Questions about energy ratings

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What Building Energy Rating would a Passive House typically achieve?
This varies from project to project, although surprisingly, a Passive House may not achieve an A1 or even A2 rating. This is because to achieve these ratings requires the use of renewable energy technologies for generation of electrical energy by photo-voltaic panels or hot water by thermal solar panels. These are not necessary for a Passive House to reach its standards although it can be introduced. A Passive House is superb for reducing energy heating costs, whilst the use of renewable energy sources are required for A ratings.

Is a Passive House also a Zero Carbon House? 
No. You still need a minimal amount of external energy to provide a comfortable and healthy indoor climate in a Passive House, although in some regions of Europe that amount would be next to zero. A Passive House tries to balance economy and ecology but of course you can turn this into a zero energy house, however this is the most expensive part and it is harder to achieve a payback. It is not a low energy house either as it exceeds these standards.

Do I need thermal mass?
No. Thermal mass is a help in the retention of solar energy. Nice to have, but not necessary as the temperature of a Passive House remains constant.