5 ms·

What does passive solar entail exactly? And can it make people comfortable on a 95 degree day?

Mz 9y ago
Passive solar includes a variety of approaches, such as thermal mass, architectural design that let's more sunlight in during winter and less in during summer and placement of deciduous trees to shade the house in summer and let sun onto it in winter. Yes, it can keep people comfortable on a hot day. It is typically far more comfortable than conventional housing.
- Johnny555 9y ago
  But don't underestimate the effect of good insulation (including windows). When the temperature hit the upper 90's here, I didn't need any air conditioning at all -- just turned on a window fan after dark to bring in cool air, then turned it off in the morning and closed the windows, pulled down the inside sunshades and closed the curtains in rooms facing the sun. The upstairs gets a little warm during the day, but is tolerable by bedtime since the outside temperature has cooled by then. The downstairs stays comfortable all day long. It helps that this is an attached condo with neighbors to each side, so there's effectively no heat coming in from the sides, just the roof, front and back of the condo.
  - Mz 9y ago
    Use of insulation and pulling down the sunshades and closing the curtains in rooms facing the sun is passive solar, in essence.
  - petre 9y ago
    Insulation alone is not sufficient. During a heat wave, after 48 to 72 hours, the heat will go through the wall, eventually. The time lag of the building material and the decrement factor are also very important. Tge time lag should ideally be close to 10-12 hours in order to dampen day/night variations in temperature. https://www.new-learn.info/packages/clear/thermal/buildings/building_fabric/properties/time_lag.html https://www.new-learn.info/packages/clear/thermal/buildings/... This is why most of the time passive solar involves carefully planning before you build. Otherwise the best you can do is sunshades, insulation, landscaping and white roofs.
    - Johnny555 9y ago
      We had 90+ degree days for 3 days in a row (and upper 80's before/after that) Night time temperatures dropped into the 60's, so by turning on the fan at night (which blew air out and upstairs window, bringing in the cool air in throughout the house), I think we would have been fine even in a longer heat wave. By morning, it was cool enough to need a blanket in bed. If temps didn't drop so significantly at night, then we may have had more problems. The house is standard wood-frame construction, so doesn't have a lot of thermal mass, though it is on a concrete slab, so that may have kept the downstairs cooler.
      - petre 9y ago
        Thermal wool has about 6 hours time lag and almost no thermal mass. The downstairs doesn't have a roof over it, so that's probably why. Typically attics/penthouses are the worst because they're sun heats them up through the roof all day long. So, white roofs, little to no thermal mass, ventilation is a solution in your area. Concrete also heats up badly and then releases the heat if it's exposed to sunshine.
lugg 9y ago
I think they mean designing homes to be more efficient in the heat to stay cool. And yes, it can help on 35c / 95f days. In Australia, even in a non aircon place I'm pretty much fine at 35c. Provided: I have a small fan, and I keep the place air tight. Having proper insulation would help a lot. It's kind of a little known trick, on really hot days (95+) you want to open the windows but you really need to keep them closed to keep the cool air in and hot air out.
- Mz 9y ago
  Generally speaking, passive solar means using energy directly from the environment for heating and cooling purposes without first turning it into electricity. So, passive solar water heaters can use black painted copper piping to heat water directly with sunlight, no electricity required. Wind is caused by solar energy and can have a cooling effect without first being converted to electricity. Etc. When done right, it is vastly more efficient and has far fewer side effects in terms of things like waste heat.
  - toomuchtodo 9y ago
    "Passive cooling techniques through reflective and radiative roofs in tropical houses in Southeast Asia: A literature review" http://www.sciencedirect.com/science/article/pii/S2095263514000399 http://www.sciencedirect.com/science/article/pii/S2095263514...
    - deleted 9y ago
      [deleted]

Mz 9y ago

Passive solar includes a variety of approaches, such as thermal mass, architectural design that let's more sunlight in during winter and less in during summer and placement of deciduous trees to shade the house in summer and let sun onto it in winter. Yes, it can keep people comfortable on a hot day. It is typically far more comfortable than conventional housing.

Johnny555 9y ago
But don't underestimate the effect of good insulation (including windows). When the temperature hit the upper 90's here, I didn't need any air conditioning at all -- just turned on a window fan after dark to bring in cool air, then turned it off in the morning and closed the windows, pulled down the inside sunshades and closed the curtains in rooms facing the sun. The upstairs gets a little warm during the day, but is tolerable by bedtime since the outside temperature has cooled by then. The downstairs stays comfortable all day long. It helps that this is an attached condo with neighbors to each side, so there's effectively no heat coming in from the sides, just the roof, front and back of the condo.
- Mz 9y ago
  Use of insulation and pulling down the sunshades and closing the curtains in rooms facing the sun is passive solar, in essence.
- petre 9y ago
  Insulation alone is not sufficient. During a heat wave, after 48 to 72 hours, the heat will go through the wall, eventually. The time lag of the building material and the decrement factor are also very important. Tge time lag should ideally be close to 10-12 hours in order to dampen day/night variations in temperature. https://www.new-learn.info/packages/clear/thermal/buildings/building_fabric/properties/time_lag.html https://www.new-learn.info/packages/clear/thermal/buildings/... This is why most of the time passive solar involves carefully planning before you build. Otherwise the best you can do is sunshades, insulation, landscaping and white roofs.
  - Johnny555 9y ago
    We had 90+ degree days for 3 days in a row (and upper 80's before/after that) Night time temperatures dropped into the 60's, so by turning on the fan at night (which blew air out and upstairs window, bringing in the cool air in throughout the house), I think we would have been fine even in a longer heat wave. By morning, it was cool enough to need a blanket in bed. If temps didn't drop so significantly at night, then we may have had more problems. The house is standard wood-frame construction, so doesn't have a lot of thermal mass, though it is on a concrete slab, so that may have kept the downstairs cooler.
    - petre 9y ago
      Thermal wool has about 6 hours time lag and almost no thermal mass. The downstairs doesn't have a roof over it, so that's probably why. Typically attics/penthouses are the worst because they're sun heats them up through the roof all day long. So, white roofs, little to no thermal mass, ventilation is a solution in your area. Concrete also heats up badly and then releases the heat if it's exposed to sunshine.

lugg 9y ago

I think they mean designing homes to be more efficient in the heat to stay cool. And yes, it can help on 35c / 95f days. In Australia, even in a non aircon place I'm pretty much fine at 35c. Provided: I have a small fan, and I keep the place air tight. Having proper insulation would help a lot. It's kind of a little known trick, on really hot days (95+) you want to open the windows but you really need to keep them closed to keep the cool air in and hot air out.

Mz 9y ago
Generally speaking, passive solar means using energy directly from the environment for heating and cooling purposes without first turning it into electricity. So, passive solar water heaters can use black painted copper piping to heat water directly with sunlight, no electricity required. Wind is caused by solar energy and can have a cooling effect without first being converted to electricity. Etc. When done right, it is vastly more efficient and has far fewer side effects in terms of things like waste heat.
- toomuchtodo 9y ago
  "Passive cooling techniques through reflective and radiative roofs in tropical houses in Southeast Asia: A literature review" http://www.sciencedirect.com/science/article/pii/S2095263514000399 http://www.sciencedirect.com/science/article/pii/S2095263514...
  - deleted 9y ago
    [deleted]