventing moisture buildup,
but this should give an overview of what considerations to take for
insulation as they relate to heat transfer mechanisms.
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