i am the Passive House consultant for Brooklyn Cohousing.
*rob*, poo mist is directly exhausted from the bathrooms to the outdoors by the exhaust side of the mechanical ventilation system.
denton, the windows can all be opened. the mechanical ventilation system provides fresh air during extreme weather when opening a window would be uncomfortable. it also captures the useful heat and moisture (or coolness and dryness) of the exhaust air stream in order to reduce heating/cooling energy needs. it also filters outdoor air so that dust and dirt do not enter, as they would when opening a window.
sam, as per previous comments, plenty of fresh air is moved through the building both by the mechanical ventilation system and by openable windows. research shows that in winter buildings with mechanical ventilation systems do in fact have cleaner, fresher air than buildings with opening windows only. this is mainly because people leave the windows closed when it's cold outside.
cmu, it is unsafe to rely on cracks in walls ("a less-tight house") for fresh air supply. if a wall is REALLY leaky (think colonial cottage), no problem. but if it's a little leaky (on par with most contemporary construction), then whenever a trickle of warm humid air passes through to the cold side of the wall, the moisture condenses out and wets the wall. once we have the right temperature range, a wet wall, and some dust, mold thrives. for this reason, if one is going to seal a wall at all (and for energy and comfort purposes this is a really good idea), then the tighter the better, and fresh air should be brought in through windows, mechanical ventilation, or purpose-built devices such as trickle vents. mechanical ventilation is great because it ensures enough air for health, but not so much as to waste energy or make the air too dry in winter.
dear all,
i am the Passive House consultant for Brooklyn Cohousing.
*rob*, poo mist is directly exhausted from the bathrooms to the outdoors by the exhaust side of the mechanical ventilation system.
denton, the windows can all be opened. the mechanical ventilation system provides fresh air during extreme weather when opening a window would be uncomfortable. it also captures the useful heat and moisture (or coolness and dryness) of the exhaust air stream in order to reduce heating/cooling energy needs. it also filters outdoor air so that dust and dirt do not enter, as they would when opening a window.
sam, as per previous comments, plenty of fresh air is moved through the building both by the mechanical ventilation system and by openable windows. research shows that in winter buildings with mechanical ventilation systems do in fact have cleaner, fresher air than buildings with opening windows only. this is mainly because people leave the windows closed when it's cold outside.
cmu, it is unsafe to rely on cracks in walls ("a less-tight house") for fresh air supply. if a wall is REALLY leaky (think colonial cottage), no problem. but if it's a little leaky (on par with most contemporary construction), then whenever a trickle of warm humid air passes through to the cold side of the wall, the moisture condenses out and wets the wall. once we have the right temperature range, a wet wall, and some dust, mold thrives. for this reason, if one is going to seal a wall at all (and for energy and comfort purposes this is a really good idea), then the tighter the better, and fresh air should be brought in through windows, mechanical ventilation, or purpose-built devices such as trickle vents. mechanical ventilation is great because it ensures enough air for health, but not so much as to waste energy or make the air too dry in winter.
best,
david
Posted by: DCoyleWhite at May 29, 2009 3:58 PM in response to Co-Housing Building May Be 'Most Energy Efficient' in NYC