Simply put, a Passive House is a building construction concept that is extremely energy efficient, comfortable, ecological and affordable. The energy efficiency of Passive Houses surpasses all other methods of building by just conserving energy. Rather than offsetting energy usage with numerous solar panels, a Passive House consultant finds ways to not expend that energy in the first place. This planning has the benefit of creating a comfortable building where temperatures remain steady, air quality is superior and monthly costs are minimized. Passive Houses are built with more attention to details; therefore create a longer lasting building while reducing energy needs for the life of the building.
Energy efficiency in Passive Houses comes from careful planning in the design process.
Planning the size and location of windows plays an important role in letting light and solar energy in but also balancing the amount of window area to minimize heat losses. Windows can be the biggest heat loss of all building components due to their low insulation values. Orientation of windows to the south in heating dominated climates is preferable to maximize solar energy gain. This however is carefully balanced with proper shading to reduce overheating in the summer.
If you go out on a very cold day, you put a warm coat, hat and boots on, right? The same concept goes for Passive House. Thick insulation levels minimize heat losses. This is achieved through high R-value insulation. R-value is a measure of how well the insulation resists heat losses. High R-value is achieved through thicker walls and/or more heat loss resistant products. The warm coat you wear on a cold day is like the walls of the house that wrap the building in a blanket of insulation. That warm hat is your buildings attic. Thicker insulation here means less heat lost. Ever stand around outside on a cold day wearing thin soled running shoes? The cold feet you get are a result of the heat being conducted out of your body to the ground. Stand around long enough and you will lose enough heat to melt footprints in to the snow or ice! Now imagine your house without insulation under the house. Heat will flow down to the ground as well. You need a thick "sole" on the "boot" of your house so the heat does not flow through to the ground. Whether you have a concrete slab or an insulated crawlspace, this is not an area to overlook.
In order to make the insulation effective, we need to stop airflow through the walls. Imagine going outside on a cold windy day wearing an open knit sweater. The wind blows right through and you get chilled. Put on a windbreaker over that sweater though and you can be nice and warm. Two components that have the same effect in a Passive House are the vapour barrier and the wind barrier. The vapour barrier stops air and moisture from leaking out from the inside and the wind barrier stops the wind from penetrating through the wall from the outside.
Heat recovery ventilator (HRV) efficiency
In order for your body to function your lungs bring in fresh air full of oxygen and exhale stale air full of carbon dioxide. An HRV does the same thing in a Passive House. A person at rest breathes about 7.5 litres of air per minute. In an enclosed space like a building, this would result in stale air over time as well as high humidity from showering, cooking and breathing. The HRV acts like the lungs exchanging stale air for fresh air, but also has an important role in recovering the heat being exhausted from the house and transferring that heat to the fresh air coming in to the building. This reduces heat losses to a minimum. However, some HRV's are more efficient at transferring that heat than others. This is where a Passive House Consultant runs the numbers on available HRV's and makes reccomendations on the best unit for your building.
Building Location, Orientation and Shading.
If you are standing outside and you are cold, would you rather be facing the sun or away from it? Standing in full sunlight or in a shadow? Passive Houses (in a heating dominated climate) are oriented to face the sun, preferably without major obstructions like tall buildings or mountains in the way. Passive House however is still possible in less than ideal locations, although there needs to be a balance with the other factors to keep the same low energy usage.
A Passive House Consultantruns all these factors through a computer simulation program to determine the right balance between components so that your building is efficient, comfortable, ecological and affordable.