Outline Specification

The Passivhaus standard is a comprehensive low energy standard intended primarily for new buildings.  The following energy performance targets define the standard and must be met in order for certification to be achieved.

Energy performance targets and air changes per hour

Specific Heating Demand

≤ 15 kWh/m2. yr

Specific Cooling Demand

≤ 15 kWh/m2. yr

Specific Heating Load

≤ 10 W/m2

Specific Primary Energy Demand

≤ 120 kWh/m2. Yr

Air Changes Per Hour

≤ 0.6 @ n50

 

The Passivhaus standard can be achieved when refurbishing buildings although this can prove costly, for more on Passivhaus refurbishment please see the EnerPHit standard. 

The standard requires that the Primary Energy demand target is met in all cases, this figure must include the space heating, domestic hot water, lighting, fans and pumps and also all of the projected appliance consumption. In addition to the primary energy demand the standard permits that either the Specific Heating Demand or the Specific Heating Load must be met.

Energy Balance

The energy balance of the proposed building must be verified using the Passive House Planning Package (PHPP) using the appropriate regional climatic dataset. Either the monthly or the annual method may be applied.

If the Specific Heat Demand is ≤ 8kWh/m2.yr or the ratio of free heat gains to heat losses is greater than 0.70 it is recormended that the monthly method is used to ensure accuracy.

The standard provides limiting backstop values for the glazing specification, ventilation system, air tightness levels and thermal-bridging as these factors should not exceed these limits in order that the thermal comfort criteria can be maintained.

Further information

The following table illustrates the elemental backstop values which should not be exceeded in order for the Passivhaus certification criteria to be met.

Design Component

 Limiting value

Walls, Roof, Floor (U-values)*

≤0.15 (W/m2K)

Glazing unit

≤0.8 (W/m2K)

Installed glazing

≤0.85 (W/m2K)

Doors

≤0.8 (W/m2K)

Infiltration (ach-1)

≤0.6 @ n50

Thermal bridging (linear ψ value)

≤0.01 (W/mK)

MVHR coefficient (η HR)

≥0.75

Ventilation electric limit

0.45 Wh/m3

Appliances

High efficiency recommended

Lighting

High efficiency recommended

On site renewables

No requirementbut SHW typical

*please note opaque U-values are only recommended targets and are not critical to certification

The backstops above apply to moderate weather regions only, for warmer climates the performance values could be reduced. Please consult your building certifier for more infomation.