Energy Efficient Design - The Passive House in Ireland
This concept is gaining traction in Ireland in recent years. The Passive House standard is a specific construction standard which results in good thermal comfort conditions in the house all year round without traditional heating systems…
More precisely, Passive house is a rigorous, voluntary standard for energy efficiency in a building, reducing its ecological footprint. It results in ultra-low energy buildings that require little energy for space heating. Typically, savings of 75% of space heating costs (compared to other new builds) are achieved or 90% compared to the average house. This means that heating bills might be 10% of those of the average house!
Concerns about man-made climate change and the escalating costs of fuel and energy mean that having your new house designed in accordance with Passive House principals becomes increasingly attractive.
The standard is achieved principally by:
Very high levels of insulation in the walls, roof and floor
Heat-recovery ventilation systems
Good orientation in relation to the sun
High Performance Windows
This standard, developed primarily in Germany, has been named Passive House because the passive heat inputs delivered externally by solar irradiation through the windows (solar gain) and provided internally by the heat emissions of appliances and occupants in the house are sufficient to keep it at a comfortable temperature throughout the heating period.
It should be noted that heat-recovery ventilation systems with associated air tightness are now nearly standard in well-designed new houses. In addition, Building Regulations require increasingly higher levels of energy efficient performance mainly through increasing levels of insulation. The Passive House is thus the next logical step: upgrade the home further by adding sufficient insulation etc so as not to require a conventional heating system and then pay for that upgrade by the saving from omitting that heating system.
Passive Houses tend to look slightly different from conventional houses in that:
Features that cost energy in practice - because of their extra surface area from which heat is lost - tend to be avoided or at least used sparingly: e.g dormers, bay-windows, long and narrow extensions to the main body and split levels.
There will be large windows to the south and south-west and small (or no) windows to the north. There will be as few external doors as possible.
There will be no fireplace/chimney as a lot of heat would be otherwise lost through traditional open fireplaces.
One surface of the roof will be oriented to the south for solar collectors.
The Passive House must be designed in detail taking into account the particular site conditions such as its orientation in relation to the sun, prevailing wind direction, level of exposure etc.
Other design issues are:
Calculating the U-values of components requiring high thermal insulation
Calculating energy balances
Designing comfort ventilation
Calculating the heat load (with reference to Irish climatic data)
Adhering to the strict heat loss and air leakage requirements
The air quality in a Passive House will be very good - as the air in the house is circulated through a filter in the ventilation system - and there will be no draughts. This will be very important if, for example, a family member suffers from asthma. These qualities apply of course to any other form of low energy house which includes a heat-recovery ventilation system and is designed to be airtight. The ventilation system in a Passive House may contain a built-in electric heater to boost the heat in the house at critical points in the day e.g. early morning.
The biggest advantage of living in a Passive House is surely that there are no (or minimal) fuel bills or maintenance costs associated with a conventional heating system.
Rigorous testing of passive houses after several years, have shown that the houses do, if properly designed, actually perform in practice (as well as on paper)!