A common misconception with Passive Houses’s is that they can heat themselves, whereas in truth they are carefully designed to ensure maximum retention of any generated heat – but the heat still has to come from somewhere.
A Passive House has a space heating energy demand of <15kWh per square metre of living space per year. Compared to the UK new-build common practice figure of 55kWh/m2/yr, this can pose a challenge.
At the time of writing, over 50,000 buildings have been certified to achieve this, providing that the Passive Housing Planning Package (PHPP) is exceptionally accurate (+/- 0.5kWh) when predicting the demand after all aspects of the building are considered.
How do you select a product that is going to provide the required heat, without compromising the energy efficient standard? Here are some of the most popular options, with their associated pros and cons.
Commonly duct mounted, an electric post heater can be used alongside a heat recovery ventilation system (MVHR) to heat the supply air as it leaves the unit.
In addition to a small limited outlay and minimal space requirement, the electric post-heater reacts to supply air temperature changes in the MVHR.
However, specifiers must also consider the potentially high running costs of the unit, in addition to the unfamiliar controls for occupants. A further problem to consider is that the units will only heat the air supplied to living areas, not wet rooms.
Like its electric counterpart, the hot water post-heater is positioned within the supply duct. However, as the name suggests, the heating is provided by hot water rather than electricity.
Benefits of a hot water post-heater include a steady integration with domestic hot water heating systems, as well as taking up minimal space and reacting to the temperature changes in the MVHR.
Like the electric post-heater however, its two sets of controls could possibly cause confusion for occupants who are unfamiliar with MVHR, and the method also fails to heat wet room areas.
Another option to consider is solar heating. Using fitted panels called collectors, solar heating collects heat from the sun and transfers it to water stored in a hot water cylinder.
This roof fitted solution benefits from low running costs and versatility – as it can be linked with MVHR, underfloor heating and/or radiant heating panels.
However, solar heating is also regarded as a high maintenance solution ideally suited to cold climates with plenty of access to sunlight, as it is entirely reliant on external conditions.
As the panels are fitted to the buildings’ roof, this solution does not suit all building orientations. A back-up heating system may also still be required.
A choice most occupants will be familiar with, gas boilers are a conventional and user-friendly solution for both heating and domestic hot water.
With a small initial outlay, gas boilers offer a large choice of heat distribution methods, from underfloor heating to designer radiators and towel racks.
Due to fluctuating gas prices, these boilers can however suffer from higher running costs than other options.
Supplying instant heat to a room, electric panel heaters offer a “plug-and-play” heating solution which is proven especially popular in refurbishment projects.
Electric panel heaters also feature towel heater options for bathrooms.
Unfortunately they do suffer from high running costs, and are known to give off an unpleasant burnt dust scent when turned on.
Consisting of a network of specially designed plasterboard panels that replace a standard panel within the wall or ceiling, radiant heating can be fitted as part of the general construction. [LINK]
Whilst the initial outlay may be high, the plasterboard panels are built into the construction and therefore take up no space within the building. In addition to low running costs, they can be used for cooling and produce no noise.
A geothermal or ground source heat pump is a heating and cooling system with low running costs and a high coefficient of performance (COP).
GSHP’s use the relatively constant temperature of the earth as a heat source in winter and a heat sink during the summer months. Available as a solution for both heating and domestic hot water, GSHP’s can offer a varied choice of distribution methods much like gas boilers.
Ground source heat pump’s do however require a portion of and for their installation and a high cost upfront.
The final option is an air source heat pump (ASHP), commonly referred to as a ‘reverse-cycle air conditioner’.
Boasting many of the same benefits as the ground source heat pump, an ASHP absorbs heat from the outside air and releases it into the dwelling via a variety of methods.
Specifiers must however be aware that a cold climate can decrease the heat pump’s coefficient of performance.
Get in touch with Zehnder to find out more about Passive House options and support.
Zehnder Group UK Ltd
Unit 4, Watchmoor Point