Questions about Heating
Does a Passive House need a conventional central heating system?
A Passive House needs some kind of space heating system. It will be considerably smaller in comparison to that required for a conventional house. A Passive House may need as little as 3kW of heat at the coldest time of the year whilst a conventional oil boiler produces 20kW.
What kind of heating system is typically used in a Passive House?
The design of the space heating required depends on the size and energy efficiency of the house. Whatever type of system is decided upon, it is important to note that the house will need some heating to all rooms in the winter period. It is a common myth that a passive house heats itself. This is not true and an adequate heating source must be considered.
What is the difference between a ‘space heating system’ and the mechanical heat recovery ventilation system (MVHR)?
The mechanical ventilation system provides a constant flow of air throughout the house via means of a fresh air supply. The incoming fresh air is heated via the extracted stale air through means of plates and conduction known as the heat recovery unit. Although the heat recovery element of the system does provide some pre-heating of the air, on cold winter days the ventilation system has a net cooling effect upon the house. On these days the space heating system comes into play and provides the required amount of heat to supply the constant temperature desired.
Does my Passive House need radiators or underfloor heating?
It is usual to find some method of heating in a Passive House. The type of system depends on the comfort levels the occupants would expect on the coldest days. Wood burning stoves to heat large spaces can be an alternative to central heating. In this instance, some sort of heating backup should be provided.
Can I control the temperature in my Passive House?
A Passive House is designed to deliver a constant 20°C throughout the dwelling although different people have different comfort levels. The heating system can be designed in such a way that the temperature can be changed via means of conventional room thermostats.
Is it true that a Passive House can’t have an open fireplace?
Yes, unfortunately, this is true. This is due to the airtightness which is completely necessary in order to achieve the Passive House Standard. An aesthetically pleasing compromise is the installation of a wood-burning stove as this has a sealed door and can also have an independent air supply.
If the house is unoccupied will the house cool down?
Yes but very slightly and definitely nothing like a conventional house. The temperature changes only very slowly. If the ventilation system and heating systems are switched off, a passive house typically loses 0.5 °C (1 °F) per day (in winter).