The practicality and cost of achieving energy efficiency is going to play an increasing part in determining the value of existing homes. Global resource depletion and the realisation that high energy costs are here to stay is generating a huge and growing interest in new-build low energy houses as an alternative.
In the world of low energy houses, what is the difference between an eco house, a zero carbon (or near zero carbon) house and a Passivhaus? There is a lot of overlap but here are some pointers:
Miller Architects Cross section through zero carbon eco house Wealden District
An eco-house is a sustainable eco-friendly home for the future. The process starts with the choice of site, the orientation of the house and the location of windows to maximise seasonal solar gains coupled with the compactness of the plan. A ‘fabric first’ approach dictates that the walls, floor and roof are very highly insulated and the windows are triple glazed. Good air tightness and the elimination of cold bridges is also required. Allied to this is an understanding of how much energy has gone into all of the components which are ideally locally sourced. The next consideration is the use of technology in the form of a ground or air source heat pump (GSHP / ASHP) for space heating and domestic hot water powered by battery power supplied by an array of solar PV panels. This can be combined with a mechanical ventilation with a heat recovery (MVHR) whole house heat recovery system that provides a balanced supply of fresh, filtered, heat recovered air to the living areas, whilst simultaneously extracting stale, moist, odorous air from ‘wet’ rooms. This system recovers a large percentage of the heat that would otherwise be wasted. Various possible combinations of these and other renewable technologies can be explored in terms of their up-front cost as a proportion of the build cost versus the projected pay-back period.
Like the name suggests, a zero carbon / or near zero carbon house produces, in theory, zero or near zero CO2 emissions by maximising energy efficiency and renewable energy. It is possible to go beyond achieving net-zero carbon emissions through a carbon negative approach that involves removing CO2 from the atmosphere by on or off-site tree planting.
Lastly Passivhaus. Passivhaus is owned by the Passivhaus Institute of Darmstadt, Germany which regulates certification. A Passivhaus must be designed by a certified Passivhaus designer, it must be computer modelled in 3-D and then computer modelled in the Passivhaus Planning Package (PHPP) which is a ‘bolt on’ to Sketch-up. The work must be tested during construction (eg air tightness) and signed-off by an independent accredited Passivhaus certifier separate to the main design team. So there is a cost to it. There is no requirement to obtain the Passivhaus ‘stamp’ on a project though the exacting Passivhaus requirements might be part of the architectural brief and the ‘stamp’ could be useful for future marketing.
Give us a call for further information and / or help with the planning of your eco house / zero and near zero carbon house / Passivhaus.
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