Passivhaus Affiliate

Technical Guidance - Internal Heat Gains in relation to living areas

Category: Guidance

Nick Grant, PHT Technical Diretor, and Alan Clarke presented a concept for new standard values for internal heat gains (IHG) in residential buildings. For the UK they ascertained that higher occupancy rates on average prevailed in smaller dwelling units (DU), as a result of which not only body heat from occupants but also the heat dissipated by electrical applications increases in relation to the area. 

Following these considerations, an approach for occupancy rates and internal heat gains has been devised by the Passivhaus Institute which will be used as a standard value for residential buildings in PHPP v9 (2015). 

It must be noted that the fluctuation range of occupancy and IHG between different dwellings is considerable even with identical dwelling sizes. As a rule, the intensity of usage will also change during the service life of the building, therefore these are only estimated average values for the model shown here, which may be higher or lower in individual cases. Nevertheless, such standard values are crucial for practical planning. An additional review using other approaches (e.g. for specific known occupancy, equipment etc.) is also possible.

Passivhaus Institute

PHPP 9 approach for IHG depending on dwelling size

The standard approach of 2.1 W/m² for IHG in winter has been modified: the standard value varies in dependence on the average living area per dwelling unit according to the grey line in the figure below.

Figure 6: IHG depending on the living area, as used in the PHPP 9, PHI

IHG that are higher than the standard PHPP value of 4.1W/m² for homes, as would result for dwelling units with a living area of less than 20 m², are not taken into account. Whether the assumptions made for small dwellings are still correct requires closer examination.

Download the full report here.

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