What is Passivhaus?
Passivhaus is a rigorous, voluntary, design and construction standard for energy efficiency in a building. It results in ultra-low energy buildings that require 90% less space heating than that of a standard new build, and thereby reduce its ecological footprint and fuel bills.
For a building to be considered a Certified Passivhaus, it must meet the following criteria:
• The Space Heating Energy Demand is not to exceed 15 kWh/m2 per year or 10W per square meter peak demand.
• The Primary Energy Demand, must not exceed 120 kWh/m2 per year.
• Building Air tightness, a maximum of 0.6 air changes per hour at 50 Pascals pressure.
• Thermal comfort must be met, with not more than 10 % of the hours in a given year over 25 °C.
• Passivhaus buildings are planned, optimised and verified with the Passive House Planning Package (PHPP).
All of the above criteria are achieved through intelligent design and implementation of the 5 Passive House principles:
• A Super insulation fabric U-values of ≤ 0.15W/m2.
• U-values for windows and doors (for both the frame and glazing) need to be ≤ 0.8W/m2K (0.85W/m2.K installed).
• Thermal bridging ideally needs to be eliminated or minimised, a psi value of <0.01W/m2K is considered thermal bridge free.
• An air pressure test must result in an n50 airtightness level of 0.6ach, averaged over pressurisation and depressurisation.
• Whole house mechanical ventilation with heat recovery (MVHR) that is 75% efficient or better, with a low specific fan power.
Although there are PassivHaus constructions in countries such as Germany and Austria that have no higher capital costs than buildings according to current building regulations, as a rule of thumb it implements a rise of the capital costs of about 5-15%. – especially in countries such as the UK and Ireland where the construction of PassivHaus buildings is still relatively new.
A large part of these costs will be compensated by the decreased running energy costs.
Example - A 2000 sq ft house will cost less than £190 per year for space heating using a standard oil boiler and maintaining at a constant temperature of 20 degrees internally day and night all year round with excellent air quality and indoor comfort.
“The core focus of the the Passivhaus standard is to dramatically reduce
the requirement for Space heating, whilst also creating excellent indoor
air quality and comfort levels”